Development of an X-band RF Gun at SLAC

Phys. Rev. ST Accel. Beams

et al. 2012

Self Cite

A design for an X-band rf photoinjector that was developed jointly by SLAC National Accelerator Laboratory (SLAC) and Lawrence Livermore National Laboratory (LLNL) is presented. The photoinjector is based around a 5.59 cell rf gun that has state-of-the-art features including: elliptical contoured irises; improved mode separation; an optimized initial half cell length; a racetrack input coupler; and coupling that balances pulsed heating with cavity fill time. Radio-frequency and beam dynamics modeling have been done using a combination of codes including PARMELA, HFSS, IMPACT-T, ASTRA, and the ACE3P suite of codes developed at SLAC. The impact of lower gradient operation, magnet misalignment, solenoid multipole errors, beam offset, mode beating, wakefields, and beam line symmetry have been analyzed and are described. Fabrication and testing plans at both LLNL and SLAC are discussed.

Section: B Lower Gradient Operationmentioning

confidence: 99%

“…An X-band rf gun has been designed and operated at SLAC as reported in [11][12][13]. This Mark 0 structure achieved peak electric fields of 200 MV=m on the cathode surface.…”

Section: Introductionmentioning

confidence: 99%

Modeling and design of anX-band rf photoinjector

Marsh

Albert

Phys. Rev. ST Accel. Beams

et al. 2012

Self Cite

“…The original X-band gun (dubbed the Mark 0) was designed and tested by Vlieks [38] with a design gradient of 200 MV=m, much higher than the typical 120 MV=m S-band gradient. The design gradient was reached, but dark current was a problem [39].…”

Section: Rf Gunmentioning

confidence: 99%

Performance of a second generation X -band rf photoinjector

Marsh

Phys. Rev. Accel. Beams

et al. 2018

rf photoinjectors produce incredibly bright electron beams enabling advanced photon science applications such as the current generation of free electron lasers and high energy x-rays and gammarays via laser-Compton scattering. A second generation 5.59 cell X-band rf gun has been developed, installed, conditioned, commissioned, tuned, and used to produce laser-Compton x-rays and multiple electron bunches. A charge per bunch from a few pC to 500 pC has been measured, consistent with a quantum efficiency of 5 × 10 −5 using a 263 nm 10 Hz photocathode drive laser. The rf gun has operated close to design performance at high gradient, and more reliably at lower gradient achieving a root mean square normalized emittance of 0.3 mm mrad at both 80 pC at 185 MV=m, and 40 pC at 165 MV=m. Thermal emittance is estimated at 0.55 mm mrad=mm. Energy spread of 0.03% has been achieved. These results agree very well with modeling predictions for the operating conditions under which the measurements were made. Unusually disruptive breakdowns were observed with an applied magnetic field of 0.5T used for emittance compensation.

“…The accelerator begins with the radio-frequency (rf) photoinjector, based on an earlier high gradient 7 MeV, 5.5-cell X-band rf photoinjector [18]. Improvements specific to our application have been implemented.…”

Section: A Accelerator Systemsmentioning

confidence: 99%

Design of narrow-band Compton scattering sources for nuclear resonance fluorescence

Albert

Phys. Rev. ST Accel. Beams

Gibson

et al. 2011

The design of narrow-band Compton scattering sources for specific applications using nuclear resonance fluorescence (NRF) is presented. NRF lines are extremely narrow (ÁE=E $ 10 À6 ) and require spectrally narrow sources to be excited selectively and efficiently. This paper focuses on the theory of spectral broadening mechanisms involved during Compton scattering of laser photons from relativistic electron beams. It is shown that in addition to the electron beam emittance, energy spread, and the laser parameters, nonlinear processes during the laser-electron interaction can have a detrimental effect on the gamma-ray source bandwidth, including a newly identified weakly nonlinear phase shift accumulated over the effective interaction duration. Finally, a design taking these mechanisms into consideration is outlined.