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HOM damping performance of JLAB SL21 cryomodule

Conference ·
OSTI ID:824824
The new SL21 cryomodule is the first 70MeV, 8-cavity string superconducting accelerator module to be installed in CEBAF. Each cavity has 7-cells, the center cells have Mark II shape and the end cells have the Mark III shape. The HOM couplers resemble the DESY welded type; two of them assembled at one end of a cavity outside of tuner hub, with 115{sup o} azimuthal apart. There is a {lambda}/4 stub fundamental power waveguide at other end of cavity. The first two passbands of TE111 and TM110 modes have to be damped to avoid beam breakup (BBU) problem at 460{micro}A current. External Q's of the HOM couplers and waveguide were measured on a copper model, on cold niobium cavities and finally in the cryomodule test without beam. This paper presents all HOM data associated with this structure. A threshold current calculated by MATBBU based on the real beam optics and HOM spectrums will be discussed. This information will also benefit next or a high beam current FEL cryomodule HOM.
Research Organization:
Thomas Jefferson National Accelerator Facility, Newport News, VA (US)
Sponsoring Organization:
USDOE Office of Energy Research (ER) (US)
DOE Contract Number:
AC05-84ER40150
OSTI ID:
824824
Report Number(s):
JLAB-ACC-03-220; DOE/ER/40150-2728
Country of Publication:
United States
Language:
English

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