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X-band Test Accelerator & New Initiatives

X-band Test Accelerator & New Initiatives. GARD Review @ SLAC. Cecile Limborg, Chris Adolphsen, Tor Raubenheimer March 11, 2013. X-Band Test Accelerator (XTA). Generation of high brightness beams is a key accelerator technology Goals for the XTA:

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X-band Test Accelerator & New Initiatives

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  1. X-band Test Accelerator & New Initiatives • GARD Review @ SLAC Cecile Limborg, Chris Adolphsen, Tor Raubenheimer March 11, 2013

  2. X-Band Test Accelerator (XTA) • Generation of high brightness beams is a key accelerator technology • Goals for the XTA: • High brightness injector (beams accelerated to 100 MeV) • Study an approach to very high brightness beams • Compact X-band linac • Study operational issues (timing, alignment, …) • Use facility to support new initiatives • Construct XTA leveraging existing infrastructure • Installed in NLCTA enclosure, uses control room and rf sources • Based on LCLS design; uses LCLS high-level controls & applications • Based on 20 years of X-band rf development 2013 General Accelerator R&D Review

  3. NLCTA Facility • 50 meter shielded enclosure containing NLCTA and XTA. • Facility has 4 X-band rf sources, 1 S-band rf gun, 1 X-band rf gun, 3 laser systems and supports a variety of acceleration and beam physics R&D activities ~50 meters 3 2013 General Accelerator R&D Review

  4. X-band Test AcceleratorCompact (~6 meters) Injector Beamline 2013 General Accelerator R&D Review

  5. High Brightness Electron SourcesState-of-the-art • Groups around the world are pushing on e- source brightness • Peak and average brightness • Focus on peak brightness largely driven by next generation radiation sources: SwissFEL, PALFEL, MARIE, MEGA-ray, … • Two separate issues: transverse and longitudinal phase space • LCLS S-band gun pushes both • Cathodes will likelyyield further improvements but gun is still limitation • Recently, strong focus on lower charge bunches Q << 1 nC • Naturally matched to higher frequency rf guns From Aug, 2008ICFA BD Newsletter 2013 General Accelerator R&D Review

  6. High Brightness Electron GunsWhat are the next Steps? • LCLS S-band rf injector performs extremely well • How to improve peak brightness? • Many incremental improvements (better field comp, load lock, …) • No concrete ideas for factor of 2 much less a factor of 10 • What about different approaches? • DC photo-injector (reduced space charge and emittance from gun) • Low rf frequency gun (reduced field tolerances and peak current) • High gradient rf gun (reduced space charge and bunch length) • X-band rf gun offers factor of ~8 improvement in brightness (in simulation) but will be challenging to implement • Broad synergies with other programs across SLAC 2013 General Accelerator R&D Review

  7. RF Gun Emittance and Brightness ScalingBenefits of shorter Wavelength • Simple scalings of emittance and brightness suggest: B ~ 1/l2and ge ~ l whereQ ~ l and sz ~ l • Many applicationsare optimizing towardlower charge beams • LCLS was designed for 1 nC and typically operates at 150 pC • Natural for highrf frequency gun From J. Rosenzweig modified by Feng Zhou for LCLS Emittance vs. Charge 2013 General Accelerator R&D Review

  8. Mark-1 X-band RF GunJoint SLAC-LLNL Collaboration • First X-band gun design was built and tested at SLAC in mid-2000’s • Mark-1 incorporateslessons from LCLS • Racetrack coupler; increased modeseparation; elliptical iris shape 2013 General Accelerator R&D Review

  9. RF Gun Simulation StudiesX-band gun 8x higher Brightness • ASTRA simulations results (after multi-parameter optimization) • High ERF,cathode to beat surface self-fieldand reach smaller rlaser and thus smaller e┴ • High dEz/ dt for short bunches Cecile Limborg 2013 General Accelerator R&D Review

  10. XTA Beamline Diagnostics • The XTA was built with extensive diagnostics similar to LCLS • Beam will be accelerated to over 70 MeV to reduce space charge • Includes 3 YAG and 3 OTR screens, large angle spectrometer, transverse deflecting cavity, rf BPMs to align structure • Goal is to fully characterize the brightness of the X-band injector 8 MeV 70 ~ 100 MeV FC Gun 200 MV/m YAG/OTR T105 ~100 MV/m TD11 (TCAV) 3MV YAG/FC FC OTR YAG/OTR Spectrometer Cavity BPMs 4 Quadrupoles with BPMs Solenoid 2013 General Accelerator R&D Review Cecile Limborg

