Photoinjector RD programs at Fermilab The A 0

Photoinjector R&D programs at Fermilab : The A 0 photoinjector & beyond Philippe Piot Fermilab & Northern Illinois University Ultra Bright electron source workshop, June 29 - July 1, 2011, The Cockcroft Institute Northern Illinois Center for Accelerator and Detector Development Ultra Bright electron source workshop, 06 -19 - 07 -01, The Cockcroft Institute

Outline • Introduction, • Accelerator science at the A 0 photoinjector (A 0 PI) & recent achievements, • Near term plans: § § • 2 high-brightness electron source Laboratory (HBSEL) Advanced Science & Technology Accelerator (ASTA) Conclusion. Ultra Bright electron source workshop, 06 -19 - 07 -01, The Cockcroft Institute

Historical context • Technology: § § • Scientific Achievements: § § § § 3 Designed, built, delivered an injector for the TESLA test facility (TTF-1) at DESY, Laser capable of providing ILC-type macropulse. Characterization of a L-band gun over a wide range of operating parameter (1999), [Carneiro et al. PRSTAB 2005]. Channeling radiation at high charge (1999 -2003) [Carrigan, PRA 2003], Observation of wakefield via electro-optical imaging (2000). [Fitch, PRL 2001]. Generation of angular-momentum dominated beams (2002 -2003), [Sun, PRSTAB 2004]. Flat beam production in a photoinjector (2000 -2005), [D. A. Edwards, LINAC 2000; Piot, PRSTAB 2006]. Plasma-wakefield acceleration and plasma lens in under-dense regime, (2003 -2004), [Thompson, J. Plas. Phys. (2010)]. Emittance exchange between the horizontal and longitudinal degrees of freedom (2008 -2010), [Koeth, PAC 09; Ruan, PRL 2011]. Pulse shaping with emittance-exchanger beamline (2010 -2011), [Sun, PRL 2010; Piot, PRSTAB 2011]. Ultra Bright electron source workshop, 06 -19 - 07 -01, The Cockcroft Institute

A 0 photoinjector (A 0 PI): introduction Electron accelerator based on 1. 3 GHz rf-gun with Cs 2 Te photocathode → Q< 10 n. C TESLA SCRF cavity → E=16 Me. V Emittance exchange beamline ( x, z) ( z, x) Round-to-flat-beam transformer x/ y~100 Extensive diagnostics Two photocathode lasers (Nd: YLF + Ti: Sp) • • • 4 Ultra Bright electron source workshop, 06 -19 - 07 -01, The Cockcroft Institute

Phase space manipulations at the A 0 PI Observed emittance exchange between the horizontal and the longitudinal phase spaces • Bunch duration measurement with streak camera Energy spread 5 [J. Ruan et al. , PRL 106 244801 (2011)]

Current-profile shaping at the A 0 PI • Generated a train of microbunches with sub-ps separation using slits Transversely. Longitudinally. EEX shaped beamline shaped beam XS 4 (w X 3 slits) X 3 X 5 (w X 3 slits) X 24 XS 3 (w X 3 slits) • Applications: § § 6 generation of narrow-band coherent radiation (next slide), Resonant excitation of wakefields + transformer ratio enhancement in PWFA and DWFA. [Y. -E. Sun et al. , PRL 105, 234801 (2010) P. Piot et al. , PRSTAB 14, 022801 (2011)]

Narrow-band Terahertz radiation • Important application of sub-ps bunch train generation: production of tunable narrow band THz radiation, • At A 0 demonstrated the generation of narrow-band THz transition radiation [P. Piot et al. , APL 98, 261501 (2011)] 7 Ultra Bright electron source workshop, 06 -19 - 07 -01, The Cockcroft Institute

Ellipsoidal bunch from Cs 2 Te photocathode • Generation of uniformly-filled 3 D ellipsoidal bunch from bunch Cs 2 Te photocathode: slaser=50 fs MC simulation (Ferrini et al. ) parametrization Laser pulse Conv. w Cs 2 Te response <1 las 00 fs er 100 p. C 600 p. C cathode y slaser=200 fs measurements N • 8 Preliminary experiment completed. [P. Piot et al. , to be presented at FEL 11 (2011)] time

Electro-optical imaging for monitoring of spatiotemporal correlation measure sub-ps slices positions OTR Goal: demonstrate the feasbility of a BPM with sub-ps resolution • laser Laser/e-beam synchronization < 300 fs relative jitter Electro-optical sampling of CTR Phase 1 of experiment completed: • § § Lasers/rf synchronized within 300 fs Image radiation field (CTR) using EO sampling Full experiment will be installed early August and runs until A 0 shutdown • 9 [T. Maxwell, et al. , PAC 09 (2009) and PAC (2011)]

