KEK, Ibaraki
We have successfully made high power test with a LL cavity package in the STF0.5 program at KEK in January to March 2008. One LL cavity package was installed in a cryomodule which could include four packages maximum. This module has been successfully operated at 15-18MV/m. In this paper, we will report the results on the cavity performance, high power capacitive coupled input coupler performance and Lorenz detuning compensated piezo tuner and ball screw mechanical tuner.
KEK, Ibaraki
Tokyo Denkai Co., Ltd., Tokyo
The promising cavity performance has been confirmed on the niobium large grain cavity at many laboratories: Jlab, DESY, and IHEP/KEK in last 4 years R&D. The gradient over 35MV/m can be expected. The niobium materials for these cavity fabrications were sliced by EDM or combination of sawing and surface machining, which are rather expensive and no way for massive production like ILC. We have developed multi-wire slicing method applying silicon wafer technology. This technology could produce 150 circular sheets in 45 hrs with very smooth surface. So far we demonstrated 60 sheets slicing in 45hrs. Next 100 sheets slicing is under way. In this talk we will present the results and some result on the cavity test fabricated this slice materials.
KEK, Ibaraki
Fermilab, Batavia
JLAB, Newport News, Virginia
We have continued high gradient R&D of ICHIRO 9-cell cavities at KEK. ICHIRO 9-cell cavity #5 (I9#5) that has no end groups on beam tube to focus on high gradient sent to Jlab as S0 tight loop study. Surface treatments and vertical test were repeated 3 times at Jlab, and then I9#5 sent back to KEK. We also repeated surface treatments and test at KEK. Maximum gradients were 36.5MV/m at Jlab, and 33.7MV/m at KEK so far. Now we are struggling with the puzzle why the results of singles do not work well on 9-cell cavities.
KEK, Ibaraki
Field flatness of ICHIRO 9-cell cavities was often degraded <70% after vertical test though it was tuned >96% before surface preparations. In order to find which process degrades flatness, we checked it at each step between EP processes to vertical test. By improving cavity jig and jig fittings, degradation of flatness was prevented <1% during jig fittings, transportations, handlings, surface rinsing and vertical tests. EP processes still degrade flatness about 5%. To cure this, we tried pri-tuning again after EP processes, then rinsed and measured. Gradient reached 33.7MV/m. Flatness of 94% was kept during this measurement. This procedure seems have no problem for cavity performance. Flatness level of >96% is in hand now. We are investigating why EP processes degrade flatness and how to prevent it.
KEK, Ibaraki
ICHIRO end single cell cavities that have HOM coupler and high power RF input port on beam tube did not reach high gradient of >40MV/m with our high yield surface preparation recipe for center cell shape singles. Gradients were limited around 18-33MVm by field emissions. For the complicate structures like HOM coupler, sulfur contaminations produced during EP processes seem sticky and hard to remove only by degreasing and HPR. We tried ethanol rinsing which can dissolve sulfur after EP process. We also tried aggressive rinsing of wiping with degreaser to remove contaminations mechanically. End single cell cavity with HOM coupler reached 48MV/m so far by modified recipe that include ethanol rinsing and wiping.
KEK, Ibaraki
Different material joint is a key issue for dressing of the SRF cavity. So far the baseline design of ILC is to use titanium Helium vessel, however, it will make very complicated procedure point of high vessel regulation code. If material is changed to SUS316L from niobium at the place close to cavity, the regulation control will be more relaxed. We have developed the joining method niobium and SUS316L applying HIP technology, and demonstrated to work in the STF program. The result will be presented in this paper.
KEK, Ibaraki
KEK has contracted a commission research from PAL on LL 9-cell cavity in 2007-2009. In this research program, we have fabricated a L-band 9-cell cavity with LL shape and made the S0 tight loop study. In this paper, the fabrication and the test result will be presented.
KEK, Ibaraki
Electropolishing is well known to have surfer contamination on niobium cavities. So far many efforts have been done in order to remove the contamination in the SRF community: H2O2 rinsing, Degreasing and Ethanol rinsing so on. Nobody understands the surfer generation mechanism, however recently we have found it. By the understating, we have taken a cure for our EP and no surfer has happened by naked eye inspection. In this pare we will present about the surfer generation mechanism and the cure.