Accelerator Test Facility Vitaly Yakimenko April 18, 2006 DOE Annual High Energy Physics Program Review Brookhaven National Laboratory

Accelerator Test Facility

Vitaly Yakimenko

April 18, 2006

DOE Annual High Energy Physics Program Review

Brookhaven National Laboratory

Vitaly Yakimenko (2/28)

Outline:• What is ATF• CO2 laser at terawatt level (5ps, 5J)• Ion beam generation experiment • 1 micron laser upgrade• Facility infrastructure upgrades for user-

operated Accelerator • Beam compression studies• Plasma Wakefield experiments• Polarized Positron Source for ILC/CLIC

development• Optical Stochastic Cooling studies at ATF


BNL Accelerator Test Facility - ATF

The ATF is a proposal-driven, advisory committee reviewed USER FACILITY for long-term R&D into the Physics of Beams.

The ATF serves the whole community: National Labs, universities, industry and international collaborations.

ATF contributes to Education in Beam Physics. (~2 PhD / year)

In-house R&D on photoinjectors, lasers, diagnostics, computer control and more (~3 Phys. Rev. X / year)

Support from HEP and BES.

The ATF features: High brightness electron

gun 75 Mev Linac High power lasers, beam-

synchronized at the picosec level (TW level CO2 laser)

4 beam lines + controls


ATF Statistics

Run time: ~ 1000 hour / yearGraduated students: 22Current number of experiments: 14Staff members: 11, 1 visitorPhys Rev X: ~ 3 / year since 1995

ATF publications

05

1015202530354045

Year

Nu

mb

er

of

pu

bli

ca

tio

ns

ATF Experiments

0

5

10

15

20

Year

Num

ber

of

expe

rim

ents

ATF Graduating Students

0

5

10

15

20

25

Year

Nu

mb

er

gra

du

ati

ng

p

er

year

an

d

cu

mu

lati

ve

Cumulative

Annual


Why we need better emittance

ICAIFEL

ThomsonX-ray

source

HGHG

1995 1998 2001 2004

STELLA

4 m

2 m

1 m

0.5 m

VISA

Dielectric WFA

Smith Purcell

experiment

Microbunchin

g

SASE @1m

Plasma WFA

To match laser accelerating or FEL beam and electron beam; or to transport through small (high frequency) accelerating channel


ATF Terawatt CO2 Laser Story (past and present)

1995 2000 2005 2010

InverseCherenkovaccelerato

rIFEL

accelerator

ThomsonX-ray

source

HGHG STELLA

Ion andProtonsource

ResonantPWA

SeededLWFA

LACARA

PASER

3 TW

300 GW

30 GW

3 GW

Nonlinear Thomsonscattering

EUV source


10 ns

200 ps

5 ps

CO2 oscillator3-atm preamplifier

10-atm regen. amplifier

10-atm final amplifier

Kerr cell

Ge switch 5 ps YAG pulse

ATF CO2 laser System delivers1 TW, 5 ps pulses


ATF COATF CO22 Laser System Laser SystemStatus and ProspectsStatus and Prospects

• Combination of four commercial and custom high-Combination of four commercial and custom high-pressure lasers allows versatile regimes of operation pressure lasers allows versatile regimes of operation to satisfy ATF users requirements:to satisfy ATF users requirements:– Strong-Field regimeStrong-Field regime (LWFA, LACARA, Compton, Ion (LWFA, LACARA, Compton, Ion

Accelerator) Accelerator) – 1 TW, 5 ps, 1 pulse every 20 sec1 TW, 5 ps, 1 pulse every 20 sec– Microbunching regimeMicrobunching regime (PWFA, PASER) (PWFA, PASER)– 1 GW, 200 ps, 1 pulse every 3 sec1 GW, 200 ps, 1 pulse every 3 sec

• Near-term plan:Near-term plan:– Improving stability, reproducibility, diagnostics and data Improving stability, reproducibility, diagnostics and data

collectioncollection

• Long-term plan:Long-term plan:– reduce pulse length below 1 ps by implementing power reduce pulse length below 1 ps by implementing power

broadening and frequency chirping with dispersion broadening and frequency chirping with dispersion compressioncompression


Ion generation experiment


Ion generation layout:

Ionspectrometers

Radiochromic film

Off-axis parabola

CO2 laser

Interferometry Nd:YAG beamLaser pre-pulse


Simulations for the gas jet.• 1D PIC SWA calculation has

been done for H plasma with initial density Nemax=3x1019 cm-3 in a triangle–shaped plasma slab with an initial width 150 m.

• The slab is irradiated by a CO2 laser pulse with duration =2 ps, 1 TW power, and intensity I=1017 W/cm2.

• Proton velocity [v/c] evolution is shown in the figure.

• A bunch of protons with lower energy spread is seen, marked by circle, with energy E=10 MeV.

• The estimated charge is about 1.8 nC.


