SRF2013 - List of Authors (Umemori, K.)

Paper

Title

Page

Precise Measurement of Superconducting Cavity Movement in Cryomodule by the Position Monitor Using White Light Interferometer

291

H. Sakai, T. Aoto, K. Enami, T. Furuya, M. Sato, K. Shinoe, K. Umemori
KEK, Ibaraki, Japan
E. Cenni
Sokendai, Ibaraki, Japan
K. Hayashi, K. Kanzaki
Tokyo Seimitsu Co. Ltd, Ibaraki, Japan
M. Sawamura
JAEA, Ibaraki-ken, Japan

Alignment of Superconducting cavity is one of the important issues for linear collider and/or future light source like ERL and X-FEL. To measure the cavity displacement under cooling to Liq He temperature more precisely, we newly developed the position monitor by using white light interferometer. This monitor is based on the measurement of the interference of light between the measurement target and the reference point. It can measure the position from the outside of the cryomodule. We applied this monitor to the main linac cryomodule of Compact ERL and successfully measured the displacement during 2K cooling with the resolution of 10 micron

TUIOC06

Study on Optimum Electron Beam Welding Condition for Superconducting Accelerating Cavities

424

T. Kubo, Y. Ajima, H. Inoue, T. Saeki, K. Umemori, Y. Watanabe, S. Yamaguchi, M. Yamanaka
KEK, Ibaraki, Japan
T. Nagata
ULVAC, Inc., Tsukuba, Japan

Optimizations of electron beam welding conditions might solve the quench problems and improve the accelerating field of the superconducting radio-frequency cavity. As a first step toward optimum conditions, basic properties of weld beads are studied by using niobium test pieces. Effects of a combination of a beam generator position and a welding direction on geometries of weld bead are shown. Good parameter-regions for electron beam welding, which yield full penetration welds without holes or weld spatters, are surveyed. Microscopic structures, such as pits or bumps due to poor welds, have greater influence on cavity performances, which are also our research objects. We introduce a model of the magnetic field enhancement at pits, where a formula for a magnetic field enhancement factor is given as a function of parameters that express a geometry of pit. Comparisons between calculations and vertical test results are also shown.

Slides TUIOC06 [15.958 MB]

TUP091

Field Emission Measure During cERL Main Linac Cryomodule High Power Test in KEK

678

E. Cenni
Sokendai, Ibaraki, Japan
K. Enami, T. Furuya, H. Sakai, M. Satoh, K. Shinoe, K. Umemori
KEK, Ibaraki, Japan
M. Sawamura
JAEA, Ibaraki-ken, Japan

A compact Energy Recovery Linac (cERL) is under construction in KEK in order to proof the performance of the key components required for the future ERL project in KEK. The main linac L-band cavities were assembled and tested in the cryomodule under high power operation, during the test information concerning field emission were gathered by means of PIN diodes rings and NaI scintillator located at the cavities ends. The data were analyzed by means of simulations, taking into account the cavities operating conditions and interaction between the accelerated electrons and the cavity surface. The resulting information are used to deduce a possible emitter location, determining if there is any change in the cavities performance with respect to the last vertical test they undertook. With PIN diode is possible to observe the radiation pattern produced by field emission, inferring the meridian where the emitter belongs. On the other hand the bremsstrahlung spectra recorded with the scintillator allow an estimation of the cavity cell where the emitter is located.

THIOC02

High Power CW Tests of cERL Main-Linac Cryomodule

855

H. Sakai, K. Enami, T. Furuya, M. Satoh, K. Shinoe, K. Umemori
KEK, Ibaraki, Japan
E. Cenni
Sokendai, Ibaraki, Japan
M. Sawamura
JAEA, Ibaraki-ken, Japan

A main linac cryomodule have been constructed for Compact ERL project. It contains two 9-cell cavities, mounted with HOM absorbers and input couplers. After cavity string assembly, they were installed into the vacuum vessel of the cryomodule. It was placed inside radiation shield of cERL and connected to a refrigerator system. The cryomodule was successfully cooled down to 2K and low power and high power measurements were carried out.

