LINAC2014 - List of Authors (Futatsukawa, K.)

Paper

Title

Page

Present Status of J-PARC LINAC LLRF Systems

224

Z. Fang, Y. Fukui, K. Futatsukawa, T. Kobayashi, S. Michizono
KEK, Ibaraki, Japan
E. Chishiro, F. Sato, S. Shinozaki
JAEA/J-PARC, Tokai-mura, Japan

The RF control systems have been developed for the J-PARC proton linac, which consists of 324-MHz and 972-MHz acceleration sections. From October 2006, we started the commissioning of the 324-MHz sections. Then the J-PARC 324-MHz 181-MeV proton linac had been operated nearly for 7 years, until May 2013. In the summer of 2013, we upgraded the J-PARC linac by adding 972-MHz acceleration sections. The output energy of the J-PARC linac was successfully upgraded to 400 MeV in December 2013, and then the operation of the J-PARC 400-MeV linac started. In the past 8 years of the J-PARC linac operation, no heavy troubles occurred in the RF control systems. Every year we made improvements on the RF control systems, according to the operation experiences. In this paper, the present status of the J-PARC 400-MeV linac RF control systems will be described in details, and an improvement plan for the LLRF systems in the future will also be introduced.

TUPP067

Chopper Operation for the Tandem Scrapers at the J-PARC Linac

581

K. Futatsukawa, Z. Fang, Y. Fukui, T. Kobayashi, S. Michizono
KEK, Ibaraki, Japan
E. Chishiro, K. Hirano, F. Sato, S. Shinozaki
JAEA/J-PARC, Tokai-mura, Japan

In the J-PARC linac, the energy upgrade from 181 MeV to 400 MeV by the installation of annular-ring coupled structure (ACS) cavities was successfully achieved in 2013. In the next stage, we will schedule the intensity upgrade by the increase of the beam current by improving the front-end in this summer. Then, the high heat load of the scraper, which stops the kicked-beam by the RF chopper, is predicted to damage the surface. Therefore, we prepare the tandem scrapers to suppress the heat load. The half of the kicked beam leads to a scraper and the residual is to the other. Its chopping expedient will be achieved by reversing the phase of the RF chopper on the periodic cycle at the low-level RF system. In this paper, I would like to introduce this system and present the result of the low-level test.

TUPP070

Status and Recent Modifications to 324-MHz RF Source in J-PARC LINAC

587

M. Kawamura, Y. Fukui, K. Futatsukawa, F. Naito
KEK, Ibaraki, Japan
E. Chishiro, K. Hasegawa, F. Sato, S. Shinozaki
JAEA/J-PARC, Tokai-mura, Japan
T. Hori
JAEA, Ibaraki-ken, Japan

This paper describes the present status of and the recent modifications to the 324-MHz RF source in the J-PARC linac. The recovery from the Great East Japan Earthquake Disaster, the status of the 324-MHz klystrons, the failure of 3 high-voltage transformers (HVTRs), and the discharge suppression for the anode-modulators are described.

Poster TUPP070 [0.660 MB]

TUPP072

Studies on Wake Field in Annular Coupled Structure

593

Y. Liu, T. Maruta
KEK/JAEA, Ibaraki-Ken, Japan
K. Futatsukawa
KEK, Ibaraki, Japan
A. Miura
JAEA/J-PARC, Tokai-mura, Japan

LINAC injector of J-PARC (Japan Proton Accelerator Research Complex) was recently successfully upgraded from 181 MeV to 400 MeV, applying a type of coupled cavity linac (CCL) structure ACS (Annular Coupled Structure). It was warmly discussed since very beginning on the wake field in the ACS cavities, where there are CCL modes with the same number as that of cells within ~50 MHz, possibly resonating with high intensity proton/H⁻ beams. One of the most important effects from the wake field is the influence on the ACS phase scan. Analytical and simulation studies, as well as the countermeasures were prepared before the energy upgrade. Fortunately we found that detuning of the ACS was unnecessary, which helped to save much work in the commissioning. In addition we got chance to make experiment studies. It was also discussed why the wake field is not so serious as we expected at the very beginning.

TUPP094

Recent Progress of Beam Commissioning at J-PARC Linac

646

T. Maruta
J-PARC, KEK & JAEA, Ibaraki-ken, Japan
K. Futatsukawa, T. Miyao
KEK, Ibaraki, Japan
M. Ikegami
FRIB, East Lansing, Michigan, USA
Y. Liu
KEK/JAEA, Ibaraki-Ken, Japan
A. Miura, H. Sako
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan

We installed Annular-type Coupled Structure (ACS) linac in year 2013 in present linac downstream to extend the beam energy from 181 to 400 MeV. The beam commissioning had been conducted for one month in last December to January, and then we successfully extract 400 MeV beam. Whereas, we stably operate the linac at peak current of 15 mA, which is equivalent to 300 kW at the extraction of 3 GeV RCS, we observe unexpected residual radiations in ACS section. In this presentation, we review the recent progress in beam commissioning and beam loss study.

