Research Activities 1991–2016

RIKEN Accel. Prog. Rep. 50 (2017)

Retrospective of my 24-year “RIBF life”
Yasushige Yano ∗1,∗21

Introduction

Ever since I joined RIKEN in 1979, I have devoted
my eﬀorts to the construction of the heavy-ion accelerator facility and the promotion of nuclear physics andapplications of heave-ion beams. In December 1986, I
completed Japan’s ﬁrst ring cyclotron (separate sectorcyclotron) named RIKEN Ring Cyclotron (RRC) under Professor H. Kamitsubo, and in 1987, I proposed
the “RI Beam Factory (RIBF)” as my dream, which
eventually led to the creation of the world-class RIbeam facility. Then, in 1997, the RIBF project wasapproved, and I undertook the construction of RIBF
with the world’s ﬁrst superconducting ring cyclotron(SRC) as its main component. In December 2006, 20years after the commissioning of the RRC cyclotron, I
successfully led the new facility to the start of its operation. Currently, the RIBF is being utilized by theinternational nuclear physics community as the world’s
leading fast RI beam facility. In April 2006, the RIBF,the RIKEN BNL Research Center in the USA, and theRIKEN RAL Muon Facility in the UK were integrated
to create the RIKEN Nishina Center for AcceleratorBased Science, and I was appointed as the ﬁrst directorof the Center. In September 2009, I stepped dawn, andnow, I am devoted to upgrading the RIBF as the senior advisor to the Center. Here, I look back on the 24years (from 1987 up to 2011) I devoted to the RIBF
project.
2Fig. 1. Layout of the RIBF

51 MeV per nucleon. This charge stripping is now processed by an ordinary thin carbon foil (presently, theshort life-time of the stripper is a serious bottle neckto increase the uranium beam intensity). The 345MeV/nucleon uranium beam from SRC is transferredto the production target, and ﬁssion fragments are isotopically selected and collected by the large-acceptancesuperconducting BigRIPS.6)
The superconducting ZeroDegree spectrometer(ZD) 6) and SHARAQ spectrometer 7) are used for theexperiments, and the large-acceptance superconducting SAMURAI spectrometer 8) has been commissioned
for experiments early in 2012. The unique electronRI scattering ring with the self-conﬁning RI ion target (SCRIT) has been completed.9) This ring will allow the precision measurement of charge distribution,
namely proton distribution inside unstable nuclei, forthe ﬁrst time. The construction of Rare-RI ring wascompleted in 2013.10) It will allow precision mass measurements with the accuracy better than 1 p.p.m. forquite rare RIs with a productivity of 1 particle perday. The RIBF is now exhibiting its powerful potentiality to explore the nuclear world that was previously
not accessible. In November 2008, 45 new radioactive
isotopes were discovered in only a 4-day experimental
run and with only 0.3 pnA beam intensity.11) Amongthem, palladium-128 is speculated to be the origin of
the second peak in the solar isotope abundance. In
another two years, this uranium beam intensity will
be increased by 400 times by installing a novel pressurized He-gas charge stripper having inﬁnite lifetime.
This decisive breakthrough has been devised by myyounger colleague, Dr. H. Okuno.12) RIBF will greatly
expand our known nuclear world up to around pink-Overview of RIBF

The RIBF 1) consists of a 22-year old facility and anew facility. These two facilities are connected to eachother underground. The layout of the RIBF is shownin Fig. 1. The RIBF is now capable of providing all ionsat 345 MeV/nucleon.2) RI beams are produced via inﬂight uranium ﬁssion or the projectile fragmentationof stable isotopes.
Consider uranium ﬁssion for instance. A uranium
35+ beam obtained from the 28 GHz superconducting ECRIS 3) is pre-accelerated by the newly operational RILAC II,4) and injected into the old RRC cyclotron. The energy of the RRC beam is boosted up
to 345 MeV/nucleon by the new cyclotron cascade offRC, IRC, and ﬁnally the superconducting ring cyclotron, SRC.5) The 35+ uranium ions are chargestripped twice before and after the fRC cyclotron, from35+ to 71+ at 11 MeV/nucleon and from 71+ to 86+ at∗1∗2

Director of RIKEN Nishina Center (2006–2009)
Chief Scientist of Cyclotron Laboratory/Accelerator Group(1991–2008)

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Research Activities 1991–2016

Fig. 2. Celebration of the ﬁrst beam extraction from theNo. 5. cyclotron (RRC) at 15:34 on Dec. 16, 1986.
Twenty years later, the ﬁrst beam from the No. 9 cyclotron (SRC) was produced.

