RF gun design for the TESLA VUV Free Electron Laser

In this paper, a detailed discussion of the rf-related beam dynamics in rf guns and accelerating cavities is presented. Other rf-gun-related aspects such as space charge and cathode physics are not treated. An effective start phase is introduced in order to yield a better description for the synchronous phase, the energy gain, and the bunch compression factor in gun cavities. Energy spread and longitudinal emittance are treated in a form applicable to guns as well as to accelerating cavities. Discussions on the transverse emittance include the chromatic emittance variation at high emission phases and effects of field asymmetries and combined solenoid-cavity sections.

Section: Emittance Growth By Field Asymmetriesmentioning

confidence: 99%

rf-induced beam dynamics in rf guns and accelerating cavities

Floettmann

2015

“…Two electron guns following this design (gun 3.1 and gun 3.2) were produced, and both were used for the measurements presented in this paper. Details of the original gun design are published elsewhere [9].…”

Section: A Gun Cavitymentioning

confidence: 99%

Detailed characterization of electron sources yielding first demonstration of European X-ray Free-Electron Laser beam quality

Stephan¹,

Boulware²,

Krasilnikov³

et al. 2010

The photoinjector test facility at DESY, Zeuthen site (PITZ), was built to develop and optimize photoelectron sources for superconducting linacs for high-brilliance, short-wavelength free-electron laser (FEL) applications like the free-electron laser in Hamburg (FLASH) and the European x-ray free-electron laser (XFEL). In this paper, the detailed characterization of two laser-driven rf guns with different operating conditions is described. One experimental optimization of the beam parameters was performed at an accelerating gradient of about 43 MV=m at the photocathode and the other at about 60 MV=m. In both cases, electron beams with very high phase-space density have been demonstrated at a bunch charge of 1 nC and are compared with corresponding simulations. The rf gun optimized for the lower gradient has surpassed all the FLASH requirements on beam quality and rf parameters (gradient, rf pulse length, repetition rate) and serves as a spare gun for this facility. The rf gun studied with increased accelerating gradient at the cathode produced beams with even higher brightness, yielding the first demonstration of the beam quality required for driving the European XFEL: The geometric mean of the normalized projected rms emittance in the two transverse directions was measured to be 1:26 ` 0:13 mm mrad for a 1-nC electron bunch. When a 10% charge cut is applied excluding electrons from those phase-space regions where the measured phase-space density is below a certain level and which are not expected to contribute to the lasing process, the normalized projected rms emittance is about 0.9 mm mrad

“…The rf gun is taken to be an S-band (2.856 GHz) 1=2-cell cavity similar to the one currently in use at the linac coherent light source (LCLS) [39]. Similar results are then confirmed using a 1=2-cell L-band (1.3 GHz) gun similar to the one used at the FLASH facility in DESY [40].…”

Section: A Subpicosecond Bunch Train Formationmentioning

confidence: 87%

Ballistic bunching of photoinjected electron bunches with dielectric-lined waveguides

Lémery

Piot

2014

We describe a simple technique to passively bunch non-ultra-relativistic (≲10 MeV) electron bunches produced in conventional photoinjectors. The scheme employs a dielectric-lined waveguide located downstream of the electron source to impress an energy modulation on a picosecond bunch. The energy modulation is then converted into a density modulation via ballistic bunching. The method is shown to support the generation of subpicosecond bunch trains with multi-kA peak currents. The relatively simple technique is expected to find applications in compact, accelerator-based, light sources and advanced beam-driven accelerator methods.