Ultra Bright Electron Source Workshop: A0 Photoinjector R&D Programs at Fermilab

1. Photoinjector R&D programs at Fermilab :The A0 photoinjector & beyondPhilippe PiotFermilab & Northern Illinois UniversityUltra 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

2. Outline Introduction, Accelerator science at the A0 photoinjector (A0PI) & recent achievements, Near term plans: • high-brightness electron source Laboratory (HBSEL) • Advanced Science & Technology Accelerator (ASTA) Conclusion. Ultra Bright electron source workshop, 06-19 - 07-01, The Cockcroft Institute

3. Historical context 3 Technology: • Designed, built, delivered an injector for the TESLA test facility (TTF-1) at DESY, • Laser capable of providing ILC-type macropulse. Scientific Achievements: • 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, LINAC2000; 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, PAC09; 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

4. A0 photoinjector (A0PI): introduction • Electron accelerator based on 1.3 GHz rf-gun with Cs2Te photocathode → Q< 10 nC • TESLA SCRF cavity →E=16 MeV • 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

5. Phase space manipulations at the A0PI • Observed emittance exchange between the horizontal and the longitudinal phase spaces Bunch duration measurementwith streak camera Energy spread 5 [J. Ruan et al., PRL 106 244801 (2011)]

6. EEXbeamline Transversely-shaped beam Longitudinally-shaped beam Current-profile shaping at the A0PI • Generated a train of micro-bunches with sub-ps sepa-ration using slits • Applications: • generation of narrow-band coherent radiation (next slide), • Resonant excitation of wakefields + transformer ratio enhancement in PWFA and DWFA. XS4 (w X3 slits) X3 X5 (w X3 slits) X24 XS3 (w X3 slits) [Y.-E. Sun et al., PRL 105, 234801 (2010) P. Piot et al., PRSTAB 14, 022801 (2011)] 6

7. Narrow-band Terahertz radiation • Important application of sub-ps bunch train generation: production of tunable narrow band THz radiation, • At A0 demonstrated the generation of narrow-bandTHz transition radiation [P. Piot et al., APL 98, 261501 (2011)] 7 Ultra Bright electron source workshop, 06-19 - 07-01, The Cockcroft Institute

8. 100 pC 600 pC slaser=50 fs Laser pulse Conv. w Cs2Teresponse y MC simulation(Ferrini et al.) parametrization bunch slaser=200 fs cathode <100 fs laser N time Ellipsoidal bunch from Cs2Te photocathode • Generation of uniformly-filled 3D ellipsoidal bunch from Cs2Te photocathode: • Preliminary experiment completed. measurements [P. Piot et al., to be presented at FEL11 (2011)] 8

9. OTR laser < 300 fsrelative jitter Electro-optical imaging for monitoring of spatio-temporal correlation Laser/e-beam synchronization • Goal: demonstrate the feasbility of a BPM with sub-ps resolution  measure sub-ps slices positions • 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 A0 shutdown Electro-optical sampling of CTR 9 [T. Maxwell, et al., PAC09 (2009) and PAC (2011)]

10. Other on-going studies at the A0PI • Investigation of coherent syn-chrotron radiation and bunch compression in the emittance-exchanging beamline. Coherent radiation characterization [T. Thangaraj, et al., PAC11 (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

11. A0PI and its transition to the high-brightness electron source Lab (HBESL) • SCRF booster cavity will be removed in October 2011  A0 will serve as an electron source development laboratory (called HBESL) • Research focuses include • 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 MeV-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). 11 Ultra Bright electron source workshop, 06-19 - 07-01, The Cockcroft Institute

12. Advanced Science & Technology Accelerator This cavity is currently at A0 <40 MeV < 750 MeV < 1 GeV 12 Ultra Bright electron source workshop, 06-19 - 07-01, The Cockcroft Institute

13. ASTA NML FLASH (DESY) FACET A0 ATF ASTA AWA NML FACET A0 ATF Peak brightness Average brightness AWA Energy (MeV) STF@NML: introduction • Variable energy from ~40 to ~1 GeV, • High-repetition rate (1-ms trains): • Exploration of dynamical effects in beam-driven acceleration methods. • L-band SCRF linac: • Well suited for beam-driven acceleration, • Photoinjector source: • Provides low-emittancebeam, • Arbitrary emittance partition: • repartition of phase spaces to match final applications, • Tailored current profiles. Ultra Bright electron source workshop, 06-19 - 07-01, The Cockcroft Institute

14. 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 pC Q= 3.2 nC Longitudinal emittance & bunch length [P. Piot, et al., IPAC10 (2010)] Ultra Bright electron source workshop, 06-19 - 07-01, The Cockcroft Institute

15. Experiments currently under consideration at ASTA • Short term: • Production of X-ray using chan-neling radiation from bright e- beams (40-MeV area) to addressDOD’s challenge 1012 photons /s/mm2/mrad2/0.1%BW in 0.01 m3, [Vanderbilt University/NIU/FNAL] • Flat beams: • Compression, • use in dielectric slab structures (40 or 250 MeV) [NIU/Tech-X], • Smith-Purcell FELs. • Longer terms: • Versatile emittance exchanger/pulse shaper, • Short-wavelength “seeded” FELs [with ANL, LANL, LBNL] • Many other possible applications discussed at a workshop in 2009. http://apc.fnal.gov/ARDWS/index.html 15 Ultra Bright electron source workshop, 06-19 - 07-01, The Cockcroft Institute

16. 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 A0PI 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. • A0PI: will be transformed into a high-brightness electron source laboratory (HBSEL): • explore novel cathodes and acceleration concepts, • support gun R&D to improve the performances of ASTA. 16 Ultra Bright electron source workshop, 06-19 - 07-01, The Cockcroft Institute