Ssgf Magazine 2013

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STEWARDSHIP

SCIENCEThe SSGF Magazine 2013-2014

PRESSUREPREDICIONSHow Sandia is refining matter modelsby applying first principles

Los Alamos: Neutron

beam record-breaker

Livermore: At the edge

of the periodic table

Plus: Former fellow goes to Washington,

more juice for Z, bringing the big bang

down to size, fission and scission, and

SSGF on the road.


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Department of Energy National Nuclear Security Administration

BENEFITS

$36,000 yearly stipend

Payment of full tuition and required fees

$1,000 yearly academic allowance

Yearly program review

12-week research practicum

Renewable up to four years

This is an equal opportunity program and is open to all qualified persons without regard to race, gender, religion, age, physical disability or national origin.

IMAGESLEFT: A metallic case

called a hohlraum holds the fuelcapsule for National Ignition Facility

experiments at LawrenceLivermore National Laboratory.

MIDDLE: At Sandia NationalLaboratories, high magnetic

fields on the aluminum side of thismagnetically launched aluminum/copper

flyer drive it into diamond targets attens of kilometers per second,

generating enormous pressures andshock waves in the diamond.

RIGHT: X-ray laser flashes generated inan undulator, an arrangement of magnets

that directs high-energy electrons. Imagecourtesy of Los AlamosNational Laboratory.

The Department of Energy National Nuclear Security Administration Stewardship Science

Graduate Fellowship (DOE NNSA SSGF) program provides outstanding benefits and

opportunities to students pursuing a Ph.D. in areas of interest to stewardship science,

such asproperties of materials under extreme conditions and hydrodynamics, nuclear science,

or high energy density physics. The fellowship includes a 12-week research experience

at Lawrence Livermore National Laboratory,

Los Alamos National Laboratory

or Sandia National Laboratories.

The DOE NNSA SSGF program is open to senior undergraduates or students in their first or second year of

graduate study. Access application materials and additional information at:

APPLY

ONLINE

www.krellinst.org/ssgf

Stewardship Science

Graduate Fellowship

Krell Institute | 1609 Golden Aspen Drive, Suite 101

Ames, IA 50010 | 515.956.3696

email: [email protected]

FOR MORE INFORMATION

APPLICATIONS DUE

MID JANUARY


3/28

STEWARDSHIP SC IENCE 13/14THE SSGF MAGAZINE PC

MUCH OFthe discussion in Washington these days revolves aroundfiscal restraint, doing more with less and the dreaded S word: sequestration.Even in this environment, there is a continuing understanding of the value

of science by NNSA leadership and the nations elected representatives.

This fourth edition of Stewardship Science: The SSGF Magazinerepresents a

milestone since the magazines publication now spans an entire class of

fellows! Our shared commitment to sustaining programs like the Stewardship

Science Graduate Fellowship represents the value we place on developing the

leaders of tomorrows scientific endeavors. The work highlighted in this issue

shows the return on those investments.

In missions that range from reducing the risks of nuclear terrorism or theproliferation of nuclear weapons technology to responding to nuclear accidents like the

one at Fukushima in Japan, NNSA relies on tools and technology based on a fundamental

understanding of nuclear science. The work of fellow Matthew Buckner at Lawrence

Livermore National Laboratory (page 4) on Accelerator Mass Spectrometry (AMS) advances

the state-of-the-art of a key diagnostic tool. AMS is used in several fields, including

detecting signatures of nuclear fuel reprocessing an important nonproliferation

function. Matthew used AutoCAD, along with simulation tools, to build a prototype

detector, install it and test it on a Livermore accelerator beamline.

At a more fundamental level, fellow Nicole Fields worked on calibrating a key material

during her research practicum at Los Alamos National Laboratory (page 7). Fieldsexamined germanium-76, an isotope researchers hope will find evidence of neutrinoless

double-beta decay. This rare interaction is key to understanding neutrinos and can

help in advancing our fundamental knowledge of the universe. She used neutron beams

from LANSCE, the Los Alamos Neutron Science Center, to simulate cosmic ray exposure

so she could calibrate the effects of this radiation for future experiments.

In related work, fellow Joshua Renner conducted his practicum at Livermore (page 7) on

the technology for time projection chambers (TPCs). These TPCs also are designed

to detect evidence of neutrinoless double-beta decay. Renner worked with physicist Adam

Bernstein on the negative ion TPC and used simulation tools to emulate ion drift behavior.

These tools provided clues to help maximize the efficiency of Livermores detector forthese rare interactions.

From fundamental exploration to prototype development, Stewardship Science fellows

are advancing the frontiers of nuclear science and helping NNSA build its future.

Christopher Deeney

L E T T E R F R O M N N S A

Investing in the Future

Christopher Deeney

Assistant Deputy Administrator

for Stockpile Stewardship

U.S. Department of Energy National

Nuclear Security Administration

With assistance from Mark Visosky

Senior Technical Advisor

TechSource, Inc., contractor to NNSA


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P2STEWARDSHIP SC IENCE 13/14 THE SSGF MAGAZINE

FEATURES LAB INITIO 10

By Jacob Berkowitz

Sandias Luke Shulenburger and colleagues are harnessing the power of quantum Monte

Carlo methods to boost matter models accuracy. Theyre already finding that elements

under extreme temperatures and pressures behave in unexpected ways.

IN THEIR ELEMENT 15By Karyn Hede

The newest, heaviest elements on the periodic table are difficult to produce and oftenquickly disappear, making it hard to quantify their properties. Livermore scientists are

finding new ways to separate and understand these strange substances.

THE BEAM COUNTERS 19By Thomas R. ODonnell

Los Alamos National Laboratorys Trident, a powerful laser that produces fleeting pulses,

has racked up a new neutron beam record. The experiment could lead to more precise

detectors and to compact neutron sources for science and nuclear forensics.

Stewardship Science: Te SSGF Magazine showcases researchers and graduate students at U.S.

Department of Energy National Nuclear Security Administration (DOE NNSA) national laboratories.

Stewardship Scienceis published annually by the Krell Institute for the NNSA Office of Defense

Sciences Stewardship Science Graduate Fellowship (SSGF) program, which Krell manages for NNSA

under cooperative agreement DE-FC52-08NA28752. Krell is a nonprofit organization serving the

science, technology and education communities.

Copyright 2013 by the Krell Institute. All rights reserved.

For additional information, please visit www.krellinst.org/ssgf or contact the Krell Institute 1609

Golden Aspen Dr., Suite 101 |Ames, IA 50010 |Attn: SSGF |(515) 956-3696

STEWARDSHIP

SCIENCEThe SSGF Magazine 2013 - 2014

I I I

I I I

FIRST-PRINCIPLE INVESTIGATO

This visualization by Sandia National LaboratLuke Shulenburger shows a charge densityfor FeO (iron oxide) calculated with quantuMonte Carlo methods. Iron oxide is of inteto geophysicists, but modeling its electronstructure is challenging. Shulenburger beloto a corps of young mathematicians whoinclude Miguel Morales of Lawrence LivermNational Laboratory, an alumnus of the NaNuclear Security Administration StewardshScience Graduate Fellowship working oufundamental properties of this and other mabased on first-principles physics. Read morstarting on page 10.

COVER


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STEWARDSHIP SC IENCE 13/14THE SSGF MAGAZINE P3

2 0 1 3 2 0 1 4

IMAGE CREDITS

Cover, Luke Shulenburger, SandiaNational Laboratories (SNL);page 1, National Nuclear SecurityAdministration; page 4, WalidYounes, Lawrence LivermoreNational Laboratory (LLNL);page 5, SNL; page 6, ATLASExperiment/CERN; page 9,Laura Berzak Hopkins; pages

10-12, Shulenburger/SNL; pages16-17, LLNL; pages 19-20,Markus Roth, TechnicalUniversity of Darmstadt;page 21, julsdesign (source:Los Alamos National Laboratory[LANL]); pages 22-23, LANL.

EDITOR

Bill Cannon

SR. SCIENCE EDITOR

Tomas R. ODonnell

DESIGN

julsdesign, inc.

COPY READERSRon WintherShelly Olsan

CONTRIBUTING WRITERS

Monte BasgallJacob Berkowitzony Fitzpatrick

Karyn HedeTomas R. ODonnell

Sarah Webb

SSGF STEERING COMMITTEE

Robert VoigtNuclear Security Division

SAIC

Darryl P. ButtDepartment of Materials Science and Engineering

Boise State University

Stephen M. SterbenzLos Alamos National Laboratory

Kimberly S. BudilLawrence Livermore National Laboratory

Ramon J. LeeperSandia National Laboratories

DEPARTMENTSFRONT LINES

4 FISSION UP CLOSE Deciphering the details of atom splitting.

FELLOWS ON LOCATION

The latest SSGF graduates design a detector, test elements for gamma

ray exposure, put tantalum under pressure, track some particles and

measure ion-stopping power.

5 Z, SUPERCHARGED Sandia plans to amp up the Z machine in the same space.

6 LITTLE BIG BANG Probing the properties of the quark-gluon plasma.

9 CONVERSATION: BRIDGINGSCIENCE, POLICY AND THE PUBLIC

Former fellow Laura Berzak Hopkins on providing science expertise to

Congress, fusions two varieties and her Why-Sci communications project.

