HIAT2015 - List of Authors (Nakagawa, T.)

Paper

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MOPA12

Status Report of the Operation of the RIKEN AVF Cyclotron

K. Suda, M. Fujimaki, N. Fukunishi, T. Kageyama, O. Kamigaito, M. Kase, M. Komiyama, K. Kumagai, T. Maie, M. Nagase, T. Nagatomo, T. Nakagawa, H. Okuno, N. Sakamoto, A. Uchiyama, T. Watanabe, Y. Watanabe, K. Yamada
RIKEN Nishina Center, Wako, Japan
S. Fukuzawa, M. Hamanaka, S. Ishikawa, K. Kobayashi, R. Koyama, T. Nakamura, M. Nishida, M. Nishimura, J. Shibata, N. Tsukiori, K. Yadomi
SHI Accelerator Service Ltd., Tokyo, Japan
Y. Kotaka, Y. Ohshiro, S. Yamaka
CNS, Saitama, Japan

The RIKEN AVF cyclotron was commissioned in 1989. Since then, it has been operated as an injector for the RIKEN ring cyclotron. The AVF cyclotron also provides low energy ion beams for the Radio-Isotope Beam separator (CRIB) of the Center for Nuclear Study (CNS), the University of Tokyo, as well as to produce RIs for commercial use. The operating time is more than 3,000 hours per year. We will report the operating status (nuclear species, energy, supply destination of accelerated ions), troubles, maintenance work, and the improvement of ion sources and diagnostics tools for the period from August 2014 to July 2015.

WEPB01

Status Report on the Operation of the RIBF Ring Cyclotrons

1

K. Ozeki, T. Dantsuka, M. Fujimaki, T. Fujinawa, N. Fukunishi, H. Hasebe, Y. Higurashi, E. Ikezawa, H. Imao, T. Kageyama, O. Kamigaito, M. Kase, M. Kidera, M. Komiyama, K. Kumagai, T. Maie, M. Nagase, T. Nagatomo, T. Nakagawa, M. Nakamura, J. Ohnishi, H. Okuno, N. Sakamoto, K. Suda, A. Uchiyama, S. Watanabe, T. Watanabe, Y. Watanabe, K. Yamada, H. Yamasawa
RIKEN Nishina Center, Wako, Japan
S. Fukuzawa, M. Hamanaka, S. Ishikawa, K. Kobayashi, R. Koyama, T. Nakamura, M. Nishida, M. Nishimura, J. Shibata, N. Tsukiori, K. Yadomi
SHI Accelerator Service Ltd., Tokyo, Japan
Y. Kotaka
CNS, Saitama, Japan

Operational status of four ring cyclotrons (RRC, fRC, IRC, SRC) from August 2014 to July 2015 is reported. We are engaging in the improvements and adjustments for increasing beam intensities year after year, and maintenances for the stabilization of beam supply. In these contributions, we will report the past performances of accelerated beams, statistics of operational and tuning time on corresponding period, as well as failures and copings with them.

WEPB14

Heavy-Ion Beam Acceleration at RIKEN for the Super-Heavy Element Search

E. Ikezawa, M. Fujimaki, Y. Higurashi, O. Kamigaito, M. Kase, M. Komiyama, T. Nakagawa, K. Ozeki, N. Sakamoto, K. Suda, A. Uchiyama
RIKEN Nishina Center, Wako, Japan
T.O. Ohki, K. Oyamada, M. Tamura
SHI Accelerator Service Ltd., Tokyo, Japan

The RIKEN heavy ion linac (RILAC) is composed of a variable-frequency Wideröe linac, an 18 GHz ECR ion source, a variable-frequency folded-coaxial radio frequency quadrupole linac (FC-RFQ) as a pre-injector, and a Charge-State Multiplier system (CSM) as a booster. The operation of RILAC was started to supply heavy ion beams for experiments in 1981. The 18 GHz ECR ion source and the FC-RFQ were installed in 1996. The CSM was installed in 2000. The maximum beam energy, boosted by the CSM, is 6.0 MeV/nucleon. A GAs-filled Recoil Isotope Separator (GARIS) was moved from the E1 experiment room of the RRC to the No. 1 target room of the RILAC in 2000. In RIKEN Nishina center, the experiment on the super-heavy element (Z=113) search was carried out at RILAC from September 2003 to October 2012. As a result, three events for Z=113 have been successfully observed. The heavy-ion beam acceleration at RIKEN for the super-heavy element search will be reported.

