Accelerator Test Facility

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

2. 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 Vitaly Yakimenko (2/28)

3. 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 BNL Accelerator Test Facility - ATF Vitaly Yakimenko (3/28)

4. ATF Statistics Run time: ~ 1000 hour / year Graduated students: 22 Current number of experiments: 14 Staff members: 11, 1 visitor Phys Rev X: ~ 3 / year since 1995 Vitaly Yakimenko (4/28)

5. 4 mm Thomson X-ray source HGHG SASE @1mm 2 mm STELLA Dielectric WFA IFEL ICA 1 mm Micro bunching VISA Smith Purcell experiment Plasma WFA 0.5 mm 1995 1998 2001 2004 Why we need better emittance To match laser accelerating or FEL beam and electron beam; or to transport through small (high frequency) accelerating channel Vitaly Yakimenko (5/28)

6. ATF Terawatt CO2 Laser Story (past and present) Ion and Proton source 3 TW Seeded LWFA LACARA Nonlinear Thomson scattering EUV source 300 GW Resonant PWA PASER HGHG STELLA 30 GW Thomson X-ray source Inverse Cherenkov accelerator IFEL accelerator 3 GW 1995 2000 2005 2010 Vitaly Yakimenko (6/28)

7. ATF CO2 laser System delivers1 TW, 5 ps pulses 3-atm preamplifier CO2 oscillator 10 ns Kerr cell 200 ps Ge switch 5 ps YAG pulse 5 ps 10-atm regen. amplifier 10-atm final amplifier Vitaly Yakimenko (7/28)

8. ATF CO2 Laser SystemStatus and Prospects • Combination of four commercial and custom high-pressure lasers allows versatile regimes of operation to satisfy ATF users requirements: • Strong-Field regime (LWFA, LACARA, Compton, Ion Accelerator) • 1 TW, 5 ps, 1 pulse every 20 sec • Microbunching regime (PWFA, PASER) • 1 GW, 200 ps, 1 pulse every 3 sec • Near-term plan: • Improving stability, reproducibility, diagnostics and data collection • Long-term plan: • reduce pulse length below 1 ps by implementing power broadening and frequency chirping with dispersion compression Vitaly Yakimenko (8/28)

9. Ion generation experiment Vitaly Yakimenko (9/28)

10. Ion spectrometers Radiochromic film CO2 laser Interferometry Nd:YAG beam Off-axis parabola Laser pre-pulse Ion generation layout: Vitaly Yakimenko (10/28)

11. 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 mm. • The slab is irradiated by a CO2 laser pulse with duration t=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. Vitaly Yakimenko (11/28)

12. Monochromatic beams with CO2 laser 10.6mm laser 1mm laser Proton energy spectrum from a structured target. (a) Solid state laser with =1m. (b) CO2 laser with =10m. The CO2 laser produces a much narrower proton spectrum because of the narrower phase space fill. Vitaly Yakimenko (12/28)

13. Nd:YAG Drive Laser Present Performance Vitaly Yakimenko (13/28)

14. Advanced Drive Laser – Goals GOALOUTLOOK • 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!) Vitaly Yakimenko (14/28)

15. 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) Vitaly Yakimenko (15/28)

16. Beam compression at ATF Rendered CAD drawing of UCLA beam compressor at ATF Coherent transition radiation (CTR) autocorrelation of compressed beam Vitaly Yakimenko (16/28)

17. Beam splitting during compression Chicane Dog-leg Experimental beam line Spectrometer Linac x-band • 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. ~2% E ~2% E Vitaly Yakimenko (17/28)

18. 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 Vitaly Yakimenko (18/28)

19. 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 Vitaly Yakimenko (19/28)

20. 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. Vitaly Yakimenko (20/28)

21. 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 Vitaly Yakimenko (21/28)

22. Micro-chicane Optical amplifier Bypass Pickup wiggler Kicker wiggler Diagnostic wiggler 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 Vitaly Yakimenko (22/28)

23. g to e+ conv. target 6GeV 4A e- beam 80MeV g beam 40MeV e+ beam ~2 m Polarized Positron Source for ILC/CLIC Conventional Non-Polarized Positrons: In our proposal • polarized g-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 Vitaly Yakimenko (23/28)

24. Compton Experiment at Brookhaven ATF (record number of X-rays with 10 mm 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 ~30mm was tested. • Nonlinear limit (more then one laser photon scattered from electron) was verified. PRL 2005. Real CCD images Nonlinear and linear x-rays Vitaly Yakimenko (24/28)

25. 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. Vitaly Yakimenko (25/28)

26. ATF Org. Chart Management/ oversight Full time Part time Needed No budget Vitaly Yakimenko (26/28)

27. ATF Budget Analysis: FY04/08 ($K) • PROJECT FY04 FY05 FY06(cur) FY07 FY08 (req) • ATF Ops $1,800 $1,800 $1,800 $1,991 $2,350 • ATF Equ $200 $110 $200 $220 $325 • ATF (BES) $500 $500 $500 $500 $575 • Totals: $2,500 $2,410 $2,500 $2,710 $3,250 • Supplemental $190 • FTE’s • (HE+BES+LDRD) 10 9 10 10 11 • Missing $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. Vitaly Yakimenko (27/28)

28. 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 Vitaly Yakimenko (28/28)