SAMPLINGS

24 BOTTLING THE SUNFellow Evan Davis probes the slim sliceof turbulence that has an outsized say

in fusion energys viability.

DIRECTORY

25 DOE NNSA SSGF FELLOWSWhere to find current fellows

and alumni.


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F R O N T L I N E S

DETECTOR UPGRADE

Matthew Bucknerspracticum at Lawrence

Livermore National Laboratory was a bit like a

high-tech physicists shop class. His plans for an

improved gas ionization chamber detector went

from computer modeling to fabrication

at a machine shop and testing.

Buckner worked with Scott Tumey at Livermores Center for Accelerator

Mass Spectrometry. Accelerator mass spectrometry, or AMS, speeds ions

to high energies, separating isotopes from surrounding material before

mass analysis. AMS is used in several fields, including detecting signatures

of nuclear fuel reprocessing an important nonproliferation function.

The device Buckner made uses AMS to measure transition metal

activation products. He simulated a previous design on a computer

and found that voltages were incorrectly applied for the detector

anodes to adequately collect electrons. After some research, he usedsimulations to tailor the new detector design to transition metal

activation products and modified grids, voltages and other aspects.

Using AutoCAD software, Buckner designed a detector enclosure

for fabrication at the labs machine shop, then built the detector and

installed it on the accelerator beam line. He and Tumey tested it

with relevant materials and Buckner compared its resolving power

with that of the original detector. The new detector is more sensitive

and bolsters the labs nuclear forensics capabilities, Tumey says.

The fellow, meanwhile, says the project was a contrast with his doctoral

work at the University of North Carolina at Chapel Hill. Under

Christian Iliadis, Buckner has studied proton capture by rare oxygen

isotopes thermonuclear reactions associated with nucleosynthesis

and energy generation in a class of stars and with explosive hydrogen

burning during classical novae. During the summer, he reports, it

was really interesting to participate in an application of the nuclear

and accelerator physics Im interested in.

Members of DOE National Nuclear Security Administration

Stewardship Science Graduate Fellowships 2013 outgoing

class share their national lab research experience.

continued on page 7

Fission Up Close

Although it releases vast amounts of energy, the processof splitting atomic nuclei is still difficult to understand

in detail. Nuclei are infinitesimally small and fission

happens incredibly quickly (within 10-20 seconds), so

its hard to study in a laboratory.

Undaunted, Lawrence Livermore National Laboratory researchers are

looking at fissions microscopic detail with the hope of improving

nuclear waste management and recycling and increasing nuclear power

production. Describing fission in detail also can help answer basic

science questions, such as how heavy elements formed in the universe.

Physicists started delving into fission theoretically 75 years ago by

simplifying the problem. Instead of looking at all the protons and

neutrons within the nucleus, they considered it as a liquid drop,

Livermores Walid

Younes says. During

fission, the drop would

stretch into an oblong

peanut shape. At

the scission point,

the narrow neck in

the peanut wouldbreak to form two

new atomic nuclei

and release energy.

Even today, with

high-performance

computers, the

data challenges for

understanding fission remain enormous. If you put all that information

into a computer, Younes says, youd quickly be looking at tens of millions

of processor hours as the simulation moves toward scission.

Despite the difficulty, Younes and his colleagues have extended the

traditional droplet model. Instead of considering the nucleus as a

single stretching blob, their calculation includes protons and neutrons

that arrange themselves within the droplet in a way thats energetically

favorable. Tey then stretch the theoretical nucleus until it breaks

naturally and probe how that force affects the individual particles.

We dont force it, he says. We dont take a knife and cut it in two.

continued on page 6

A schematic illustration of microscopic fission

calculations for plutonium-240. The arrows

epresent evolution of the nucleus in the calculation

across its energy surface toward its breaking

point. On the right are three examples of the

nuclear configuration near breaking.

F E L L O W S O N L O C A T I O N


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Z, Supercharged

By far the worlds largest, most powerful and mostsuccessful pulsed-power accelerator, Sandia National

Laboratories Z machine is poised to become even

more powerful.

Te Z machine named for z-pinch, a type of plasma device driven by

pulsed-power accelerators generates an 80-terawatt electrical power

pulse. Its 33 meters in diameter and fills the high bay of Building

983 on the labs Albuquerque, N.M., campus. Tanks to LD technology,

for linear transformer driver, over time Z will become Z 300, a

300-terawatt machine that will fit the same space.

Te Z 300 will generate twice the current and four times the power that

Z now generates, says William Stygar, manager of the labs Advanced

Accelerator Physics Department, which specia lizes in pulsed-power

accelerator physics. With that capability, Z 300 will be able to perform

ultra-precise high energy density physics experiments in support of

various Department of Energy missions, including the Stockpile

Stewardship Program of the National Nuclear Security Administration.

Stygar is confident that Z 300 will quadruple pressures for conducting

material-physics experiments with plutonium, uranium and other

critical elements; achieve thermonuclear ignition in an inertially confineddeuterium-tritium plasma; quadruple the energy and power radiated

by non-thermal X-ray sources for weapon-physics and weapon-effects

experiments; and quadruple the energy and power radiated by thermal

X-ray sources for laboratory astrophysics, radiation opacity and

radiation transport experiments.

John Porter, senior manager of Sandias Z accelerator sciences group,

was the first to propose building a next-generation LD accelerator

that fits inside the same building.

Te High Current Electronics Institute (HCEI) at omsk, Russia, beganwork on LD technology about 10 years ago. Sandia has developed the

technology to its present state. Stygar, a Sandia researcher since 1982,

says Russia, Israel, France, England, China and other countries already

use LD technology to drive high energy density physics experiments.

LD technology dates back to 1920s, when Erwin Marx described his

self-named generator. Tirty-six Marx generator-driven pulsed-power

modules create the 26-megampere, 80-terawatt pulse that powers Z.

A Marx generator creates a 1 microsecond-long power pulse. Z

experiments, however, require a 100-nanosecond power pulse, so

four stages of pulse compression must reduce the span of the Marxpulse. Pulse-compression hardware introduces electrical impedance

mismatches, causing multiple internal reflections of the Z power pulse

and reducing Zs efficiency. In addition, Stygar says, pulse compression

hardware substantially complicates the design of a machine like Z,

increasing maintenance costs and ramping up the difficulty of

developing an accurate accelerator circuit model and conducting

accelerator simulations.

An LD generates a 100-nanosecond power pulse in a single step,

which eliminates the need for additional pulse-compression hardware,

Stygar says. As a result, an LD module is twice as efficient as aMarx-driven module, substantially more compact, less costly to

maintain and easier to simulate.

Te belly of the LD beast is a collection of 20 bricks arrayed in a

circle like the spokes of a wheel. Each shoebox-sized brick holds a

200-kilovolt switch and two 100-kilovolt capacitors. Te bricks are

inside an annular enclosed metal cavity that looks like a g iant Life

Savers candy, Stygar says.

Z 300 will be driven by 90 LD modules, each consisting of 33 LD

cavities (each cavity is 2 meters in diameter and .22 meters thick)stacked horizontally, like a Life Savers roll. Altogether, Z 300 will

have 2,970 cavities, each producing a 100-nanosecond-long,

105-gigawatt power pulse.

Each cavity converts, in a single step, the energy stored in its

capacitors to the 100-nanosecond pulse, Stygar says. Hence, Z 300

will not need any additional pulse compression hardware.

But it will need some work to upgrade LD cavities from a 79-gigawatt

electrical pulse, the current standard, to the labs 105-gigawatt pulse

goal. o get there, technicians will replace existing switches with new,more advanced ones now under development by researchers from

Kinetech Inc. and Sandia. Teyll also use upgraded capacitors from

technology company General Atomics. Voss Scientific also participates

in the project.

Stygar says the plan is to first operate an LD cavity at 105 gigawatts.

Ten the team of about 17 technicians and researchers will build an

LD module with 33 cavities that generates a 3.5-terawatt electrical

power pulse. After we demonstrate successful operation of this

module, we will be ready to build Z300.

Tony Fitzpatrick


8/28


F R O N T L I N E S

Although scission the last part of fission is incredibly important,

its also the hardest to understand. Physicists would follow the

process up to this point of no return but didnt have the tools to

examine the nucleus as it fragments. Younes and his team now use their

framework to examine scission and have gotten as far as calculating

some properties of the resulting nuclear splinters.

Researchers can examine the pairs of nuclei that form as the nucleus

comes apart. Most break into a variety of combinations with different

energies, so Younes and colleagues are interested in which fragments

form and how frequently. Understanding scission is so challenging,

in part, because the breakup of a single nucleus into two doubles the

complexity: two sets of properties now, plus the nuclei are interacting,

introducing still another variable that can affect the system.

Little Big Bang

Equipped with particle accelerator-colliders, scientists areglimpsing conditions like those scant microseconds after the

Big Bang began our universe 13.8 billion years ago. By bashing

together energized heavy gold or lead ions accelerated to

near-light speed, they trigger so-called Little Bangs that help reveal

states of matter that are even odder than theyd anticipated.

