CYCLOTRONS AND FFAGS:FROM NISHINA’S PIONEERING WORK TO RI-BEAM FACTORY*
Michael Craddock, University of British Columbia and TRIUMF, Vancouver, B.C., Canada
CLASSICAL CYCLOTRONSAbstract
The first cyclotron to operate outside the USA was built
by Yoshio Nishina's group at RIKEN (1935-7). It wasquickly followed by three more Japanese machines,
establishing a tradition that has produced many importantresearch cyclotrons, culminating in the world's mostpowerful - the superconducting SRC at the RIKEN RIBF.
Moreover, technology transfer has enabled Japaneseindustry to produce and sell numerous smaller cyclotrons
around the world, mostly for isotope production. Japanesescientists have also led the development of Fixed-Field
Alternating-Gradient (FFAG) accelerators - from the firstsuggestion by Ohkawa in 1953 to Mori's construction of
the first proton FFAG in 2000. This leadership has
continued with the latter's recent pioneering studies of
ADSR using a 3-ring FFAG complex to drive the KURRI
reactor, and investigations of novel non-scaling FFAGs
by ex-members of his team..

Cyclotrons, of course, began at Berkeley in 1930.
Ernest Lawrence’s invention revolutionized nuclear
physics at that time, promising the capability of reachingunlimited energies for the study of nuclear structure andreactions - and of doing novel research in biology andmedicine with artificially produced isotopes. Figure 1
shows Lawrence and his student Stanley Livingston standing inside the magnet yoke of what was at first a 27-inchdiameter-pole cyclotron, later enlarged to 37 inches. Notethe characteristic shape of that magnet because we will
come across several more examples later on. Many suchmagnets had been built for Poulsen Arc radio-wave
generators in the days before tubes became available.

INTRODUCTIONFirst I must thank the organizers of these special
lectures for granting me the privilege of speaking about
Dr. Nishina’s work in pioneering cyclotrons in Japan, andabout how those scientists who were inspired by him havenot merely continued that tradition but led Japan to a
position of accelerator leadership today. Secondly, I mustacknowledge my debt to previous writers on the history ofJapanese cyclotrons, particularly Dr. Yasuo Hirao, whose
invaluable 1986 article [1] I have plagiarized shamelessly.
Other useful accounts are those by Kim [2], Low [3] andHeilbron and Seidel [4].
The story of cyclotrons in Japan is an impressive one,
beginning with Dr. Nishina’s 26-inch cyclotron and culminating, for the moment at least, in the huge superconducting ring cyclotron for RIKEN’s RadioIsotope Beam
Factory. Nor has this success been confined to theacademic sphere: part of RIKEN’s mandate was totransfer technology to industry – and indeed Japanesecompanies have been among the most active in building
commercial cyclotrons for industry and medicine.
I have included Fixed-Field Alternating-Gradient(FFAG) accelerators in this talk both because they are
members of the cyclotron family of fixed-magnetic-field
accelerators (McMillan [5]), and because of their verystrong links with Japan. The first suggestion for an FFAG
was made in 1953 by Tihiro Ohkawa [6], who had once
worked in Nishina’s lab. Then 10 years ago, Yoshiharu
Mori [7] was the first to build a proton FFAG – and laterwent on to build the 3-ring FFAG complex at the Kyoto
University Research Reactor Institute – currently carryingout tests of Accelerator-Driven Subcritical Reactor
operation (ADSR) [8].

Figure 1: Lawrence (right) and Livingston with the
27-inch (later 37-inch) cyclotron.
Anyhow, as we heard in the first talk, Yoshio Nishina
had been in Europe for most of the 1920s, working on avariety of topics, mostly as an experimenter, but also intheory, first with Rutherford, and then successively with
Born, Bohr and Pauli. When he returned to RIKEN at theend of the decade, fired up with enthusiasm for modern
physics, he was given his own laboratory and started an
ambitious research programme with groups in quantum
theory, cosmic rays, nuclear physics and radiobiology.
By 1935, Nishina had acquired sufficient funding tobuild a cyclotron of his own. As you can see from theshape (Figure 2), it was again based on a Poulsen Arc
magnet. With advice from Lawrence and the experience
gained by his assistants, Yasaki and Sagane, whom he had
sent to Berkeley, it was brought into operation [9] by
April 1937 – the first outside the US - a remarkableachievement considering how well established all theEuropean laboratories were.

