Simulation study of direct current vacuum breakdown and its application to high-gradient accelerating structures

It is well known that radio frequency breakdown is one of the main limitations in high frequency accelerators. Similarities have been detected between breakdowns in direct current vacuum gaps and those in superconducting radio frequency cavities. Therefore, cavity break- downs due to electric field phenomena can be understood by studying direct current vacuum breakdowns. Significant irregularity of a surface and a variety of involved processes objectively stipulate a number of factors which may lead to a breakdown. In this paper, the effects of surface conditions, accelerator gradient, pulse length, and operating frequency on the breakdown have been studied by using COMSOL simulation package. It was found that the dependence of breakdown rate on accelerating gradient and pulse length follows scaling laws. Based on the time evolutions of electron density and the potential in cone-cylinder electrode configuration at the pressure of 0.1 Pa, the time scale of a vacuum breakdown has been established. It was also confirmed that the emission from an electrode surface can be regarded as a major factor leading to electrical breakdown in vacuum. The obtained results could be very useful in high-gradient accelerating structures.

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Experimental Studies of a High-Gradient X-band Welded Hard-Copper Split Accelerating Structure

Journal of Physics D Applied Physics ◽

10.1088/1361-6463/ac4632 ◽

2021 ◽

Author(s):

Ronald Agustsson ◽

Paul Carriere ◽

Osvaldo Chimalpopoca ◽

Valery A. Dolgashev ◽

Maria A Gusarova ◽

...

Keyword(s):

Electron Beam ◽

Thermal Loading ◽

Electron Beam Welding ◽

Copper Alloys ◽

Pulse Length ◽

Experimental Studies ◽

Breakdown Rate ◽

High Gradient ◽

Electromagnetic Design ◽

Accelerating Structure

Abstract Recent research on high-gradient radio frequency (RF) accelerating structures indicates that the use of hard copper alloys provides improvement in high gradient performance over annealed copper. Such structures are made by bonding individually manufactured parts. However, there are no well-established bonding techniques that preserve the hardness, surface finish and cleanliness required for high gradient operation. To preserve the copper hardness, RadiaBeam has developed a joining technique based on electron beam welding. This technique provides efficient bonding with strong, clean welds and minimal thermal loading, while maintaining a clean inner RF environment. Our RF design and fabrication methodology limits the small heat affected zone to the outer cavity envelop, with virtually no distortions or thermal loading of critical RF surfaces. It also incorporates provisions to precisely control the gap despite conventional issues with weld joint shrinkage. To date we have manufactured and validated an RF accelerating structure joined by electron-beam welding that incorporates a novel open split design to significantly reduce the assembly complexity and cost. In this paper, we will present the electromagnetic design of this structure, discuss bonding, and present the results of high-power tests, where the accelerating gradients of 140 MV/m with surface peak fields of 400 MV/m were achieved for flat-top pulse length of 600 ns with an RF breakdown rate of 10-4 1/(pulse∙m).

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Performance Comparison of Phase Change Materials and Metal-Insulator Transition Materials for Direct Current and Radio Frequency Switching Applications

Technologies ◽

10.3390/technologies6020048 ◽

2018 ◽

Vol 6 (2) ◽

pp. 48 ◽

Cited By ~ 7

Author(s):

Protap Mahanta ◽

Mohiuddin Munna ◽

Ronald Coutu

Keyword(s):

Radio Frequency ◽

Phase Change ◽

Direct Current ◽

Phase Change Materials ◽

Performance Comparison ◽

Insulator Transition ◽

Metal Insulator Transition ◽

Metal Insulator

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Direct-current and radio-frequency characterization of submicron striped-channel field effect transistor structures using focused ion beam and electron-beam lithography

Journal of Vacuum Science & Technology B Microelectronics Processing and Phenomena ◽

10.1116/1.585948 ◽

1992 ◽

Vol 10 (6) ◽

pp. 2945 ◽

Cited By ~ 1

Author(s):

M. M. Hashemi

Keyword(s):

Electron Beam ◽

Radio Frequency ◽

Direct Current ◽

Electron Beam Lithography ◽

Field Effect ◽

Field Effect Transistor ◽

Focused Ion Beam ◽

Ion Beam ◽

Effect Transistor

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A New Automatic Demultiplexing Method for NRZ-OOK Polarization-Division Multiplexed System

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.204-210.1636 ◽

2011 ◽

Vol 204-210 ◽

pp. 1636-1639

Author(s):

Qi Jing ◽

Yong Qing Huang ◽

Yang An Zhang ◽

Ming Lun Zhang ◽

Li Dong Mei

Keyword(s):

Radio Frequency ◽

Direct Current ◽

Beam Splitter ◽

System Simulation ◽

Polarization Controller ◽

Polarization Beam Splitter ◽

Optical Polarization ◽

Control Signals ◽

Detection Window

A new automatic optical polarization demultiplexing method for NRZ-OOK polarization division multiplexed (PDM) system is proposed. The detected power differences of both the direct current (DC) and the radio frequency (RF) are used as control signals which are sensitive to the angles between the polarization controller (PC) and the polarization beam splitter (PBS). The characteristics of those control signals are thoroughly analyzed, and the best RF detection window is calculated out through system simulation.

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Abstract 60: Inducible Arrythmogenicity of Direct Current Electroporation Ablation: Insight from a Series of Acute Canine Studies

Circulation Research ◽

10.1161/res.121.suppl_1.60 ◽

2017 ◽

Vol 121 (suppl_1) ◽

Author(s):

Alan Sugrue ◽

Chance Witt ◽

Christopher V DeSimone ◽

Deepak Padnanabhan ◽

Ammar Killu ◽

...

Keyword(s):

Direct Current ◽

Superior Vena ◽

Pulmonary Veins ◽

Pulse Length ◽

Experimental Studies ◽

Tissue Destruction ◽

Ecg Gating ◽

Actual Mechanism ◽

Membrane Poration ◽

Current Energy

Background: The use of direct current electroporation has the potential for significant utility because of its non-thermal approach to tissue destruction. However, the fear of inducibility of cardiac arrhythmias (particular ventricular fibrillation) when using electroporation remains of concern due to membrane poration and ion flux during periods of vulnerability occurring in ventricular repolarization. Objectives: Critically examine the incidence of arrhythmias in a series of acute canine studies to retrospectively determine cause and safe electoporative dosing margins. Methods: We performed electroporation ablation in 6 acute canine studies. These were experimental studies performed at sites critical in arrhytmogenesis. Sites included the pulmonary veins, left atrial appendage, superior vena cavae, right atrium and ventricle. Electroporation was delivered using an ECG gating algorithm so that QRS complexes are tagged and direct current energy is not delivered during the vulnerable portion of the T wave. Results: In 6 acute canine experiments, we delivered a total of 62 electroporation applications for ablation purposes. The average electroporation dosage delivered involved an average of 1427 Volts (range 750-3000 V), Pulse length of 100 ms, and number of pulses of 20.2 (range 10-100). AF was induced in 27.4% of electroporiatve applications. Atrial flutter/tachycardia occurred in 8.1%. VF occurred in only one application at a location of the left superior pulmonary vein. Conclusion: These data suggest that induction of VF is relatively uncommon with ECG gating and highlight its importance when using this modality. However, the induction of AF occurs with higher frequency. The actual mechanism as to why this occurs requires further systematic study.

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