Los Alamos National Laboratory physicist Ivan Vitev is among the

theorists attempting to understand these tiny-bang states, known as

quark-gluon plasmas, or QGPs. Tats because QGPs are by definition

not observable on the time scales at which detectors make experimental

measurements, Vitev says.

QGPs themselves refute normal rules of the strong interaction, a

fundamental force that keeps matters core components quarks and

gluons bound in an unbreakable embrace. Scientists think the Big

Bangs stupendous energy burst let quarks and gluons very briefly roam

free. But within a few microseconds, they cooled enough to rejoin as

the building blocks of protons, neutrons and other contemporary

fundamental particles.

Little Bang experiments artificial ly boost particle energy levels just

enough to recreate those last moments when quarks and gluons werestill approximately free, Vitev says. Tese semi-liberated QGPs were

expected to be gaseous. But when the Relativistic Heavy Ion Collider

(RHIC) at Brookhaven National Laboratory began producing them in

the summer of 2000, puzzled scientists instead found them acting

like perfect liquids, flowing with practically no viscosity.

Such discoveries, also observed at CERN accelerators in Europe, have to

be interpreted by theory to extract the information, Vitev says. We

have only a very short time about a millionth of a bill ionth of a second

when this plasma state lives and develops features we are looking

for in experimental data. Tats too fleeting for accelerator detector

measurements, so theorists must instead conduct thought experiments.

Tose reconstruct QGP qualities by using particles formed after the

quarks and gluons recombine. Tats what makes the field exciting

and at the same time difficult.

Vitevs contributions began with a paper published in 2002, the year

he received his doctoral degree from Columbia University. It laid the

theoretical foundation for jet tomography, which can be used once in a

blue moon, he says, whenever a comparatively rare heavy ion collision

creates especially energetic quarks or gluons. One quark or gluon maycollide with another and bounce apart like billiard balls at azimuths

roughly 180 degrees apart. After ricocheting, one of the resulting

particles continues on at a high speed and energy. Te other rapidly

loses both in a shower of fragments the jet while passing through

and interacting with the detectors plasma medium.

Experimentalists can then study the measurable byproducts. For

example, if one of the particles is a rare Z boson or a photon, the data

can be tagged for comparison with the final byproduct of its counterpart.

Researchers know those fragments are spaced by a predictable azimuth

and that one has interacted with the plasma medium, whereas theother hasnt. Tey can reliably use this information to recreate details

about the immeasurable QGP itself, such as its density and temperature.

Vitev compares this method to positron emission tomography and

radiography because both those medical techniques create images by

processing signals from particle behavior within a medium.

His theoretical work is part analytic and part computational, he

says, and his codes run on local computer clusters at Los Alamos,

where he started in 2004 as a J. Robert Oppenheimer Fellow and

now works in the Teoretical Division.

Monte Basgall

continued from page 4


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continued from page 4

ISOTOPE HOPES

It will take some sensitive detectors to answer

basic questions about the nature of matter

in the universe. Fellow Nicole Fields

project during her Los Alamos National

Laboratorypracticum will help researchers

calibrate properties of a key material that

could do the job.

Working with Steve Elliott and the Neutron Science and TechnologyGroups weak interactions team, Fields examined germanium-76, an

isotope researchers hope will find evidence of neutrinoless double-beta

decay. This rare particle interaction is key to understanding neutrinos

the chargeless, nearly massless byproducts of nuclear reactions and

advance knowledge of the universe.

But germanium-76, when above ground, may interact with naturally

occurring cosmic rays, creating radioactive contaminants that could

interfere with experiments. The Los Alamos researchers wanted to test

other elements that produce similar radioactivity at much higher rates.

By counting gamma rays from those other materials, the researcherscould estimate how much cosmic ray exposure the germanium

received and account for that in their measurements.

Fields exposed foils comprised of the other elements cadmium, zinc

and niobium to neutron beams at the Los Alamos Neutron Science

Center to simulate cosmic ray exposure, but at higher levels. Then she

used a detector to count gamma rays and determine which and how

many radioactive isotopes resulted. With the neutron flux that hit the

foils and the measured cosmic ray neutron flux, Fields could predict

which radioactive isotopes would be good indicators of neutron

exposure from space.

Fields and her advisor, Juan Collar at the University of Chicago,

and Elliott are all collaborators on Majorana, an international

experiment that will use germanium-76 to seek signs of neutrinoless

double-beta decay.

PARTICLE TRACKER

Joshua Rennerspracticum project at Livermorewas the same as his

doctoral research at the University of California, Berkeley, only different.

In both, Renner worked on technology for time projection chambers, or TPCs,

designed to detect evidence of neutrinoless double-beta decay. Its key to

understanding neutrinos and to advance knowledge of the universe.

TPCs track charged particles released when two larger particles collide

or, in some cases, when atoms of fissionable materials split. In essence,

the energetic particles scientists seek knock loose electrons from atoms of

a gaseous material (the detector medium) in the TPC. The number of

freed electrons characterizes the particles energy.

At UC Berkeley and Lawrence Berkeley National Laboratory, Rennerworked under James Siegrist, now associate director of the Department

of Energy Office of Science for the High Energy Physics program. The

group collaborates with other institutions to develop a prototype

detector using xenon as a detector medium thus the acronym

NEXT, for Neutrino Experiment with a Xenon TPC.

At Livermore, Renner worked with physicist Adam

Bernstein on the negative ion TPC. It uses negative ion

drift, in which freed electrons attach to gas particles,

forming negative ions. The ions drift through an electric

Although the LLNL scientists are beginning to get a picture of what

scission looks like, questions remain. For example, physicists continue to

discuss the role of certain neutrons in the fission process. Tese scission

neutrons, in the neck of that splitting peanut, sometimes are emitted

as the nucleus breaks. We would like to be able to calculate what those

neutrons are doing from a microscopic point of view, Younes says. On

the atomic scale, this fundamental science also could help researchers

understand a variety of scientific problems that come up with multiple

particles. Scission is such an extreme example of the quantum

many-body problem.

Fission is the most computationally challenging problem in nuclear

physics, Younes says, partly because it incorporates so many complex

dynamic phenomena. It produces a lot of different kinds of observables

and is incredibly rich in the type of phenomena that you can study.

Sarah Webb

his visualizes jet quenching in a lead-lead collision in the Large Hadron Colliders ATLAS detector at a center of

mass energy of 2.76 TeV per nucleon-nucleon pair. Green and yellow bars represent particle tracks and energyeposition into the detector subsystems. An energetic jet is clearly visible at 1 oclock. The gray cone shows

heres a jet (a large energy deposition in a narrow cone) in this direction. Its away-side partner at 7 oclock

s completely missing, having dissipated its energy into the plasma.


10/28


11/28


As a 2010-11 American Physical

Society Congressional Science

Fellow, you got an inside look at

how science policy develops in

Washington. What did you take

away from your year in D.C.?

I think the general public has this idea

that if you are a scientist you know all

kinds of science. I was working in Congresswhen the Fukushima disaster unfolded. I

was asked to write a memo explaining

the different features and factors involved

in the [Japanese] nuclear power plant

and contrasting that to what the media

were reporting. I also would get questions

because someone thought: This is

science. You give it to the scientist. For

example, I did research on poppy growing

in Afghanistan and how it affects the opium

trade. Thats certainly outside my sphere

of knowledge. But as scientists, we are

trained in research skills.Although we

apply them to our specific fields, I learned

you also can apply those research skills

to a variety of topics. There was a general

comfort with getting research questions

that you dont know the answer to and

figuring out how to answer them.

Certainly, working in Congress really drove

that point home. I learned that there is a critical

role for scientists to play in policy. There doesnt

have to be this barrier between the policymakersand scientists.

After that year, you could have stayed

in Washington and pursued a career in

science policy, but you chose to return

to a research position at Lawrence

Livermore National Laboratory. How

did you make that decision?

I am still excited about science and research,

so I wasnt certain I was ready to completelystep away from research. Livermore provides a

lot of opportunities as far as career advancement

merging with science policy, so that was

definitely a big draw for me.

What are you working on now?

My graduate research was in magnetic fusion.

Now Im part of the research staff at the National

Ignition Facility, so Im working in inertial fusion,

which to anyone outside the field is exactlythe same. But its completely different. Im

studying different types of high energy density

implosions driven by NIF, which is an enormous

laser facility. The goal is to reach ignition,

which is a self-sustaining burn of light fuel

deuterium and tritium. Im in the design

physics group, so I work on the type of target

the laser hits and on shaping the laser pulse

both in power and in time, which is an

important part of how the implosion performs.

How did your time as an SSGF Fellow

inform your career choices?

During my practicum I worked at Sandia National

Laboratories, where I focused on developing

advanced materials for plasma-facing

components in magnetic fusion reactors. That

was an interesting and important introduction

to the national lab system and opened my

eyes to the career opportunities there. Also,

my initial introduction to science policy came

through the fellowship. At our annual

gatherings there always are opportunities

for connections to policymakers in D.C.

You recently co-founded a forum called

Why-Sci.com to connect nonscientists

with scientists and research. Why should

scientists communicate directly with

the public?

