SRF2011 - List of Authors (Shinoe, K.)

Paper

Title

Page

Cooling Properties of HOM Absorber Model for cERL in Japan

350

M. Sawamura
Japan Atomic Energy Agency (JAEA), Gamma-ray Non-Destructive Assay Research Group, Tokai-mura, Ibaraki-ken, Japan
E. Cenni
Sokendai, Ibaraki, Japan
T. Furuya, H. Sakai, K. Umemori
KEK, Ibaraki, Japan
K. Shinoe
ISSP/SRL, Chiba, Japan

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 80K with a GM refrigerator was also carried out to check the thermal tolerance of the HIP ferrite.

TUPO005

High Power Tests of KEK-ERL Input Coupler for Main Linac Under LN2 Condition

356

H. Sakai, T. Furuya, N. Nakamura, K. Umemori
KEK, Ibaraki, Japan
E. Cenni
Sokendai, Ibaraki, Japan
M. Sawamura
JAEA, Ibaraki-ken, Japan
K. Shinoe
ISSP/SRL, Chiba, Japan

We fabricated the prototype of an input coupler, which has two ceramic windows to keep the inside of the superconducting cavity clean, for ERL main linac and performed the high power test. Required input power is about 20kW with standing wave condition for the cavity acceleration field of 20MV/m. In this high power test, the one ceramic window, named as a cold window, was installed into the vacuum insulating chamber and cooled by liquid Nitrogen. First, the multipacting at 10kW level prevented the power increasing. By using the pulse processing method for 8 hours, power finally reached the 25kW with standing wave condition. We could also keep feeding 20kW power into coupler for 16 hours. The maximum measured temperature rises under feeding the 20 kW power to coupler were 120K near the bellows parts and these are not so severe values to operate ERL main linac. After power test, 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 and cracks were observed. From these results of high power test, this prototype coupler satisfied our thermal and RF requirements.

THPO034

Vertical Test Results on KEK-ERL 9-Cell L-Band Superconducting Cavity

789

E. Cenni
Sokendai, Ibaraki, Japan
T. Furuya, H. Sakai, K. Umemori
KEK, Ibaraki, Japan
M. Sawamura
Japan Atomic Energy Agency (JAEA), Gamma-ray Non-Destructive Assay Research Group, Tokai-mura, Ibaraki-ken, Japan
K. Shinoe
ISSP/SRL, Chiba, Japan

In order to develop the Energy Recovery Linac at KEK, we are studying the performance of two prototype L-band superconducting cavities by means of vertical tests. After annealing, electro polishing, high pressure rinsing and baking, several vertical tests has been performed and the cavities have been inspected through rotating X-ray and temperature mapping system. The performance limiting factor has been found to be the field emissions. We have observed X-ray emission and temperature raise along the cavity wall. The quench locations have been determined with a good agreement between X-ray and temperature sensors. During vertical test we have 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 have suddenly appeared after some quenches. They remained in the same location also after the warming up. The cavities have fulfilled the requirement for the KEK-ERL main linac reaching an accelerating field of more than 20 MV/m.

FRIOA06

Construction of cERL Cryomodules for Injector and Main Linac

956

K. Umemori, T. Furuya, E. Kako, S. Noguchi, H. Sakai, M. Satoh, T. Shishido, K. Watanabe, Y. Yamamoto
KEK, Ibaraki, Japan
E. Cenni
Sokendai, Ibaraki, Japan
M. Sawamura
JAEA, Ibaraki-ken, Japan
K. Shinoe
ISSP/SRL, Chiba, Japan

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. At injector part, electron beams are accelerated up to 5-10 MeV by three 2-cell cavities. Prototype 2-cell cavities show excellent performance of about 40 MV/m. However, heating problem exists on HOM couplers. Improvement of cooling is essential for stable CW operation. Input coupler is another big issue. High power test stand was constructed using a 300 kW klystron. Prototype couplers could deliver from several tens to a hundred kW of RF power. At main linac part, HOM damped 9-cell cavities are applied. Two prototype cavities were manufactured. Initially their performance was limited by field emission. But it was overcome and they reached to more than 20 MV/m. A prototype input coupler is also fabricated for main linac. It successfully propagates 25 kW standing wave and also thermal cycle tests were passed. Prototype HOM absorbers are also fabricated and several tests were carried out. For both parts, cryomodules are under construction. They will be completed in 2012.

