R&D at Bates

1. R&D at Bates William S. Graves MIT-Bates Laboratory Presentation to MIT X-ray laser Accelerator Science Advisory Committee September 18-19, 2003

2. Technical Challenges • Achieve ~10 fs timing synchronization between FEL output, seed lasers, and pump-probe lasers. • Necessary RF phase and amplitude stability for timing above. • Stability in energy per pulse, timing, and pointing appropriate for a user facility. • Reduced power consumption for CW operation. • Reliable laser seed generation including tunability and stability. • Development of fast RF or ferrite switches necessary to deliver beam to multiple undulators. • Development of a high repetition rate, high brightness photoinjector. • Development of tunable undulators. Matching of undulator resonance. Orbit correction over tuning range. • Electron beam diagnostics. • Coherent photon beam diagnostics at short wavelength.

3. Bates accelerator layout 200 m Energy compressor chicane R56 = -3400 mm 500 MeV per pass 1 kHz rep rate 2856 MHz DC photoinjector GaAs cathode 360 kV thermionic source

4. R&D program at Bates • Demonstrate some of the key technologies at lower energy including • Development of stable HHG seed source. • Seeding FEL with ultrashort HHG pulses. • Development of tunable seed laser • Cascaded HGHG FEL output • Cascaded HGHG at BNL • Timing synchronization of FEL, seed, and pump lasers below 100 fs • Timing synchronization of laser and RF and e-beam. • Support for LUX injector development. An FEL using an upgraded Bates linac could drive a 10 nm FEL enabling prototype user experiments and development of coherent optical beam handling methods.

5. Hardware for R&D program • Equipment to be added includes • S-band photoinjector • Chicane bunch compressor? • Multiple undulators • Ti:Sapp and equipment for HHG seed generation • Diagnostics • RF upgrade or cryomodules? • Photon beamlines

6. Bates Modulators A. Zolfaghari, W. North New Solid State Modulator deck with Switch Tubes • Switch-Tube Specifications • Maximum Operating Hold-Off Voltage 175kV • Maximum Peak Pulse Current 50 Amps per output • (100A total) • Minimum voltage across the modulator 18kV • Output Pulse Duration 0-55s • Maximum Duty factor 4% • (limited by Switch Tube Cooling) • Maximum Pulse Repetition 5kHz • Short Term Stability  0.02% • Current to 80A (fixed beam • switch tube collector voltage) Rise: 0.6s Fall: 0.2s Solid-State Switch Specifications High voltage Input 1-17.5kV DC (positive polarity) Maximum Pulse Current 75 A 1 sec Peak Current 100 A Intrapulse Voltage Drop <200V @ 100 A Pulse Width 1 to 50 sec Maximum Repetition Rate 5 kHz Rise Time ~ 1 sec Fall Time load dependent Cooling Passive Oil Cooling Maximum Power Dissipation 3,000 W

7. Schedule • Laser/RF timing synchronization currently under development (Kaertner group). • NSF and DOE expected to solicit accelerator R&D proposals for FY05. • Submit proposal by 1/04

8. Budget • Laser timing measurements ~$20k + postdoc • HGHG cascade at BNL ~$100k? • S-band injector at Bates ~$1M • Undulator at Bates ~$1-2M • RF upgrade at Bates ~$4M for 1 GeV single pass • Test RF recycler at BESSY ~$20k • Modulator for LUX ~$300k • Fast e-beam switch ~$100k • HHG seed generation $1M