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Journal Articles

Superconducting twin quarter wave resonator for acceleration of low velocity heavy ions

Kabumoto, Hiroshi; Takeuchi, Suehiro; Matsuda, Makoto; Ishizaki, Nobuhiro; Otokawa, Yoshinori

Proceedings of 14th International Conference on RF Superconductivity (SRF 2009) (Internet), p.849 - 853, 2009/11

The JAEA-Tokai tandem accelerator was built for basic science researches with heavy ions. Its superconducting booster was developed for increasing the acceleration energy of ions. We have designed and fabricated a superconducting twin-quarter-wave resonator (Twin-QWR) made of niobium and copper for the acceleration of low velocity heavy ions from TRIAC facility. The resonator has two inner conductors and three acceleration gaps which give a resonant frequency of 129.8 MHz and an optimum beam velocity of 6% of the light velocity. Each inner conductor resonates like in a coaxial quarter-wave line resonator. The resonator was designed to have a separatable structure so that we could treat the inner conductors part fully made of high purity niobium apart from the outer conductor made of niobium and copper. We obtained an acceleration field gradient of 5.8 MV/m at an RF power input of 4 W.

Journal Articles

J-PARC upgrade

Ouchi, Nobuo

Proceedings of 14th International Conference on RF Superconductivity (SRF 2009) (Internet), p.934 - 940, 2009/09

J-PARC is in the first phase now. Proton beams have reached to the all experimental facilities up to now, and user operation of MLF started in 2008. Superconducting proton linac (SCL) from 400 to 600 MeV and the Transmutation Experimental Facility are planned in the second construction phase. SCL will consist of 11 cryomodules and two 9-cell 972 MHz elliptical cavities will be installed in each cryomodule. As two cavities will be driven by one klystron, phase stability between two cavities under the Lorentz force detuning in the pulsed operation is most important issue to be developed. A prototype cryomodule was fabricated, which was designed to be less Lorentz force detuning, and two cavity excitation was tested. The phase stability at 2K is satisfactory acceptable, while it deteriorates at 4K due to the microphonic noise. Design of SCL and the experimental results of the prototype cryomodule are presented.

Journal Articles

ERL HOM absorber development

Sawamura, Masaru; Furuya, Takaaki*; Sakai, Hiroshi*; Umemori, Kensei*; Shinoe, Kenji*

Proceedings of 14th International Conference on RF Superconductivity (SRF 2009) (Internet), p.698 - 701, 2009/09

HOM absorbers are one of the key components to determine the ERL cavity performance to reduce the HOM problem for the high current operation. When a beam line HOM damper is installed inside the cryomodule, the HOM damper is cooled down to liquid nitrogen temperature. The RF absorber used for the HOM damper is required to have good frequency and temperature properties. Some ferrites and ceramics are tested for permittivity and permeability of frequency-dependence and temperature-dependence measured with a GM refrigerator from room temperature to 40 K. The HOM damper is designed by optimizing the parameters such as length, thickness and position with microwave simulation codes. Test models of the HOM damper are being designed and fabricated to test the RF, mechanical, cooling and temperature properties.

Journal Articles

Development of input power coupler for ERL main linac in Japan

Sakai, Hiroshi*; Furuya, Takaaki*; Sakanaka, Shogo*; Takahashi, Takeshi*; Umemori, Kensei*; Ishii, Atsushi*; Nakamura, Norio*; Shinoe, Kenji*; Sawamura, Masaru

Proceedings of 14th International Conference on RF Superconductivity (SRF 2009) (Internet), p.684 - 688, 2009/09

We started to develop an input coupler for a 1.3GHz ERL superconducting cavity for ERL main linac. Required input power is about 20kW for the cavity acceleration field of 20MV/m and the beam current of 100mA in energy recovery operation. The input coupler is designed based on the STF-BL input coupler and some modifications are applied for the CW 20kW power operation. We fabricated input coupler components such as ceramic windows and bellows and carried out the high-power test of the components by using a 30kW IOT power source and a test stand constructed.

Journal Articles

Status of 9-cell superconducting cavity development for ERL project in Japan

Umemori, Kensei*; Furuya, Takaaki*; Sakai, Hiroshi*; Takahashi, Takeshi*; Shinoe, Kenji*; Sawamura, Masaru

Proceedings of 14th International Conference on RF Superconductivity (SRF 2009) (Internet), p.355 - 358, 2009/09

Superconducting cavities have been developed for realizing the high current future ERLs. Along with high accelerating gradient of 15-20 MV/m, strong HOM damping is important issue for the ERL main linac. We designed an HOM damped 9-cell cavity and fabricated a niobium 9-cell proto-type cavity. After a series of surface treatments, vertical tests were performed. At present, the accelerating gradient is limited to 15-17 MV/m due to field emissions. A rotating X-ray mapping system was developed and observed some X-ray traces. We report on these activities.

Journal Articles

Compact ERL linac

Umemori, Kensei*; Furuya, Takaaki*; Kako, Eiji*; Noguchi, Shuichi*; Sakai, Hiroshi*; Sato, Masato*; Shishido, Toshio*; Takahashi, Takeshi*; Watanabe, Ken*; Yamamoto, Yasuchika*; et al.

Proceedings of 14th International Conference on RF Superconductivity (SRF 2009) (Internet), p.896 - 901, 2009/09

Construction of the Compact ERL is planned in Japan, in order to test the key technology to realize a future ERL based X-ray light source. The operation of 60-200 MeV beam energy and 100 mA beam current are proposed. The superconducting cavity is one of the key components and applied for the injector part and the main linac part. At the injector part, most challenging issue is an input coupler, which has to handle more than 300 kW input power per cavity. On the other hand, strong HOM damping is required for the main linac, in order to avoid beam instabilities and large heat load at cryomodules. Status of cavity developments, together with cryomodule developments, including input couplers and HOM couplers/absorbers, are described in this paper.

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