Monochromatic beams with CO2 laser

Proton energy spectrum from a structured target. (a) Solid state laser with =1m. (b) CO2 laser with =10m. The CO2 laser produces a much narrower proton spectrum because of the narrower phase space fill.

1m laser 10.6m laser


Nd:YAG Drive Laser Present Performance

Demonstrated Nd:YAG System performance:

Energy on cathode 0-40 JPulse duration (FWHM): 8 ps

gaussianRange of beam size on cathode (Ø) 0.2 - 3 mmTop-Hat Beam Profile Modulation (P-P)

<25%

Shot-to-shot stability (rms):

Timing <0.2 ps Energy <2 % Pointing (fraction of beam Ø) <0.3%Drift (8 hour P-P)

Timing <1ps Energy <15 % Pointing (fraction of beam Ø) <1%

0 50 100 150 200 250

350

300

250

200

150

100

50 100 150 200 250 300 350 400 450 500 550 6000

100

200

300

Laser Oscillator-to-Clock Relative Phase [ps ]

-2.2

-2

-1.8

-1.6

-1.4

4:00 PM 4:00 AM 4:00 PM 4:00 AM 4:00 PM

Laser Energy Histogram

-8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4

Variation from mean [%]

Freq

uenc

y [a

rb. u

nits

]

=1.1%7500 shots


Advanced Drive Laser – GoalsGOAL OUTLOOK

• 100 mJ available UV on cathode (3x more than now)

• Energy jitter 0.2% rms ~ 1% p-p (5x better than now)

• Timing jitter < 200 fs rms (already demonstrated)

• Profile Uniformity ≤ 5% p-p(from desired arbitrary profile) (3x better than now)

• Pointing Jitter ≤ 1% p-p (already demonstrated)

• Temporal shaping (expect sub-ps temporal resolution)

• Fast turn-on (already under 15 minutes)

• High Reliability (already provide >1500 hours / year)

• Simple operation (~turn-key) (almost there now!)


ADL – Development Status•Yb:glass ultrafast oscillator, preamplifier fibers, and pump diode have been delivered

•Several key subsystems have been demonstrated elsewhere

•Now beginning tests of fiber preamps at kHz repetition rate to allow for low noise amplification, and the possibility to use feedback to achieve parts per thousand amplitude stability

•In a few months, oscillator + preamplifiers alone will produce enough energy to support the “Optical Fast Detector” experiment and are compact enough to situate near the experimental hall

•Later, test power amplifier utilizing bulk Yb:S-FAP crystal to provide ~1 ps bandwidth at full photoinjector energy requirement, without complex regenerative cavity

AfterCompression 125 fs

J. Limpert, et. al., Opt. Express. 10, 628-638 (2002)


Beam compression at ATF

Rendered CAD drawing of UCLA beam compressor at ATF

Coherent transition radiation (CTR) autocorrelation of compressed beam


Beam splitting during compression

• Interaction of the Coherent Synchrotron Radiation (CSR) with the beam itself leads to energy modulation along the beam.

• It produces two distinct beams (due to two stages of compression: chicane and dog-leg) very useful for some experiments at ATF (two beam PWA).

• X band linac section is needed to deliver clean, low energy spread compressed beam to user experiments

• Structure is available, ATF has a spare modulator, SLAC needs $350K to manufacture X-band klystron for ATF

• Three experimental groups will immediately benefit.

ChicaneDog-leg

LinacExperimental beam line

Spectrometer

EE

~2%

~2%

x-band


Plasma Wakefield experiments at ATF

• Multi-bunch Plasma Wakefield Acceleration at ATF, AE31. Spokepersons T. Katsouleas and P. Muggli, Univ. Southern California.

• Laser Wakefield Acceleration Driven by a CO2 Laser, AE32, Spokesperson W. Kimura, STI Optronics

• Ion Motion in Intense Beam-Driven Plasma Wakefield (UCLA, J. Rosenzweig)

• Plasma density measurement 1016-1019 by Stark broadening


STELLA-LW: Staged Electron Laser Acceleration – Laser Wakefield

• Experiment investigates two new plasma-based acceleration schemes– Seeded SM-LWFA – use seed e-beam bunch to create

wakefield, amplify wakefield using ATF TW CO2 laser beam.

– Pseudo-resonant LWFA – use laser/plasma interaction to sharpen laser pulse shape thereby enabling near-resonant generation of wakefield

• Performed initial test of seed and witness e-beam bunches sent into capillary discharge– Seed breaks apart into mini-seed and mini-witness

bunches– Witness bunch follows ~10 ps after mini-witness bunch– Observed acceleration of mini-witness and witness

electrons implying good wakefield formation – >300 MeV/m gradient measured


Time resolved plasma density measurements

ATF supports operation of the gas filled and ablation capillaries, and provides equipment and expertise for single-shot time-resolved plasma density measurements.