The reason its so important to build that

bridge is two-fold. In times of fiscal constraint

like we are in and will likely continue to be in,

its important to explain why peoples tax

dollars should fund what scientists are workingon. Second, its important for the public

to understand that from their new, quiet

refrigerator to their iPod, science goes into all

of that. Its important for people to understand

that scientific research really does affect them

and those investments can improve their lives.

One of the biggest take-home messages I

learned in D.C. is that people are excited

about science. So many people I met in D.C.

who dont know about science were excited

to learn more. My office [former Sen. Kent

Conrad, D-N.D.] asked me to give a lunchtime

mini-lecture on fusion and ongoing plasma

physics experiments. It was exciting to see

the interest, and I think part of it was the

direct interaction with a scientist who was

willing to explain what they do. Thats the

model for Why-Sci.com.

BRIDGING SCIENCE,POLICY AND HE PUBLIC

C O N V E R S A T I O N

Laura Berzak Hopkins

Physicist, Lawrence Livermore

National Laboratory

DOE NNSA SSGF Class of 2010

Its important to explain

why peoples tax dollars

should fund what scientis

are working on.


12/28


Title image: Snapshot from a simulation of xenon in

which liquid atoms (red) are solidifying (green) at a

high temperature and pressure.

Jacob Berkowitz is a science writer and, most recently,

author of The Stardust Revolution: The New Story of

Our Origin in the Stars(Prometheus Books, 2012).

C O V E R S T O R Y

Lab iniioBY JACOB BERKOWITZ


13/28


While in high school in Lawrence, Luke Shulenburger would bike or walk up he hil l

o he Universiy o Kansas, where proessors menored he precocious een in

mah, physics, chemisry and compuer science.

By his senior year, his exracurricular educaion had led him o he Naional

Junior Science a nd Humaniies Symposium and his fi rs paper in Physics Leters A,

co-auhored wih his menors and published when he was an undergraduae a he

Massachusets Ins iue o echnology.

I also led him o a career-defining conundrum. While sudying organic chemisry

and sruggl ing o memorize reacion rules, he wondered why chemiss didn work

like physiciss: mahemaically, rom undamenal firs principles.

Why couldn you jus solve he equaions behind everyhing? says Shulenburger,

now a saff scienis in he high energy densiy physics heory group a Sandia Naional

Laboraories in New Mexico. Ive been playing around wih ha ever since.

Scientists at Sandia National Laboratories

are out to make first-principles chemical

models, hoping to reduce error and

illuminate experiments on materials

under extreme conditions.

Luke Shulenburger

W


14/28


oday, Shulenburger has ound his inellecual home. Hes par o a new generaion

o young Sockpile Sewardship program researchers a Naional Nuclear Securiy

Adminisraion laboraories who are driven o creae models o mater based no

primarily on experimenal daa, bu on firs-principles physics equaions ab iniio,

lierally rom he beginning, models.

A he hear o his vision is Quanum Mone Carlo (QMC), a compuaional modelingechnique ha grew rom work a Los Alamos Naional Laboraory in he early

1950s. Sixy years laer, QMC is finding is greaes expression in exreme parallel

compuing applicaions on DOEs high-end supercompuers.

As a resul, wo decades since he las U.S. underground nuclear es, Shulenburger

and colleagues are aking sewardship science ino a new era. Tey are harnessing

he combinaion o QMC echniques, dramaic new insighs ino maerials a he

exreme and v isions o ever more powerul compuing o creae a new race or

accuracy beween experimenaliss and heoriss.

Experimenal resuls w ill a lways be needed o ground our research, bu our goal iso provide a more complee picure, says Shulenburger, who presened his laes

QMC work a he American Physical Sociey meeing in Ma rch 2013.

BEYOND APPROXIMATIONSShulenburger wasn he firs o dream o heoreically predicing he physical and

chemical properies o mater rom firs principles. Te pioneers o quanum heory

long shared ha vision. Te ormulaion o he Schrdinger equaion describing he

quanum behavior o elecrons held he promise o heoreically solving any chemical

ineracion. In pracice, however, he equaion his a compuaional Moun Everes.

Problems scale exponenially wih he number o paricles. Tus, even wih enormous

compuing power, exac soluions are obainable only or molecules wih jus aew elecrons.

o vaul his quanum mulibody hurdle, compuaional scieniss have developed

ways o approximae soluions o he Schrdinger equaion. Each approximaion

incorporaing a mix o experimenal

daa and wha physiciss call physics

inuiion makes he equaion more

compuaionally racable.

Te problem is ha every approximaion

also disors realiy o some exen.Tus, approximaions are erile

ground or improvemen or he

Sockpile Sewardship Programs

Predicive Capabiliy Framework,

which a ims o sig nificanly reduce

modeling uncerainies.

Te common hread ha links all

o my research is he eliminaion o

approximaions o develop a more

precise abiliy o simulae maerialsunder exreme condiions,

Shulenburger says.

Since joining Sandia in 2010, Shulenburger

has aken a wo-pronged approach o

reduce approximaions in models o

elemens across he periodic able

under exreme pressure.

Firs is adaping and applying QMCPACK,

a new QMC code opimized or use onDOEs massively parallel leadership-class

compuers. (See sidebar, New Code

esed Agains he Elemens.)

Te workhorse o quanum compuaional

approximaion is densiy uncional

heory, or DF. Te echnique was

developed several decades ago and now

has housands o users and applicaions

agile enough o run on smarphones.

Bu DF alers in describing how materbehaves under exreme condiions,

paricularly or heavy aoms.

Tis is where QMCPACK eners he

picure. QMC uses a sochasic, random

sep-sampling echnique o solve wave

equaions, an approach wih a compleely

differen and poenial ly inier class o

approximaions han DF.

A visualization of a charge

density for solid argon,calculated with quantum

Monte Carlo methods.


15/28


Miguel Morales

Apair of young DOE scientists is confident that anew first-principles quantum simulation codewill provide unprecedented predictive accuracy in

modeling elements across the periodic table under

sun-like extremes of temperature and pressure.

Their optimism is based on QMCPACK, for

Quantum Monte Carlo Package. Quantum Monte

Carlo isnt a widespread method yet, says Miguel

Morales, a staff scientist in the Condensed Matter

and Materials Division at Lawrence Livermore National

Laboratory. In terms of stockpile stewardship, the

challenge for us is to develop QMCPACK to the

point at which theres trust in its predictive capabilities.

QMCPACK was created under the leadership ofthe University of Illinois David Ceperley, a pioneer

in developing the quantum Monte Carlo family

of methods.

Ceperley, also a staff scientist at the universitys

National Center for Supercomputing Applications,

worked with fellow professor and physicist Richard

Martin to mentor a talented group of graduate

students. Many of those students now are Department

of Energy staff scientists applying QMCPACK to the

most challenging stockpile stewardship problems.

Jeongnim Kim, a scientist in the Computational

Chemistry and Materials Division at Oak Ridge

National Laboratory, leads QMCPACKs

ongoing development.

QMCPACK is completely designed with extreme

parallelism in mind, Morales says. Test runs on

Oak Ridges petaflops-capable supercomputer

showed the code could be scaled up to the entire

machine with little loss in efficiency. In a discipline

in which modeling a dozen individual electrons is

considered an admirable feat, QMCPACK has

demonstrated its capable of modeling thousands

of particles in a computationally cost-effective way.

Morales and Sandia National Laboratories Luke

Shulenburger both of whom, along with Kim,

worked with Ceperley on QMCPACK are testing

the code in a benchmarking program to predictively

model elements under extreme conditions. Were

going to touch on elements across the periodic table

and identify those areas where we do well and those

where we need to work harder, Morales says. Last

year, with Ceperley and colleagues, he co-wrote a

paper on hydrogen and helium under extreme

conditions for Reviews of Modern Physics.

Probably for the light elements, were there, sa

Shulenburger, who recently used QMCPACK to

reveal a possible new beryllium solid-solid phase

transition under high pressure. But as you get to

the heavier elements, its much more difficult from

the computational point of view.

In a 2010 Proceedings of the National Academy

of Sciencespaper, Morales used QMC ab initio

simulations to confirm and pinpoint a liquid-liquid

transition in high-pressure hydrogen of interest to

planetary scientists considering giant gas planetslike Jupiter.

Morales and Shulenburger are working with Sand

and Livermore colleagues to extend the QMCPAC

benchmarking to other elements, including gold,

silver and molybdenum. Applying QMCPACK inclu

porting the code to other supercomputers, includ

Cielo at Los Alamos and Sequoia, the IBM Blue

Gene/Q at Livermore.

The effort also has involved porting QMCPACK to

run on graphics processing units, or GPUs. These

massively parallel, energy-efficient chips develop

for video games are giving a low-cost, high-efficienc

boost to high-performance computing. Notes

Shulenburger, With GPUs you almost have to thi

of your problem in a whole different way about

how to decouple everything into parallel tasks to

extent thats previously unheard of. The approac

ideal for QMC, a naturally parallelizable techniqu

Titan, a world-leading computer at Oak Ridge, alrea

gets most of its processing power from GPUs. Kenn

Esler of Stone Ridge Technologies, another of

Ceperleys University of Illinois disciples, recently

ported QMCPACK to run on them.

