A Self-consistent Power Relation for an Inverse Compton Scattering Theory

In a self-consistent manner, the total power for linear inverse Compton scattering between a Gaussian electron beam colliding head on with a Gaussian laser beam is obtained. The theory is shown to agree with well-known limiting cases. Coupling among harmonic modes is explicitly shown in the resultant power relation. Even so, for the parameters of interest, harmonic modes are negligible compared to the fundamental mode. Total power calculations are of importance in detector calibration. The theory is applied using practical linear accelerator and laser parameters

UNLV EM-Dot Research, Highlights of Improvised Electric Detonator (Wire Melt) Research, and Comments on Basic Research with UNLV Non-Equilibrium Plasma Pinch

UNLV EM DOT •Patented –Patent Number: 7,482,814 [1/27/2009] •Novel Differential Dot –Wide bandwidth & Matched –Symmetric, shielded sensor –Measures the E and B fields at a single point in space simultaneously •Transient Calibration Technique Developed –Excellent Agreement –Low inductance test stand –relatively uniform B-field –Low capacitance test stand –relatively uniform E-field –Test stand is the limiting factor at this tim

A Simplistic Plasma Dust Removal Model Employing Radiation Pressure

A simple heuristic model is developed to examine the feasibility of using radiation pressure as a means to transport plasma dust out of the path of the forthcoming electron or photon beam. A slow electromagnetic surface wave coupled to a planar target or substrate exerts the required pressure in the removal process. The model is examined using data and parameters from single-shot radiography experiments. Optimal source requirements are identified for a typical radiography experiment. Source energies and powers are a minimum over an optimum band of frequencies where both conduction and plasma oscillation effects are mutually significant. Above the band of frequencies, dissipative losses in the surface supporting the surface wave increases exponentially with frequency. Below the optimal band, the energy concentration over the plume at the surface structure decreases significantly with frequency, thereby requiring higher source energies/powers for plasma removal

Modeling, Fabrication, and Optimization of Niobium Cavities – Phase I: Quarterly Progress Report May 15, 2001 - August 15, 2001

Multipacting is one of the major loss mechanisms in rf superconductivity cavities for accelerators. This loss mechanism limits the maximum amount of energy/power supported by the cavities. Optimal designs have been identified in others’ studies. In practice, these designs are not easily manufactured. Chemical etching processes used to polish the cavity walls result in a nonuniform surface etch compromising the optimal geometrical design. Past multipacting studies have not examined the impact of wall perturbations. It is the purpose of this study to examine the chemical etching process in the design of niobium cavities so to maximize the surface quality of the cavity walls while minimizing the multipacting losses. Single and multiple cavity cell geometries are to be investigated. Optimization techniques will be applied in search of the chemical etching processes, which will lead to cavity walls with near ideal properties

Modeling, Fabrication, and Optimization of Niobium Cavities: Phase II

Niobium cavities are important parts of the integrated NC/SC high-power linacs. Over the years, researchers in several countries have tested various cavity shapes. They concluded that elliptically shaped cells are the most appropriate shape for superconducting cavities. The need for very clean surfaces led to the use of a buffered chemical polishing procedure for surface cleaning to get good performance of the cavities. This proposal discusses the second phase of research in the second year of the project. The first phase (starting Summer 2001) has resulted in improving the basic understanding of multipacting and the process of chemical etching. Based on our conclusions so far, as well as our interaction with personnel of Los Alamos National Laboratory (LANL), we propose to focus on the following topics in the second phase of this project: 1. Continue optimizing the cavity shape to reduce or minimize the possibilities of multipacting. 2. Redesign the etching process to maximize surface uniformity. 3. Experimental study of multipacting conditions. 4. Experimental study of the etching process and the resulting quality of the surface

Modeling, Fabrication, and Optimization of Niobium Cavities: Final Phase

Niobium cavities are important parts of the integrated NC/SC high-power linacs. Over the years, researchers in several countries have tested various cavity shapes. They concluded that elliptically shaped cells are the most appropriate shape for superconducting cavities. The need for very clean surfaces lead to the use of a buffered chemical polishing produce for surface cleaning to get good performance of the cavities. This is the third and final phase of the study. The first phase has resulted in improving the basic understanding of multipacting and the process of chemical etching. The second phase has resulted in an experimental setup of a fluid flow experiment with experimentation to be completed in the third year. Other experimental activities include the evaluation of a vacuum system and various vacuum equipment purchases and modifications. An optimization code for a five cell niobium cavity based on resonant frequency and mode number was developed. Based on our conclusions so far, as well as our interaction with personnel at Los Alamos National Laboratory (LANL), we propose to focus on the following topics in the third phase of this project: 1. Optimize the cavity shape based on the desired resonant frequency and examine multipacting of that structure. 2. Studying secondary electronic emission from a niobium test piece under cryogenic conditions. 3. Experimental study of the etching process using flow visualization techniques. 4. Redesign the etching process to maximize surface uniformity

Modeling, Fabrication, and Optimization of Niobium Cavities – Phase I: Quarterly Progress Report November 20, 2001 - February 20, 2002

Multipacting is one of the major loss mechanisms in RF superconductivity cavities for accelerators. This loss mechanism limits the maximum amount of energy/power supported by the cavities. Optimal designs have been identified in others’ studies. In practice, these designs are not easily manufactured. Chemical etching processes used to polish the cavity walls result in a nonuniform surface etch. A nonuniform surface etch will leave some unclean areas with contaminants and micron size particles. These significantly affect multipacting. Further, a nonuniform etch will leave areas with damaged grain structure, which is not good for superconducting properties. Typically, the depth of chemical polishing etch ranges between 10 to 150 microns. It is the purpose of this study to examine the chemical etching process in the design of niobium cavities so to maximize the surface quality of the cavity walls while minimizing the multipacting losses. Single and multiple cavity cell geometries are to be investigated. Optimization techniques will be applied in search of the chemical etching processes, which will lead to cavity walls with near ideal properties

Modeling, Fabrication, and Optimization of Niobium Cavities Phase III: Quarterly Report

This quarterly report provides an update to the last phase of the Modeling, Fabrication, and Optimization of Niobium Cavities. Designing the experimental setup of secondary electron emission was well underway in early summer of 2003 when funding was made available for this portion the study. By March 2004, many of the components of the experimental study reached UNLV with some assembly accomplished. The first secondary electron emission (SEE) measurement was made from the surface of a Faraday cup in September 2004. At a particular beam energy, the current measured with the Faraday cup and electrometer changed sign over a range of energies. Three studies in support of this last phase are being conducted in parallel

Modeling, Fabrication, and Optimization of Niobium Cavities: Phase III Second Quarterly Report

Niobium cavities are important parts of the integrated NC/SC high-power linacs. Over the years, researchers in several countries have tested various cavity shapes. They concluded that elliptically shaped cells are the most appropriate shape for superconducting cavities. The need for very clean surfaces lead to the use of a buffered chemical polishing produce for surface cleaning to get good performance of the cavities. The third phase concludes the experimental a fluid flow study and optimization study. The first quarter and second quarter of phase three also begins the experimental set-up of secondary emission studies from niobium in superconducting mode. This study is to be completed by the end of the third year