| Paper | Title | Page |
|---|
| TUP60 | High Power Input Couplers for the STF Baseline Cavity System at KEK | 270 |
| | - E. Kako, H. Hayano, S. Noguchi, T. Shishido, K. Watanabe, Y. Yamamoto
KEK
| |
| | An input coupler, which consists of a cold coupler and
a warm coupler, has two Tristan-type coaxial disk rf
windows. There is no tuning mechanism for varying
coupling for simplicity and cost reduction. Fabrication of
four input couplers was completed, and the rf
measurements with low rf power were carried out. The
input couplers were assembled with coupling waveguides
and doorknob-type transitions, and they were installed in
a high power rf system. High power tests of four input
couplers were carried out in the test stand with a 5 MW
pulsed klystron. Rf processing up to 1.0 MW in a 1.5
msec and 5 Hz operation (1.9 MW in a short pulse) was
successfully performed without any troubles. One cavity
for the STF Phase-0.5 was assembled with an input
coupler and a tuning system, and the cavity was installed
in one of the 6m-cryomodules. Rf processing of the input
coupler in the cryomodule was carried out at room
temperature up to 250 kW in a 1.5 msec step pulse and 5
Hz operation. First cool-down and high power test of the
cryomodule had been started in October, 2007. | |
| WEP10 | Vertical test results on the STF baseline 9-cell cavities at KEK | 453 |
| | - E. Kako, H. Hayano, S. Noguchi, T. Shishido, K. Umemori, K. Watanabe, Y. Yamamoto
KEK - H. Sakai, K. Shinoe
ISSP, Univ. of Tokyo - S. I. Moon
POSTECH - Q. J. Xu
IHEP, CAS
| |
| | The STF-Baseline superconducting cavity system,
which includes four TESLA-type 9-cell cavities, input
couplers and frequency tuners, has been developed for the
future ILC project. A main improvement in the cavity
system is a very stiff design in a He vessel and a cavity
tuning system, which can relax a cavity deformation due
to Lorentz force. Making clear the performance level of
four 9-cell cavities, which were fabricated by a Japanese
company and were prepared by existent infrastructures at
KEK, is the most important purpose in the whole vertical
test. Total 14 vertical tests on four 9-cell cavities were
carried out repeatedly. The obtained Eacc,max in the final
performance was 29.4 MV/m in the #2 cavity, and the
others are 20.8, 20.5 and 20.2 MV/m, where the Qo
values higher than 1x1010 was achieved in all cavities.
Peculiar phenomena, like increasing of Qo values with
higher Eacc or very slow degradation of Qo values, were
observed in the vertical tests. Summary of the vertical test
results on four 9-cell cavities is described in this paper. | |
| WEP13 | Cavity diagnostic system for the vertical test of the baseline SC cavity in KEK-STF | 464 |
| | - Y. Yamamoto, H. Hayano, E. Kako, S. Noguchi, T. Shishido, K. Umemori, K. Watanabe
KEK - H. Sakai, K. Shinoe
ISSP, Univ. of Tokyo - S. I. Moon
POSTECH - Q. J. Xu
IHEP, CAS
| |
| | Four STF-Baseline superconducting cavities were
fabricated from 2005 to 2006. They were named BL1, 2,
3 and 4. The feature is that these cavities have the stiffer
structure than TESLA cavity. From Feb/2006 to Feb/2007,
the vertical tests were done totally 14 times at KEK.
These cavities were re-processed and measured
repeatedly. The surface treatment processes are composed
of Centrifugal Barrel Polish (CBP), Electro-Polish (EP)
and High Pressure Rinsing (HPR). And, HF or H2O2
rinsing were added as the additional process later.
In the vertical tests, a monitoring system was
introduced to search the heating spot on the equator and
to check the radiation level around the cavity. It is
composed of the carbon resistors and the PIN photo
diodes. They were attached on the equator of each cell
every 90 degree, a few resistors around the HOM couplers and a
few diodes on the top and bottom flanges of the cavity.
MX-100 (YOKOGAWA) for the carbon resistors and
NR-1000 (KEYENCE) for the PIN photo diodes are used
as the data logger. The sampling time is 100 or 200msec.
The heating spot was successfully observed during the
test. The appearance of that on the equator was coincident
with the quench of the cavity. On the other hand, the
diodes were useful for checking the presence or absence
of the field emission and they also were useful for
monitoring the radiation level during the RF processing.
The mapping display was introduced to identify the
location. Consequently, it is conceivable that the quality
of the electron beam welding was somewhat poor, when
the dumbbells were connected. | |
| WEP30 | New HOM coupler design for ERL injector at KEK | 530 |
| | - K. Watanabe, H. Hayano, S. Noguchi, E. Kako, T. Shishido
KEK
| |
| | The development of superconducting cavities and
cavity package for ILC and ERL project is under way at
STF (Superconducting RF Test Facility) in KEK. The
TESLA-style coaxial HOM couplers have a problem at
CW operation, which it is pick-up probe and inner
conductor heating of HOM coupler.
The pick-up probe heating was observed at vertical tests.
The probe heating study for CW operation (changing
pick-up probe geometry and probe gap) tried at vertical
tests by using the KEK STF Baseline 1.3 GHz 9-cell
superconducting cavity, and simulated by using HFSS
code ver9.1 for estimate the relation of the limit E-field of
probe heating and the probe surface current.
The design of proto-type coaxial HOM couplers of CW
operation for ERL-injector at KEK was tried based on this
information. The probe heating is generated due to the
probe surface current by the RF load of accelerating mode.
Therefore, as one method, it can be controlled if the RF
load of accelerating mode is reduced by putting the high
pass filter between the coupling loop and the notch filter.
In addition, the target beam current of ERL is about
100mA, therefore, we were considered that the cooling of
inner conductor of HOM coupler by liquid He. It is
necessary to be expected the heating of inner conductor
by RF load of accelerating mode and HOM power of
excited in the beam. The design was held based on these.
In this report, a design of HOM coupler for ERLinjector
at KEK is presented. | |