THPP073

Cavity Excitation of the Chopped Beam at the J-PARC Linac

1023

K. Futatsukawa
KEK, Ibaraki, Japan

In the J-PARC linac, the beam energy at the injection of the rapid-cycle synchrotron (RCS) was upgraded up to 400 MeV by the installation of 25 additional cavities, annular-ring coupled structure (ACS), in 2013. The initial frequency of RCS was shifted to 1.227 MHz because of the change the injection-beam velocity. At the linac, the beam is chopped as the comb-like structure with this frequency (intermediate-pulse) by the RF deflector. The component of this RCS frequency excited the PC1 mode of DTL2 and was the cause of the RF-control difficulty. Additionally, it could be confirmed that other chopping operations, which does not have specific intermediate-pulses for example, drove other modes. In this paper, I would like to introduce this phenomena and the counterplan as the RF control.

THPP089

High Power Conditioning of Annular-Ring Coupled Structures for the J-PARC Linac

1053

THPOL07

use link to see paper's listing under its alternate paper code

H. Ao, T. Ito, Y. Nemoto, H. Oguri, N. Ouchi, J. Tamura
JAEA/J-PARC, Tokai-mura, Japan
H. Asano
Nippon Advanced Technology Co. Ltd., Ibaraki-prefecture, Japan
Z. Fang, K. Futatsukawa, K. Nanmo, T. Sugimura
KEK, Ibaraki, Japan

The linac of Japan Proton Accelerator Research Complex (J-PARC), which is an injector to a 3-GeV synchrotron, comprised a 3-MeV RFQ, 50-MeV DTLs and 181-MeV Separated-type DTLs. From September 2013, 25 annular-ring coupled structure (ACS) cavities were additionally installed to increase the linac beam energy up to 400 MeV and achieve 1-MW beam power of the 3-GeV synchrotron. After installation work the high power conditioning was started from December 2013 and most of the ACS cavities were conditioned within three weeks. We passed through some troubles and finally finished conditioning all the cavities until the middle of January 2014. In this paper, we present the conditioning results and how to handle the issue in the conditioning process.

Slides THPP089 [7.756 MB]

Paper	Title	Page
MOPP072	Present Status of J-PARC LINAC LLRF Systems	224
	Z. Fang, Y. Fukui, K. Futatsukawa, T. Kobayashi, S. Michizono KEK, Ibaraki, Japan E. Chishiro, F. Sato, S. Shinozaki JAEA/J-PARC, Tokai-mura, Japan
	The RF control systems have been developed for the J-PARC proton linac, which consists of 324-MHz and 972-MHz acceleration sections. From October 2006, we started the commissioning of the 324-MHz sections. Then the J-PARC 324-MHz 181-MeV proton linac had been operated nearly for 7 years, until May 2013. In the summer of 2013, we upgraded the J-PARC linac by adding 972-MHz acceleration sections. The output energy of the J-PARC linac was successfully upgraded to 400 MeV in December 2013, and then the operation of the J-PARC 400-MeV linac started. In the past 8 years of the J-PARC linac operation, no heavy troubles occurred in the RF control systems. Every year we made improvements on the RF control systems, according to the operation experiences. In this paper, the present status of the J-PARC 400-MeV linac RF control systems will be described in details, and an improvement plan for the LLRF systems in the future will also be introduced.

TUPP067	Chopper Operation for the Tandem Scrapers at the J-PARC Linac	581
	K. Futatsukawa, Z. Fang, Y. Fukui, T. Kobayashi, S. Michizono KEK, Ibaraki, Japan E. Chishiro, K. Hirano, F. Sato, S. Shinozaki JAEA/J-PARC, Tokai-mura, Japan
	In the J-PARC linac, the energy upgrade from 181 MeV to 400 MeV by the installation of annular-ring coupled structure (ACS) cavities was successfully achieved in 2013. In the next stage, we will schedule the intensity upgrade by the increase of the beam current by improving the front-end in this summer. Then, the high heat load of the scraper, which stops the kicked-beam by the RF chopper, is predicted to damage the surface. Therefore, we prepare the tandem scrapers to suppress the heat load. The half of the kicked beam leads to a scraper and the residual is to the other. Its chopping expedient will be achieved by reversing the phase of the RF chopper on the periodic cycle at the low-level RF system. In this paper, I would like to introduce this system and present the result of the low-level test.

