IPAC2013 - List of Authors (Imao, H.)

Paper

Title

Page

Progress Towards High-Intensity Heavy-Ion Beams at RIKEN RIBF

333

O. Kamigaito, T. Dantsuka, M. Fujimaki, T. Fujinawa, N. Fukunishi, H. Hasebe, Y. Higurashi, E. Ikezawa, H. Imao, T. Kageyama, M. Kase, M. Kidera, M. Komiyama, H. Kuboki, K. Kumagai, T. Maie, M. Nagase, T. Nakagawa, M. Nakamura, J. Ohnishi, H. Okuno, K. Ozeki, N. Sakamoto, K. Suda, H. Watanabe, T. Watanabe, Y. Watanabe, K. Yamada, H. Yamasawa
RIKEN Nishina Center, Wako, Japan

The RIKEN RIBF(Radioactive Isotope Beam Factory) accelerator complex has been designed and constructed to provide heavy-ion beams from D to U ions with the energy of 400 MeV/u to the maximum. Though the goal intensity is 1 particle μ amperes for the whole mass range, the intensities of very heavy-ions from Ca to U are still not satisfactory. In 2012, owing to the intensity upgrade of ⁴⁸Ca beams from ECR ion source, the beam current of ⁴⁸Ca was 400 pnA which was improved by factors of 2 in comparison with that in 2011. Since 2011, the new injector RILAC2 has been successfully commissioned and operated very stably for beam service time, increasing the U beam intensity by an order of magnitude. Because it was no longer realistic to use carbon foil to strip the charge of intense U beams, in 2012 the Low-Z gas stripper system instead of the standard carbon foil system has been introduced and successfully worked. To accelerate the ²³⁸U⁶⁴⁺ beams provided by the Low-Z gas stripper, modification of the following Fixed-frequency Ring Cyclotron was performed. In 2012, 15 pnA uranium beams which was four times larger than that provided in 2011 has been achieved.

THPPA01

Realization of New Charge-state Stripper for High-power Uranium Ion Beams

3135

H. Imao
RIKEN Nishina Center, Wako, Japan

Recent works to realize the new charge-state stripper using recirculating helium gas are presented. Very limited lifetimes of conventional solid-state strippers due to huge dE/dx for very heavy ion beams (e.g., for uranium ions, several thousand times larger than protons at the energy around 10 MeV/u) were a principal bottleneck for their multi-stage acceleration at high intensities. The new stripping system is characterized by its infinite lifetime, efficient stripping and small beam degradation even for the world’s most intense uranium ion beams provided by the RIBF (more than 1 pμA at the injected energy of 11 MeV/u). Successful operations of the system in 2012 greatly contribute to the remarkable expansion of the accelerator performance of the RIBF that will allow an enormous breakthrough for exploring new domains of the nuclear world in the next several years; the peak intensity of the uranium beam has reached 15.1 pnA (almost 10¹¹ pps) at 345 MeV/u and the average intensity provided for the users has become ten times higher than it was in 2011.

Slides THPPA01 [6.535 MB]

THPWO038

Electron Stripping of High-intensity ²³⁸U Ion Beam with Recirculating He Gas

3851

H. Imao
RIKEN Nishina Center for Accelerator-Based Science, Wako, Saitama, Japan
T. Dantsuka, M. Fujimaki, N. Fukunishi, H. Hasebe, O. Kamigaito, M. Kase, H. Kuboki, K. Kumagai, T. Maie, H. Okuno, T. Watanabe, Y. Watanabe, K. Yamada, Y. Yano
RIKEN Nishina Center, Wako, Japan

Next-generation in-flight RI beam facilities such as RIBF and FRIB pursue powerful and energetic ²³⁸U ion beams to produce thousands of new isotopes. For their efficient acceleration, a durable electron stripper in the intermediate energy region around 10-20 MeV/u is indispensable. However, there is no available stripper for the U beams with the intensity of more than 1 puA so far because of the lifetime problem of thin solid strippers caused by high energy loss. 　In the present study, a novel electron stripping system employing high-flow rate He gas circulation (200 L/min) has been developed. He gas with the thickness of 0.6 mg/cm² is confined and separated from beamline vacuum using five-stage differentially-pumped sections. To avoid huge gas consumption, a clean gas recycling is achieved with multi-stage mechanical booster pump array. The recycling rate of He gas was achieved as more than 99%. The system was successfully operated in user runs with U³⁵⁺ beams more than 1 puA injected at 10.8 MeV/u for the first time. U⁶⁴⁺ beams were stably delivered to subsequent accelerators with the stripping efficiency of 23% without any deterioration of the system.