Morales says the challenge QMCPACKs advocate

face is to build a series of success stories, convinc

others of its accuracy and utility. To the extent th

we can start using correct first-principle predictio

of materials at high density, we will start to identify

problems in stockpile stewardship models curren

being used. There are still many hurdles to cross,

I think its just a matter of time.

NEW CODE TESTED AGAINST THE ELEMENT

QMC is an excellen fi wih sockpile

sewardship because i has he poenialo deermine maerials properies

wih exremely small uncerainies,

Shulenburger says. Tis is criical o

verificaion and valida ion proving

models ac as inended and reducing

uncerainy. Wih QMC you have he

opporuniy o ge he physics righ

even where your inuiion ai ls you.

QMC algorihms also are naurally

parallelizable on several levels, providinghe ideal models or peascale compuers

ha can do quadril lions o scienific

calculaions a second and exascale

machines a leas a housand imes

more powerul han hose. I you give

me a bigger compuer o run on and

orunaely he DOE has los o big

compuers I can make he saisical

approximaion error as small as I wan.

Alhough QMC provides one avenueor reducing approximaions, anoher

approach quanifies how much each o

hose approximaions poenially

skews simulaions.

Many researchers working o i mprove

QMCs accuracy have ocused on

reducing he fixed-node approximaion,

known o limi ab iniiocalculaions o


16/28


condensed mater and nuclear reacions. Te approximaion is a compuaional

compromise ha addresses he ermion sign problem, one o he major unsolvedproblems in modeling he physics o many-paricle quanum sysems.

In a sysem wih wo or more elecrons, he wave uncion has regions wih opposie

signs: one posiive, he oher negaive. However, or efficiency, QMC ypically

calculaes only in an approximaion o he posiive space. Tis fixed-node approximaion

is he mos difficul o eli minae and is a undamenal uncerainy in QMC

calculaions oday.

Shulenburger and colleagues are pursuing a comprehensive soluion o he sign

problem. Hes already made significan progress by showing ha, in pracice, i

migh be less imporan han previously hough in solving imporan sockpilesewardship problems. My work has ound ha i is rarely he deermining acor

or high-accuracy simulaions, Shulenburger says. Te way we pariion he

problem ino ighly bound and chemically acive pieces is ar more imporan

han his more heoreically undamenal quesion.

QMC INSIGHTS TO MATTER AT THE EXTREMEApproximaions nowihsanding, QMC already has proven is wor h in revealing

a dramaical ly new map o maters errain a exreme emperaures and pressures.

From firs principles, says Lawrence Livermore Naional Laboraorys Miguel

Morales, weve idenified a compleely new se o saes o mater ha appearwhen you compress maerials, and many o hese were compleely unexpeced.

Morales is a Livermore saff scienis and an alumnus o he DOE Naional Nuclear

Securiy Adminisraion Sewardship Science Graduae Fellowship. Hes collaboraing

wih Shulenburger o sysemaically apply QMCPACK a code hey boh helped

develop as graduae sudens a he Universiy o Ill inois o predic he equaions

o sae or elemens a high emperaures and pressures.

Teyve boh winessed he power o ab iniiomodels o redefine our undersanding

o maerial behaviors a he exreme condiions criical o sockpile sewardship

and fields such as planeary geophysics.

For example, previous models assumed ha delocalized elecrons ones a high

pressure, sripped rom heir nuclei orm a uniorm elecron curain ions inerac

agains. In pracice has no always wha happens, Morales says. Insead, in aoms

rom such elemens as aluminum and sodium under exreme pressure, delocalized

elecrons congregae in he voids o he ionic latice, creaing sable elecride srucures.

Similarly, Shulenburger says, scieniss now are reassessing models o large aoms

ha ignored inner elecrons. One o he ascinaing hings abou high-pressure

science is you can ge o he poin where

hese previously chemically iner innerelecrons sar o mater, because he

energy scales go up and up as you bring

he ions closer and closer ogeher, and

acoring his in undamenally changes

he properies o maerials a hese

exreme condiions.

Shulenburger was inroduced o

real-world high-pressure maerials

problems as a pos-docoral researcher

a he Carnegie Insiuions GeophysicalLaboraory in Washingon, D.C. Tere,

researchers sudy he behavior o minerals

squeezed a enormous pressures and

emperaures inside he Earh.

In his ime a Sandia, Shulenburgers

come ull circle in his desire o ge down

o ab iniiobasics. Working closely wih

Sandias engineers and experimenaliss,

his QMC fine-uning ocuses on making

his firs-principles echnique useul inhe Sockpile Sewardship Programs

applied big picure.

When I was a grad suden a Illinois, i I

could ell you abou he phenomenon

o a solid under pressure, ha i mealizes

and heres why, you probably wouldn

have cared as much abou exacly a

wha emperaure a nd pressure ha

happened, he says. Bu a Sandia, where

an engineer may acually incorporaehose daa ino plans or a device, you

care a lo more abou he deails. So

Ive goten a lo more ocused in erms

o how o produce a high-precision

quaniaive resul raher han jus

geting a qualiaive sense o he

physics o a problem.

Shulenburgers come full circle in his

desire to get down to ab initiobasics.


17/28


IN THEIR

ELEMENTBY KARYN HEDELawrence LivermoreNational Laboratory

scientists are probing

properties of atoms on

the edge of the periodic

table. Their rapid

separation techniques

could have ramifications

for nuclear forensics.

For yearshe periodic ablehas exised in limbo, is oherwise orderlysacks and rows o elemens peering ou ahe botom wih a series o elemens haseemed o signal chemiss had exhausedheir ideas. Running across he lower righrow, he elemens rom No. 113 o No. 118

read as a series o Us.One migh guesshese sood or unknown.

A leas some o hese orphans final ly

now have names ha acknowledge heir

discovery. Elemen 114 is flerovium, afer


18/28


he Flerov Laboraory o Nuclear Reacions in Dubna, Russia, where i was firs

creaed. Likewise, No. 116 now is livermorium, a fer Lawrence Livermore Naional

Laboraory. Te labs collaboraed on he discoveries and sill cooperae on pushing

he edge o he periodic able, seeking he ouer limi o possible elemens.

Perhaps no living scienis is more associaed wih elemen discovery han Livermores

Ken Moody, a radiochemis and member o Livermores super heavy elemen group.Moody, who was involved in discovering elemens 113 o 118, has spen years rying o

undersand he cenral issue o how aomic nuclei balance he repulsion beween

proons wih he nuclear glue ha binds hem. Jus how heavy can an elemen ge,

he wonders, beore clusers o posiively charged proons promp nuclear fission?

Tis lingering issue moivaes nuclear chemiss in he super heavy elemen group.

Bu he ools and echnology required o address his undamenal quesion also

have ound applicaions in nuclear orensics, acinide chemisr y and oher fields.

Once a new elemen is discovered, group

leader Dawn Shaughnessy says, he nexquesion is wha are (is) chemical properies and

how does i relae o is neighboring elemens in

he periodic able? Doing hose experimens is

challenging because you are lierally doing

chemisry on a single aom o somehing

ha only lass a shor amoun o ime.

Teir fleeing exisence means we have scan

or,in some cases, no inormaion abou he

chemical properies o he heavy elemens

occupying he las ew blocks in period 7, helas row on he periodic able. For example,

we know ha elemen 118 exised only by

measuring alpha paricles released in is nearly immediae decay o livermorium

and hen o flerovium. Is he same or nearly al l he ma n-made elemens: Scieniss

only know heyve been here by couning radioacive emissions as hey decay.

Years ago, Moody descr ibed his work o his elemenary school-aged daugher.

Her incredulous response You mean you don acually know wheher you have

anyhing unil i goes away? encapsulaes he difficulies o working wih such

ephemeral species.

CHEMISTRY BY ANALOGYMos super heavy elemens can be sudied only a he ew places ha have colliders

capable o firing ions calcium, generally a one o he acinide elemens, such

as curium or cal iornium, a speeds approaching 30,000 kilomeers per second.

Experimens using hese rares o elemens are boh pracically and financially

difficul, so he Livermore eam wans

o probe he chemisry o analogous

elemens in he same verical group,

whose bonding and chemical behavior

should be similar. Te idea is o perec

analyical mehods using elemens ha

can reliably be made in a sandard ion

acceleraor, hen ranser hose mehods o

sudy he super heavy elemens.

Given he challenge o undersandinghe chemical behavior o an aom wih

a hal-lie o less han a minue, he

Livermore researchers mus develop swif

chemical mehods and ways o auomae

ofen-repeiive experimens. Dubnium,

or example, exiss in several isoopes

ha have hal-lives rom 35 seconds o

up o one day. Te problem wih he

more sable orm o he elemen, which

is named or he Flerov Laboraorys

locaion, is ha generally is possible ogenerae only one aom o i per day.

We need a chemisry where he kineics

are really as, Shaughnessy says.I

may be ha wih a sandard chemisry

on a sable elemen you can le your

experimen si and equil ibrae or a

long ime. We don have ha luxury.

