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Title: High gradient tests of metallic mm-wave accelerating structures

Abstract

This study explores the physics of vacuum rf breakdowns in high gradient mm-wave accelerating structures. We performed a series of experiments with 100 GHz and 200 GHz metallic accelerating structures, at the Facility for Advanced Accelerator Experimental Tests (FACET) at the SLAC National Accelerator Laboratory. This paper presents the experimental results of rf tests of 100 GHz travelling-wave accelerating structures, made of hard copper-silver alloy. The results are compared with pure hard copper structures. The rf fields were excited by the FACET ultra-relativistic electron beam. The accelerating structures have open geometries, 10 cm long, composed of two halves separated by a variable gap. The rf frequency of the fundamental accelerating mode depends on the gap size and can be changed from 90 GHz to 140 GHz. The measured frequency and pulse length are consistent with our simulations. When the beam travels off-axis, a deflecting field is induced in addition to the decelerating longitudinal field. We measured the deflecting forces by observing the displacement of the electron bunch and used this measurement to verify the expected accelerating gradient. We present the first quantitative measurement of rf breakdown rates in 100 GHz copper-silver accelerating structure, which was 10 –3 per pulse, withmore » peak electric field of 0.42 GV/m, an accelerating gradient of 127 MV/m, at a pulse length of 2.3 ns. The goal of our studies is to understand the physics of gradient limitations in order to increase the energy reach of future accelerators.« less

Authors:
 [1];  [1];  [1];  [1];  [1];  [1];  [1];  [1];  [2];  [1];  [1]
  1. SLAC National Accelerator Lab., Menlo Park, CA (United States)
  2. INFN/LNF Frascati, Roma (Italy)
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1375441
Report Number(s):
SLAC-PUB-17104
Journal ID: ISSN 0168-9002; PII: S0168900217305557; TRN: US1702561
Grant/Contract Number:  
AC02-76SF00515
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Nuclear Instruments and Methods in Physics Research. Section A, Accelerators, Spectrometers, Detectors and Associated Equipment
Additional Journal Information:
Journal Volume: 864; Journal Issue: C; Journal ID: ISSN 0168-9002
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS

Citation Formats

Dal Forno, Massimo, Dolgashev, Valery, Bowden, Gordon, Clarke, Christine, Hogan, Mark, McCormick, Doug, Novokhatski, Alexander, O'Shea, Brendan, Spataro, Bruno, Weathersby, Stephen, and Tantawi, Sami G. High gradient tests of metallic mm-wave accelerating structures. United States: N. p., 2017. Web. doi:10.1016/j.nima.2017.05.014.
Dal Forno, Massimo, Dolgashev, Valery, Bowden, Gordon, Clarke, Christine, Hogan, Mark, McCormick, Doug, Novokhatski, Alexander, O'Shea, Brendan, Spataro, Bruno, Weathersby, Stephen, & Tantawi, Sami G. High gradient tests of metallic mm-wave accelerating structures. United States. doi:10.1016/j.nima.2017.05.014.
Dal Forno, Massimo, Dolgashev, Valery, Bowden, Gordon, Clarke, Christine, Hogan, Mark, McCormick, Doug, Novokhatski, Alexander, O'Shea, Brendan, Spataro, Bruno, Weathersby, Stephen, and Tantawi, Sami G. Wed . "High gradient tests of metallic mm-wave accelerating structures". United States. doi:10.1016/j.nima.2017.05.014. https://www.osti.gov/servlets/purl/1375441.
@article{osti_1375441,
title = {High gradient tests of metallic mm-wave accelerating structures},
author = {Dal Forno, Massimo and Dolgashev, Valery and Bowden, Gordon and Clarke, Christine and Hogan, Mark and McCormick, Doug and Novokhatski, Alexander and O'Shea, Brendan and Spataro, Bruno and Weathersby, Stephen and Tantawi, Sami G.},
abstractNote = {This study explores the physics of vacuum rf breakdowns in high gradient mm-wave accelerating structures. We performed a series of experiments with 100 GHz and 200 GHz metallic accelerating structures, at the Facility for Advanced Accelerator Experimental Tests (FACET) at the SLAC National Accelerator Laboratory. This paper presents the experimental results of rf tests of 100 GHz travelling-wave accelerating structures, made of hard copper-silver alloy. The results are compared with pure hard copper structures. The rf fields were excited by the FACET ultra-relativistic electron beam. The accelerating structures have open geometries, 10 cm long, composed of two halves separated by a variable gap. The rf frequency of the fundamental accelerating mode depends on the gap size and can be changed from 90 GHz to 140 GHz. The measured frequency and pulse length are consistent with our simulations. When the beam travels off-axis, a deflecting field is induced in addition to the decelerating longitudinal field. We measured the deflecting forces by observing the displacement of the electron bunch and used this measurement to verify the expected accelerating gradient. We present the first quantitative measurement of rf breakdown rates in 100 GHz copper-silver accelerating structure, which was 10–3 per pulse, with peak electric field of 0.42 GV/m, an accelerating gradient of 127 MV/m, at a pulse length of 2.3 ns. The goal of our studies is to understand the physics of gradient limitations in order to increase the energy reach of future accelerators.},
doi = {10.1016/j.nima.2017.05.014},
journal = {Nuclear Instruments and Methods in Physics Research. Section A, Accelerators, Spectrometers, Detectors and Associated Equipment},
number = C,
volume = 864,
place = {United States},
year = {Wed May 10 00:00:00 EDT 2017},
month = {Wed May 10 00:00:00 EDT 2017}
}

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