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Sawamura, Masaru; Hajima, Ryoichi; Nagai, Ryoji; Nishimori, Nobuyuki
Proceedings of 15th International Conference on RF Superconductivity (SRF 2011) (Internet), p.165 - 168, 2012/06
We are proposing non-destructive assay system of nuclear materials with laser Compton scattering combined with an energy-recovery linac (ERL) and a laser. To construct this system for nuclear safeguards and security purpose, it is important to make the accelerating cavity small. The spoke cavity has advantages over the elliptical cavity to use for our proposing system. We are designing a spoke cavity favorable to compact cavity. Design optimization calculation of the spoke cavity shape is being carried out with 3D electro-magnetic field simulation code and generic algorithm. The results will be presented.
Sawamura, Masaru; Furuya, Takaaki*; Sakai, Hiroshi*; Umemori, Kensei*; Shinoe, Kenji*; Cenni, E.*
Proceedings of 15th International Conference on RF Superconductivity (SRF 2011) (Internet), p.350 - 352, 2012/06
The HOM absorber model was designed and fabricated according to results of ferrites and ceramic properties measurement at low temperature. The HOM absorber model uses the RF absorber of HIP (Hot Isostatic Press) ferrite attached on the copper base. The comb-type RF bridge is adopted at the beam pipe connection between the HIP ferrite part and the flange part. Both parts of the RF bridge are connected with a bellows to reduce the heat load into the superconducting cavity. The HOM absorbers are also required to have good thermal transmission properties to effectively remove the HOM absorption power. The HOM absorber without ferrite was used to measure the thermal properties at liquid nitrogen temperature. Prototype of HIP ferrite model was fabricated. The thermal simulation calculation was also performed. Thermal cycle test between the room temperature and 80 K with a GM refrigerator was also carried out to check the thermal tolerance of the HIP ferrite.
Sakai, Hiroshi*; Furuya, Takaaki*; Nakamura, Norio*; Umemori, Kensei*; Shinoe, Kenji*; Sawamura, Masaru; Cenni, E.*
Proceedings of 15th International Conference on RF Superconductivity (SRF 2011) (Internet), p.356 - 360, 2011/07
We fabricated the prototype of an input coupler with two ceramic windows for ERL main linac and performed the high power test. In high power test, the one cold window was installed into the vacuum insulating chamber and cooled by liquid nitrogen. First, the multipacting limited the power level to 10 kW. The pulse processing method for 8 hours enabled the final power level to 25 kW with standing wave condition. We could also keep 20 kW power feeding into the coupler for 16 hours. The maximum measured temperature rises under feeding the 20 kW power to coupler were 120 K near the bellows parts and these are not so severe values to operate ERL main linac. The thermal cycle test of cold window of coupler was done. After 10-times thermal cycle tests between the room temperature and liquid nitrogen temperature, no leaks or cracks were observed. From these results of high power test, this prototype coupler satisfies our thermal and RF requirements.
Cenni, E.*; Furuya, Takaaki*; Sakai, Hiroshi*; Umemori, Kensei*; Shinoe, Kenji*; Sawamura, Masaru
Proceedings of 15th International Conference on RF Superconductivity (SRF 2011) (Internet), p.789 - 794, 2011/07
In order to develop the Energy Recovery Linac, we are studying the performance of two prototype L-band superconducting cavities by means of vertical tests. The cavities were inspected through rotating X-ray and temperature mapping system. The performance limiting factor was found to be the field emissions. We observed X-ray emission and temperature raise along the cavity wall. The quench locations were determined with a good agreement between X-ray and temperature sensors. During vertical test we experienced some interesting phenomena such as quality factor degradation and X-ray burst. In the first case the degradation was observed even at low field, however we recovered it with a warming up to room temperature without additional surface treatment. In the latter case new emitters suddenly appeared after some quenches. They remained in the same location also after the warming up.
Umemori, Kensei*; Furuya, Takaaki*; Kako, Eiji*; Noguchi, Shuichi*; Sakai, Hiroshi*; Sato, Masato*; Shishido, Toshio*; Watanabe, Ken*; Yamamoto, Yasuchika*; Shinoe, Kenji*; et al.
Proceedings of 15th International Conference on RF Superconductivity (SRF 2011) (Internet), p.956 - 961, 2011/07
The Compact ERL (cERL) project is advanced in Japan. Its aim is to demonstrate the circulation of 100 mA electron beams with energy of 35-200 MeV. Superconducting cavities are key components for realizing ERL and used for injector part and main linac part. Critical issue for the injector part is the development of input power coupler. Prototype input couplers were fabricated and high power test was performed. Cooling ability of HOM coupler is also important for CW operation of cavity. At main linac part, HOM damped 9-cell cavities are applied to avoid BBU instabilities. Prototypes were fabricated for the cavity, the input coupler and the HOM absorber. Their performance was investigated. For both parts, cryomodules are under construction and will be completed in 2012.
