Georg Bollen Michigan State University

D. Leitner, D. Alt, T. M.Baumann, C. Benatti, B. Durickovich, K. Kittimanapun, A. Lapierre, L. Ling-Ying, S. Krause, F. Montes, D. Morrissey, S. Nash, R. Rencsok, A. Rodriguez, C. Sumithrarachchi, S. Steiner, S. Schwarz, M.

Syphers, S. Williams, W. Wittmer, X. Wu and others

Georg BollenMichigan State University

ReA12 -Update

Facility for Rare Isotope BeamsFast, Stopped, and Reaccelerated Beams for

Science• Rare isotope production via in-flight technique

with primary beams up to 400 kW, 200 MeV/u uranium

• Fast, stopped and reaccelerated beam capability

• NSCL will provide pre-FRIB science opportunities with fast, stopped and reaccelerated beams

• New equipment must integrate into FRIB in the future

ReAccelerator Facility

G. Bollen, Recoil Separator for ReA12Workshop, MSU 2014

FRIB Construction Underway

• FRIB project completion in 2022– managed to early completion in 2020

NSCL only Facility in the World that Provides Fast, Stopped, and Reaccelerated Beams of Rare Isotopes

Fast Beams Gas Stopper Stopped beams Reaccelerated Beams

Space for future expansion of the science program

ReAccelerator Facility

Gas Stopper

A1900 Fragment Separator

K1200 Cyclotron

K500 Cyclotron

MoNALISA

Sweeper Magnet

SECAR (design)JENSA

ANASEN, FSU SuNCFFDJANUS..

SEETFSeGAHiRA Triplex Plunger CAESARLENDA GRETINA (DOE national user facility)

BCSNERO DDASCAESAR

RFFS

Momentum Compression Beam Line)

BECOLA

S800

AT-TPC

Cycstopper off line commissioning

20 meter

ReA3 Hall

ReA6-12 Hall

LEBIT, Minitrap


In-flight Fragmentation Offers A Wide Variety Of Rare Isotopes

NSCL’s Coupled Cyclotron Facility has produced >1000 RIBs and >870 RIBs have been used in experiments with > 90% availability

FRIB will provide 1000-10000 times higher beam rates

FRIB

CCF

Fast Rare Isotope Beam Production at NSCL and FRIB

FRIB

CCF

• 1000x higher primary beam power


The ReAccelerator (ReA)From fast to stopped to reaccelerated beams

He gas-cell

Room-temperature RFQ

b=4.1

%

> 80 MeV/u

EBIT charge breeder1+ Q+

Trapped ions ~ 200 eV

≤ 60 keV

Highly charged ion beam,

12 keV/u x A

(2≤A/Q≤5)

Magneticsector

Achromatic Q/A separator

Electrostaticsector

Continuous stable heavy ion beam>80

MeV/u

Superconducting RF linac

Thin foiltarget

<1 eV

b=8.5

%

600 keV/u

80.5 MHzMHB RB

**Production & In-flight separation

“Stopping” area

12 keV/u

48Ca 0.3 - 20 MeV/u238U 0.3 - 12 MeV/u

Final configuration, ReA12

Initial configuration, ReA3:48Ca 0.3 - 6 MeV/u

238U 0.3 - 3 MeV/u

A few MeV’s/u

• Continuous injection (currently) & accumulation (~1 s - 200 ms)

• Pulsed extraction (~ 1 - 50 Hz)


Stopped Beam FacilitiesReady to Deliver Beams

DC beams

> 80 MeV/u

Thermalizae iosn in gas cell with helium as a buffer gas

Rare-isotope beams

from the production

area

Analyzing dipole magnet

Si detectors to measure b-decay activity for particle ID

& beam transport optimization

DC beams, up to 60 keV

Purpose of beam stopping: Decelerate the rare-isotope beams Reduce the emittance for

reacceleration

Si detector to measure b-decay activity for particle

ID & beam transport optimization


Stopped Beam FacilitiesContinuing Upgrades

• Multifaceted approach– Linear gas stopper (heavier ion beams)– Cyclotron gas stopper (lighter ion beams)– Solid stopper (certain elements, highest intensity)