Paper	Title	Page
MOPFI025	Progress Towards High-Intensity Heavy-Ion Beams at RIKEN RIBF	333
	O. Kamigaito, T. Dantsuka, M. Fujimaki, T. Fujinawa, N. Fukunishi, H. Hasebe, Y. Higurashi, E. Ikezawa, H. Imao, T. Kageyama, M. Kase, M. Kidera, M. Komiyama, H. Kuboki, K. Kumagai, T. Maie, M. Nagase, T. Nakagawa, M. Nakamura, J. Ohnishi, H. Okuno, K. Ozeki, N. Sakamoto, K. Suda, H. Watanabe, T. Watanabe, Y. Watanabe, K. Yamada, H. Yamasawa RIKEN Nishina Center, Wako, Japan
	The RIKEN RIBF(Radioactive Isotope Beam Factory) accelerator complex has been designed and constructed to provide heavy-ion beams from D to U ions with the energy of 400 MeV/u to the maximum. Though the goal intensity is 1 particle μ amperes for the whole mass range, the intensities of very heavy-ions from Ca to U are still not satisfactory. In 2012, owing to the intensity upgrade of ⁴⁸Ca beams from ECR ion source, the beam current of ⁴⁸Ca was 400 pnA which was improved by factors of 2 in comparison with that in 2011. Since 2011, the new injector RILAC2 has been successfully commissioned and operated very stably for beam service time, increasing the U beam intensity by an order of magnitude. Because it was no longer realistic to use carbon foil to strip the charge of intense U beams, in 2012 the Low-Z gas stripper system instead of the standard carbon foil system has been introduced and successfully worked. To accelerate the ²³⁸U⁶⁴⁺ beams provided by the Low-Z gas stripper, modification of the following Fixed-frequency Ring Cyclotron was performed. In 2012, 15 pnA uranium beams which was four times larger than that provided in 2011 has been achieved.

THPPA01	Realization of New Charge-state Stripper for High-power Uranium Ion Beams	3135
	H. Imao RIKEN Nishina Center, Wako, Japan
	Recent works to realize the new charge-state stripper using recirculating helium gas are presented. Very limited lifetimes of conventional solid-state strippers due to huge dE/dx for very heavy ion beams (e.g., for uranium ions, several thousand times larger than protons at the energy around 10 MeV/u) were a principal bottleneck for their multi-stage acceleration at high intensities. The new stripping system is characterized by its infinite lifetime, efficient stripping and small beam degradation even for the world’s most intense uranium ion beams provided by the RIBF (more than 1 pμA at the injected energy of 11 MeV/u). Successful operations of the system in 2012 greatly contribute to the remarkable expansion of the accelerator performance of the RIBF that will allow an enormous breakthrough for exploring new domains of the nuclear world in the next several years; the peak intensity of the uranium beam has reached 15.1 pnA (almost 10¹¹ pps) at 345 MeV/u and the average intensity provided for the users has become ten times higher than it was in 2011.
	Slides THPPA01 [6.535 MB]

THPWO038	Electron Stripping of High-intensity ²³⁸U Ion Beam with Recirculating He Gas	3851
	H. Imao RIKEN Nishina Center for Accelerator-Based Science, Wako, Saitama, Japan T. Dantsuka, M. Fujimaki, N. Fukunishi, H. Hasebe, O. Kamigaito, M. Kase, H. Kuboki, K. Kumagai, T. Maie, H. Okuno, T. Watanabe, Y. Watanabe, K. Yamada, Y. Yano RIKEN Nishina Center, Wako, Japan
	Next-generation in-flight RI beam facilities such as RIBF and FRIB pursue powerful and energetic ²³⁸U ion beams to produce thousands of new isotopes. For their efficient acceleration, a durable electron stripper in the intermediate energy region around 10-20 MeV/u is indispensable. However, there is no available stripper for the U beams with the intensity of more than 1 puA so far because of the lifetime problem of thin solid strippers caused by high energy loss. 　In the present study, a novel electron stripping system employing high-flow rate He gas circulation (200 L/min) has been developed. He gas with the thickness of 0.6 mg/cm² is confined and separated from beamline vacuum using five-stage differentially-pumped sections. To avoid huge gas consumption, a clean gas recycling is achieved with multi-stage mechanical booster pump array. The recycling rate of He gas was achieved as more than 99%. The system was successfully operated in user runs with U³⁵⁺ beams more than 1 puA injected at 10.8 MeV/u for the first time. U⁶⁴⁺ beams were stably delivered to subsequent accelerators with the stripping efficiency of 23% without any deterioration of the system.