Livermore uses an auomaed device ha

inroduces a sample as a gas-borne aerosolo a esing cha mber, deposis i on a

porous glass ri, adds acids o conver

he sample ino a liquid and roaes i

or subsequen chemical separaion and

measuremen. Te device hen moves

o a cleaning posiion and roaes back

o collec anoher sample. Te device

allows he chemiss o repea an experimen

abou once a minue or days or weeks,Karyn Hede is a freelance journalist whose work has appeared in Science,

Scientific American, New Scientist, Technology Review and elsewhere.

In this artists conception, calcium

ions travel down an accelerator at

a high velocity, about 30,000

kilometers per second, towarda rotating californium target.


19/28


gahering enough daa o undersand how

heavy elemens such as Nos. 104, 105

and 106 adsorb or desorb rom a surace.

Following he periodic able would

lead scieniss o expec ha dubnium

(elemen 105) shares properies wih

analum (No. 73, jus above dubnium

in period 6) and niobium (No. 41, wo

rows up in period 5), Moody says.

Te good news is ha i does. Buhe ineresing hing is ha you would

expec i o be more similar o analum

han niobium, jus because i is c loser

in aomic weigh, bu in some sysems

we have ound i is closer o niobium.

In some ways, he research pis periodic

able aher Dmiri Mendeleev agains

Alber Einsein. When a nucleus

becomes large enough, is posiive

charge causes elecrons orbiing io spin so as ha relaivisic effecs

make predicing is behavior difficul.

I you jus pu elemen 114 in he periodic

able i should si under lead, Shaughnessy

says. Bu here are nuclear orbial

models ha say i should no behave

Narek Gharibyan, a postdoctoral researcher,

works on chemical separations of heavy

lements at Lawrence Livermore National

aboratory. The lab is known for its skill at

eparation methods, which are useful to

dentify uranium sources.

The new element 118 travels through

the accelerator to a detector. Quicklyseparating and observing the new atom

is key to understanding its properties.

like lead.I should behave like a noble gas, somehing iner ha doesn reac.

And ha would be a big deal in erms o how we undersand he periodic able.

Te research groups goal is o undersand how elemen 114, flerovium, behaves. o ge

here, hey are developing very as chemisry using some o he l igher elemens in

group 14, such as lead and in. Te researchers are sudying ligands, binding agens

ha can pull lead or in ou o a mixure. Tey also collaborae wih exas A&MUniversiy and he Universiy o Nevada, Las Vegas (UNLV) o sudy new maerials

ha wil l separae super heavy elemens quickly and efficienly rom inerering

background producs. Several docoral sudens have conduced heir hesis research

on chemical exracion and on analyzing behavior down a specific group in he

periodic able.

FINDING AN ATOM IN A HAYSTACKLivermore scieniss masered isoopic separaion mehods in an era o open-air

nuclear ess beore 1962. For example, he labs Cener or Acceleraor Mass

Specromery can separae and coun a handul o uranium-236 aoms rom a

sample o several grams. Such exacing separaions are essenial when rying oideniy he source o uranium aken rom one o dozens o sies where mined

ore is processed and enriched or energy producion or weapons.

Te challenge, Moody says, is aking decades o separaions and analyical experise and

applying i o he needs o modern nuclear orensics. In he 1960s, he research eam had

ime o careu lly scruinize a es s producs. oday, he goal is o supply answers

ha quickly locae he source o, or example, illegally obained uranium. Perhaps

jus as imporan, he researchers wan o rack he maerial sources should a erroris

organizaion succeed in deonaing a diry bomb or oher nuclear weapon. In a blas

scenario, he nuclear orensics group would analyze debris and reverse-engineer

wha device was used and how i was buil.

Te problems you have doing he heavy elemen chemisry are ofen similar o he

problems you would have in a (nuclear) orensics ype o scenario, Shaughnessy says.

You are looking or a very small amoun o somehing in a large marix o background

maerial. You wan o separae i quickly because every hing is radioacive, and you

wan o ge he answer as soon as possible. We are always look ing or new mehods

o very rapid separaion echniques.

In recen years, Livermore also has culivaed experise in developing chemical

signaures ha le he scieniss ideniy where and how a paricular sample o

uranium was produced. Now heyre working on parsing how i ges o where isseized. o ha end, Livermore has eamed wih UNLV researchers o rapidly

ideniy uranium samples. Graduae sudens and pos-docoral researchers

ofen spli heir ime beween he wo locaions.

Jonahan Plaue, one such docoral suden, recenly discovered ha differen

uranium samples precipiaed ino unique and reproducible crysal line shapes

depending on heir origin. Tis projec, which ormed an imporan par o his

disseraion, could help o rapidly ideniy inerdiced samples rom a specific

locaion or produced hrough a similar process.


20/28


I we had a real-world sample, we now believe ha simply by looking a he shape

or shapes o he paricles we may be able o iner he process or processes ha were

used o produce hose paricles, says Ian Hucheon, a physicis and leader o he

chemical & isoopic signaures group in Livermores Chemical Sciences Division.

Par o Hucheons group specializes in he exacing work o measuring he

abundances o uranium isoopes in

surprisingly complex, small samples.

(See sidebar, Rare Earh.)

Looking ahead, he research eam aims

o avoid he chemical separaion sep

alogeher. Insead, he researchers in

Hucheons group are poining lasers aallou samples o aomize hem. An

ionizing laser fired a he cloud would

ransorm only he aoms o ineres,

usually uranium or pluonium, ino an

ionized sae. Ideally, he uranium or

pluonium would absorb he phoons,

wih all oher elemens invisible, hen

would be drawn ino a mass specromeer

or couning. Te mehod also would be

applicable o all he ac inide elemens,

bu o make i pracica l much moreinormaion abou he aomic energy

levels o hese elemens mus be colleced.

oward ha end, he group collaboraes

wih researchers a he Naval Pos Graduae

School in Monerey, Cali ., o sudy he

aomic energy levels o he heavy elemens

in he acinide period he 15 elemens

beween Nos. 89 and 103. Ta includes

uranium o curium, he mos ineresing

ones or nuclear orensics.

We hink ha his new echnique,

called resonance ionizaion mass

specromery, gives us he abiliy o do

analyses on he ime scale o much less

han a day, Hucheon says. Te

required mass specromeer will be

buil a Livermore while he basic

research projec is underway.

Ulimaely, Shaughnessy envisions a

mobile sysem ha would make nuclearorensics field-deployable.

We really should be hinking o

compleely new echnology, she says.

I could hink o probably five projecs

omorrow ha a suden could go

launch on. Ta could make a huge

difference in nuclear orensics.

The rare appearance of a meteor streaking over Russia in 2013 shocked localobservers but offered scientists another chance to learn more about the origins ofthe universe. For inside each slice of meteorite debris are some of the earliest building

blocks of solid matter once-molten droplets produced by high-temperature processes

at the birth of the solar system.

Few opportunities exist to study the remnants of such phenomena here on Earth, but

a recent discovery at Lawrence Livermore National Laboratory may have opened up a

new possibility.

Ian Hutcheon, a physicist who studies heterogeneous materials in the nanometer to

micrometer scales, was examining some of the glassy debris created during outdoor

nuclear testing in the 1950s and 60s. He realized that microscopic patterns in the

glassy spherules created moments after a powerful nuclear blast resemble those in

chondrules, the glassy spheres found in primitive meteorites.

It turns out that these fallout particles, even

though they are made of glass, are not

homogeneous, Hutcheon says. You find

large variations in both the elementalcomposition and, even more intriguing,

in the isotopic composition. Hutcheons

research team found that within a single

marble-like spherule, pockets of uranium-235

(the isotope found in a nuclear device) and

uranium-238 (the uranium form found in the

environment) exist side-by-side and unmixed,

along with various blends of the two.

What this tells us is that these spherules

were made in the aftermath of the detonation

by a process or processes that had to mix

materials coming from the device with

material coming from the environment.

Hutcheons nearly 40 years of experience studying meteorite inclusions may provide

clues to the mixing processes that occur in the seconds after a nuclear blast. His

research could offer a new avenue for combining nuclear forensics with the physics

of early solar system formation.

RARE EARTH

Cross section of a 2 milimeter-diameter

glassy spherule produced during a nuclear

test, mounted in epoxy. On the left, an

optical micrograph shows a large central

cavity surrounded by many smaller

bubbles. On the right, a scanning electron

microscopic image shows variations in

chemical composition that reveal cluesto the rate of cooling and solidification.

The light band at the perimeter is

enriched in calcium and iron.


21/28

RESEARCHERS USING LOS ALAMOS

NATIONAL LABORATORYS TRIDENT

LASER HAVE GENERATED POTENT

NEUTRON PULSES, OPENING NEW

AVENUES FOR SCIENCE.

A Trident laser shot,

delivering as much as 200

quintillion watts of energy

per square centimeter to a

deuterium-carbon target.

THE INTERCOM ECHOES THROUGH THE TRIDENT LASER

FACILITY AT LOS ALAMOS NATIONAL LABORATORY. A echnician

speaks. We are preparing or a sysem sho o he norh arge area. She warns saff

o avoid high-volage hardware and he laser bay. Do no break any inerlocks .