• Cyclotron gas stopper well underway– Yoke, poles, coils, cryostat fabricated, stopping chamber

manufactured. System assembled– Cool down of magnet started– Ion transport and extraction techniques demonstrated

• Cryogenic linear gas stopper– Higher beam purity, faster extraction, higher beam rates– NSF-MRI funding (information received)


Re-Accelerator ReAState-Of-The-Art RIB Post-Accelerator and the First

Coupled toA Fragmentation Facility

EBIT CBRFQ

CM2CM3 (2014)

CM1

ReA3

ReA6

SECAR

AT-TPC

ReA6 Equipment & Beamlines

TBD

D-LineN4 Stopped beamsA1900

L-Line

General Purpose Line

2010/10: RFQ commissioning started2011/04: CM1 first beam acceleration2011/06: CM2 first beam acceleration2012/04: first 1+-n+ acceleration2013/06: Experimental hall beam line2013/08: First rare isotope experiment2014/05: Cryomodule 3 installation


ReA Will Provide World Unique BeamsTop Energies (ReA3 to ReA12)

“n-rich” “n-deficient”

Original cavity performance

Measured cavity performance


Original cavity performance


ReA energy upgrade continues to be a key user demandG. Bollen, Recoil Separator for ReA12Workshop, MSU 2014

ReA Design Choices: EBIT Charge Breeder

0.085 moduleFY14

0.041 modulesRT RFQ

MHB

Achromatic Mass Separator

Pilot source for linac tuning

n+ RIB beam

EBIT1+ RIB beamEBIT:• Short breeding time• High ionization efficiency• Charge state flexibility• Low beam contamination• 0.5 ≥ Q/A ≥ 0.2


Charge Breeding In The EBIT Source

q+ q+

V1+1+

2+2+

Pulsed extraction

1+1

Radial electron-beam space-charge potential

Axial potential well from the trap electrodes

Highly charged ions

Trap electrodes

Magnetic fieldElectroncollector

Electrongun

Electronbeam

Continuous injection and accumulation (~100 ms)

A+

Pulsed extraction (ms to ms) AQ+

Over-the-potential barrier injection Lower-the-barrier extractionV

Continuous injection


Measured Charge Breeding EfficiencyEfficiency in single charge states of injected 39K stable-isotope beams

ReA EBIT not yet operated at full current


Improving EBIT Efficiency with Beam Bunching

• Continuous injection into EBIT charge breeder– Ultimately needed for highest beam intensity

(FRIB)– 30% efficiency (for all charge states)

demonstrated with present electron gun• In-flight capture of ion bunches

increases efficiency– Capture efficiency ecapt = 30% (DC) ecapt =

100% (pulsed)– Higher efficiency for breeding into single

charges state– Reduced breeding times

• New beam buncher is under construction– Cryogenic cooler and buncher based on gas

filled RFQ ion trap – Optimized for fast cooling and bunching

(<100ms)– Optimized for high rate capability (107 ions per

bunch 108 ions/s) - compatible with NSCL’s CCF beam rates

• Status– Assembly underway– Start commissioning in fall

2013

2014

Dynamic capture of ion bunch doesn’t rely on 1+ 2+ charge breeding


0.085 moduleFY14

0.041 modulesRT RFQ

MHB

Q/A

Pilot source

ReA Design Choices: RT-RFQ With External Buncher And High Efficiency SC-Linac

n+ RIB beam

EBIT1+ RIB beam

SRF LINAC 80.5 MHz RF frequencyFlexible energy range (deceleration 300keV/u to maximum linac energy in small stepsExternal multi harmonic buncher to minimize the longitudinal emittance


Room Temperature Radio Frequency Quadrupole (RFQ)