Figure 2: Nishina’s 26-inch cyclotron. The two boxes infront contained rabbits for radiobiological experiments.
But hardly was the paint dry on this machine than
Nishina was planning a larger one. Indeed, as experiments began he was already ordering parts for a 60-inch
cyclotron, just as Lawrence was in Berkeley. Truly a man
built in the Lawrence mould! Again, there was close
collaboration with Berkeley, with Lawrence ordering two
magnets, hoping to make both less costly, and also someother parts that were less expensive to produce in the US.
Thus Nishina had a very early start on building this large
cyclotron (Figures 3-5).

Figure 4: (Left) The 60-inch cyclotron’s two dee stems –quarter-wave resonators supporting the dees – with Dr.
Nishina standing between them. (Right) One of the dee
stems is consigned to Tokyo Bay – a sad day for physics.

Figure 5: Dr. Nishina pleads with the dismantling team:“This is ten years of my life - it has nothing to do withbombs” [11] - but to no avail.

Figure 3: The 200-ton magnet for the 60-inch cyclotron,with Dr.Nishina (centre) and staff (1938).
This came into operation for the first time in 1939
producing 9-MeV protons, a world record for a brief
period, though with very low beam intensity. In fact,some major redesign was needed, and with wartime
shortages and the Berkeley link broken, it was only in1944 that the intensity was raised to 4 μA, and thenquickly to 180 μA of protons and 350 μA of deuterons,
enabling a full experimental program to begin [10].
But that success was cut short by the end of the Second
World War. In November 1945, the US Secretary of War,
prompted by General Groves, authorized the destructionof all the cyclotrons in Japan: both cyclotrons were dumped into Tokyo Bay. Subsequent protests by Compton andother US scientists led to the Secretary of War’s admissionthat it was a mistake – cold comfort for RIKEN scientists!

Besides RIKEN, Osaka and Kyoto Universities had
also built cyclotrons. Seishi Kikuchi, originally fromRIKEN, had moved to Osaka and also obtained funds fora cyclotron in 1935. Figure 6 (left) shows his 24-inch
machine, which in 1938 was producing 20 μA of 5-MeV
deuterons. At Kyoto, they were a little later, starting construction of a rather larger 39-inch cyclotron in 1940. But
only the magnet (Fig. 6 (right)) was complete by the endof the war. Both cyclotrons were consigned to Osaka Bay.

Figure 6: (Left) The Osaka 24-inch cyclotron. (Right) The
Kyoto 39-inch magnet.

Although the Japanese machines had been destroyed,
the experience gained with them had produced a generation of knowledgeable cyclotron physicists and engineers,
ambitious to continue their research. But post-war conditions were economically difficult (Figure 7 (left)) and it
was not until the 1950s that the three centres were able tobegin construction. Figure 7 (right) shows the most ambitious, Osaka’s 44-inch cyclotron, completed in 1954. Thismachine was notable for having been submerged in a
1961 typhoon, after which it was moved from downtown
to a hilltop location.

Figure 9: The RIKEN 84-inch heavy-ion cyclotron. The
red arrow at the top identifies a young employee about
whom we will hear more (and who gave the previoustalk), Kamitsubo-san.

SYNCHROCYCLOTRON
Figure 7: (Left) Diffusion pump transport, Osaka, 1953.
(Right) The 44-inch Osaka cyclotron.
Kyoto’s Institute of Chemical Research started overwith a 41-inch cyclotron (Figure 8). This was completed
in 1955, producing strong beams of 7 MeV/u deuterons
and alpha particles and operating well into the 1980s.
Today it stands outside the ICR, a handsome monument
to pioneering days.

