Bob Siemann, SLACHigh Energy Physics Advisory Panel

October 30, 20001. Introduction2. Advanced Accelerator Research at SLAC3. Two-Beam Linear Collider

Concept, Research, and Future4. Plasma Wakefield Experiments

Wakefield Accel., e+ & e- Dynamics, Center for Advanced Accelerator and Beam Physics

High Energy Physics � Energy Frontier

The Livingston curve is the context

1,000 TeV

10,000 TeV

100,000 TeV

1,000,000 TeV

100 TeV

10 TeV

1 TeV

100 GeV

10 GeV

1 GeV

100 MeV

10 MeV

1 MeV

1930 1950 1970

Year of Commissioning

1990 2010

Par

ticl

e E

ner

gy

Proton Storage RingsColliders

ProtonSynchrotrons

Electron Linacs

Synchrocyclotrons

Proton Linacs

Cyclotrons

ElectronSynchrotrons

Sector-FocusedCyclotrons

ElectrostaticGenerators

RectifierGenerators

Betatrons

Electron PositronStorage Ring Colliders

Electron ProtonColliders

LinearColliders

A “Livingston plot” showing the evolution of accelerator laboratory energy from 1930 until 2005. Energy of colliders is plotted in terms of the laboratory energy of particles colliding with a proton at rest to reach the same center of mass energy.

SC RF or High Power RF,Linear Collider

TeV Linear Collider

Digital Signal Processing, Storage Ring

PEP-II, KEK-B, DAPHNE

SC RF, Storage RingCESR, LEP

SC Magnets, Storage RingTevatron, HERA, LHC

Technology &Topology

Accelerator

Today�s High Energy Physics Program

Exponential growth of ECM through accelerator physics and technology innovation has lead to� Many of the discoveries central to our understanding of particle physics � Multi-TeV collisions

Advanced Accelerator Research at SLAC

Accelerator research and development has always been a major component of the SLAC program

Advanced accelerator research at SLAC

� High power microwave sources, components and linear accelerators� Storage rings �SPEAR was not the first storage ring, but it was the critical step in the evolution of the storage ring topology that is central to almost all of today�s experiments� Linear colliders � The SLC was the first and only operating linear collider. It was an essential first step towards high energy e+e- collisions.

� On the �R� side of R&D� Research into �advanced� technologies and concepts that could provide the next innovations needed by particle physics

�Advanced�� In many cases one is applying or extending physics and technology that is its own discipline to acceleration � ex. plasma physics, digital signal processing� This interdisciplinary attracts a broad range of scientists that extends well beyond classical accelerator physics

Advanced Accelerator Research at SLAC

Advanced accelerator R&D activities� 3D electromagnetic calculations� Final focus designs using a low

energy beam as a lens� High frequency RF� High power RF pulse compression� Laser driven structures� Plasma acceleration� Plasma focusing� Pulsed heating as a gradient limit� Two-beam acceleration

crossedlaser beams

electronbeam

LEAP acceleration cell: Two Gaussian beams of 850 nm laser light cross at 1.4o to form the acceleration field. Electrons are injected between the prisms into the crossed laser field.

Mm-wave sheet-beam klystron:Prototype fabricated by LIGA (deep X-ray lithography). The center of this 3.5� diawafer is a 92 GHz, 1 MW klystron circuit. The surrounding features are for quality control and non-contact measure-ments.

First obser-vation of focusing of e+:Measurement of plasma focusing of a 30 GeV positron beam. 1.5×1010 e+ per pulse.

Two-Beam Linear Collider� Offers high-gradient acceleration which scales to multi-

TeV energy and higher frequency.� Basic idea is a transformer: Decelerate high-current, low-

energy beam, accelerate low-current, high-energy beam.� Efficiently accelerate a low-energy, high-current beam.� Compress energy by multi-turn stacking in a ring.� Distribute beam pulses to high-gradient accelerator.� Decelerate Drive Beam and Accelerate Main Beam.

� Net effect: Map energy from a long-pulse accelerator to different locations along the high-gradient linac. Allows the use of low-frequency, conventional RF technology for Drive Beam acceleration.

The Two-Beam Transformer Concept

Accelerator Structure Accelerator StructureAccelerator StructureAccelerator Structure

F Quad BPM

760 MW 760 MW

D Quad BPM

B P M

Q u a d

MAIN LINAC

Two-Beam Module Layout

Two Beam Acceleration (TBA)

Drive Beam Deceleration (190 A, 1.3 GeV - 1.5 MV/m)

Main Beam Acceleration (0.8 A, 8 GeV + 93 MV/m)

DRIVE LINAC

Decelerator Structure Decelerator Structure

Schematic Layout of a Two-Beam Linear Collider

� The total pulse length of the Drive Beam Accelerator is set equal to the twice the total length of the high gradient linac.

� The first half of the drive beam pulse is used for positrons while the second half is used for the electrons.

� The configuration above uses recirculation to use fewer drive beam RF sources but with longer length.

3-20008534A01

Combiner Rings

IP

Drive Beam Linac

350 MeV Decelerator LoopDecelerator Loop

3p/2 Arc3p/2 Arc

Injection Transport

Drive Beam Recirculation Loop

e– Main Linac

3p/2 Arc

2 GeV 2 GeV

4 GeV

Damping Ring

Injector Linac

Scavenger Loop

e+

e–

Issues and Studies� Gradient and choice of RF frequency (SLAC/NLC).� Efficient Drive-Beam Acceleration (CTF3).� Drive-beam combiner/energy compression (CTF3).� Deceleration and RF power production (CTF2, CTF3).� Compatibility as an upgrade to conventional approach (SLAC)� Energy Reach (SLAC)

� To upgrade energy, increase length of linac and drive-beam transport.� Drive Beam complex is the same, except for longer pulse length.