WEPB22

Supply of Metallic Beams from RIKEN 18-GHz ECRIS Using Low-Temperature Oven

1

K. Ozeki, Y. Higurashi, M. Kidera, T. Nakagawa
RIKEN Nishina Center, Wako, Japan

In the RIKEN 18-GHz electron cyclotron resonance ion source, the practical use of low-temperature oven was achieved for the supply of metallic beams. At the RIKEN Radioisotope Beam Factory, Ca-48 beam is one of the important beams, as a primary beam to produce the secondary beam of neutron-rich medium-heavy nuclei. In order to enhance the intensity and stability of Ca-48 beam, we newly introduced a low-temperature oven and so-called "hot liner." A mixture of CaO and Al powders was placed into the crucible of the oven and heated to produce metallic calcium by a reductive reaction. We succeeded in high-intensity and stable supply of Ca-48 beam, as well as the reduction of material consumption rate. In addition, we succeeded in the supply of Zn-70 beam using the low-temperature oven. In supplying Zn-70 beam, only the ZnO powder was placed into the crucible, and the hot liner was not used. In this contribution, the configuration of low-temperature oven, the effect of the hot liner, the supply situations of Ca-48 and Zn-70 beams for a long-term experiment, and the attempts to supply other metallic beams using the low-temperature oven will be reported.

WEPB24

Development of an Online Emittance Monitor for Low Energy Heavy Ion Beams

1

V. Tzoganis, O. Kamigaito, M. Kase, T. Nagatomo, T. Nakagawa
RIKEN Nishina Center, Wako, Japan
V. Tzoganis
The University of Liverpool, Liverpool, United Kingdom
V. Tzoganis
Cockcroft Institute, Warrington, Cheshire, United Kingdom

RIKEN's 18 GHz ECR ion source supplies the AVF cyclotron with beams ranging from protons to heavy ions as xenon. From comparison with the use of the RILAC (RIKEN Linear Accelerator) and beam transport simulations it was found that the transport efficiency is much lower. To this extend and with the aim to understand the ECR beam production, beam dynamics and optimize the beam transfer we have developed an emittance monitor based on the pepperpot method. The device is composed of a perforated copper plate, transparent scintillator and a CMOS camera for image capturing. Parameters of interest for scintillator's performance are the light yield and radiation hardness. Quartz was found to be resilient to damage and having linear light emission. A real time algorithm written in LabVIEW manages the data acquisition and the 4D phase space distribution calculation. Provided this information, we can investigate parameters such as inter-plane correlation and emittance dependence on extraction specifications, beam current and the magnetic field in the ion source. In this contribution we are presenting the emittance meter design, algorithm description and a set of typical measurements.

WEPB26

Emittance Measurement of Low Energy Proton Beam Extracted from RIKEN 18-GHz Superconducting ECR Ion Source with the Pepper-Pot Emittance Meter

T. Nagatomo
RIKEN, Saitama, Japan
O. Kamigaito, M. Kase, T. Nakagawa, V. Tzoganis
RIKEN Nishina Center, Wako, Japan
V. Tzoganis
The University of Liverpool, Liverpool, United Kingdom
V. Tzoganis
Cockcroft Institute, Warrington, Cheshire, United Kingdom

Emittance measurements are of high importance for beam quality assessment and optimization of beam transport. For the case of ECR ion sources providing highly charged heavy ions, the naturally high emittance of beams extracted under strong magnetic field poses extra challenges for efficient beam transport. Moreover, the transverse inter-plane correlation of the 4D emittance is considered to be important so that the beam brightness increases. For the further understanding of the ECR source and increasing the brightness we have developed emittance monitor based on the pepperpot method that allows the measurement of the 4D emittance. The emittance meter consists of a pepperpot plate and a transparent scintillating screen behind it. As a first step, the emittance meter is installed behind the analyzing magnet, and we have obtained beamlet images with 6.52-keV proton (~100eμA) provided by the RIKEN 18-GHz Superconducting ECR ion source. The beam transport is simulated with the Monte Carlo method (GEANT4). The estimated spatial and phase space distribution are reasonably consistent with those obtained with the emittance meter. Ways to optimize the beam transport are also discussed.

THM1C01

Further Improvement of Performance of RIKEN 28GHz SC-ECRIS and Search for the Optimum Structure of ECR Ion Sources

T. Nakagawa
RIKEN/RARF/CC, Saitama, Japan
Y. Higurashi, J. Ohnishi
RIKEN Nishina Center, Wako, Japan

To search for the optimum structure of the ECR ion source, we studied the effect of the main parameters (magnetic field, etc) of RIKEN SC-ECRIS on the beam intensity for various heavy ions (Ar~U) with 18 and 28GHz. In the systematic studies, we observed that the beam intensity is strongly dependent on these parameters. For examples, optimum value of Bmin for maximizing the beam intensity was dependent on the microwave frequency (~0.8Becr (18GHz), 0.6~0.65Becr (28GHz)) and gas pressure. We found that the optimum value of Br to maximize then beam intensity is strongly dependent on Bmin in a certain condition. Based on these studies, even though we used the magnetic field lower than the ordinary "High-B mode", we obtained more than 200euA of U³⁵⁺ at lower RF power. We could dramatically reduce the consumption rate of metal U form ~8.6 to ~2.8mg/h to produce 150euA of U³⁵⁺. In this contribution, we present the effect of main parameters on the beam intensities for various heavy ions and mechanisms in detail. We show how to optimize the performance to obtain the intense U beam. Based on these studies, we also describe the optimum structure for higher microwave frequency.

Slides THM1C01 [2.402 MB]