1. ASTA G UN C OMMISIONING R ESULT AND P OTENTIAL APPLICATION FOR I NVERSE COMPTON SCATTERING G AMMA - RAY SOURCE Jinhao Ruan

2. O UTLINE Introduction/ASTA Layout Status of Subsystems Photoinjector Gun Laser Capture Cavities Cryomodule(s) Gun commissioning Near future schedules Application for intense gamma ray source using ICS Summary

3. O VERVIEW OF THE F ACILITY

4. F ULL ASTA L AYOUT

5. FY14 - 50 M E V I NJECTOR + 1 C RYOMODULE Goal: installation complete and beam commissioning started by end of CY13 RF gun + RF system and photocathode laser system (Done) 2 SRF booster cavities (CC1 and CC2) + RF systems (CC2 is ready, CC1 need more attention) 50 MeV beam line elements and instrumentation to the low energy dump (2 girder is in and the third one is close) Low energy beam dump. (Dump installed) SRF cryomodule (RFCA002/CM2) (7 cavity has been commissioned) Installation of 1st AARD experiment (high brightness X- ray channeling source) (Will be installed in girder 3) electron gun booster cavities flat beam transform chicane beam dump 1 st cryomodule test beamlines beam dump spectrometer magnet 50 MeV Beam Energy ASTA Photoinjector

6. S TATUS – P HOTOINJECTOR G UN

7. S TATUS – L ASER D IAGRAM Preamp ~3 single pass amp

8. U SER I NTERFACE

9. S YSTEM P ERFORMANCE : S EED L ASER

12. S YSTEM P ERFORMANCE : A MPLIFIER

13. S YSTEM P ERFORMANCE : UV SECTION

15. S YSTEM P ERFORMANCE

16. C URRENT L ASER SYSTEM S TATUS Laser is up running with 3MHz pulse train and 5Hz repetition frequency User interface is set up The longest flat pulse could be easily up to 200~300  s. Some tuning (~3-4 hours) would be needed for 500~600  s long pulse train with lower charge. Laser system is designed to be upgradable for up to 1.3GHz in principle, which will be essential to the ICS proposal.

17. Two ‘Booster’ cavities – single cavities each in their own cryomodule Capture Cavity 2 - first SRF device delivered and operational at NML Last operated in February 2012 22 MV/m, 1 ms pulse, 5 Hz LLRF & LFDC operational Capture Cavity 1 was previously the A0 Photoinjector workhorse Upgrade in progress Achieved ~29 MV/ m in January, 2013 test at HTS ‘Modern’ cryomodule Some delays – upgrading cryomodules is never simple! Installation expected in later summer, 2014 S TATUS – C APTURE C AVITIES 17 ASTA Users Meeting 23-24 July 2013

18. S TATUS – C APTURE C AVITIES 18 ASTA Users Meeting 23-24 July 2013 CC1 refurbishment at MP-9

19. S TATUS – C RYOMODULE CM2 was cooled down at Nov, 2013 So far 7 of 8 cavities is conditioned. Several of them already reached designed gradient of 31MV/m 19

20. G UN C OMMISSIONING M ILESTONE SO FAR Conditioning of the gun with 3MW Klystron is finished at 2013 Photoelectrons first produced at ASTA on June 20, 2013 Molybdenum (uncoated) cathode First visible on Loss Monitor, Faraday cup Charge is very limited due to the low QE CsTe cathode is installed in Feb 2014. Photoelectron from CsTe was observed at Mar. 18 2014

21. F IRST E LECTRONS J UNE 20 2013

22. F IRST ELECTRONS FROM C S T E C ATHODE First Gun Phase scan done with the CsTe cathode

23. F IRST ELECTRONS FROM C S T E C ATHODE 100 us long electron bunch train on the faraday cup. Later calibration resolved the current is more than 1.5nC/bunch

24. F IRST ELECTRONS FROM C S T E C ATHODE Signal from the wall current monitor

25. F IRST ELECTRONS AT 9- WAY YAG SCREEN

26. QE MAP OF THE NEW C ATHODE The average QE from the cathode is about 1~1.5% according to the calculation. Courtesy of Dean. Edstrom

27. D ETAILED GUN P HASE SCAN Blue curve is the ASTRA simulation curve for charge vs gun phase. Green curve was also from ASTRA. The black circle is the experiment data. The initial try fit the rising edge relatively well, however still need better understanding at falling edge