Fig. 3. Cover page of the popular Japanese science magazine “Parity” published in June, 1987.

coloured (in-ﬂight ﬁssion) and sky-blue-coloured (projectile fragmentation) regions, which contain a hypothetical r-process pathway (green arrow) to create theuranium element at the moment of super-nova explosion, when we will achieve a primary beam intensityof 1 pμA for all ions. The RI-intensity produced at
the edge of the regions is estimated by the GSI’s simulation program EPAX2.13) The signiﬁcant challengeof uncovering the mystery of the element genesis hasbegun.
3on the commissioning of the RIKEN Ring Cyclotron
in the popular Japanese science magazine “Parity.” A
photo of the RRC cyclotron was shown on the cover
page, as shown in Fig. 3. In the article, we wrote that
our future dream is to create the world’s leading “RIbeam factory.”
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From RARF to RIBF

In the same year, when the discovery of high-TC
superconductivity was a hot topic, I was invited toattend a panel discussion on superconductivity andatomic energy. In this panel presentation, I presented avery conceptual drawing of the RI beam factory basedon a superconducting sector-magnet cyclotron. In myscheme, I would later add an SRC and an RI beam collider downstream of the then newly operational RRC
cyclotron.
In 1995, eight years after the RRC commissioning, atwo-year R&D budget of nearly $2M was approved.
By then, the RIBF plan consisted of a single big
150 MeV/nucleon SRC and a MUlti-use Experimental
Storage rings, MUSES.15) MUSES aimed at realizing
the world’s ﬁrst electron-RI beam collider. However,this SRC had a serious problem in its design. In 1996,
we had to conclude that the beam injection to this SRC
was impossible because the central region was too narrow to set up the injection elements. This was the ﬁrst
hurdle we struggled to overcome.
Incidentally, the same year, I was invited over thephone by Professor B. Sinha, the then director of theVECC, in Calcutta, India to his oﬃce to take the photograph shown in Fig. 4 of us shaking hands to celebrate the conclusion of an MOU. During the ﬂight

RARF

Let us look back on the 24 years, devoted to theRIBF project, from 1987 to date.
The RIKEN Nishina Center 14) established in 2006
is also my creation, and it is the ﬁrst Japanese research center named after one of our great pioneering scientists. Dr. Nishina is called the Japanese father of nuclear science, and he mentored the ﬁrst two
Japanese Nobel Prize winners, Professors H. Yukawaand S. Tomonaga. Furthermore, the developmentof Japanese accelerators was initiated from his cyclotrons. I spent three and half years as the ﬁrst director of the RIKEN Nishina Center, and now my youngercolleague, Dr. H. En’yo, has succeeded me. Professor
W.F. Henning, the former director of GSI, was appointed as the deputy director in charge of RIBF in2010.
Figure 2 shows a photograph of our team celebrating
the ﬁrst beam extraction from the RRC cyclotron. The
memorable moment occurred at 15:34 on December 16,
1986. Twenty years later, the ﬁrst beam came out fromthe SRC cyclotron.
In 1987, Prof. M. Ishihara and I wrote a news article

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RIKEN Accel. Prog. Rep. 50 (2017)

Fig. 4. VECC-RIKEN MoU conclusion meeting at Calcutta, India in 1996.

