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Title: HOM identification by bead pulling in the Brookhaven ERL cavity

Abstract

Several past measurements of the Brookhaven ERL at superconducting temperature produced a long list of higher order modes (HOMs). The Niobium 5-cell cavity is terminated with HOM ferrite dampers that successfully reduce the Q-factors to tolerable levels. However, a number of undamped resonances with Q {ge} 10{sup 6} were found at 4 K and their mode identification remained as a goal for this paper. The approach taken here consists in taking different S{sub 21} measurements on a copper cavity replica of the ERL which can be compared with the actual data and also with Microwave Studio computer simulations. Several different S{sub 21} transmission measurements are used, including those taken from the fundamental input coupler to the pick-up probe across the cavity, between probes in a single cell, and between beam-position monitor probes in the beam tubes. Mode identification is supported by bead pulling with a metallic needle or a dielectric sphere that are calibrated in the fundamental mode. This paper presents results for HOMs in the first two dipole bands with the prototypical 958 MHz trapped mode, the lowest beam tube resonances, and high-Q modes in the first quadrupole band and beyond.

Authors:
; ; ; ;
Publication Date:
Research Org.:
BROOKHAVEN NATIONAL LABORATORY (BNL)
Sponsoring Org.:
USDOE SC OFFICE OF SCIENCE (SC)
OSTI Identifier:
1048208
Report Number(s):
BNL-98176-2012-CP
R&D Project: KBCH139; 18074; KB0202011; TRN: US1204153
DOE Contract Number:  
DE-AC02-98CH10886
Resource Type:
Conference
Resource Relation:
Conference: International Workshop on Higher Order Mode Diagnostics and Suppression in SC Cavities (HOMSC12); Daresbury, UK; 20120625 through 20120627
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 43 PARTICLE ACCELERATORS; BEAM POSITION; CAVITIES; COMPUTERIZED SIMULATION; COPPER; DIELECTRIC MATERIALS; DIPOLES; FERRITE; MONITORS; NIOBIUM; PROBES; QUADRUPOLES; REPLICAS

Citation Formats

Hahn H., Calaga, R., Jain, P., Johnson, E.C., and Xu, W. HOM identification by bead pulling in the Brookhaven ERL cavity. United States: N. p., 2012. Web.
Hahn H., Calaga, R., Jain, P., Johnson, E.C., & Xu, W. HOM identification by bead pulling in the Brookhaven ERL cavity. United States.
Hahn H., Calaga, R., Jain, P., Johnson, E.C., and Xu, W. Mon . "HOM identification by bead pulling in the Brookhaven ERL cavity". United States. https://www.osti.gov/servlets/purl/1048208.
@article{osti_1048208,
title = {HOM identification by bead pulling in the Brookhaven ERL cavity},
author = {Hahn H. and Calaga, R. and Jain, P. and Johnson, E.C. and Xu, W.},
abstractNote = {Several past measurements of the Brookhaven ERL at superconducting temperature produced a long list of higher order modes (HOMs). The Niobium 5-cell cavity is terminated with HOM ferrite dampers that successfully reduce the Q-factors to tolerable levels. However, a number of undamped resonances with Q {ge} 10{sup 6} were found at 4 K and their mode identification remained as a goal for this paper. The approach taken here consists in taking different S{sub 21} measurements on a copper cavity replica of the ERL which can be compared with the actual data and also with Microwave Studio computer simulations. Several different S{sub 21} transmission measurements are used, including those taken from the fundamental input coupler to the pick-up probe across the cavity, between probes in a single cell, and between beam-position monitor probes in the beam tubes. Mode identification is supported by bead pulling with a metallic needle or a dielectric sphere that are calibrated in the fundamental mode. This paper presents results for HOMs in the first two dipole bands with the prototypical 958 MHz trapped mode, the lowest beam tube resonances, and high-Q modes in the first quadrupole band and beyond.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2012},
month = {6}
}

Conference:
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