T he

BY THOMAS R. ODONNELL

STEWARDSHIP SC IENCE 13/14THE SSGF MAGAZINEP19

BEAM COUNTERS


22/28


Scieniss Juan Fernndez and Markus Roh lisen rom a nearby office. Fernndez

leads Los Alamos experimenal plasma physics group. Roh is a laser plasma

physicis rom Germanys echnical Universiy o Darmsad. Shos are always

a litle bi like a rocke launch, Roh says. Bu insead o sending off saellies,

riden is firing oodles o high-energy neurons.

Is February, and Roh is aking a break beween sho seups on his second

riden visi in under a year. In spring and summer 2012, he was a Rosen Scholar,serving a research ellowship a LANSCE, he Los A lamos Neuron Science Cener.

LANSCE includes he Lujan Cener, where a kilomeer-long acceleraor generaes

neuron beams or invesigaing maerials, proein srucures, nanomaerials and

oher subjecs.

Some o wha he Lujan Cener does in a kilomeer, riden now does in a ew

mill imeers, hanks o a collaboraion involving Roh, Fernndez and oher

researchers rom Germany and rom Los Alamos and Sandia Naional Laboraories.

Te 2012 experimens produced he larges neuron beams a shor-pulse laser has

ever made: An objec placed a cenimeer rom he source would ge a burs o

neurons a a densiy o 4 quinillion 1018 per square cenimeer per second.Tose neurons also move as, wih energies as high as 150 megaelecron vols

(MeV, or a million elecron vols). Convenional acceleraor echnology like ha

a he Lujan Cener delivers many more neurons bu over a long period. Ta

makes he wo echniques complemenary, Fernndez says.

Te sheer number o energeic neurons,delivered in incredibly shor burss,

makes he riden beams suiable or

muliple uses, rom deciphering he

undamenals o radiaion damage o

ideniying il lici nuclear maerials. Te

echnology also may advance neuron

research as insiuions wihou he space

and money or linear acceleraors embrace

compac neuron-generaing lasers.

Tas probably he mos exciingaspec, says Frank Merril l, a neuron

scienis and eam leader or he

advanced imaging group in Los

Alamos Physics Division. Is his

novel way o generaing neurons

ha may open applicaions nobody

has hough abou because (neuron

beams) were so expensive o generae

and build.

ridens unusual properies and somephysics wizardry make i possible.

LASER JOCKSTe voice on he inercom indicaes he

power level o capaciors ha soon will

discharge in ridens high-inensiy

beam. Tweny-five percen charge.

Fernndez and Roh, Merrill says, are

laser jocks: physiciss who know how

o use shor-pulse lasers o do all k indso ascinaing hings. Alhough he

wo collaboraors are unsure abou he

nickname No sel-respecing laser

scienis would call us laser jocks,

Fernndez jokes hey agree lasers are

key o heir research. Juan and I are

more he users, Roh says. We really

are he ex perimenal side.Thomas R. ODonnell, senior science editor, has written extensively about

research at the DOE national laboratories. He is a former science reporter

at The Des Moines Register.

Researcher Markus Roth at work in the target

chamber at Los Alamos National LaboratorysTrident laser, where scientists often join lab

technicians in preparing shots.


23/28


ON TARGETFify percen charge.

Compared o larger laser aciliies, li ke NIF and he Universiy o Rochesers

Omega, research a riden is more hands-on, Fernndez and Roh say. Los Alamos

echnicians are involved, bu he scieniss hemselves ofen work ogeher o seup arges and insrumens, geting heir hands dir y, Fernndez says. Graduae

sudens work alongside hem o make as many shos as possible in a day. Roh

adds, o sum i up, we are having a pary here. He laughs. Is really a grea

eam, bu o course we are working hard.

For he neuron beam experimen, riden arges a super-hin plasic oil. Few

big lasers can use such oils because o prepulse a weak bu sign ifican burs o

ligh ha heas or desroys he arge beore he main pulse can hi i. riden is

known or is high conras, meaning he prepulse is negligible. You can shoo

arges ha are very hin, Fernndez says, so you can move he whole oil a

once, as opposed o a racion. Ta helps o accelerae he resuling plasmaions o unprecedened energies.

Te oils oher key propery is is composiion: carbon and deuerium, a hydrogen

isoope ha pairs a neuron wih each aoms lone proon. Te researchers ocus

ridens beam ighly and fire i in jus rill ionhs o a second, hiting he oil wih

200 quinil lion wats o energy per square cenimeer, equivalen o ocusing all he

suns ligh ino a spo he size o a pencils ip. Te arge is reduced o a plasma o

elecrons and deuerons deuerium nuclei, comprised o one neuron and one proon.

Te physics legerdemain ha occurs nex is vial o creaing a powerul neuron

beam wihou a gian linear acceleraor. Mos plasmas are opaque o lasers; heyreflec he beam like a mirror. Bu under ridens high inensiy, plasma generaed

rom he oil becomes relaivisically ransparen, Roh and Fernndez say. I

Merrill s specialy is deecors o coun

neurons and measure heir energies. He

and his colleagues develop sensiive

diagnosics or he Naional Igniion

Faciliy, or NIF, he gian laser buil a

Lawrence Livermore Naional Laboraoryo implode iny hydrogen-filled capsules

and, i successul, rigger nuclear usion.

NIF is in demand and shos are difficul

and expensive, so rouinely using he

laser o es diagnosics isn easible.

Merrill and his collaboraors need a

NIF sand-in: someplace ha readily

generaes copious neurons in a

shor pulse.

riden, a neodymium glass laser, can

deliver 200 ril lion wats o energy in

pulses as shor as hal a picosecond,

a ril lionh o a second. Roh says is

repuaion as one o he worlds bes

shor-pulse laser sysems drew him o

Los Ala mos. Alhough hes a plasma

physicis, I had neurons always on

my mind and worked on previous

atemps o produce hem wih lasers.

Older sysems, however, werenpowerul enough o yield significan

numbers or energies.

Merrill, o course, also had neurons on

his mind. Roh, afer arr iving a he lab

las year, gave a seminar on his plans.

Merrill caugh hi m laer in a hallway.

Te Los Ala mos deecor researcher

needed a source or brigh neuron

pulses. Te German visior waned o

show lasers could provide hem. A eamassembled o find a soluion.

Experiments at the Trident laser hit a thin,

carbon-deuterium foil with an intense laser pulse,

driving deuterium nuclei into a beryllium rod. The

nuclei displace beryllium neutrons and also break

apart, generating an intense neutron beam.


24/28


sars when elecromagneic waves rom he laser ligh push elecrons ino he

arge. Te number o elecrons available seadily decreases as heyre pushed

o he back o he oil.

A he same ime, he laser inensiy ramps up, Roh says. Te elecrons have

o oscillae in ha elecromagneic wave. Because he inensiy is so high, he

elecrons are acceleraed o he speed o ligh, sop, acceleraed o he speed

o ligh, sop, a every cycle o he laser pulse. Ta means mos o he ime

elecrons are acceleraed o near ligh speed.

Heres where Einsein seps in. Under relaiviy, elecrons become heavy as hey

accelerae. Wih laser inensiy increasing, heyre no longer able o ollow he

beam because o sop a very heavy elecron akes a longer ime han o sop a ligh

elecron, Roh says. In quadri llionhs o a second, he elecrons ca n no longer

ollow he elecromagneic waves, he oil becomes ransparen and he beam

passes. Suddenly, he laser breaks hrough ha oil a nd caches up wih he

elecrons ha are already pulling on he ions on he oher side. Te laser couples

efficienly o all elecrons in he volume, no jus hose on he plasma surace.

Te researchers call his effec breakou aferburner he laser breaks hrough

he oil and ransers energy hrough he elecrons o he deuerons, accelerainghem in a burs. Te linked proon and neuron slam ino a shielded beryllium

rod placed jus 5 mill imeers beyond he oil.

Beryll ium aoms have a large cross secion, meaning heir neurons have a high

probabiliy o ineracing wih incoming proons and neurons. Like a cue bal l

hiting a clump o bil liard balls, he deuerons send beryllium neurons flying.

Meanwhile, some deuerons break apar, generaing addiional neurons, Merril l

says. You ge some added oomph. Wha we ound is you ge higher-energy

neurons rom ha piece o he process.

Te neuron beam could be even bigger, Fernndez says, i he oils were pure ornearly pure rozen deuerium an idea Roh plans o ry laer his year.

For Merrill and his deecor-developing colleagues, he ough par was finding he

neurons amid he noise X-ray and elecromagneic radiaion byproducs. Tey

sifed hem wih a ime-gaed sysem, essenially a high-speed shuter ha opens

afer X-rays pass bu beore neurons arrive. We could find he swee spo,

admiting he neurons o ineres while in essence, everyhing else was quie.

I anyhing, he laser researchers

did heir jobs oo well, Merrill says,

producing neurons a energies greaer

han he and his colleagues need or

NIF neuron deecors. (See sidebar,

Capuring Neurons.)

ON THE PHYSICS EDGESeveny-five percen charge.

Beore hese experimens, riden had

never acceleraed deuerium ions. Tis

whole relaivisic regime is really he

edge o he known physics, Roh says.