Fig. 5. Yearly trends in iron price from 1980 to 2006.

from Narita to Calcutta, I came up with an idea thatthe single big SRC should be split into smaller butwith larger central-region SRC and an IRC cyclotron
having a structure similar to the RRC.
The inset of Fig. 4, my memo in the travel note bookwhere I jotted down this idea. In 1997, the construction budget was approved. In the ﬁgure, “SRC” and“IRC” can be seen.16) We requested $750M in total,but I was strongly requested by the government to reduce this cost by a signiﬁcant amount. However, we
still had serious problems in the SRC design. In 1998,I concluded that this SRC design included too manytechnical problems to be solved, and all the problems
are due to the large valley-region leakage ﬂux in thelong term.
After recognizing this serious design drawback, I
could not sleep well until, in 1999, I decided to coverwhole valley regions with thick iron plates to absorb
leakage ﬂux. This was the simplest solution to solve
all the problems.17) The only problem was that the required mass of iron amounted to 8,000 tons, which is
1,000 tons heavier than the Eiﬀel Tour in Paris. Thus,
the world’s ﬁrst, strongest, and heaviest SRC was born.
This structure has self-radiation shielding capability as
well. In November 2005, full excitation of the SC sector magnets was achieved.
Figure 5 shows the yearly trends of iron price from1980 to 2006. We purchased 8,000 tons near the period
when the price was minimum. In order to constructthis super-facility, this stroke of luck was indispensable.

Fig. 6. A photo of the RIBF control room taken when theﬁrst beam was extracted from the SRC at 16:00 on December 28, 2006.

one more inexpensive cyclotron, fRC, to upgrade theﬁnal energy to 340 MeV/nucleon. Moreover, BigRIPS
should be a large-aperture SC separator that can accept large-emittance ﬁssion fragments. These are thepresent design.17)
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The ﬁrst beam and beyond

The ﬁrst beam was extracted from the SRC at themoment indicated in Fig. 6, I had been declaring foryears to the international accelerator community thatthe ﬁrst beam would be extracted exactly 20 years after the ﬁrst beam was extracted from the RRC cyclotron. Although the beam was slightly delayed, wealmost well were successful.19) “Science” magazine and“Nature” magazine reported the completion of RIBF.

In 1999, an RIA project of the USA based on SC
linacs was proposed, and the “white paper” of theproject stated that the 150 MeV/nucleon uranium
beam planned to be supplied through the RIBF projectis insuﬃcient to eﬃciently produce RI beams by inﬂight ﬁssion. Instead, 400 MeV/nucleon should beachievable.18) Then, in 2001, I decided that we addS-3

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Research Activities 1991–2016

In June 2007, the International Nuclear Physics
Conference (INPC’07) was held in Tokyo, and I wasgiven an extra session to deliver a ﬂash report on theﬁrst outcome of RIBF: the discovery of a very neutronrich isotope, palladium 125, by the in-ﬂight ﬁssion ofa 345-MeV/nucleon uranium beam. Incidentally palladium 112 was discovered using Dr. Nishina’s cyclotron.20) In his experiment, he discovered a much
more surprising “symmetric ﬁssion” of uranium by fastneutrons, unlike the well-known “asymmetric ﬁssion”
by slow neutrons. When closing my talk, I declaredthat a great endeavour has begun to explore areas of
the nuclear world that have been inaccessible thus far.
In the opening session of the conference, the Emperordelivered a very moving message to the audience about
the tragedy of Japan and Japanese people caused by
the atomic bombs and the role of the nuclear physics
community.
Incidentally, during my directorship since 1992, I enjoyed the honour of guiding the Emperor on a tour ofour cyclotron facilities twice, ﬁrst in 1992 and thenin 2006. I believe that now, the Japanese Emperorand Empress are the most informed royal couple in
the world on cyclotrons.
How about MUSES? In 2001, the GSI reported thatthe luminosity obtained in MUSES is too low to create scientiﬁc impacts because the RIKEN system isbased on a DC beam, rather than a pulsed beam. We
absolutely agreed. Therefore, in 2003, I decided togive up the MUSES project, and instead decided toconstruct much better cost-eﬀective high-performancealternatives, namely the SCRIT for precision chargedistribution measurement by electron scattering (thisnovel scheme was devised by my younger colleague,Dr. M. Wakasugi), and the Rare RI ring for precisionmass measurement. The top of Fig. 7 shows a photograph of the completed electron-RI scattering system, and the bottom diagram shows its principle, theessence of which is that we utilize the unfavorable “iontrapping” phenomenon positively. We published twoPRL papers on the experimental proof of principle.21)
6Fig. 7. Self-conﬁning RI ion target (SCRIT) for e-RI scattering experiments.

Fig. 8. Dr. Nishina’s cyclotrons and the original RIKEN
campus.

