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Title: RF Breakdown in Normal Conducting Single-Cell Structures

Abstract

Operating accelerating gradient in normal conducting accelerating structures is often limited by rf breakdown. The limit depends on multiple parameters, including input rf power, rf circuit, cavity shape and material. Experimental and theoretical study of the effects of these parameters on the breakdown limit in full scale structures is difficult and costly. We use 11.4 GHz single-cell traveling wave and standing wave accelerating structures for experiments and modeling of rf breakdown behavior. These test structures are designed so that the electromagnetic fields in one cell mimic the fields in prototype multicell structures for the X-band linear collider. Fields elsewhere in the test structures are significantly lower than that of the single cell. The setup uses matched mode converters that launch the circular TM{sub 01} mode into short test structures. The test structures are connected to the mode launchers with vacuum rf flanges. This setup allows economic testing of different cell geometries, cell materials and preparation techniques with short turn-around time. Simple 2D geometry of the test structures simplifies modeling of the breakdown currents and their thermal effects.

Authors:
; ; ; ; ; ;
Publication Date:
Research Org.:
Stanford Linear Accelerator Center (SLAC)
Sponsoring Org.:
USDOE
OSTI Identifier:
876600
Report Number(s):
SLAC-PUB-11707
TRN: US0601254
DOE Contract Number:
AC02-76SF00515
Resource Type:
Conference
Resource Relation:
Conference: Particle Accelerator Conference (PAC 05), Knoxville, Tennessee, 5/16/2005-5/20/2005
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; ACCELERATORS; BREAKDOWN; ECONOMICS; ELECTROMAGNETIC FIELDS; FLANGES; GEOMETRY; LINEAR COLLIDERS; SHAPE; SIMULATION; STANDING WAVES; TEMPERATURE DEPENDENCE; TESTING; Accelerators,ACCPHY

Citation Formats

Dolgashev, V.A., Nantista, C.D., Tantawi, S.G., /SLAC, Higashi, Y., Higo, T., and /KEK, Tsukuba. RF Breakdown in Normal Conducting Single-Cell Structures. United States: N. p., 2006. Web.
Dolgashev, V.A., Nantista, C.D., Tantawi, S.G., /SLAC, Higashi, Y., Higo, T., & /KEK, Tsukuba. RF Breakdown in Normal Conducting Single-Cell Structures. United States.
Dolgashev, V.A., Nantista, C.D., Tantawi, S.G., /SLAC, Higashi, Y., Higo, T., and /KEK, Tsukuba. 2006. "RF Breakdown in Normal Conducting Single-Cell Structures". United States. doi:. https://www.osti.gov/servlets/purl/876600.
@article{osti_876600,
title = {RF Breakdown in Normal Conducting Single-Cell Structures},
author = {Dolgashev, V.A. and Nantista, C.D. and Tantawi, S.G. and /SLAC and Higashi, Y. and Higo, T. and /KEK, Tsukuba},
abstractNote = {Operating accelerating gradient in normal conducting accelerating structures is often limited by rf breakdown. The limit depends on multiple parameters, including input rf power, rf circuit, cavity shape and material. Experimental and theoretical study of the effects of these parameters on the breakdown limit in full scale structures is difficult and costly. We use 11.4 GHz single-cell traveling wave and standing wave accelerating structures for experiments and modeling of rf breakdown behavior. These test structures are designed so that the electromagnetic fields in one cell mimic the fields in prototype multicell structures for the X-band linear collider. Fields elsewhere in the test structures are significantly lower than that of the single cell. The setup uses matched mode converters that launch the circular TM{sub 01} mode into short test structures. The test structures are connected to the mode launchers with vacuum rf flanges. This setup allows economic testing of different cell geometries, cell materials and preparation techniques with short turn-around time. Simple 2D geometry of the test structures simplifies modeling of the breakdown currents and their thermal effects.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = 2006,
month = 2
}

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  • We report the results of the first high power tests of single-cell traveling-wave and standing-wave structures. These tests are part of an experimental and theoretical study of rf breakdown in normal conducting structures at 11.4 GHz. The goal of this study is to determine the gradient potential of normal-conducting rf-powered particle beam accelerators. The test setup consists of reusable mode converters and short test structures and is powered by SLAC's XL-4 klystron. This setup was created for economical testing of different cell geometries, cell materials and preparation techniques with short turn-around time. The mode launchers and structures were manufactured atmore » SLAC and KEK and tested in the SLAC Klystron Test Lab.« less
  • We report the results of ongoing high power tests of single-cell standing wave structures. These tests are part of an experimental and theoretical study of rf breakdown in normal conducting structures at 11.4 GHz. The goal of this study is to determine the maximum gradient possibilities for normal-conducting rf powered particle beam accelerators. The test setup consists of reusable mode launchers and short test structures powered by SLACs XL-4 klystron. The mode launchers and structures were manufactured at SLAC and KEK and tested at the SLAC klystron test laboratory.
  • Our experiments are directed toward the understanding of the physics of rf breakdown in systems that can be used to accelerate electron beams at {approx}11.4 GHz. The structure geometries have apertures, stored energy per cell, and rf pulse duration close to that of the NLC or CLIC. The breakdown rate is the main parameter that we use to compare rf breakdown behavior for different structures at a given set of rf pulse parameters (pulse shape and peak power) at 60 Hz repetition rate. In our experiments, the typical range of the breakdown rate is from one per few hours tomore » {approx}100 per hour. To date we have tested 29 structures. We consistently found that after the initial conditioning, the behavior of the breakdown rate is reproducible for structures of the same geometry and material, and the breakdown rate dependence on peak magnetic fields is stronger than on peak surface electric fields for structures of different geometries. Below we report the main results from tests of seven structures made from hard copper, soft copper alloys and hard-copper alloys. Additional details on these and other structures will be discussed in future publications.« less
  • The operating accelerating gradient in normal conducting accelerating structures is often limited by rf breakdown. The behavior of the rf breakdown depends on multiple parameters, including the input rf power, rf circuit, cavity shape and material. Here we discuss recent experimental data and theoretical studies of rf breakdown physics.