Mechanical design upgrade of the APS storage ring rf cavity tuner Page: 1 of 5
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MECHANICAL DESIGN UPGRADE OF THE APS STORAGE RING RF
CAVITY TUNER coW F- F 70 503
J. Jones, D. Bromberek, Y. Kang, R. Kustom, L. Morrison, R. Piech, E. Rotela, 'AI
S. Sharma, I.C. Sheng.
Advanced Photon Source, Argonne National Laboratory
9700 South Cass Avenue, Argonne, Illinois 60439 USA
The Advanced Photon Source (APS) storage ring (SR)
rf system employs four banks of four spherical, single-cell
resonant cavities. Each cavity is tuned by varying the cav-
ity volume through insertion/retraction of a copper piston
located at the circumference of the cavity and oriented per-
pendicular to the accelerator beam. During the commis-
sioning of the APS SR, the tuners and cavity tuner ports
were prone to extensive arcing and overheating. The exist-
ing tuners were modified to eliminate the problems, and
two new, redesigned tuners were installed. In both cases
marked improvements were obtained in the tuner mechani-
cal performance. As measured by tuner piston and flange
surface temperatures, tuner heating has been reduced by a
factor of five in the new version. Redesign considerations
discussed include tuner piston-to-housing alignment, tuner
piston and housing materials and cooling configurations,
and tuner piston sliding electrical contacts. The tuner rede-
sign is also distinguished by a modular, more maintainable
The APS SR rf cavity tuners have been redesigned to
improve mechanical and vacuum performance while main-
taining consistent rf performance. The tuner consists of a
moveable piston that is inserted/retracted into the 352-
MHz spherical cavity, thus changing the volume and the
frequency of the resonant cavity. The approximate size of
the components are as follows: the rf cavity radius is 13
inches, the tuner piston radius is 2.75 inches, and the over-
all length of the tuner is 25 inches. The piston, housing,
electrical contacts, bellows, and drive have all been rede-
signed. The piston diameter and motorized drive perfor-
mance have been maintained to allow consistent rf
feedback and controls. Diagnostic thermocouples have
been added to the tuner piston within the vacuum housing
and to the exterior of the piston housing mounting flange
to monitor tuner temperatures for interlock and perfor-
mance logging purposes. Figure 1 is a section drawing of
the tuner assembly highlighting major design features. The
tuner piston is shown in the approximate cavity-tuned
WATER RETURN VACUUM BRAZE JOINT
PISTON THERMOCOUPLES FEEDTHROUGH OOLD PLATED HOUSING SURFACE
a. ~HOUSING THERMOCOUPLES LOCATION
PISTON THERMOCOUPLES LOCATION r- SINGLE CELL CAVITY PORT
-. . - . -
MODULAR PISTON DRIVE
SECONDARY CONTACT FINGERS ,OPTIONAL,
PRIMARY CONTACr FINGERS-
TAPERED PISTON END HOUSING
- HOUSING CLING CHANNEL
Figure 1: APS storage ring rf cavity tuner.
DiSTR OF THis DOmC t is U iNLmTED
The submitted manuscript has been created by the universityy of Chicago as Operator of Argonne National Laboratory ("Argonne") under Contrct No. W-31 -109-ENG-38
with the U.S. Department of Energy. The U.S. Go emment retains for itself, and others acting on its behalf, a paid-up. nonexclusive. irrevocable worldwide license in said
article to reproduce, prepare derivative works, distrbute copies to the public. and perform publicly and display publicly, by or on behalf of the Government.
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Jones, J.; Bromberek, D. & Kang, Y. Mechanical design upgrade of the APS storage ring rf cavity tuner, article, August 1, 1997; Illinois. (https://digital.library.unt.edu/ark:/67531/metadc699025/m1/1/: accessed March 25, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.