Dr. Nishina’s dreamclotrons. This old aerial picture shows the original
RIKEN campus, which was located near the center ofTokyo. On the top-right corner of this picture, there
used to be Nishina’s laboratory. The two buildings
indicated in white dots housed his No. 1 and No. 2 cyclotrons. The No. 2 cyclotron, commissioned in 1944
just before the end of World War Two, was the world’s
largest cyclotron at that time, and was about to startexperiments. However, as many of you know, these
cyclotrons and at the same time Dr. Nishina’s dreamwere killed by the War, as shown in the “Life” magazine issued in December 1945 (Fig. 9).
Since then, sixty six years have passed. I believe now
that Dr. Nishina’s dream has been realized. However,my dream will take a little more time to come true.

One day before the ﬁrst International Particle Accelerator Conference (IPAC’10) in Kyoto, Japan, “Special lectures to commemorate the 120-th anniversaryof Birth of Yoshio Nishina” was held. In this lecture meeting, distinguished Professors presented talks
about Dr. Nishina and the advancement of particle accelerators and their applications in Japan. One of thelecturers, Professor M. Craddock, spoke about a verysuggestive and impressive review story of Japanese cyclotrons from Dr. Nishina’s pioneering work up to thepresent RI Beam Factory. The lecture notes can beviewed on RIKEN Nishina Center’s home page.
Figure 8 shows photographs of Dr. Nishina’s cy-S-4

Research Activities 1991–2016

RIKEN Accel. Prog. Rep. 50 (2017)14) http://www.nishina.riken.jp/.
15) Y. Yano, T. Katayama, Proc. EPAC’94, p. 515.
16) Y. Yano, A. Goto, T. Katayama, Proc. PAC’97, p. 930.
17) Y. Yano, A. Goto, M. Kase, T. Katayama, Proc. CYCLOTRON’01, p. 161.
18) ISOL Task Force Report to NSAC, 22 November 1999.
19) Y. Yano, Proc. PAC’07, p. 700 (2007).
20) Y. Nishina, T. Yazaki, K. Kimura, M. Ikawa, Nature,p. 660 (1939).
21) M. Wakasugi et al., Phys. Rev. Lett. 100, 164801(2008); T. Suda et al., Phys. Rev. Lett. 102, 102501(2009).

Fig. 9. Disassembling of No. 1 and No. 2 cyclotrons recported in “Life” magazine in 1945. 1945
LIEF.

Acknowledgments
I wish to give my special thanks to many, many
Japanese and foreign colleagues and collaboratorsand the presidents of RIKEN, especially Professor
A. Arima. Without his strong support, this big project
could not have started. Furthermore, I wish to express my gratitude to the International Advisory Committees (IACs) and the International Technical Advisory Committees (TACs) of the RIBF project, whichhave continuously led us in the right way, to the Governments that have strongly supported this project,and also to the companies that have helped us realize
RIBF.
References
1) Y. Yano, Nucl. Instrum. Methods Phys. Res. B 261,1009 (2007).
2) O. Kamigaito et al., Proc. Cyclotrons’10.
3) Y. Higurashi et al., Proc. IPAC’10, p. 4191.
4) K. Yamada et al., Proc. IPAC’10, p. 789.
5) H. Okuno et al., IEEE Trans. Appl. Supercond. 18,
226 (2008).
6) T. Kubo et al., IEEE Trans. Appl. Supercond. 17, 1069(2007).
7) S. Uesaka et al., AIP Conf. Proc. 1224, 573 (2010).
8) Y. Shimizu et al., The International Nuclear Physics
Conference 2010, INPC2010, July 5, 2010, University of British Columbia, Vancouver, Canada, J. Phys.
Conf. Ser.
9) M. Wakasugi, T. Suda, Y. Yano, Nucl. Instrum. Methods Phys. Res. A 532, 216 (2004).
10) Y. Yamaguchi et al., Nucl. Instrum. Methods Phys.
Res. B 266, 4575 (2008).
11) T. Ohnishi et al., J. Phys. Soc. Jpn. 79, 073201 (2010).
12) H. Okuno et al., Phys. Rev. ST Accel. Beams 14,033503 (2011).
13) K. Suemmerer, B. Blank, Phys. Rev. C 61, 034607(2000).

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