2006/2007 Facility upgrades• Diagnostics for the chicane bunch compressor• Interferometer for beam pulse length

measurements • Laser interaction chamber• Degauss relays for magnets• Vacuum valve interlocks• Temperature/humidity/pressure monitoring

(more than 30 sensors)• Linac phase shifter upgrade• CO2 laser transport line to the laser lab


Optical Stochastic Cooling• It is feasible to cool gold and proton beams at full

energy in RHIC and possibly Pb at LHC using a multistage amplifier.

• Optical parametric amplifier based on CaGeAs2 was suggested and experimentally tested at ATF

• Bypass experiment with ATF electron beam – Will demonstrate lattice control, optical amplifier and

adequate diagnostics– It is similar to previously successful ATF staged laser

accelerator (STELLA and STELLA II) experiments.– requires dedicated manpower

Pickup wiggler Kicker wiggler Diagnostic wiggler

Optical amplifier Micro-chicane

Bypass


Polarized Positron Source for ILC/CLICConventional Non-Polarized Positrons:

In our proposal • polarized -ray beam is generated in Compton back-scattering

inside optical cavity of CO2 laser beam and 6 GeV e-beam produced by linac

• The required intensities of polarized positrons are obtained due to 10 times increase in e-beam charge (relative to non-polarized case) and CO2 laser system.

• Laser system relies on commercially available lasers but needs R&D for the new mode of operation

6GeV 4A e- beam 80MeV beam

40MeV e+ beam

to e+ conv. target

~2 m


Compton Experiment at Brookhaven ATF (record number of X-rays with 10 m laser)

• More then 108 x-ray photons were generated in the experiment/ PRST 2000. NX/Ne-

~0.1. (0.2 as of 4/6/06)• Interaction point with high power laser focus of

~30m was tested. • Nonlinear limit (more then one laser photon scattered

from electron) was verified. PRL 2005.

Real CCD imagesNonlinear and linear x-rays


Polarized Positron Source (PPS) summary

• Compton back scattering based PPS is a backup scheme for ILC and the only choice for CLIC

• We propose Compton-based PPS inside optical cavity of CO2 laser beam and 6 GeV e-beam produced by linac.

• The proposal utilizes commercially available units for laser and accelerator systems.

• The proposal requires high power picosecond CO2 laser mode of operation developed at ATF. (ATF is the only facility in the world with operational Joule/picosecond CO2 laser system.)

• 3 year laser R&D is needed to verify laser operation in the non-standard regime.


DOE HE,S. Aronson, ALD –

(Contact)

S. DawsonChair, Physics Department

V. YakimenkoDirector ATF, Accelerator

External program committee

S. Chattopadhyay, Chair

M. WoodleMechanical Engineer

M. MontemagnoElectrical Engineer

I. Pogorelsky, Physicist,

Laser

I. PavlishinEngineer,

Laser

D. DavisTechnicianMech./Laser

M. BabzienEngineer,

LaserK. KuscheEngineer,

Safety

DOE BES D. Gibbs, ALD –(Contact)

R. MaloneSr. Tech. ArchitectComputer Control

Scientist,Accelerator

A. Karostoshevsky,Mechanical designer

K. TuohyGroup Secretary

D. StolyarovResearch Associate,

Laser

T. CorwinTechnician

Electr./Mech.

R. PalmerATF Program Director

Research Associate,Accelerator

Management/oversight

Full time

Needed No budget

Part time

ATF Org. Chart


ATF Budget Analysis: FY04/08 ($K)

PROJECT FY04 FY05 FY06(cur) FY07 FY08 (req)ATF Ops $1,800$1,800$1,800 $1,991$2,350ATF Equ $200 $110 $200 $220 $325ATF (BES) $500 $500 $500 $500 $575

Totals: $2,500$2,410$2,500 $2,710$3,250Supplemental $190FTE’s(HE+BES+LDRD) 10 9 10 10 11Missing $250

Recent reduction in the scientific personnel by 2 has negatively affected facility efficiency. Number of Accelerator Scientists reduced from 2.5 to 0.5 => Part time accelerator operations.


Conclusion• The experimental program at ATF is strong, broad

and relevant to HEP• It is aimed at near, intermediate and long term

accelerator R&D:– Beam brightness, compression (LCLS)– Polarized Positron Source (ILC and CLIC) – Optical Stochastic Cooling (RHIC and LHC upgrades)– Beam and laser based Plasma Wakefield Accelerators

(PWA), ion movement in the PWA (ILC upgrade)– Laser based accelerators (post ILC)– Compact, high brightness laser based proton, ion and

neutron sources (medical applications, injector, security …)

• ATF plays important role in education of accelerator scientists

• The support and progress of the user experiments is seriously limited by the accelerator staff level

Documents

Accelerator Test Facility Vitaly Yakimenko April 18, 2006 DOE Annual High Energy Physics Program Review Brookhaven National Laboratory