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Title: Absorber Materials at Room and Cryogenic Temperatures

Abstract

We recently reported on investigations of RF absorber materials at cryogenic temperatures conducted at Jefferson Laboratory (JLab). The work was initiated to find a replacement material for the 2 Kelvin low power waveguide Higher Order Mode (HOM) absorbers employed within the original cavity cryomodules of the Continuous Electron Beam Accelerator Facility (CEBAF). This effort eventually led to suitable candidates as reported in this paper. Furthermore, though constrained by small funds for labor and resources, we have analyzed a variety of lossy ceramic materials, several of which could be usable as HOM absorbers for both normal conducting and superconducting RF structures, e.g. as loads in cavity waveguides and beam tubes either at room or cryogenic temperatures and, depending on cooling measures, low to high operational power levels.

Authors:
Publication Date:
Research Org.:
Thomas Jefferson National Accelerator Facility, Newport News, VA (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1029324
Report Number(s):
JLAB-ACC-11-1442; DOE/OR/23177-1910
TRN: US1105736
DOE Contract Number:
AC05-06OR23177
Resource Type:
Conference
Resource Relation:
Conference: IPAC2011, 4-9 Sep 2011, San Sebastian, Spain
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; ACCELERATORS; CEBAF ACCELERATOR; CERAMICS; CRYOGENICS; ELECTRON BEAMS; WAVEGUIDES

Citation Formats

F. Marhauser, T.S. Elliott, A.T. Wu, E.P. Chojnacki, E. Savrun. Absorber Materials at Room and Cryogenic Temperatures. United States: N. p., 2011. Web.
F. Marhauser, T.S. Elliott, A.T. Wu, E.P. Chojnacki, E. Savrun. Absorber Materials at Room and Cryogenic Temperatures. United States.
F. Marhauser, T.S. Elliott, A.T. Wu, E.P. Chojnacki, E. Savrun. 2011. "Absorber Materials at Room and Cryogenic Temperatures". United States. doi:. https://www.osti.gov/servlets/purl/1029324.
@article{osti_1029324,
title = {Absorber Materials at Room and Cryogenic Temperatures},
author = {F. Marhauser, T.S. Elliott, A.T. Wu, E.P. Chojnacki, E. Savrun},
abstractNote = {We recently reported on investigations of RF absorber materials at cryogenic temperatures conducted at Jefferson Laboratory (JLab). The work was initiated to find a replacement material for the 2 Kelvin low power waveguide Higher Order Mode (HOM) absorbers employed within the original cavity cryomodules of the Continuous Electron Beam Accelerator Facility (CEBAF). This effort eventually led to suitable candidates as reported in this paper. Furthermore, though constrained by small funds for labor and resources, we have analyzed a variety of lossy ceramic materials, several of which could be usable as HOM absorbers for both normal conducting and superconducting RF structures, e.g. as loads in cavity waveguides and beam tubes either at room or cryogenic temperatures and, depending on cooling measures, low to high operational power levels.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = 2011,
month = 9
}

Conference:
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  • In the framework of the 12 GeV upgrade project for the Continuous Electron Beam Accelerator Facility (CEBAF) improvements are being made to refurbish cryomodules housing Thomas Jefferson National Accelerator Facility's (JLab) original 5-cell cavities. Recently we have started to look into a possible simplification of the existing Higher Order Mode (HOM) absorber design combined with the aim to find alternative material candidates. The absorbers are implemented in two HOM-waveguides immersed in the helium bath and operate at 2 K temperature. We have built a cryogenic setup to perform measurements on sample load materials to investigate their lossy characteristics and variationsmore » from room temperature down to 2 K. Initial results are presented in this paper.« less
  • Understanding the short term elastic properties, (i.e. the instantaneous modulus) of Kapton is essential in determining the loss of prestress during storage and operation of SSC dipole magnets. The magnet prestress contributes directly to the coil response to the Lorentz forces during ramping. The instantaneous modulus is important in extrapolating short term stress relaxation data to longer times. Most theoretical fits assume a time independent component and a time dependent component. The former may be represented by the Kapton modulus near zero K where all relaxation processes have been frozen'' out. Modulus measurements at 77K and 4.2K may point tomore » a correct value for the near zero K modulus. Three companion papers presented at this conference will be: Stress Relaxation in SSC 50 mm Dipole Coils'' Temperature Dependence of the Viscoelastic Properties of SSC Coil Insulation (Kapton)'' Theoretical Methods for Creep and Stress Relaxation Studies of SSC Coil.''« less
  • Understanding the short term elastic properties, (i.e. the instantaneous modulus) of Kapton is essential in determining the loss of prestress during storage and operation of SSC dipole magnets. The magnet prestress contributes directly to the coil response to the Lorentz forces during ramping. The instantaneous modulus is important in extrapolating short term stress relaxation data to longer times. Most theoretical fits assume a time independent component and a time dependent component. The former may be represented by the Kapton modulus near zero K where all relaxation processes have been ``frozen`` out. Modulus measurements at 77K and 4.2K may point tomore » a correct value for the near zero K modulus. Three companion papers presented at this conference will be: ``Stress Relaxation in SSC 50 mm Dipole Coils`` ``Temperature Dependence of the Viscoelastic Properties of SSC Coil Insulation (Kapton)`` ``Theoretical Methods for Creep and Stress Relaxation Studies of SSC Coil.``« less