The Photocathode Electron Gun (PEG) at SLAC is required to produce bunch intensities of up to 10 electrons within 2 ns (8 Amps). Operation of PEG has demonstrated a ‘Charge Limit’ phenomenon, whereby the charge that can be extracted from the gun with an intense laser beam saturates at significantly less than 10 electrons (the expected ‘Space Charge Limited’ charge) when the photocathode Quantum...

A goal of the Gun Test Facility (GTF) at SLAC is to investigate the production of highbrightness electron beams for the Linac Coherent Light Source (LCLS) X-ray FEL. High brightness in the rf photocathode gun occurs when the time-sliced emittance is nearly the same as the cathode thermal emittance and when the slices are all lined up, i.e., their Twiss parameters are nearly identical. In collab...

A comparison of electron beam parameters from a 1.6 cell S-band rf gun with Cu and Mg cathode at the SLAC Gun Test Facility are reported. The lower work function of Mg compared to Cu theoretically increases the quantum efficiency for a fixed laser wavelength and also increases the thermal emittance. Slice emittance measurements at low charge (15 pC) set an upper limit on the thermal emittance o...

The SLAC Gun Test Laboratory apparatus, the first two meters of which is a replica of the SLAC injector, is used to study the production of intense, highly–polarized electron beams required for the Stanford Linear Collider and future linear colliders. The facility has been upgraded with a Mott polarimeter in order to characterize the electron polarization from photocathodes operating in a DC gu...

The slice transverse emittance of an electron beam is of critical significance for an x-ray FEL. In a photocathode RF gun, the slice transverse emittance is not only determined by the emission process, but also influenced strongly by the nonlinear space charge effect. In this paper, we study the slice transverse emittance evolution in a photocathode RF gun using a simple model that includes eff...

We report the design, fabrication and characterization of a carbon nanotube enabled open-type X-ray system for medical imaging. We directly grew the carbon nanotubes used as electron emitter for electron gun on a non-polished raw metallic rectangular-rounded substrate with an area of 0.1377 cm² through a plasma enhanced chemical vapor deposition system. The stable field emission properties with...

An acceleration element is proposed for compressing the electron pulse duration in a femtosecond photoelectron gun. The element is a compact metal cavity with curved-shaped walls. An external voltage is applied to the cavity where a special electric field forms in such a way that the slow electrons in the electron pulse front are accelerated more than the fast electrons, and consequently the el...