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Accelerator test Facility Vitaly Yakimenko April 2, 2009
Accelerator Test Facility § The ATF is the only proposal-driven, advisory committee reviewed, USER FACILITY for long-term R&D into the Physics of Beams in the world. § The ATF features: § High brightness e- gun, 85 Mev Linac § High power lasers beam-synchronized at the picosec level (Unique TW CO 2) § High brightness X ray source § 4 beam lines + controls § The ATF serves the whole community: National Labs, universities, industry and international collaborations. § ATF contributes to Education in Beam Physics. (~2 Ph. D / year) § In-house R&D on photoinjectors, lasers, diagnostics, computer control and more (~3 Phys. Rev. X / year) ATF: A Unique resource world-wide in the comprehensive nature of the facilities. Supported by both HEP and BES. Experiments are funded by HEP, BES, SBIR, NSF, DOD …
BNL Accelerator Test Facility - ATF
BNL/SLAC/UCLA 1. 6 Cell Gun • Gun was designed, build and tested in diverse collaboration. • It was tested at User Facility. • Needs of user experiments pushed reliability and brightness. • ATF played key role in changing community perception from “It will never be stable” to “let’s order one”. • Few dozen variations are operated world wide. 4 mm HGHG SASE @1 mm Compton STELLA 2 mm IFEL ICA Dielectric WFA VISA Micro bunching 1 mm Smith Purcell 0. 5 mm 1995 PWFA 1998 2001 2004 • Gun is commercially available from multiple sources. • High brightness R&D is effectively in hibernation at ATF as very limited funds prioritized to unique Terawatt CO 2 laser development.
Inverse Free Electron Laser • Proposed by R. Palmer • – J. Appl. Phys. 43, 3014 -23 (1972). First Staging of Two Laser Accelerators CO 2 beam Tested at ATF as accelerator. – PRL 77, 2690 (1996) • Used as key element in ATF experiments: – Microbunching: PRL 80, 4418 (1998) – STELLA, PRL 86, 4041 (2001) – HGHG, Science, 289 (2000) 932, PRL 86, 5902 (2001) – STELLA II, PRL 92, 54801 (2004) – PASER, PRL 97, 134801 (2006) … • IFEL is key element to: – Preserve emittance during compression at LCLS – High Gain Harmonic Generation – Optical stochastic cooling – Short X ray beams at ALS STELLA Accelerator (IFEL 2) -90 o -2. 6 mm Buncher (IFEL 1) 0 o 90 o 2. 6 mm • IFEL is a typical example of continued surprises of applicability of Advanced Accelerator R&D.
Beam splitting during compression Chicane Linac E • • • Dog-leg x-band ~2% E Experimental Spectrometer beam line ~2% 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
Plasma wake fields Phys. Rev. Lett. 91, 014802 (2003) Phys. Rev. Lett. 101, 054801 (2008) Ongoing: • Phys. Rev. Lett. 100, 074802 (2008) Resonant excitation of plasma wake fields using trains of electron bunches • The current filamentation instability, akin to the Weibel instability E
Multi-bunch Plasma Wake Field Experiment Measured train of drive bunches excites high amplitude wake field Complex interaction was studied in simulations 8 Bunch Train generated with the mask Characteristics of resonant interaction observed in first results IEEE NPSS Particle Accelerator Science and Technology Doctoral Student Award in 2009
CO 2 laser upgrade to 10 TW Multi Me. V Ions LWFA Ion beams 3 TW Accel. in vacuum LACARA 300 GW CO 2 laser layout Nonlinear Thomson EUV PASER 30 GW HGHG STELLA Thomson X-ray ICA IFEL 3 GW 1995 2000 2005 2010 Fiber laser as sub-ps slicer 200 fs 1 n. J 300 fs 250 m. J Currently: ~5 -10 J in train of 3 ps pulses Plan for: 10 J in single 1 ps beam Needed: sub-ps. slicer, CO 2 isotopes in regen. , new window, further simulations
CO 2 laser pulse diagnostics Streak camera Mixing crystal Spectrometer Diffractive grating Filter Streak camera CO 2 Interferometer Pyrocamera 10μm Laser diode 0. 9 μm 0. 8 μm 25 ps 1. 3 cm-1 Fourier transform Δt = 0 5 ps 10 ps Measured Simulated wavenumber Single-shot on-line measurements. Time resolution ~10 ps. Allows monitoring pulse splitting due to spectral modulation by the CO 2 rotational lines. Multi-shot method. Sub-ps resolution. Measure duration of individual pulse in the train (3. 5 ps FWHM) Verifies coherence within the train. time 25 ps Measured Simulated time Single-shot method. Indirect monitoring of the time structure related by the Fourier-transform.
