1. Working Group 7 Pulsed Linac and Injection Summary D. Johnson, S. Nagaitsev, D. Raparia for Working Group 7 participants September 9, 2010

2. Goals: – Develop a self-consistent concept for H- injection into the first circular accelerator – Preliminary identification of performance upgrade paths Presentations: – 3 to 8 GeV Pulsed Linac design and Options – Foil Issues – Recycler Injection with Carbon Foils – Laser Stripping Options Joint Meeting w/ WG6, – Intrabeam stripping Discussion

3. 3-8 GeV Pulsed Linac Options S. Nagaitsev Assumptions – Front end: 3 GeV CW linac, H-, 1 mA – Inject into MI or Recycler for Neutrino Program – Upgradable for future NFMC Leverage on existing ILC and XFEL cryomodule and rf power system designs – 1.3 GHz, ≤ 2 ms at ≤ 10 Hz – multiple cavities per Klystron Other possible options 1.Single long pulse (26 ms at 2 Hz) – laser stripping in MI or Recycler Requires cw rf system  expensive Potential savings by reducing energy to 6 GeV -> directly into MI 2.~5 ms pulses at 10 Hz (like RCS) – foil stripping and accumulation in Recycler No 5-ms Klystrons…

4. Foil Issues D. Raparia Presented analytical description for determining foil hits Discussed impact of various phase painting schemes Discussed foil, heating, scattering, lattice design, Maximum Number of Foil Traversal (Low Intensity) To Minimize the emittance for higher Luminosity, No painting Example: Polarized proton program at BNL Average Number of Foil Traversal (Moderate Intensity) To get desire (uniform) charge density in real space Example: Project –X, J-Park Minimum number of Foil Traversal (High Intensity) To extend the foil lifetime and lower the radiation Example: SNS, μ-Factory, PS2 Absolute minimum number of foil traversal can be determine without going through lengthy simulation For 2 mA-2ms x 6 injections  Foil life time, radiation will not be an issue  Foil Linac Beam

5. Recycler Foil Injection D. Johnson Presented current Recycler (MI) injection concept with symmetrical straight section (motivated by SNS and JPARC experiences) Presented beam current / injection cycle options from – Proton Driver 27 mA 1 ms where injected beam dominated foil temperature issues to – Proj X currents of 1-4 mA and 4 to 1 ms currents where circulating beam dominate foil temperature and loss issues – CW linac option with 1 mA and 27 ms where circulating beam define foil temperature and radiation options Discussed foil material and orientation issues -> build upon experience from SNS and JPARC

6. Linac Current/Inj. Time Scenarios ParameterPD IPD IIPX 0I*IIIIIIV (CW) Avg. Linac current [mA]27994211 Inj. Time [ms]1.04331.082.164.2827.72 No. turns/inj9727097 1943852310 No. of injections1136661 Total inj. turns97270582 11642310 325 bunch int.7.8E082.6E081.2E08 5.8E072.9E07 Intensity/turn1.7E125.6E112.5E11 1.3E116.6E10 Intensity/inj1.6E14 2.4E13 1.5E14 Parasitic hits4 3 9 3 --------32/17 2 64/32 2 118/60 2 Foil temp at hottest point1960 1 2100 1880 1 2100 --------- --------1900 4 900 -------- * 2D foil hit distribution plots 1 top number injected beam bottom number added in circulating beam for 1mm inj. beam sigma 2 number of hits for corner foil/estimate for 8mm strip foil 3 using a 6 mm horizontal strip foil 4 Maximum temperature and equilibrium temp at hottest point

7. Laser Stripping Options D. Johnson A lot of activity in the community on both theoretical and technological front – PRST-AB 13, 050101 (2010) “Laser-assisted H- charge exchange injection in magnetic fields”, T. Gorlov, V. Danilov, A. Shishlo – PRST-AB 13, 074002 (210) “Effective calculation of laser stripping via a broad shape resonance”, T. Gorlov, V. Danilov – Beam Recycling Optical Resonator Development as SNS – Optical Resonant Cavity development at LBNL How to get required photon energy density with the required time structure and duty factor… MW peak intensities, 102 W average power, 10’s ps pulse length, ms pulse durations, and duty factors for ½ Hz to 60 Hz? Options – Direct production of required light – High Q Optical Resonator – Hybrid Solution

8. Laser Power Estimates for 8 GeV laser Assisted Stripping Wavelength [nm]190010641900106419001064 ellipticalcircularStrong Field Incidence angle [deg]49.894.649.894.649.894.6 Peak Power, P0 [MW]1.16 6.32.19.7 Micropulse energy [mJ]0.080.40.080.40.140.63 Power at 325 Mhz [kW]261302613047210 Micropulse duration (rms) [ps]29272927 X-rms size [mm]4.38.02.1222 Y-rms size [mm]1.91.82.1222 X’-divergence [mr]1.40.51.7.700 Y’-divergence [mr]0.92.11.7.700 *Timofey Gorlov (SNS) Required Laser Parameters for 98% stripping Efficiency

9. Laser Amplifier Advancement “High sustained average power CW and ultrafast Yb:YAG near-diffraction-limited cryogenic solid-state laser” David C. Brown*, et.al. Snake Creek Lasers, LLC, Hallstead, PA, 18822 – Produced kW CW output beam power at 1029 nm. – 50 Mhz seed laser with 1-1.5 nJ pulse energy amplified to 15.2  J with a FWHM pulse width of 12.4 ps and a peak power of 1.23 MW. Unique crystal assembly in a distributed arrangement to minimize heating in any crystal and minimize any thermal re-population. Cryo amplifier essentially runs DC

10. Some Numbers Restrict ourselves to 1  m laser wave length, compare results of cryogenic amplification of the mode-locked seed laser with our requirements. The published results are a first demonstration of an ultra-fast amplifier SCLNo fieldXStrong fieldX Freq [Mhz]503256.53256.5 Pulse energy [uJ]154002663040 Pulse width(rms) [ps]12272 2 Pulse width(FWHM) [ps]28632 2 Average power [kW].758130171210277 Peak power1.2659.78

11. Conclusions There is a desire for injection directly into the Main Injector – Requires small injection time on the order of 10’s of ms to keep MI dwell time short -> CW low linac current or fast linac cycle 60 hz – There is currently not the technology for strip injection of CW beams – Need continued R&D effort in laser stripping or alternative foil designs If we were to forced to decide on a pulsed linac configuration TODAY Pulsed (3-8 GeV) linac is operated with 2-4 mA, ~ 1-2 ms, 10 Hz for 1.3 GHz there is a 5-MW Klystron TH2104C (2 ms, 10 Hz) 2-4 CM’s per Klystron (150 – 300 kW per cavity) At 25 MV/m, 2-4 mA need 50-100 kW per cavity for beam Do not need fast shifters From Proton Driver studies  For injection from a pulsed linac injection prefers higher beam current and lower injection time

12. Conclusions IF we delay decision on 3 to 8 (6) GeV linac design – Set up R&D into power sources for CW linac – Continue R&D into laser stripping as an enabling technology – CW would enable direct injection into MI (bypassing fixed energy RR) – Both CW and laser stripping link directly into upgrades for future Neutrino Factory/Muon Collider Laser Stripping will work for either Pulsed or CW linac – Continue collaboration with SNS, LBNL, Salt Creek for further laser amplifier and optical cavity development