Slides FRIOA06 [6.489 MB]

Paper	Title	Page
TUPO003	Cooling Properties of HOM Absorber Model for cERL in Japan	350
	M. Sawamura Japan Atomic Energy Agency (JAEA), Gamma-ray Non-Destructive Assay Research Group, Tokai-mura, Ibaraki-ken, Japan E. Cenni Sokendai, Ibaraki, Japan T. Furuya, H. Sakai, K. Umemori KEK, Ibaraki, Japan K. Shinoe ISSP/SRL, Chiba, Japan
	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 80K with a GM refrigerator was also carried out to check the thermal tolerance of the HIP ferrite.

TUPO005	High Power Tests of KEK-ERL Input Coupler for Main Linac Under LN2 Condition	356
	H. Sakai, T. Furuya, N. Nakamura, K. Umemori KEK, Ibaraki, Japan E. Cenni Sokendai, Ibaraki, Japan M. Sawamura JAEA, Ibaraki-ken, Japan K. Shinoe ISSP/SRL, Chiba, Japan
	We fabricated the prototype of an input coupler, which has two ceramic windows to keep the inside of the superconducting cavity clean, for ERL main linac and performed the high power test. Required input power is about 20kW with standing wave condition for the cavity acceleration field of 20MV/m. In this high power test, the one ceramic window, named as a cold window, was installed into the vacuum insulating chamber and cooled by liquid Nitrogen. First, the multipacting at 10kW level prevented the power increasing. By using the pulse processing method for 8 hours, power finally reached the 25kW with standing wave condition. We could also keep feeding 20kW power into coupler for 16 hours. The maximum measured temperature rises under feeding the 20 kW power to coupler were 120K near the bellows parts and these are not so severe values to operate ERL main linac. After power test, 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 and cracks were observed. From these results of high power test, this prototype coupler satisfied our thermal and RF requirements.

THPO034	Vertical Test Results on KEK-ERL 9-Cell L-Band Superconducting Cavity	789
	E. Cenni Sokendai, Ibaraki, Japan T. Furuya, H. Sakai, K. Umemori KEK, Ibaraki, Japan M. Sawamura Japan Atomic Energy Agency (JAEA), Gamma-ray Non-Destructive Assay Research Group, Tokai-mura, Ibaraki-ken, Japan K. Shinoe ISSP/SRL, Chiba, Japan
	In order to develop the Energy Recovery Linac at KEK, we are studying the performance of two prototype L-band superconducting cavities by means of vertical tests. After annealing, electro polishing, high pressure rinsing and baking, several vertical tests has been performed and the cavities have been inspected through rotating X-ray and temperature mapping system. The performance limiting factor has been found to be the field emissions. We have observed X-ray emission and temperature raise along the cavity wall. The quench locations have been determined with a good agreement between X-ray and temperature sensors. During vertical test we have 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 have suddenly appeared after some quenches. They remained in the same location also after the warming up. The cavities have fulfilled the requirement for the KEK-ERL main linac reaching an accelerating field of more than 20 MV/m.

FRIOA06	Construction of cERL Cryomodules for Injector and Main Linac	956
	K. Umemori, T. Furuya, E. Kako, S. Noguchi, H. Sakai, M. Satoh, T. Shishido, K. Watanabe, Y. Yamamoto KEK, Ibaraki, Japan E. Cenni Sokendai, Ibaraki, Japan M. Sawamura JAEA, Ibaraki-ken, Japan K. Shinoe ISSP/SRL, Chiba, Japan
	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. At injector part, electron beams are accelerated up to 5-10 MeV by three 2-cell cavities. Prototype 2-cell cavities show excellent performance of about 40 MV/m. However, heating problem exists on HOM couplers. Improvement of cooling is essential for stable CW operation. Input coupler is another big issue. High power test stand was constructed using a 300 kW klystron. Prototype couplers could deliver from several tens to a hundred kW of RF power. At main linac part, HOM damped 9-cell cavities are applied. Two prototype cavities were manufactured. Initially their performance was limited by field emission. But it was overcome and they reached to more than 20 MV/m. A prototype input coupler is also fabricated for main linac. It successfully propagates 25 kW standing wave and also thermal cycle tests were passed. Prototype HOM absorbers are also fabricated and several tests were carried out. For both parts, cryomodules are under construction. They will be completed in 2012.
	Slides FRIOA06 [6.489 MB]