  11. XTA HardwareProject started in 2011 TCAV • Starting with Mark-0rf gun and old T105accelerator structure • Mark-1 is fabricated • New T105 is almostready Mark-1 rf gun View from dump YAG, Laser Injection chamber 2013 General Accelerator R&D Review Linac Cecile Limborg

  12. XTA Commissioning ResultsAs of end of February, 2013 • XTA routinely operated with charges up to 30-40 pC • Energy at ~8 MeV from gun and ~70 MeV out of linac • Transverse deflector installed and commissioned • Bunch lengths measured to be 250 fsrms for ~20pC, in agreement with simulations • Tuning to small emittances is sensitive to strong jitter and low OTR light level • Laser noise reduced from 350-500 fsrms down to 70 fsrms • Contribution modulator HVPS measured ~175ppm rms (iedF~ 0.6 degrms, dV/V ~3e-4); Contribution from LLRF still under investigation • OTR replaced by combined dual YAG/OTR • Low charge studies • QE relatively low; increased by lengthening laser pulse • Plans to measure thermal emittance and maybe laser cleaning Cecile Limborg 2013 General Accelerator R&D Review

  13. Future XTA Commissioning TimelineComplete commissioning in FY2013 • Goal: demonstrate injector performance by end of 2013 • Continue with Mark-0 rf gun through August, 2013 • Measure cathode properties: QE and thermal emittance; try laser cleaning • Work on improving jitter sources: LLRF and modulators • Optimize slice emittance and bunch length • Install Mark-1 rf gun and new T105 in August down • Measure cathode properties: QE and thermal emittance • Optimize slice emittance and bunch length • Program is interlaced with other NLCTA efforts • Operate a shift per day roughly 50% of time 2013 General Accelerator R&D Review

  14. New Initiatives with X-band RF GunInverse Compton Source and Ultra-fast Electron Diffraction • The high brightness source will enable many future programs • Improved beams for E-163 or Echo-75 at the NLCTA or LCLS or FACET • MEGA-ray experiments at LLNL (or SLAC) • An Inverse Compton Source at XTA • An Ultra-fast Electron Diffraction source at XTA • Ultra-fast Electron Diffraction • Large dEz/ dt in gun will allow large velocity compression of bunch • X-Band technology (gun + compressor) promises • 1pC, few fsrms • 8pC, 20 fsrms • 2-3 orders of magnitude better than present technology REGAE @ DESY with divergence < 0.5 mrad Siwick @ McGill 2013 General Accelerator R&D Review

  15. Why Inverse Compton Scattering (ICS)?Narrow bandwidth and high spectral brilliance • Narrow spectral bandwidth key to improving S/N 2013 General Accelerator R&D Review

  16. Inverse Compton Source Characteristics • Two features of ICS source make it very powerful • Easy variation of photon energy (pulse-by-pulse, if desired) • Scan resonances, contrast enhahncement, etc. • Narrow bandwidth with highly correlated Eg and q • Core spectral width is ~0.1%  improved S/N and reduced dose • Wide set of possible applications ranging from medical (oncology & imaging), industrial (spectroscopy & imaging), science and security 16 2013 General Accelerator R&D Review

  17. Inverse Compton Scattering Sources • Two primary approaches to beam generation: • Ring-based with high rep rate but larger emittance • Linac-based with brighter beams • SCRF linac has benefits of both • Very different technical challenges • Brightness of source depends onelectron source brightness • For high energy g’s a linac is likely to provide a compactcost-effective path • Many applications are dose limitedand don’t require huge fluxes ThomX ICS design MIT ICS design 2013 General Accelerator R&D Review 17

  18. Some Existing or Planned ICS Facilities 2013 General Accelerator R&D Review

  19. Scientific Opportunities with ICSExamples of Applications • Developing a compact source with modest flux at high photon energy will complement DOE SR light sources • It would provide a relatively compact (room sized) system at a moderate cost but with high performance needed for research http://www.emsl.pnnl.gov/root/publications/docs/compact_xray.pdf 2013 General Accelerator R&D Review Anne Sakdinawat, Yijin Liu, Mike Toney

  20. Impact (Beyond Office of Science)Example: Understanding lifecycle of rare earth elements • New Critical Materials Hub recently created at DOE EERE • “… challenges in critical materials, including mineral processing, manufacture, substitution, efficient use, and end-of-life recycling; …” • Rare earth K-shell binding energies range from 4 to 65 keV • A moderate energy ICS would penetrate typical core samples • An ICS-based microscopy system could be instrumental as an experimental tool in the analysis of the morphology and composition of rare earth materials throughout their life cycle. Anne Sakdinawat, Yijin Liu, Mike Toney 20 2013 General Accelerator R&D Review