Bu he researchers had some guidance:

Teoriss a Los Alamos Compuaional

Physics Division, including Brian Albrigh,

Chengkun Huang, Lin Yin and Huichun

Wu, prediced opimum arge hicknesses

or a given laser inensiy. Ta helped he

experimenaliss generae neurons onhe firs sho, no couning wo ohers

done o check alignmen. I knew riden

A Trident shot as seen through a t

chamber port. The laser is known f

high contrast, meaning it has little

prepulse a short, weak burst of

before the main laser p

Like a cue ball hitting a clump of billiard balls,

the deuterons send beryllium neutrons flying.


25/28


was a grea laser, bu I never would have

dreamed ha wed ge resuls on he

hird sho on he firs day, Roh says.

Alhough ar smaller han a linea r

acceleraor, riden sill isn porablebecause is a mulipurpose research aciliy.

A sysem designed specifically o generae

neurons could fi on a ruck, making

he echnology available or a range o

research and pracical uses, i ncluding

sockpile sewardship experimens.

One use is flash radiography o assemble

deailed movies o mass evoluion over

iny ime incremens. Wih a neuron

source firing 60-nanosecond pulses,Merrill says, researchers could sring

ogeher reeze-rames o as, dynamic

evens like how meal deorms under

an explosive orce. Because maerials

absorb neurons a differen energies,

beams a lso could peer inside maerials

in ways X-rays can. Neuron radiography

ells researchers no only how much o

a maerial is presen he mass bu

also wha kind o maerial i is perhaps

aluminum in one par and seel in anoher.

In a simi lar way, he high-inensiy,

high-energy beams riden produces

are suied or acive inerrogaion

scanning conainers o spo hidden

nuclear maerials, perhaps a pors and

border crossings. Deecors could rack

paricles and radiaion emited when a

neuron beam passes hrough a conainer,

providing invesigaors signaures o

maerials inside, says research eammember Andrea Favalli, a scienis in

Los Ala mos Nuclear Engineering and

Nonprolieraion Division. Hes sudying

he riden beam or acive inerrogaion

applicaions. Oher such sysems have

been esed, says Favalli, a naive Ialian,

including one he helped develop a he

Join Research Cenre o he European

Commission. Tose, however, ofen relied on muliple measuremens or measuremens

over long periods. Te laser-driven beam could generae neuron signaures wih a

single rapid burs. Tere are many, many possible applicaions and more are

coming, Favalli says.

Te curren round o shos, in ac, is sudying acive inerrogaion. Te eam ound

ha passing he beam hrough a depleed uranium sample clearly delayed many o

he neurons. Delayed neurons is a signaure o fission, indicaing he presence o a

nuclear maerial.

***One hundred percent.

Shot 23-73 is complete. All areas are clear.

Wih ha and many oher shos, research on he riden neuron beam coninues.

Many are par o Favalli s acive inerrogaion projec, bu scieniss also wi ll sudy

opimizing he pulse o produce neurons wih a specific range o peak energies,

Merrill says. Te researchers also w ill address flucuaions in he number o

neurons each pulse generaes.

CAPTURING NEUTRONS

There already are neutron detectors at NIF, the National Ignition Facility,Frank Merrill says, but researchers need better ones.In a sense, the instruments are like digital cameras. A camera with more pixels captures a finer

image. A detector with better resolution provides a more accurate picture of neutron generation

and distribution in NIF shots.

NIF implosions are little tiny things, involving capsules of about 100 microns in diameter, says

Merrill, team leader for the Advanced Imaging Group in Los Alamos National Laboratorys Physics

Division. You dont want to just see theres a neutron source 100 microns in diameter. You want to

see some of the details inside. Top resolution now is about 10 microns and researchers are

constantly investigating ways to improve it. It would be wonderful if we got to 1 micron, but thats

a fairly significant technical challenge, he adds.

With bright neutron sources like the one Merrill and other researchers developed at Los Alamos

Trident laser, detector scientists will have greater access to testing. But in some ways, Trident is too

good. NIF typically produces neutrons with energies of around 14 megaelectron volts (MeV). Thelaser-driven neutrons at Los Alamos are up to 150 MeV. Its nice to have the higher energies,

Merrill says, but we were interested in the sweet spot, kind of zero to 30 MeV.

Never fear: The scientists use a high-tech gating system essentially a precise shutter to filter

out the speediest neutrons. Since they move faster, they arrive at the detectors first. Neutrons the

scientists seek come a hair later only after theshutter opens. That gated system is how we

were able to only look at the energy range we were interested in, Merrill adds.


26/28


S A M P L I N G S

Bottling the Sun

BY EVAN DAVIS

A metall ic feminine voice rings out through the control room:

Tree. wo. One. Zero. Entering pulse. Dozens of scientists and engineers

hold their breath and fix their eyes on the large computer display at the

front of the room. A warm, guttural hum fills the air, the ground

softly vibrates, and a flash of light appears on monitors throughout

the room.

In fractions of a second, millions of watts of power heat dilute gas to

200 mill ion degrees Fahrenheit, 10 times the temperature of the suns

core. At this temperature, the gas atoms are stripped of their electronsand their positively charged nuclei whiz by at 1 million miles per

hour. Some of these nuclei smash into each other with just the right

orientation and speed to fuse, forming an altogether different nucleus

and releasing an enormous amount of energy.

Te pulse ends almost as soon as it began. Te gas cools, the glow fades

from the monitors, and scientists scramble to analyze the data. en

minutes until next shot, the voice states, reminding the researchers

they must work quickly so theyre ready to coax every last bit of

performance out of their machine in the next experiment.

Its a typical day of operation at the Massachusetts Institute of

echnologys Alcator C-Mod reactor, located down a humble side street

in urban Cambridge, Mass. C-Mod is a compact nuclear fusion reactor

designed to study the scientific and engineering challenges that must

be overcome to make this technology a viable energy source.

Fusion is the energy of the sun and stars. Many scientists and engineers,

including my MI colleagues and me, want to bottle the sun for power

generation on Earth. When fully developed, fusion will provide

continuous power from abundant, virtually inexhaustible fuels, such

as deuterium, a hydrogen isotope harvested from seawater. Fusionpower plants will not directly produce any greenhouse gases. Tey

also would produce no long-lived nuclear waste, and there is no risk

of a meltdown or nuclear materials spreading for use in weapons.

okamaks like C-Mod are the leading candidates for successful fusion

reactor designs. Tese doughnut-shaped vacuum vessels use powerful

magnetic fields (2 to 3 esla, about the strength used in typical magnetic

resonance imaging (MRI) medical devices) to suspend a plasma in space,

preventing the hot core from touching any material walls. o prevent The author is a third-year fellow at the Massachusetts Institute of

Technology and this his winning entry in the 2013 SSGF Essay Slam.

melting the walls, the plasma temperature must drop from hundreds

of millions of degrees in the core to a few thousand at the reactor

wall, creating one of the largest thermal gradients in the universe.

Unfortunately, small-scale turbulence allows the plasma to leak through

the tokamaks magnetic fields. Indeed, Nobel laureate Richard Feynman

once described confining plasma within a tokamak as trying to hold Jell-O

with rubber bands: its possible, but its taxing and youl l probably lose at

least part of the Jell-O. A dozen or so scientists work on C-Mod with the

express purpose of understanding and controlling this turbulence.

Researchers at C-Mod and several other tokamaks over the past two

decades have identified several desirable operating modes that suppress

these detrimental turbulent fluctuations. In particular, weve discovered

that the potential fusion gain in tokamaks is strongly controlled by

parameters in the last inch or so of the plasmas edge.

My colleagues and I are working to develop and test a first-principles

computer model of this edge turbulence so that we can predict and

optimize a devices performance before its even built. Developing such a

model requires a strong coupling between experiment, computation,and theory. Tat means youll find me scrambling to set-up C-Mods

phase contrast interferometer before the days experiments begin

and fervently analyzing the measured turbulent density fluctuations

between shots. In the evenings, I run edge turbulence simulations on

the worlds most powerful supercomputers, aiming to validate the

code by comparing it with my experimental measurements. Its a

long, arduous process, but this crucial element of physics must be

understood if were to advance to a viable reactor.

Fusion science has progressed exponentially since its inception, and

we now stand poised to make a viable reactor for the first time. Aninternational collaboration is constructing IER, the first device

expected to reach and exceed fusion breakeven the point at which

energy put into the reaction equals the energy it produces.

C-Mod is the only tokamak that operates at the same densities and

heat fluxes as those expected in IER, so its thrilling to be here

and extremely important that our research continue.

Evan Davis


27/28


CLASS OF 2013

MATTHEW BUCKNERSchool: University of North Carolina,

Chapel HillDiscipline: Nuclear AstrophysicsAdvisors: Tomas Clegg and Christian Iliadis

Practicum: Lawrence LivermoreNational LaboratoryContact: [email protected]

NICOLE FIELDSSchool: University of ChicagoDiscipline: Astroparticle PhysicsAdvisor: Juan CollarPracticum: Los Alamos National LaboratoryContact: [email protected]

KRISTEN JOHNSchool: California Institute of echnologyDiscipline: Aerospace EngineeringAdvisor: Guruswami RavichandranPracticum: Lawrence Livermore

National LaboratoryContact: [email protected]

JOSHUA RENNERSchool: University of California, BerkeleyDiscipline: Nuclear/Part

Documents

Ssgf Magazine 2013