� Some of these issues can be addressed in a test facility.� CERN is planning a test facility, CTF3, which will convert the

present LEP injector to a two-beam test facility.

Conversion of LPI to Two-Beam Test at CERN

� SLAC will contribute electron gun and injector design.

Energy Compression by interleaving bunches in a combiner ring

� The injection region uses matched RF deflectors to interleave four bunches at the quarter points of the cycle

Intensity

Initial pulse train

1 2 3 4

Final pulse train

� Extraordinarily high fields developed in beamplasma interactions

� Many questions related to the applicability ofplasmas to high energy accelerators andcolliders

P. Catravas, S. Chattopadhyay, E. Esarey, W. LeemansLawrence Berkeley Laboratory

R. Assmann, F.-J. Decker, R. Iverson, M. J. Hogan, R.H. Siemann, D. Walz, D. WhittumStanford Linear Accelerator Center

B. Blue, C. E. Clayton, R. Hemker, C. Joshi, K. A. Marsh, W. B. Mori, S. WangUniversity of California Los Angeles

T. Katsouleas, S. Lee, P. MuggliUniversity of Southern California

� E-157: First experiment to study Plasma WakefieldAcceleration (PWFA) of electrons over meter scaledistances

� Physics for positron beam drivers qualitativelydifferent (suck-in vs. blow-out) ����E-162

Li Plasma

193 nmIonization

Laser

1.4 mσ = 0.7 mmE = 30 GeV

Streak Camera2 × 1010 e-

12 m

0.1 - 4×1014 cm-3 CherenkovRadiator

OTR Radiators

E-157 PWFA UCLA

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

-8 -4 0 4 8

05190cec+m2.txt 8:26:53 PM 6/21/00impulse model

BPM data

θ (m

rad)

φ (mrad)

plasma

gasbeam

Blowout region

Ion channel

laser

θφ

1. Electron Beam Refraction at the Gas�Plasma Boundary

0

50

100

150

200

250

300

-2 0 2 4 6 8 10 12

05160cedFit.2.graph

σX

DS

OTR

(µm

)

K*L∝ne1/2

σ0 uv Pellicle=43 µm

εN=9×10-5 (m rad)β0=1.15m

2. Transverse Wakefields and Mismatched Beam���� Betatron Oscillations

Ener

gy o

r Spo

t Siz

e [a

.u.]

-10 -5 0 5 10-100

-50

0

50

100

150

200

Mea

n En

ergy

Cha

nge

[MeV

]

TextEnd

Time Relative to the Center of the Bunch [ps]

Energy difference with respecct to plasma OFF run TA06010ce.mat

TA06010ca.mat

Slic

e en

ergy

(MeV

)

Slice time (ps)

Head Tail

~ E(t) x(t)

Time [a.u.]

3. Longitudinal Wakefields ���� Core De-acceleration and

Tail AccelerationThree Highlights!

Impulse Model Data

E-157 PWFA UCLA

� Run 1: A First Look at Positron Propagation in Long Homogeneous and Hollow Plasmas.� Use working E-157 apparatus

� Positrons in homogeneous and hollow plasmas� Transverse dynamics (time integrated & time resolved) in the �suck-in� regime

� Run 2: High Resolution Energy Gain Measurements of Positrons� Move to new location in FFTB to build true imaging spectrometer

� Positrons in homogeneous and hollow plasmas� Detailed structure of longitudinal wakes (acceleration)

� Run 3: High Resolution Energy Gain Measurements of Electrons� Electrons in homogeneous and hollow plasmas

� Matched beam propagation in a long plasma

� Higher resolution acceleration measurements

Experimental Program

E-162e+ & e- Dynamics in PWFA UCLA

UCLA, USC, Stanford Pre-proposal to NSF for a Physics Frontiers Center

Principal InvestigatorsR. Byer, Stanford Applied PhysicsC. Joshi, UCLA Electrical EngineeringT. Katsouleas, USC Electrical EngineeringW. Mori, UCLA Physics & Electrical EngineeringJ. Rosenzweig, UCLA PhysicsR. Siemann, SLAC & Stanford Applied Physics

The Center� PI�s with diverse experience in plasmas, lasers, particle sources, RF, computer simulation & classical accelerator physics. Committed to making the Center a major part of their research activities.� SLAC would host the Center and make unique facilities including the FFTB and NLCTA available. This leverages the investment in the Center.

Center for Advanced Acceleratorand Beam PhysicsUCLA

� Based on the NLCTA (NLC Test Accelerator) -300 MeV, 11.4 GHz linac with a ~ 200 nsec long beam with X-band bunches

� Low Energy Hall for experiments with ~50 MeV beam available most of the time

� High Energy Hall for experiments with ~300 MeV beam that would have to be scheduled together with NLC RF development

� New injector - A single bunch, RF gun� Two laser rooms for RF gun laser and

experimental laser

The Center�s Program� Begin with plasma acceleration experiments at the FFTB & high brightness electron source physics.� In parallel, add experimental halls and lasers to the NLCTA complex. The resultant ORION facility would be designed for rapid turn-around of experiments through shared diagnostics, layout, etc.� ORION would support a wide-ranging program in plasma, laser driven, RF acceleration.� Computer modeling is an integral part of the Center

ORION

Center for Advanced Acceleratorand Beam PhysicsUCLA