28. E NERGY CALIBRATION OF THE ELECTRON Estimation using Magnet deflection (By Darren ) Establish beam to 9 way YAG screen Using correct magnets to deflect beam Fitting the curve with the known magnet field map and derived the beam energy Estimation using Solenoid scan (By Giulio) Establish beam to YAG screen Adjusting the main and bucking solenoid setting to record the beam size Use ASTRA calculation to derive the energy and also emittance value. However small charge is preferred because of the space charge effect

29. E NERGY CALIBRATION OF THE ELECTRON Courtesy of Darren Crawford

30. E NERGY CALIBRATION OF THE ELECTRON Courtesy of Darren Crawford

31. E NERGY CALIBRATION OF THE ELECTRON Courtesy of Dr. Giulio Stancari

32. E NERGY CALIBRATION OF THE ELECTRON Courtesy of Dr. Giulio Stancari

33. P OSSIBLE APPLICATION Peak brightness of various x-ray sources as a function of their operating photon energy. (Courtesy of F.V. Hartemann at Lawrence Livermore National Laboratory.[5])

34. I NVERSE C OMPTON SCATERRING Relativistic Electron E e Incident laser Light ε 1 Scattered Photon ε 2 θ1θ1 π-θ2π-θ2 In the case of head on collision

35. C HARACTERISTICS OF ICS SOURCE Tunable and near-monochromatic gamma rays can be obtained over the entire spectrum. The gamma rays can be produced in ultra-short pulses. A much lower electron beam energy- on the order of 300 times lower- is needed to produce a given photon energy, which means that the device can be relatively compact and inexpensive than conventional light sources. Conversely, photons with much higher energy than are available through the conventional light sources (>1 MeV) can be produced. The bandwidth can be small and is not limited by the length of an undulator. The peak brightness scales as  5 due to quadratic growth of photon energy, quadratic narrowing of the opening angle and linear reduction in the e-beam source area. The gamma ray polarization is easily adjusted by changing the incident laser polarization.

36. W HY ASTA? The required photon scattering cross section in this case is very small (  th =6.65e -29 m 2 ), which implies increasing challenge to achieve increasing brightness. ASTA is using SRF technology. Currently it runs at 3MHz pulse rate, however there’s still room to improve. At the same time we also need to increase the number of photons with enhancement cavity design.

37. A NTICIPATED BEAM PARAMETERS FOR ICS Incident laser parameters Wavelength λ 1.054  m Pulse Length (rms) 3 ps Peak power P 0 10 TW Intensity Spot size 50  m Raileigh Length 5 mm Electron pulse parameter Beam Energy E b 250 ~ 800 MeV Beam charge 0.1~1 nC Beam pulse length (rms) 5 ps Beam radius (rms) at IP 20  m Beam energy spread (  E/E b ) 0.1% Normalized beam emittance ~ 5 mm mrad Beta function ~ 10 cm Anticipated gamma ray parameter Photon Energy E g 0.8 ~ 9 MeV Photo pulse length (rms) 3 ps Rep Rate 3 MHz # of bunches in Macrobunch 3000 Average photon flux in 1% bandwidth 10 12 cps Photon / bunch 3.3  10 8 Peak brightness (0.1% bandwidth) 10 23 photons/(s mm 2 mrad 2 ) Angular spread (1/γ) 2 ~ 0.7 mrad

38. P ROPOSED LOCATION FOR ICS EXPERIMENT Stage 1: Proof of principle experiment using 250MeV(1 cryomodule) Stage 2: Laser upgrade to achieve high rep operation Stage 3: Final setup for user oriented ICS setup Gamma Ray Enhancement cavity

39. O UTLOOK Figure 9: Comparison of the proposed source at ASTA to other existing and planned ICS gamma-ray sources normalized to 10 MeV (adapted from D. Habs and U. Köster, Applied Physics B 103, 2011, Courtesy of Dr. Alex Murokh from RadiaBeam Technologies)

40. C URRENT ASTA S CHEDULE

41. S UMMARY Photoinjector has been commissioned successfully. CC1 and CC2 will be commissioned at the end of this FY First user experiment will be carried out very soon. Potential x-ray source using ICS at ASTA is proposed Thanks to all the people involved

42. T HANK YOU FOR YOUR ATTENTION !

43. F IRST ELECTRONS FROM C S T E C ATHODE