SRF2017 - List of Authors (Powers, T.)

Paper

Title

Page

Simulation and Measurements of Crab Cavity HOMs and HOM Couplers for HL-LHC

881

J.A. Mitchell, T.J. Jones
Lancaster University, Lancaster, United Kingdom
R. Apsimon, G. Burt, N.C. Shipman
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
I. Ben-Zvi, S. Verdú-Andrés, B. P. Xiao
BNL, Upton, Long Island, New York, USA
R. Calaga, A. Castilla, A. Macpherson, N.C. Shipman, A. Zwozniak
CERN, Geneva, Switzerland
T. Powers, H. Wang
JLab, Newport News, Virginia, USA
N.C. Shipman
UMAN, Manchester, United Kingdom

Two Superconducting Radio-Frequency (SRF) crab cavities are foreseen for the High Luminosity LHC (HL-LHC) upgrade. Preliminary beam tests of the Double Quarter Wave (DQW) crab cavity will take place in the Super Proton Synchrotron (SPS) in 2018. For damping of the cavity's Higher Order Modes (HOMs) the DQW has three identical on-cell, superconducting HOM couplers. The couplers are actively cooled by liquid heluim. In this paper, electromagnetic simulations of the HOMs and HOM couplers are presented. A novel approach to pre-installation spectral analysis of the HOM couplers is then presented, detailing both simulated and measured data. Measurements of the cavity HOMs at warm and in Vertical Test Facilities (VTFs) at both JLAB and CERN are detailed, comparing the measured characteristics of each mode to that of the simulated data-sets. Finally, the measured cavity data is compared with the test box measurements to see by what extent any reduction in damping can be predicted.

Poster THPB059 [8.192 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-THPB059

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FRXBA04

Analysis and Management of Microphonics in Operational SRF Cavities with Bandwidths of Approximately 10 Hz

T. Powers
JLab, Newport News, Virginia, USA

Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177.
Superconducting Radio Frequency Cavity detuning can be due to several effects. These effects include helium pressure variations, vibrations driven by external narrow band sources such as HVAC motors, cooling water systems, tuner motor operation, cryogenic system machinery, and occasionally cryogenic system instabilities such as thermo-acoustic oscillations. They can also be driven by broadband white or pink noise which, in general, will excite the resonant modes of the structure. All of these affect the cavity resonant frequency. Variations that occur at frequencies above a few tenths of a Hertz are considered microphonics. Jefferson Lab is the first lab to install and operate a large number of SRF cavities with relatively high loaded-Qs, 88 in CEBAF and 16 in the LERF. This work will focus on the approaches and measurements that one should consider when designing a system in order to understand the modal nature of the structure, the measurement techniques for determining the extent of the microphonics, and the mitigations that can be implemented in order to reduce the effects of outside perturbances. Examples of results at various other institutions will also be presented.

Slides FRXBA04 [6.842 MB]

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Paper	Title	Page
THPB059	Simulation and Measurements of Crab Cavity HOMs and HOM Couplers for HL-LHC	881
	J.A. Mitchell, T.J. Jones Lancaster University, Lancaster, United Kingdom R. Apsimon, G. Burt, N.C. Shipman Cockcroft Institute, Lancaster University, Lancaster, United Kingdom I. Ben-Zvi, S. Verdú-Andrés, B. P. Xiao BNL, Upton, Long Island, New York, USA R. Calaga, A. Castilla, A. Macpherson, N.C. Shipman, A. Zwozniak CERN, Geneva, Switzerland T. Powers, H. Wang JLab, Newport News, Virginia, USA N.C. Shipman UMAN, Manchester, United Kingdom
	Two Superconducting Radio-Frequency (SRF) crab cavities are foreseen for the High Luminosity LHC (HL-LHC) upgrade. Preliminary beam tests of the Double Quarter Wave (DQW) crab cavity will take place in the Super Proton Synchrotron (SPS) in 2018. For damping of the cavity's Higher Order Modes (HOMs) the DQW has three identical on-cell, superconducting HOM couplers. The couplers are actively cooled by liquid heluim. In this paper, electromagnetic simulations of the HOMs and HOM couplers are presented. A novel approach to pre-installation spectral analysis of the HOM couplers is then presented, detailing both simulated and measured data. Measurements of the cavity HOMs at warm and in Vertical Test Facilities (VTFs) at both JLAB and CERN are detailed, comparing the measured characteristics of each mode to that of the simulated data-sets. Finally, the measured cavity data is compared with the test box measurements to see by what extent any reduction in damping can be predicted.
	Poster THPB059 [8.192 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-THPB059
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

FRXBA04	Analysis and Management of Microphonics in Operational SRF Cavities with Bandwidths of Approximately 10 Hz
	T. Powers JLab, Newport News, Virginia, USA
	Funding: This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177. Superconducting Radio Frequency Cavity detuning can be due to several effects. These effects include helium pressure variations, vibrations driven by external narrow band sources such as HVAC motors, cooling water systems, tuner motor operation, cryogenic system machinery, and occasionally cryogenic system instabilities such as thermo-acoustic oscillations. They can also be driven by broadband white or pink noise which, in general, will excite the resonant modes of the structure. All of these affect the cavity resonant frequency. Variations that occur at frequencies above a few tenths of a Hertz are considered microphonics. Jefferson Lab is the first lab to install and operate a large number of SRF cavities with relatively high loaded-Qs, 88 in CEBAF and 16 in the LERF. This work will focus on the approaches and measurements that one should consider when designing a system in order to understand the modal nature of the structure, the measurement techniques for determining the extent of the microphonics, and the mitigations that can be implemented in order to reduce the effects of outside perturbances. Examples of results at various other institutions will also be presented.
	Slides FRXBA04 [6.842 MB]
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)