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

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 2 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 2013 General Accelerator R&D Review 3 ~50 meters

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

5. High Brightness Electron Sources State-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 likely yield further improvements but gun is still limitation Recently, strong focus on lower charge bunches Q << 1 nC Naturally matched to higher frequency rf guns 5 From Aug, 2008 ICFA BD Newsletter 2013 General Accelerator R&D Review

6. High Brightness Electron Guns What 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 6 2013 General Accelerator R&D Review

7. RF Gun Emittance and Brightness Scaling Benefits of shorter Wavelength Simple scalings of emittance and brightness suggest: B ~ 1/ 2 and  ~  where Q ~ and  z ~ Many applications are optimizing toward lower charge beams LCLS was designed for 1 nC and typically operates at 150 pC Natural for high rf frequency gun 7 From J. Rosenzweig modified by Feng Zhou for LCLS Emittance vs. Charge 2013 General Accelerator R&D Review

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

9. RF Gun Simulation Studies X-band gun 8x higher Brightness ASTRA simulations results (after multi-parameter optimization) High E RF,cathode to beat surface self-field and reach smaller r laser and thus smaller  ┴ High dE z / dt for short bunches 9 X-Band Test Acc. (Simulations)LCLS (Simulations and measurements) Q [pC]  x,95% [mm-mrad]  l [mm] B peak = Q/  l /    e   x,95% [mm-mrad]  l [mm] B peak = Q/  l /    e  2500.250.22817.5 2500.280.18417.30.400.6202.52 200.0750.10932.60.150.2204.04 100.0760.05531.5 100.1180.04217.1 10.0160.08048.8 10.0360.02530.9 2013 General Accelerator R&D Review Cecile Limborg

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 2013 General Accelerator R&D Review 10 Gun 200 MV/m YAG/ FC T105 ~100 MV/m TD11 (TCAV) 3MV OTR YAG/OTR FC 4 Quadrupoles with BPMs 8 MeV70 ~ 100 MeV Spectrometer Solenoid Cavity BPMs Cecile Limborg

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

12. XTA Commissioning Results As 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 fs rms 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 fs rms down to 70 fs rms Contribution modulator HVPS measured ~175ppm rms (ie d  ~ 0.6 deg rms, 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 12 2013 General Accelerator R&D Review Cecile Limborg

13. Future XTA Commissioning Timeline Complete 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 13 2013 General Accelerator R&D Review

14. New Initiatives with X-band RF Gun Inverse 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 dE z / dt in gun will allow large velocity compression of bunch X-Band technology (gun + compressor) promises - 1pC, few fs rms - 8pC, 20 fs rms 2-3 orders of magnitude better than present technology 14 with divergence < 0.5 mrad REGAE @ DESY 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 15 BremstrahlungChannelingComptonUndulator E  ~ 0 – E b E  ~ 100  3/2 E  ~ 4  2 E  ~ 2x10 -4  2 100% BW10% BW1~0.1% BW0.1% BW High fluxModerate fluxLow fluxModerate flux 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 E  and  » 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 2013 General Accelerator R&D Review 16

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 on electron source brightness  For high energy  ’s a linac is likely to provide a compact cost-effective path  Many applications are dose limited and 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 18 FacilityType X-ray E (keV) Rep. Rate (Hz) Bunches/ pulse Source size† (  m rms) Spectral flux (approx.) (ph/s/% BW) PLEIADES (LLNL) Linac10-100101 10 8 10% BW AIST LCS (Japan) Linac10-40101-1004010 7 -10 9 4-10% BW LUCX (Quantum Beam) SC linac~5-5012.5 Hz 100 (future 8x10 3 ) 8?? *NERL (UTNL, Tokyo) Linac10-801010 4 75 x 6010 9 -2x10 10 few % BW *MITSC linac3-3010 8 12.4 10 14 25% BW (>10 15 future ERL, FEL?) *MXI Systems (Tennessee) Linac8-10010110 10 10% BW *PLASMONX (SPARC, Italy) Linac20-3801015-10 10 9 ~10% BW (future FEL?) Lyncean Tech (California) ring7-3565 x 10 6 130-50 10 9 3-4% BW (future 5 x 10 11 ) *NESTOR (Kharkov IPT) ring~6-90020-700 x 10 6 135?? *ThomX (France) ring50-9021 x 10 6 140-7010 13 25% BW 2013 General Accelerator R&D Review

19. Scientific Opportunities with ICS Examples 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 2013 General Accelerator R&D Review http://www.emsl.pnnl.gov/root/publications/docs/compact_xray.pdf 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. 2013 General Accelerator R&D Review 20 Anne Sakdinawat, Yijin Liu, Mike Toney

21. Impact (Beyond Office of Science) Example: Understanding Carbon Sequestration and Storage Goal: understand the flow and storage of hydrocarbons Determine generative potential and 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: 1.High beam energy (for penetrating large specimens) 2.Brightness (for desired resolution) 3.Energy tunability (in order to retrieve elemental distribution) 2013 General Accelerator R&D Review 21 Anne Sakdinawat, Yijin Liu, Mike Toney

22. Impact (Beyond Office of Science) Example: Microbeam Radiation Therapy (MRT) Goal: Radiosurgery with reduced impact to surrounding tissue Microbeam Radiation 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., PLoS One. 2010 Feb 3;5(2): e9028. DilmanianNatl Acad SciSerduc PLoS One. “Growing experimental evidence is showing remarkable tolerance of brain and spinal cord to irradiation with microbeam arrays delivering doses up to 400 Gy with a beam width up to 0.7 mm” (Neurol Res. 2011 Oct;33(8):825-31)Neurol Res. Rat studies performed with 100 ~ 350 keV photons; need ~MeV x-rays for people. ICS would be a possible, compact source 2013 General Accelerator R&D Review 22 SerducSerduc, et al., PLoS One. 2010 Feb 3;5(2): e9028PLoS One.

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 >10 7  /s of 0.1 ~ 2 MeV photons with B >10 9 (  /s/mm 2 /mrad 2 /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 (I 0 ~ 1x10 14 W/cm 2 ) - 5 cm e - beta, 250 pC,  < 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) 23 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  ’s Support for hutch and experiments from external programs Start with staged approach to illustrate feasibility NLCTA Dump Echo-75 beamline XTA/ICS beamline NLCTA Enclosure Experimental hutch (upgrade for Echo beamline as well) 2013 General Accelerator R&D Review

25. Staged Construction of ICE-X ICE-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  ’s – March, 2014 Start construction of  -hutch – July, 2014 Operate ICS at 50 to 200 keV – Sept, 2014 Upgrade with multibunch and 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 25 2013 General Accelerator R&D Review

26. Summary 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 26 2013 General Accelerator R&D Review