Electron beam driven plasmas are rich in complex physics, including atomic physics, molecular physics, plasma physics, collisions, plasma chemistry, thermodynamics, and scattering. The study of such a system is paramount for understanding and modeling of ionospheric physics and low-temperature plasmas. A reduced order model known as the rigid beam model has recently been developed by NRL to...
Copper is widely used in electric vehicles, for example in bus bars for motors and battery modules. Of course, it is also used in accelerators.
The optical properties of pure liquid copper near the melting point have been investigated [1] using density functional theory with the Quantum ESPRESSO package [2].
In this paper, the atomic and electronic structure of pure liquid copper from the...
In this work we present our efforts to simulate the effect of Ohmic heating due to field emission on the morphology (shape) of a surface region. A popular model of field emission leading to material supply and eventual vacuum arc breakdown relies on the existence of protrusions with high electric field enhancement factors (β). β can sometimes be initialized to values as high as 100. However,...
For the development of X-band deflecting structure at Shanghai Synchrotron Radiation Facility (SSRF), two units of X-band deflecting structures totally including six RF structures have been used on SXFEL successfully for ultra-fast beam diagnostics. The construction of another new FEL facility has started from 2018, which is named Shanghai high repetition rate XFEL and extreme light facility...
In the presence of strong electric fields, a plasma-induced arc of intense current is capable of establishing a connection between two metal surfaces, even within the confines of ultra-high vacuum conditions. According to the hypothesis, the presence of tall and sharp nanotips on a surface exposed to strong electric fields undergoes heating via field emission currents, ultimately resulting in...
The behavior of plasma in the anode region of a DC discharge is complex due to its dependence on the geometry of the anode, gas type and pressure, and discharge current. Understanding this behavior is an ongoing effort due to its importance in developing a general theory for gas discharges and designs for charged particle sources. The anode plasma sheath displays interesting phenomena such as...
The role of the magnetic field in vacuum arcing has been neglected in many experimental and computational studies, while it is present in many applications. Future accelerators such as muon colliders and technologies such as vacuum interrupters involve significant magnetic fields that potentially influence the plasma initiation dynamics of vacuum arcing, as they can significantly focus the...
A relativistic one-dimensional particle-in-cell (PIC) Monte Carlo Collision (MCC) model is developed to study velvet cathode plasma formation and expansion in high-voltage diodes. Velvet cathodes are used in high-power vacuum diodes for pulsed power systems such as magnetically insulated line oscillators (MILOs) for generating high-power microwaves (HPMs) and magnetically insulated...
Obtaining field-emission-free operation of a DC high voltage photo-electron gun (photogun) can be challenging, particularly at bias voltages > 200 kV. Polarized electron beams employ delicate GaAs-based photocathodes. Any level of field emission from the photogun cathode electrode can degrade the vacuum inside the photogun leading to a rapid decrease in photocathode quantum efficiency. High...
At KEK, fireball-triggered RF breakdowns [1] have been observed in 509-MHz normal-conducting accelerating cavities. It has been found that the breakdown was caused by a high-temperature microparticle that we call “fireball” now. Recently, the fireball-triggered breakdown attracts interests again in relation to the SuperKEKB accelerator that is suffering from sudden beam losses. A hypothesis is...
One of the most extensively studied characteristics of vacuum breakdown (VBD) is the conditioning process and the VBD occurrence statistics, in various systems, including Radio-Frequency (RF) accelerators and pulsed-DC large electrode systems. Despite abundant data on VBD statistics, drawing useful conclusions regarding the physical processes that determine various patterns within those data...
Large area diodes under high vacuum (1e-6 Torr) can exhibit similar characteristics to pressurized arcs via several mechanisms such as stimulated emission of ions, thermal ion emission, and bipolar ion flow. Generally these diodes are under high electric field stresses (above 200kV/cm) where field emission of electrons from the cathode are expected. The ions in each mechanism above are...