Inverse Thomson Scattering Phys. Rev. Lett. 96, 054802 (2006) • • Hands on tests of quantum Vs. classical physics are great educational tools Started as US/Japan collaboration for ILC positron source Record brightness and efficiency were demonstrated X-ray source is being used for user experiments to test applicability for material science Collaboration with UCLA/Italy brought equipment from ESRF.
Polarized Positrons Source for ILC, CLIC, Super B Conventional Non. Polarized Positrons: Polarized g-ray beam is generated in the Compton back scattering inside optical cavity of CO 2 laser beam and 6 Ge. V e-beam produced by linac. Laser cavity needs R&D. 6 Ge. V e- 60 Me. V g beam g to e+ conv. target 30 Me. V e+ beam ~2 m First tests of the laser cavity: 3% over 1 ms
Ion beams generation with 10 mm laser Normalized emittance is <0. 1 mm Unusually sharp energy spectrum Ep (Me. V) Generated proton beams are used for user experiment to study graphene… 1 2
Conditions for Bubble formation Laser power threshold: Accelerated charge scales as: cavity trapped e- laser Final energy : Bubble can be formed in a finite window of plasma densities: 10 micron laser unlikely to offer record gradient in this application, but it might solve problems for practical applications: lower plasma density, longer channel, more stable, controlled final energy and higher charge. Compton Sources for X/g Rays: Physics and
Compton back scattering – compact sub 100 fs x ray source 0. 5 ps 50 J “Dream beam” accelerator 5 ps 10 J Compton Sources for X/g Rays: Physics and
Vitality of the program • Only fraction of experimental programs at ATF was discussed in the presentation. • The universities, small businesses and industries contribute resources and make program very diverse • Experimentalists from 13 universities visited ATF in the last six months: – – – UCLA, USC, U. of Texas SUNY SB, Columbia Yale U. of Milan, Pisa, Rome, Sassari U. Glasgow, Imperial College, Oxford • Six SBIR projects from five different companies are using or planning on using ATF resources in a near future
Very short tests • Delta undulator from Cornell • Second momentum cavities (Far-Tech) • …
ATF Organization Chart DOE BES J. Misewich, ALD –(Contact) DOE HE, S. Vigdor, ALD – (Contact) T. Ludlam Chair, Physics Department L. Littenberg HEP Ass. Chair, Physics Dept. R. Palmer ATF Program Director External program committee J. Rosenzweig, Chair V. Yakimenko Director ATF, Accelerator I. Pogorelsky, Physicist, Laser Physicist, Accelerator Engineer, Laser, HV J. Park Research Associate, Accelerator M. Babzien Engineer, Laser R. Malone Computer Control M. Polyansky, Research Assistant, Laser M. Woodle Engineer Mechanical A. Karostoshevsky, Mechanical designer Management/ oversight Full time staff M. Montemagno Engineer Electrical Part time K. Kusche Safety Engineer T. Corwin Technician Electr. /Mech. Needed hire K. Tuohy Group Secretary D. Davis Technician Mech. /Laser
Discussion • User facility or Lab project support: – – – Scientific staff mentality Support scientists Staff retention Time to study problem and not to concentrate on a solution Long undefined timeline VS. will defined project schedule • It is difficult if not impossible to predict beneficiary of the research, yet HEP is paying for it • Students: – will make mistakes, facility will be scrutinized more when students involved. – Trained students more likely work outside of HEP. • Planning how to preserve facility during difficult budget time is important.