| Paper | Title | Page |
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| MOPEB073 | Single Crystal Niobium Development | 438 |
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KEK and Tokyo Denkai have developed new niobium ingot slicing technique. 150 pieces of the large grain niobium discs can be sliced in two days by using of this technique. Tokyo Denkai installed the slicing machine in December 2009. During the development of the slicing technique, we found that crystal growth mechanism in Electron Beam Melting. It gave us the suggestion to make a single crystal niobium ingot. This paper describes the production process of low cost and short production time niobium discs and single crystal niobium ingot development. |
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| WEPE004 | High Gradient Behaviors of Large Grain ICHIRO Single Cell Cavity by Chemical Polishing | 3344 |
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We have started high gradient R&D with the combination of ICHIRO shape, sliced large grain niobium, and chemical polishing (CP). We fabricated one large grain ICHIRO single cell cavity that had end cell shape of ICHIRO 9-cell but no end group. We processed this cavity surface by centrifugal barrel polishing (CBP) and CP. This cavity successfully achieved the high gradient of 42MV/m at the first vertical test. We made series test by repeating CP on this cavity. The results of series test will be reported. |
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| WEPE005 | High Field Q-slope Problem in End Group Cavities | 3347 |
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In our high gradient R&D of ICHIRO cavities at KEK, we have found some problems related to HOM coupler and high power RF input coupler port on beam tube: end group. One is the difficulties of rinsing in complex structures like HOM coupler. The other is Q-slope at high filed more than 40MV/m. The cavities without end group did not show such a high field Q-slope. At first step, we tested much stronger and aggressive rinsing method; wiping, brushing, and mega-sonic rinsing, against end group. The details and results of these rinsing effects will be reported. |
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| WEPE006 | Vacuum Evacuation Effect on ICHIRO 9-cell Cavities during Vertical Test | 3350 |
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We have continued high gradient R&D of ICHIRO 9-cell cavities at KEK. The maximum gradient of ICHIRO 9-cell cavity #5 that has no end groups on beam tube was still limited around 36MV/m so far. The 9-cell performances were sometimes limited by triggered field emission (FE) by multipactings. We suspected the residual gas in the cavity might be one of the sources of triggered FE. The cavity was closed during vertical test in our system. Other labs evacuated cavity during vertical test. In order to improve the vacuum of cavity during vertical test, we made evacuation system in our cavity test stand. The comparison of results for vertical test with and without evacuation will be reported. |
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| WEPE009 | Application of MO Sealing for SRF Cavities | 3359 |
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Dr. Matsumoto in KEK and his colleague have developed the MO flange for vacuum sealing of normal conducting high peak power RF wave-guide. This is impedance free sealing. We have applied this sealing to SRF cavity technology instead of indium sealing. We used pure aluminum gasket for the sealing material. We had a difficulty on the titanium flange but succeeded to establish leak tightness in super-fluid Helium by stainless flange. In this paper, we will report the R&D results. |
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| WEPE010 | Improvements of Cleaning Methods for High Q-slope Problem in Full End Single Cell Cavity | 3362 |
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We are developing LL high gradient SRF cavity for ILC. Recently we have observed a Q-slope problem at higher gradient over 35-40MV/m on the full end single cell cavities, which have a HOM coupler and an input coupler on a beam tube. This problem might be due to poor rinsing in such a complicate structure. We have studied to strengthen cleaning by improvement of the nozzle shape used high pressure water rinsing, inside ultrasonic cleaning, steam cleaning, and so on. In this paper we will report these results. |
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| WEPE011 | Large Grain 9-cell Cavities R&D at KEK | 3365 |
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We are developing large grain/single crystal niobium material for ILC collaborating with Tokyo Denkai. These materials are very much promising to obtain high SRF cavity performance with cost-effective production. We have fabricated two 9-cell cavities from these large grain niobium materials and made cold test to evaluate the SRF performance. In this paper, we will report cavity fabrications and preparations and cold test results. |
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| WEPE014 | Design and Model Cavity Test of the Demountable Damped Cavity | 3374 |
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We have designed Demountable Damped Cavity (DDC) for ILC main linac. DDC has two design concepts. One is the coaxial waveguide for HOM damping, which can strongly couple HOM's. Accelerating mode is reflected by a choke filter. The axial symmetry can reduce the beam kick effect. The other concept is demountable structure which can make easy cleaning of end group in order to suppress the Q-slope problem at a high field. In this paper we will report the RF design and measurement results in model cavity. |