skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: RF breakdown and high gradient limits.

Abstract

A number of recent papers describing a model of breakdown and high gradient limits should be directly applicable to all rf and DC applications. Although based on low frequency rf measurements, the model can explain and reproduce the effects of a wide range of variables, (B fields, gas pressure, materials, breakdown rate dependence on electric fields, frequency and pulse length, etc.), and also some superconducting rf behavior. Highlights of this program include: the highest accelerating gradients ever recorded, new models of breakdown and high gradient operation that seem to explain all high gradient behavior, and new technology for surface measurement and control.

Authors:
;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
973763
Report Number(s):
ANL-HEP-CP-06-66
TRN: US1002028
DOE Contract Number:
DE-AC02-06CH11357
Resource Type:
Conference
Resource Relation:
Conference: 12th Advanced Accelerator Concepts Workshop; Jul. 10, 2006 - Jul. 15, 2006; Lake Geneva, WI
Country of Publication:
United States
Language:
ENGLISH
Subject:
43 PARTICLE ACCELERATORS; ACCELERATORS; BREAKDOWN; ELECTRIC FIELDS

Citation Formats

Norem, J., and High Energy Physics. RF breakdown and high gradient limits.. United States: N. p., 2006. Web. doi:10.1063/1.2409155.
Norem, J., & High Energy Physics. RF breakdown and high gradient limits.. United States. doi:10.1063/1.2409155.
Norem, J., and High Energy Physics. Sun . "RF breakdown and high gradient limits.". United States. doi:10.1063/1.2409155.
@article{osti_973763,
title = {RF breakdown and high gradient limits.},
author = {Norem, J. and High Energy Physics},
abstractNote = {A number of recent papers describing a model of breakdown and high gradient limits should be directly applicable to all rf and DC applications. Although based on low frequency rf measurements, the model can explain and reproduce the effects of a wide range of variables, (B fields, gas pressure, materials, breakdown rate dependence on electric fields, frequency and pulse length, etc.), and also some superconducting rf behavior. Highlights of this program include: the highest accelerating gradients ever recorded, new models of breakdown and high gradient operation that seem to explain all high gradient behavior, and new technology for surface measurement and control.},
doi = {10.1063/1.2409155},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}

Conference:
Other availability
Please see Document Availability for additional information on obtaining the full-text document. Library patrons may search WorldCat to identify libraries that hold this conference proceeding.

Save / Share:
  • A number of recent papers describing a model of breakdown and high gradient limits should be directly applicable to all rf and DC applications. Although based on low frequency rf measurements, the model can explain and reproduce the effects of a wide range of variables (B fields, gas pressure, materials, breakdown rate dependence on electric fields, frequency and pulse length, etc.), and also some superconducting rf behavior. Highlights of this program include: the highest accelerating gradients ever recorded, new models of breakdown and high gradient operation that seem to explain all high gradient behavior, and new technology for surface measurementmore » and control.« less
  • Stanford Linear Accelerator Center and UC Davis have been investigating high gradient RF breakdown and its effects on pulse shortening in high energy microwave devices. RF breakdown is a critical issue in the development of high power microwave sources and next generation linear accelerators since it limits the output power of microwave sources and the accelerating gradient of linacs. The motivation of this research is to find methods to increase the breakdown threshold level in X-band structures by reducing dark current. Emphasis is focused on improved materials, surface finish, and cleanliness. The test platform for this research is a travelingmore » wave resonant ring. A 30 MW klystron is employed to provide up to 300 MW of traveling wave power in the ring to trigger breakdown in the cavity. Five TM{sub 01} cavities have previously been tested, each with a different combination of surface polish and/or coating. The onset of breakdown was extended up to 250 MV/m with a TiN surface finish, as compared to 210 MV/m for uncoated OFE copper. Although the TiN coating was helpful in depressing the field emission, the lowest dark current was obtained with a 1 {micro}inch surface finish, single-point diamond-turned cavity.« less
  • The authors are developing techniques for processing the high gradient (75MV/m) X-band accelerating structures for the NLC. Accelerometers attached to the structures detect surprisingly large acoustic signals believed to be due to RF heating. On a pulse that causes breakdown, these signals increase substantially, producing up to 50 G accelerations at >20KHz. The timing and amplitude of these acoustic signals can provide information on the location and mechanism of the breakdowns.
  • The paper describes voltage break down phenomenon and preventive measures in components of 250 KW CW, C band Klystron under development at CEERI Pilani. The Klystron operates at a beam voltage of 50 kV and delivers 250 kW RF power at 5 GHz frequency. The Klystron consists of several key components and regions, which are subject to high electrical stress. The most important regions of electrical breakdown are electron gun, the RF ceramic window and output cavity gap area. In the critical components voltage breakdown considered at design stage by proper gap and other techniques. All these problems discussed, asmore » well as solution to alleviate this problem. The electron gun consists basically of cathode, BFE and anode. The cathode is operated at a voltage of 50 kV. In order to maintain the voltage standoff between cathode and anode a high voltage alumina seal and RF window have been designed developed and successfully used in the tube. (author)« less
  • RF breakdown is one of the major factors determining performance of high power rf components and rf sources. RF breakdown limits working power and produces irreversible surface damage. The breakdown limit depends on the rf circuit, structure geometry, and rf frequency. It is also a function of the input power, pulse width, and surface electric and magnetic fields. In this paper we discuss multi-megawatt operation of X-band rf structures at pulse width on the order of one microsecond. These structures are used in rf systems of high gradient accelerators. Recent experiments at Stanford Linear Accelerator Center (SLAC) have explored themore » functional dependence of breakdown limit on input power and pulse width. The experimental data covered accelerating structures and waveguides. Another breakdown limit of accelerating structures was associated with high magnetic fields found in waveguide-to-structure couplers. To understand and quantify these limits we simulated 3D structures with the electrodynamics code Ansoft HFSS and the Particle-In-Cell code MAGIC3D. Results of these simulations together with experimental data will be discussed in this paper.« less