C-band accelerators have been of particular interest in recent years due to their ability to provide high gradients and transport high charge beams for applications such as colliders and medical technologies. These technologies are made possible by new advancements in high gradient technologies that can suppress the breakdown rate in a particular structure by using distributed coupling,...
In order to address the needs of the high brightness electron beam and novel cathode communities, the CYBORG (CrYogenic Brightness-Optimized Radiofrequency Gun) beamline was developed and constructed at UCLA. The primary accelerating cavity is a 1/2 cell C-band structure designed to operate at cryogenic temperatures and accelerating gradients above 100 MV/m with a removable back plate for...
A cryogenic, HV conditioning system integrated in a stand-alone cryocooler is operated at FREIA laboratory in Uppsala in order to investigate the fundamental mechanisms of field emission and breakdown nucleation. A series of high-field measurements has been carried out with pairs of metal electrodes (copper, niobium and titanium) at temperatures ranging from ambient down to 4K.
The cryogenic...
In order to investigate the mechanisms behind vacuum arc formation, it is beneficial to use as many diagnostic tools as possible at a wide temperature range for different metals. The cryogenic HV pulsing system in FREIA laboratory is experimentally following this line of research. We study vacuum arc breakdowns and surface conditioning using high-repetition rate DC pulses at a wide range of...
The occurrence of breakdown events are a primary limiting factor for future accelerator applications aiming to operate under high field-gradient environments. Experimental evidence often leads to a hypothesis that breakdown events are associated with temperature and dark current spikes on the surface of RF devices. In the past decade, there has been increased interest in unveiling the...
This talk presents theoretical work on the nano-protrusion hypothesis. We review and expand the theorical work on the study of the electron beam shape, as a mean to determine the dimensions of the hypothetical nano-protrusion where the electrons come from. State-of-the-art field emission theory and computational tools have been used to calculate the kinetic energy of the electrons as a...
Jensen’s model[1] for General Thermal-Field (GTF) emission enables increased precision for injecting electrons self-consistently into physics simulations where electron emission is important, such as vacuum arcs, transmission lines in pulsed power systems, or vacuum diodes. Due to increased computational expense, however, it is important to understand when simpler models may be reasonably...