Slides THIOC02 [12.842 MB]

Paper	Title	Page
MOP069	Precise Measurement of Superconducting Cavity Movement in Cryomodule by the Position Monitor Using White Light Interferometer	291
	H. Sakai, T. Aoto, K. Enami, T. Furuya, M. Sato, K. Shinoe, K. Umemori KEK, Ibaraki, Japan E. Cenni Sokendai, Ibaraki, Japan K. Hayashi, K. Kanzaki Tokyo Seimitsu Co. Ltd, Ibaraki, Japan M. Sawamura JAEA, Ibaraki-ken, Japan
	Alignment of Superconducting cavity is one of the important issues for linear collider and/or future light source like ERL and X-FEL. To measure the cavity displacement under cooling to Liq He temperature more precisely, we newly developed the position monitor by using white light interferometer. This monitor is based on the measurement of the interference of light between the measurement target and the reference point. It can measure the position from the outside of the cryomodule. We applied this monitor to the main linac cryomodule of Compact ERL and successfully measured the displacement during 2K cooling with the resolution of 10 micron

TUIOC06	Study on Optimum Electron Beam Welding Condition for Superconducting Accelerating Cavities	424
	T. Kubo, Y. Ajima, H. Inoue, T. Saeki, K. Umemori, Y. Watanabe, S. Yamaguchi, M. Yamanaka KEK, Ibaraki, Japan T. Nagata ULVAC, Inc., Tsukuba, Japan
	Optimizations of electron beam welding conditions might solve the quench problems and improve the accelerating field of the superconducting radio-frequency cavity. As a first step toward optimum conditions, basic properties of weld beads are studied by using niobium test pieces. Effects of a combination of a beam generator position and a welding direction on geometries of weld bead are shown. Good parameter-regions for electron beam welding, which yield full penetration welds without holes or weld spatters, are surveyed. Microscopic structures, such as pits or bumps due to poor welds, have greater influence on cavity performances, which are also our research objects. We introduce a model of the magnetic field enhancement at pits, where a formula for a magnetic field enhancement factor is given as a function of parameters that express a geometry of pit. Comparisons between calculations and vertical test results are also shown.
	Slides TUIOC06 [15.958 MB]

TUP091	Field Emission Measure During cERL Main Linac Cryomodule High Power Test in KEK	678
	E. Cenni Sokendai, Ibaraki, Japan K. Enami, T. Furuya, H. Sakai, M. Satoh, K. Shinoe, K. Umemori KEK, Ibaraki, Japan M. Sawamura JAEA, Ibaraki-ken, Japan
	A compact Energy Recovery Linac (cERL) is under construction in KEK in order to proof the performance of the key components required for the future ERL project in KEK. The main linac L-band cavities were assembled and tested in the cryomodule under high power operation, during the test information concerning field emission were gathered by means of PIN diodes rings and NaI scintillator located at the cavities ends. The data were analyzed by means of simulations, taking into account the cavities operating conditions and interaction between the accelerated electrons and the cavity surface. The resulting information are used to deduce a possible emitter location, determining if there is any change in the cavities performance with respect to the last vertical test they undertook. With PIN diode is possible to observe the radiation pattern produced by field emission, inferring the meridian where the emitter belongs. On the other hand the bremsstrahlung spectra recorded with the scintillator allow an estimation of the cavity cell where the emitter is located.

THIOC02	High Power CW Tests of cERL Main-Linac Cryomodule	855
	H. Sakai, K. Enami, T. Furuya, M. Satoh, K. Shinoe, K. Umemori KEK, Ibaraki, Japan E. Cenni Sokendai, Ibaraki, Japan M. Sawamura JAEA, Ibaraki-ken, Japan
	A main linac cryomodule have been constructed for Compact ERL project. It contains two 9-cell cavities, mounted with HOM absorbers and input couplers. After cavity string assembly, they were installed into the vacuum vessel of the cryomodule. It was placed inside radiation shield of cERL and connected to a refrigerator system. The cryomodule was successfully cooled down to 2K and low power and high power measurements were carried out.
	Slides THIOC02 [12.842 MB]