Abstracts Brochure - CERN

MOPCH184
MOPCH185
26-Jun-06 16:00 - 18:00 MOPCH — Poster Session
successfully tested for PEP-II. Electromagnetic simulations are used to optimize different waveguide dimensions and
ensure ceramic matching in a T shaped, stainless steel copper plated waveguide configuration. Simulations suggest
the possibility of multipacting at different RF power levels and various corrective actions are considered (minimize
the ultrahigh vacuum and RF exposed surfaces, anti-multipacting ceramic coating, applying a second frequency as
perturbation factor). The option for a double ceramic window configuration is also analyzed. Coupler protection during
RF conditioning and cryomodule operation will be achieved with appropriate instrumentation (ceramic cooling,
rapid gauges and vacuum controllers, arc detectors, electron pickups, temperature sensors).
Electric Discharge Plasma Etching of Bulk Niobium for SRF Cavities
L. Vuskovic, S. Popovic, M. Raskovic (ODU) H.L. Phillips, A-M.
Valente-Feliciano (Jefferson Lab)
102
Cavity surface preparation has been one of
the major problems in superconducting radio-frequency
(SRF) accelerator technology.
Accelerator performance depends directly on
the physical and chemical characteristics at the SRF cavity surface. The primary objective of our work is to explore
the effects of various types of electric discharge plasmas to minimize surface roughness and eliminate or minimize
deterioration of cavity properties by oxygen, hydrogen and other chemical contaminants. To optimize the plasma
etching process, samples of bulk Nb are being exposed to three types of electrical discharge in various experimental
set-ups. The surface quality obtained by the three methods was compared with samples treated with buffer chemical
polishing techniques. Surface comparisons are made using digital imaging (optical) microscopy, scanning electron
microscopy, and atomic force microscopy. In preliminary tests, samples compared with those treated conventionally
have shown comparable or superior properties. Tests have also shown that surface quality varies with plasma
conditions and their optimization to obtain the best SRF cavity surface is a major goal of the ongoing work.
Superconducting RF Cavity Development at AES
J. Rathke, A. Ambrosio, H. Bluem, M.D. Cole, M. Falletta, D.
Holmes, E. Peterson, T. Schultheiss, A.M.M. Todd, R. Wong (AES)
We describe the status of several novel SRF
accelerator projects that are ongoing at Advanced
Energy Systems (AES). These include
a high-current, 704 MHz, 5-cell SRF cry-
omodule and SRF gun that are being developed in collaboration with Brookhaven National Laboratory and which will
form part of a ring that will test ERL operation up to 0.5A in 2007. This work supports electron cooling of RHIC. An
SRF booster cryomodule with three single cell 748.5 MHz cavities and a harmonic correction cavity is under assembly
at Jefferson Laboratory where it will be tested to 100 mA with a DC gun. A first-of-a-kind 9 cell high gradient, reentrant
shape cavity is under construction for Cornell University. This is the first multicell cavity built using this cell
shape. For ILC, AES is fabricating four 9-cell TESLA-type cavities for delivery to Fermilab in the fall of 2006. These
cavities are destined for use in one of the first "American built" cryomodules. As an outgrowth of RIA development
work over the last 5 years, AES is fabricating the niobium details for six quarter wave resonators to be used in the
ATLAS accelerator at Argonne National Lab.