– Pulsed operation (160kW, 25%)– Energy Boost: 12 keV/u - 600 keV/u– 4-rod structure, 92 cells, 3.3 m long– Buncher : 80.5MHz, 161MHz, (241.5 MHz)– Nom 82 % beam capture measured

Longitudinal acceptance (white area) Beam at the entrance of RFQ

0

100

200

300

400

500

600

700

880 890 900 910 920 930 940 950C

ount

s (a

rb.u

nit)

nsec

FWHM0.52 nsec

12.54 nsec

Beam bunch after RFQ

MHB


Cryomodule 3 Makes ReA3 CompleteInstallation on Platform Started

• Ten β=0.085 cavities were redesigned to reliably provide high gradient acceleration fields

0 8 16 24 32Ep [MV/m]

108

109

1010

Q0

3181003-023

cavitysolenoid

CM4 (FRIB prototype phase I, 2014)

Cryomodule 3


0

10

20

30

40

50

0 20 40 60 80 100

Cou

nts

Energy [MeV]

241Am calibration source

16O5+ 40Ar13+

87Rb28+

Reaccelerator Testing with Pilot BeamEBIT CB

RFQ

CM2

CM3 (2014)

CM1SECAR

AT-TPCD-LineN4 Stopped beamsA1900

First RIB beam delivered

Low Energy Experimental hall

Pilot Beam

Charge Bred BeamRb+ → Rb28+

from the EBIT

Linac transmission RIB beams ≈ 70%


ANASEN Detector JENSA Gas Jet Target

(SECAR)

At-TPC Line

Experimental Equipment for ReA3Installation Started in May 2013

First radioactive beam experiment with ReA3

(8/2013)


Optimizing ReA Beam Time StructureInvestigating Different Beam Scenario with

EBIT• EBIT provides flexibility in time structure of extracted beams,

ranging from release of very short to long pulses. • 2nd EBIT would provide option for near continuous beam.• Study of extraction of very short pulses (50 ns) underway

0 1 2 3 4

0 1 2 3 4

0 1 2 3 4Train

Conventional

Ramp

Time [ms]

D. Bazin


Optimizing ReA Beam Time StructureInvestigating ReA Bunch Spacing Options

• With 80.5 MHz ReA components, bunch spacing is 12.4 ns• TOF experiments require larger bunch spacing • Designing 16 MHz “pre-buncher”

(Alt, Syphers, et al.)

RFQ

• Proposing different frequency re-buncher after RFQ or Linac to remove “satellite” bunches

• Can create continuous 62 ns spacing; a pulsed EBIT in conjunction would allow greater spacing

3D EM design of PB electrodes

EBIT

D. Bazin


Optimizing ReA Beam Time StructureInvestigating ReA Bunch Spacing Options

• Very short pulses 50 ns from EBIT– No principal show stopper to reach very short pulses (50 ns)

» Being investigated» May require trap electrode optimization

• Maximizing beam throughput– Extraction pulse length determines number of ions– Desired repetition rate may not empty EBIT before next injection/breeding

cycle– May require trap electrode optimization and more sophisticated in trap ion

gymnastics


Summary• ReA is the first re-accelerator coupled to a fragmentation facility

– First reaccelerated radioactive ion beam to users was delivered 8/2013• Beam stopping commissioned and being upgraded

– Linear gas catcher (FRIB R&D provided by ANL) operational and improved– Cyclotron gas stopper construction underway– Linear cryogenic gas cell development scheduled for funding

• Charge breeding– Demonstrated and efficiencies good starting point– Parallel approach to further increase efficiencies

» Adding dedicated cryogenic beam cooler and buncher» Increasing current densities

• Accelerator– Better-than-design performance – 3rd cryomodule assembled and being installed ReA3 nears completion– Adding more β=0.085 cryomodules will lead to ReA12

• ReA has significant potential to taylor beam properties to experiment needs– Developments are under way


Documents

Georg Bollen Michigan State University