Abstracts Brochure - CERN

MOPCH — Poster Session 26-Jun-06 16:00 - 18:00
Optimization of the BCP Processing of Elliptical Nb SRF Cavities
Bulk niobium (Nb) electropolished SRF cavities
performing at or above 35 MV/m is an
aggressive goal recently put forth by the International
Linear Collider (ILC) collabora-
C. Boffo, C. A. Cooper, A.M. Rowe (Fermilab) G. Galasso (University
of Udine)
tion. Buffered chemical polishing (BCP) is still the most cost effective and least complex processing technique known
today to optimize the surface properties of high gradient single crystal and relatively low gradient polycrystalline
SRF cavities. BCP will be the preferred chemical process in the production of the nine-cell third harmonic 3.9 GHz
cavities at Fermilab. The internal shape of these cavities will result in uneven material removal rates between iris and
equator of the cells. We will describe a thermal-fluid finite element model adopted to simulate the etching process,
and thus revealing the issues at hand. Experimental work, such as flow visualization tests performed to verify the
simulation, will also be discussed. Finally we are presenting results obtained with a novel device, which allows to
homogenize the flow pattern and to resolve the problem.
High Power Testing RF System Components for the Cornell ERL Injector
There are two high power 1300 MHz RF
systms under development for the Cornell
University ERL Injector. The first system,
based on a 16 kWCW IOT transmitter, will
provide RF power to a buncher cavity. The
S.A. Belomestnykh, R.P.K. Kaplan, M. Liepe, P. Quigley, J.J.R. Reilly,
V. Veshcherevich (Cornell University, Laboratory for Elementary-
Particle Physics)
second system employs five 120 kWCW klystrons to feed 2-cell superconducting cavities of the injector cryomodule.
All components of these systems were ordered and some have already been delivered, including the IOT transmitter
(manufactured by Thales-BM), 20 kWCW AFT circulator, 170 kWCW circulators (Ferrite Co.) and two prototype input
couplers for superconducting cavities. A special LN2 cryostat has been designed and built for testing/processing the
input couplers. The results of the first high-power tests are presented.
High Field Q-slope Studies Using Thermometry
An important limitation for SRF niobium
cavities is a high field Q-slope. In investigation
of this problem we use a thermometry
system. It allows us to distinguish between
G.V. Eremeev (Cornell University, Laboratory for Elementary-Particle
Physics)
different problems, which occur during cavity testing, and distinguish between different areas showing high field Qslope.
We have found interesting correlations between high field slope measured with thermometry readings and the
thermometer locations in magnetic field, electric field and weld regions of the cavity. Also we have found changes in
the Q-slope with "in-situ" baking and grain size.
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