Joe Frisch: Synchrotron radiation sources and free ... - Conferences

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High Brightness Electron Sources The beam phase space will not decrease after the electron source: A high brightness source is critical for LINAC based FELs. Electrons emitted with some transverse momentum spread Current dependant “space charge” forces counteract the accelerating field Electric field accelerates electrons away from the cathode Want short electron pulse to allow compression to high peak currents Emittance ~ radius X transverse energy spread Minimum cathode radius set by space charge limit -> want as high a gradient as practical Want minimum transverse momentum spread (cold beam). Surface roughness can increase transverse momentum spread, want < 10s of nanometers. 14
Electron Guns RF guns used at SLAC <strong>and</strong> most proposed XFELs RF cavities can support very high fields (120MV/M for LCLS) Short pulse (~picosecond) laser to generate photo-electrons Low repetition machines (LCLS 120Hz) typically use copper cathodes, low QE (3x10 -5 @260nm), but high gradient High repetition rate superconducting machines may use higher QE (Cs 2Te, ~10% at 260nm) cathodes to reduce laser power (may require reduced gradient) RF GUN: 0.5 πmm-mr measured at 250pC Pulsed DC (500kV, 3us, 10MV/M) gun used at SCCS <strong>and</strong> SACLA at Spring-8. Thermal emission from heated cathode to produce beam. 0.7πmm-mr measured at 300pC NOTE: emittance measurements not directly comparable due to different bunch lengths! Maesaka et. Al. SCCS, Spring-8 D. Dowell et al 3mm 15
Page 1 and 2: Synchrotron Radiation Sources and F
Page 3 and 4: X-ray Beam Parameters • Energy /
Page 5 and 6: Grazing incidence mirror Focusing X
Page 7 and 8: Undulator Radiation Most high brigh
Page 9 and 10: Accelerators Synchrotron LINAC Acce
Page 11 and 12: Light Source: Petra III at DESY •
Page 13: LINACS • Single pass devices •
Page 17 and 18: 100fs Room Temperature 200ns 10ms P
Page 19 and 20: Energy Time Initial beam Gun 6 MeV
Page 21 and 22: Bunch Compression - Wakefields •
Page 23 and 24: FELs: Gain and Coherent Emission
Page 25 and 26: Undulator as emission mechanism 25
Page 27 and 28: Self Amplified Spontaneous Emission
Page 29 and 30: � � � u p 2� � � 2 �
Page 31 and 32: Gain, Saturation and Taper LCLS Gai
Page 33 and 34: Seeding • FEL light is amplified
Page 35 and 36: Laser Seeding (ECHO) Laser fundamen
Page 37 and 38: Synchrotron Multi-User Capability S
Page 39 and 40: Future Light X-ray Sources • Most
Page 41 and 42: Low energy injector gun Recirculati
Page 43 and 44: Attosecond FELs • Operation at lo
Page 45 and 46: Laser-Plasma Accelerators - LBNL Po
Page 47 and 48: What isn’t covered here: • Almo
Page 49: Discussion • Imagine you want to

Joe Frisch: Synchrotron radiation sources and free ... - Conferences

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