Consensus reached in the last few years that fourth generation light source will most likely be a X-ray or a UV coherent source based on single-pass high-gain free electron laser (FEL), such as Self Amplified Spontaneous Emission (SASE), or seeded high-gain harmonic -generation (HGHG) free electron lasers. High -gain (> 10) required for single-pass FEL puts great constrain on the quality of ele...

A high brightness, low emittance photocathode rf gun is starting operation at UCLA as an injector to a 20 MeV linac. This linac will initially be used to drive FELs, plasma wakefield accelerators, and to test plasma lenses. The gun is a 1 89 cell ~r-mode standing wave structure running at 2.856 GHz, and has a copper photocathode. In the initial commissioning of the gun, photoelectron beams of u...

We experimentally investigate surface-plasmon assisted photoemission to enhance the efficiency of metallic photocathodes for high-brightness electron sources. A nanohole array-based copper surface was designed to exhibit a plasmonic response at 800 nm, fabricated using the focused ion beam milling technique, optically characterized and tested as a photocathode in a high power radio frequency ph...

Transmission electron microscopy has been employed to study the structure of polycrystalline CsI thin "lms and its transformation under exposure to humid air and UV irradiation. The catastrophic degradation of CsI thin "lm photocathode performance is shown to be associated with the "lm dissolving followed by its re-crystallization. This results in the formation of large lumps of CsI crystal on ...

Accelerator Test Facility at Brookhaven National Laboratory (BNL ATF) operates with 5 MeV photocathode gun and 70 MeV linac for different range of experiments with a few picoseconds and a few micrometers emittance electron bunch. Many conducted experiments require beam with good spatial resolution and short length as well. NdYaG laser pulse turns to the electron bunch in the gun with space char...

Ultrafast time-resolved electron diffraction based on a photocathode rf electron gun is being developed in Osaka University to reveal the hidden dynamics of intricate molecular and atomic processes in materials. The photocathode rf gun generates a femtosecond-bunch electron beam by femtosecond laser driving. The transverse emittance, bunch length and energy spread were measured. The growths of ...

Metal organic {Ni₄O₄} clusters, known oxidation catalysts, have been shown to provide a valuable route in increasing the photocurrent response on silicon nanowire (SiNW) photocathodes. {Ni₄O₄} clusters have been paired with SiNWs to form a new photocathode composite for water splitting. Under AM1.5 conditions, the combination of {Ni₄O₄} clusters with SiNWs gave a current density of -16 mA/cm², ...

We present the femtosecond synchronization between an 800-nm photocathode laser and an S-band RF oscillator using an optical-RF phase detection system at KAERI-WCI Accelerator. A 79.33-MHz commercial Ti:sapphire photocathode laser oscillator is locked to a 2.856-GHz RF master oscillator (RMO) using a fiberloop-based optical-microwave phase detector (FLOMPD), which results in 13 fs (rms) out-of-...

New developments in HPD design are presented, triggered by applications in high energy physics and astrophysics. The presented HPD designs are based on three innovations. (i) In order to achieve the highest possible surface coverage in a RICH detector, we introduced a photoelectron focussing method which is efficient to the periphery of the photocathode. (ii) To prevent positive ion feedback in...

The progress of various high-brightness electron source technologies, specially laser based electron sources, such as photocathode RF gun, DC and pulsed photo-gun, and laser plasma electron source, will be reviewed. The physics processes of those sources to realize best performance are clarified according to three basic ideas. They are transverse space charge emittance compensation, space charg...