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| WEPEC016 | Preparation Status of Cryomodule Tests of Tesla-like Cavities in S1-Global Project at KEK | 2926 |
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Cryomodule tests of four Tesla-like cavities is under preparation for S1-global project at KEK. An average maximum accelerating gradient (Eacc,max) of four cavities in the vertical tests at 2 K was reached to approximately 25 MV/m. Conditioning of four STF-2 input couplers was carried out at a high power test stand with a 5MW-pulsed klystron. Two types of frequency tuning system with a slide-jack tuner and a piezo tuner is installed at the center or end position of the He jacket. String asssembly of the four cavities will be started in March, and the first cool-down test of the cryomodule is scheduled in June, 2010. |
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| WEPEC024 | Present Status of Superconducting Cavity System for cERL Injector Linac at KEK | 2944 |
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A superconducting cavity system has been developing for cERL injector Linac at KEK. Two prototype 2-cell niobium cavities and two prototype input couplers were fabricated. The vertical tests of the cavities at 2 K were carried out to qualify their performance. The rf conditioning of the input couplers were carried out at a high power test stand with a cw-300kW klystron. The results of the cavity performances at high gradients and the conditioning of the input couplers will be presented in this paper. |
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| WEPEC032 | Surface Inspection on MHI-01~09 Cavities | 2962 |
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Nine 1.3 GHz 9-cell superconducting cavities (MHI-01 ~ 09) for International Linear Collider (ILC) project were fabricated from 2005 to 2009 at KEK-STF. The vertical test (with temperature and X-ray mapping) and optical inspection using by high resolution camera system for nine cavities were carried out from 2006 to 2009 for STF Phase-I project and S1-Global project at KEK. The cavities were separated to three series. The first series is MHI-01 ~ 04 (fabricated at 2005). They were made the Centrifugal barrel polishing (CBP) at initial surface treatment. The second series is MHI-05 and 06 (fabricated 2008). The third series is MHI-07 ~ 09 (fabricated at 2009). The surface treatments of second and third series cavity were made only Electro Polishing (EP) process (without CBP), because of the EBW seams of equator and iris were improved by the feedback of optical inspection method. A good correlation has been so far observed between the hot spots localized by thermometry measurements in the vertical test and the positions of surface defects found by this system. The result of optical inspection will be reported in this paper. |
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| WEPEC033 | Repair Techniques of Superconducting Cavity for Improvement Cavity Performance at KEK-STF | 2965 |
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The repair techniques of superconducting cavity is important to obtain better yield of accelerating gradient of superconducting 1.3 GHz 9-cell cavities. The techniques for repair of the cavity are combination of the optical inspection, make a replica of defect, the local grinding and the result of temperature mapping in vertical test. The pit type defect (size: 0.7 mm x 0.5 mm, depth: about 115 um) was found at the quench location of MHI-08 cavity at 16 MV/m by optical inspection after 1st vertical test at June 2009. The location of defect is boundary between EBW seam and heat affected zone at 172 degree of 2-cell equator. If a cause of field limitation for MHI-08 is really this pit type defect, then the cavity can repair to remove the defect by mechanical grinding method. The defect was removed completely by the special grinding machine. After grinding, Electric polishing process and optical inspection were carried out to check the surface condition at grinding area. The 2nd vertical test of MHI-08 was carried out at October 2009. The accelerating field was improved from 16 MV/m to 27 MV/m. The result of repair of MHI-08 will be reported in this paper. |
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| TUPE091 | Recent Progress in the Energy Recovery Linac Project in Japan | 2338 |
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Future synchrotron light source using a 5-GeV-class energy recovery linac (ERL) is under proposal by our Japanese collaboration team, and we are conducting active R&D efforts for that. We are developing super-brilliant DC photocathode guns, two types of cryomodules for both injector and main superconducting linacs, 1.3 GHz high CW-power rf sources, and other important components. We are also constructing a compact ERL for demonstrating the recirculation of low-emittance, high-current beams using those key components. We present our recent progress in this project. |
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| WEPE008 | Construction of the S1-Global Cryomodules for ILC | 3356 |
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In an attempt at demonstrating an average field gradient of 31.5 MV/m as per the design accelerating gradient for ILC, a program called S1-Global is in progress as an international research collaboration among KEK, INFN, FNAL, DESY and SLAC. The S1-Global cryomodule will contain eight superconducting cavities from FNAL, DESY and KEK. The cryomodule will be constructed by joining two half-size cryomodules, each 6 m in length. The module containing four cavities from FNAL and DESY has been constructed by INFN. The module for four KEK cavities is being modified at present. The assembly of the cryomodules is scheduled from January 2010, and the operation of the system is scheduled from June 2010 at the KEK-STF. In this paper, the construction of the S1-Global cryomodule will be presented. |
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| WEPE012 | Summary of Vertical Tests for S1-Global Project in KEK-STF | 3368 |
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Vertical tests of five 1.3GHz 9-cell cavities (MHI#5-#9) have been done totally 17 times from 2008 to 2009 for S1-Global project in KEK-STF, which is planned in 2010. MHI#7 cavity achieved 33.6MV/m, which was the best result, and the others below 30MV/m. After the exchange for new EP acid on May/2009, many brown stains (niobium oxide) were observed on the interior surface of the cavity, and onset gradient of radiation level measured at the top flange of cryostat was much lower. After several vertical tests, the effect by this phenomenon was gradually relaxed. After four cavities reached above 25MV/m, the gradient suddenly dropped due to the unknown cause at the next vertical test. Two of four cavities were recovered above 25MV/m at the final vertical test again. However, any cavity in KEK-STF did not reach ILC specification (Eacc=35MV/m, Q0=0.8x1010) yet. This means that more improvement for cavity fabrication and surface treatment is necessary. In this presentation, the summary of the vertical tests for S1-Global project in KEK-STF will be reported. |
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| WEPE013 | Summary of Results and Development of Online Monitor for T-mapping/X-ray-mapping in KEK-STF | 3371 |
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Vertical test for 1.3GHz 9-cell cavity has been routinely carried out over one year since 2008 in KEK-STF. Temperature mapping (T-mapping) system using 352 carbon resistors was introduced to identify the heating location at thermal quenching of the cavity. T-mapping system in STF identified perfectly the heating location in every vertical test for S1-Global project. As X-ray-mapping system, 142 PIN diodes were used, and the x-ray emission site was detected under heavy field emission. During the vertical test, it is convenient to display the result of T-mapping and X-ray-mapping by online monitor system. For this purpose, the new online monitor system was developed by using EPICS (Experimental Physics and Industrial Control System) and Java script, and introduced in recent several vertical tests. As a data acquisition system, nine data loggers (MW100, YOKOGAWA) are used, and signals from totally 540 channels are stored every 0.1 sec. The online display for T-mapping and X-ray-mapping is updated automatically every 5 seconds. In this report, the summary of T-mapping/X-ray-mapping result and the online monitor system will be described in detail. |