  21. Impact (Beyond Office of Science)Example: Understanding Carbon Sequestration and Storage • Goal: understand the flow and storage of hydrocarbons • Determine generative potentialand pay type (i.e., gas vs. oil) to catalog the organic resources • This type of investigation needs to be carried out at different length scales (resolution from ~mm to micron-level to 30 nanometers) • Desired features of the source: • High beam energy (for penetrating large specimens) • Brightness (for desired resolution) • Energy tunability (in order to retrieve elemental distribution) Anne Sakdinawat, Yijin Liu, Mike Toney 21 2013 General Accelerator R&D Review

  22. Impact (Beyond Office of Science)Example: Microbeam Radiation Therapy (MRT) • Goal: Radiosurgery with reduced impact to surrounding tissue • MicrobeamRadiation Therapy (MRT) has been studied at BNL and ESRF:Dilmanian, et al., Natl Acad Sci 2006 Jun 20;103(25):9709-14; Serduc, et al., PLoSOne. 2010 Feb 3;5(2): e9028. • “Growing experimental evidence is showing remarkable tolerance of brain and spinal cord to irradiation with microbeamarrays delivering doses up to 400 Gy with a beam width up to 0.7 mm” (Neurol Res. 2011 Oct;33(8):825-31) • Rat studies performed with 100 ~ 350 keVphotons; need ~MeV x-rays for people. • ICS would be a possible, compact source Serduc, et al., PLoSOne. 2010 Feb 3;5(2): e9028 22 2013 General Accelerator R&D Review

  23. Inverse Compton Experiment at X-band (ICE-X) • Goal: high brightness gamma beam for precision experiments • Optimizing the system with photon science/medical school experts • Flux of >107g/s of 0.1 ~ 2 MeV photons with B >109 (g/s/mm2/mrad2/0.1%) • Narrow bandwidth achieved with high brightness beam and long-pulse laser interaction  reasonable beam and laser parameters • Commercially available 10 Hz, 3J, 3ns, YAG pump laser with 30 um laser waist (I0 ~ 1x1014 W/cm2) • 5 cm e- beta, 250 pC, ge < 0.4 mm-mrad • Stable beam and laser  simpler operating conditions • Upgrades to increase flux & brightness by >1000 • Upgrade laser to 120 Hz • Operate with multibunch train (30 bunches / rf pulse) 2013 General Accelerator R&D Review

  24. Inverse Compton Experiment at X-band (ICE-X)Build on the XTA • Build on the X-band Test Area (100 MeV X-band photo-injector) • Build experimental hutch and borrow interaction laser • Lengthen accelerator to generate 235 MeV e- 2 MeV g’s • Support for hutch and experiments from external programs • Start with staged approach to illustrate feasibility NLCTA Enclosure NLCTADump Echo-75 beamline Experimental hutch (upgrade for Echo beamline as well) XTA/ICS beamline 2013 General Accelerator R&D Review

  25. Staged Construction of ICE-XICE-Lite (FY2014 – FY2015) • Start from 100 MeV XTA configuration • Complete XTA injector demonstration – October, 2013 • Borrow YAG pump laser system (3J, 3ns, 10 Hz at 1 um) • Add IR and laser to generate g’s – March, 2014 • Start construction of g-hutch – July, 2014 • Operate ICS at 50 to 200 keV – Sept, 2014 • Upgrade with multibunchand laser rep. rate for 1000x flux and brightness – FY2015 • Upgrade linac to 235 MeV  ICE-X • Install old T105 and two additional T55 structures • Double klystrons in Station 2 2013 General Accelerator R&D Review

  26. Quality and impact of research over the last four years: Working on new e- source with order-of-magnitude improvement in brightness XTA has gone from concept to beamline in <2 years and commissioning has begun Expected deliverables over the next 5-10 years: Demonstration of a new high brightness electron source Key accelerator technology Utilization of electron source to demonstrate an optimized high energy, high brightness ICS Broad potential impact in medicine, industry, security as well as science Benefits of additional investments: Need 1.5 M$/yr in FY14 and FY15 to complete modification to ICS Impacts of reduced investment: Loss of opportunity to demonstrate HEP contribution to accelerator technology Why at SLAC? Unique environment with required accelerator, laser and photon science expertise Summary 2013 General Accelerator R&D Review

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