Other on-going studies at the A 0 PI • Investigation of coherent synchrotron radiation and bunch compression in the emittanceexchanging beamline. Coherent radiation characterization [T. Thangaraj, et al. , PAC 11 (2011)] • OTR polarization effects in measurements of small beam sizes [A. H Lumpkin, et al. , PRSTAB 060704 (2011)] 10 Ultra Bright electron source workshop, 06 -19 - 07 -01, The Cockcroft Institute

A 0 PI and its transition to the high-brightness electron source Lab (HBESL) SCRF booster cavity will be removed in October 2011 A 0 will serve as an electron source development laboratory (called HBESL) • Research focuses include • § § § 11 Optimization of beam brightness through advanced laser shaping techniques, R&D toward field emission sources (field-emission array [Vanderbilt]) or Carbon nanotubes [Radiabeam Tech. phase II SBIR (pending)], Low energies phase-space tailoring, Compact Me. V-scale accelerators using advanced acceleration concepts (direct-field laser acceleration [MIT/DESY/NIU], dielectric wakefield tests) Support and R&D for improvements of ASTA facility electron source performances (next slide). Ultra Bright electron source workshop, 06 -19 - 07 -01, The Cockcroft Institute

Advanced Science & Technology Accelerator This cavity is currently at A 0 <40 Me. V 12 < 750 Me. V < 1 Ge. V Ultra Bright electron source workshop, 06 -19 - 07 -01, The Cockcroft Institute

STF@NML: introduction • • ASTA NML A 0 ATF AWA FACET § FLASH (DESY) • ASTA NML • ATF Peak brightness Average brightness AWA Well suited for beam-driven acceleration, Photoinjector source: § • Exploration of dynamical effects in beam-driven acceleration methods. L-band SCRF linac: § FACET A 0 Variable energy from ~40 to ~1 Ge. V, High-repetition rate (1 -ms trains): Provides low-emittance beam, Arbitrary emittance partition: § Energy (Me. V) § repartition of phase spaces to match final applications, Tailored current profiles. Ultra Bright electron source workshop, 06 -19 - 07 -01, The Cockcroft Institute

ASTA photoinjector Transverse emittance • • Uses FLASH-type L-band rf gun (anticipated 40 MV/m), Nominal laser is 3 -ps with possibility to have flat-top distribution (stacking with a-BBO crystals), Beam quality comparable to FLASH (uncompressed) Variable transverse emittance ratio (flat beams) Slice parameters Q= 20 p. C Q= 3. 2 n. C Longitudinal emittance & bunch length [P. Piot, et al. , IPAC 10 (2010)] Ultra Bright electron source workshop, 06 -19 - 07 -01, The Cockcroft Institute

Experiments currently under consideration at ASTA Short term: • § Production of X-ray using channeling radiation from bright ebeams (40 -Me. V area) to address DOD’s challenge 1012 photons /s/mm 2/mrad 2/0. 1%BW in 0. 01 m 3, [Vanderbilt University/NIU/FNAL] § Flat beams: • • • Compression, use in dielectric slab structures (40 or 250 Me. V) [NIU/Tech-X], Smith-Purcell FELs. Longer terms: • § § § 15 Versatile emittance exchanger/ pulse shaper, Short-wavelength “seeded” FELs [with ANL, LBNL] Many other possible applications discussed at a workshop in 2009. http: //apc. fnal. gov/ARDWS/index. html Ultra Bright electron source workshop, 06 -19 - 07 -01, The Cockcroft Institute

Summary • Over the last decade, Fermilab has been an active player in photoinjector R&D and application to AARD: - e- source for linear collider + short-wavelength FELs, novel phase space manipulations: flat beam, emittance exchange, current tailoring technique. Phase space manipulations pioneered at A 0 PI have many applications: beam-driven acceleration, light sources, … • Formation of the Illinois Accelerator Research Center (IARC) • § § ASTA: will incorporate most of these manipulations flexible, powerful facility to support a vibrant AARD program. A 0 PI: will be transformed into a high-brightness electron source laboratory (HBSEL): • • 16 explore novel cathodes and acceleration concepts, support gun R&D to improve the performances of ASTA. Ultra Bright electron source workshop, 06 -19 - 07 -01, The Cockcroft Institute