TUPP070	Status and Recent Modifications to 324-MHz RF Source in J-PARC LINAC	587
	M. Kawamura, Y. Fukui, K. Futatsukawa, F. Naito KEK, Ibaraki, Japan E. Chishiro, K. Hasegawa, F. Sato, S. Shinozaki JAEA/J-PARC, Tokai-mura, Japan T. Hori JAEA, Ibaraki-ken, Japan
	This paper describes the present status of and the recent modifications to the 324-MHz RF source in the J-PARC linac. The recovery from the Great East Japan Earthquake Disaster, the status of the 324-MHz klystrons, the failure of 3 high-voltage transformers (HVTRs), and the discharge suppression for the anode-modulators are described.
	Poster TUPP070 [0.660 MB]

TUPP072	Studies on Wake Field in Annular Coupled Structure	593
	Y. Liu, T. Maruta KEK/JAEA, Ibaraki-Ken, Japan K. Futatsukawa KEK, Ibaraki, Japan A. Miura JAEA/J-PARC, Tokai-mura, Japan
	LINAC injector of J-PARC (Japan Proton Accelerator Research Complex) was recently successfully upgraded from 181 MeV to 400 MeV, applying a type of coupled cavity linac (CCL) structure ACS (Annular Coupled Structure). It was warmly discussed since very beginning on the wake field in the ACS cavities, where there are CCL modes with the same number as that of cells within ~50 MHz, possibly resonating with high intensity proton/H⁻ beams. One of the most important effects from the wake field is the influence on the ACS phase scan. Analytical and simulation studies, as well as the countermeasures were prepared before the energy upgrade. Fortunately we found that detuning of the ACS was unnecessary, which helped to save much work in the commissioning. In addition we got chance to make experiment studies. It was also discussed why the wake field is not so serious as we expected at the very beginning.

TUPP094	Recent Progress of Beam Commissioning at J-PARC Linac	646
	T. Maruta J-PARC, KEK & JAEA, Ibaraki-ken, Japan K. Futatsukawa, T. Miyao KEK, Ibaraki, Japan M. Ikegami FRIB, East Lansing, Michigan, USA Y. Liu KEK/JAEA, Ibaraki-Ken, Japan A. Miura, H. Sako JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
	We installed Annular-type Coupled Structure (ACS) linac in year 2013 in present linac downstream to extend the beam energy from 181 to 400 MeV. The beam commissioning had been conducted for one month in last December to January, and then we successfully extract 400 MeV beam. Whereas, we stably operate the linac at peak current of 15 mA, which is equivalent to 300 kW at the extraction of 3 GeV RCS, we observe unexpected residual radiations in ACS section. In this presentation, we review the recent progress in beam commissioning and beam loss study.

THPP073	Cavity Excitation of the Chopped Beam at the J-PARC Linac	1023
	K. Futatsukawa KEK, Ibaraki, Japan
	In the J-PARC linac, the beam energy at the injection of the rapid-cycle synchrotron (RCS) was upgraded up to 400 MeV by the installation of 25 additional cavities, annular-ring coupled structure (ACS), in 2013. The initial frequency of RCS was shifted to 1.227 MHz because of the change the injection-beam velocity. At the linac, the beam is chopped as the comb-like structure with this frequency (intermediate-pulse) by the RF deflector. The component of this RCS frequency excited the PC1 mode of DTL2 and was the cause of the RF-control difficulty. Additionally, it could be confirmed that other chopping operations, which does not have specific intermediate-pulses for example, drove other modes. In this paper, I would like to introduce this phenomena and the counterplan as the RF control.

THPP089	High Power Conditioning of Annular-Ring Coupled Structures for the J-PARC Linac	1053
THPOL07	use link to see paper's listing under its alternate paper code
	H. Ao, T. Ito, Y. Nemoto, H. Oguri, N. Ouchi, J. Tamura JAEA/J-PARC, Tokai-mura, Japan H. Asano Nippon Advanced Technology Co. Ltd., Ibaraki-prefecture, Japan Z. Fang, K. Futatsukawa, K. Nanmo, T. Sugimura KEK, Ibaraki, Japan
	The linac of Japan Proton Accelerator Research Complex (J-PARC), which is an injector to a 3-GeV synchrotron, comprised a 3-MeV RFQ, 50-MeV DTLs and 181-MeV Separated-type DTLs. From September 2013, 25 annular-ring coupled structure (ACS) cavities were additionally installed to increase the linac beam energy up to 400 MeV and achieve 1-MW beam power of the 3-GeV synchrotron. After installation work the high power conditioning was started from December 2013 and most of the ACS cavities were conditioned within three weeks. We passed through some troubles and finally finished conditioning all the cavities until the middle of January 2014. In this paper, we present the conditioning results and how to handle the issue in the conditioning process.
	Slides THPP089 [7.756 MB]