Figure 8: The Kyoto 41-inch cyclotron. The notice warns:“CAUTION – Magnet - Take care of YOUR WATCH!”
RIKEN had been the first (in 1953) to commission apost-war cyclotron, a more modest 26-inch model, having
found yet another Poulsen Arc magnet! But they soon
began on a much more ambitious project, an 84-inch
machine employing a 340-ton magnet, one of the largestever classical cyclotrons. This came into operation in
1966, enabling protons to be accelerated to ~20 MeV, andheavier ions (C, N, O) to ~10 MeV/u [12] – presaging thefuture direction of the lab’s research.

In the 1950s the Institute of Nuclear Study (INS) was
formed at the University of Tokyo. The group there, led
by Hiroo Kumagai, built a 280-ton cyclotron with 63-inch
poles to a novel design (Figure 10). It could be operated
either in fixed frequency (FF) mode to give high-intensity
variable-energy proton beams from 7 to 15 MeV (1957),
or in frequency-modulated (FM) mode to yield a fixedenergy beam of 57 MeV (1958) [13].

Figure 10: The INS 63-inch cyclotron: (Left) H. Kumagaiwith the prototype magnet. (Right) Alternative dees for
operating in FM mode (above) or FF mode (below). The
dees could be moved along rails for insertion into thecyclotron (to the left).

SECTOR-FOCUSED CYCLOTRONSThen came the age of sector-focused cyclotrons. The
first two Japanese designs came into operation in 1974.
That at INS, led by Yasuo Hirao, was a three-sector
machine [14] with 168-cm poles producing 10-μA beamsof 45-MeV protons, and also 17-MeV/u alphas and6 MeV/u Ne6+ (Figure 11).

Back in 1987, RIKEN, led by Hiromichi Kamitsubo,
had produced a similarly massive machine, the 2100-ton
K540 RIKEN Ring Cyclotron (RRC) [17]. This has 4
radial sectors and can accelerate heavy ions to an energyof 540(Q/A)2 MeV/u (where Q is their charge and A their
atomic mass number), or protons to 210 MeV. A K70
compact cyclotron was also built as the injector.

Figure 11: The INS SF cyclotron. Inset: Yasuo Hirao.
A new institute had also been created at Osaka, theResearch Center for Nuclear Physics (RCNP). The group
there, led by Michiya Kondo, also built a 3-sector machine (Figure 12). This had 230-cm poles, giving 50-μA
85-MeV proton beams, and up to 30-MeV/u alphas [15].
Figure 14: The RIKEN Ring Cyclotron and staff. Inset:
Hiromichi Kamitsubo.
But this was only the beginning – the RRC seems tohave been a breeder, which under the leadership ofYasushige Yano, has spawned another three ring cyclotrons! These are the K570 fixed-frequency Ring Cyclotron (fRC), the K980 Intermediate Ring Cyclotron (IRC),
and the K2600 Superconducting Ring Cyclotron (SRC).
Operating in cascade, together with the heavy-ion linac
RILAC and the RRC, these form the RadioIsotope Beam
Factory (RIBF).
Figure 12: The RCNP Osaka AVF cyclotron; the magnet
is almost hidden behind the rf equipment
This machine now acts as injector to a much larger
6-sector 400-MeV spiral-sector ring cyclotron (Figure 13),completed by Iwao Miura’s team in 1991 [16]. This is thesecond-highest-energy proton ring cyclotron after PSI’s
590-MeV machine. It also delivers light ion beams of
140 MeV/u for 3He, 100 MeV/u for deuterons and alphas,and 70 MeV/u for slightly heavier ions. Its specialty is
producing beams with very high energy resolution.
Figure 15: The RIBF cyclotron complex
The most notable of the three is the SRC - the world’s
most massive (8,300 tons) and most powerful (K2600)
cyclotron (Figure 16) – capable of accelerating ions ofany mass to 345 MeV/u. Each of its 6 radial magnet
sectors is powered by separate superconducting coils –the first cyclotron in which this has been attempted. The
140-ton cold mass was first cooled down at the end of2005 and the first full-energy beam (27Al10+) was extracted in 2006; a full-energy U86+ beam followed in 2007 [18].
This pioneering machine is surely a fitting centrepiece fora Nishina Center!
Figure 13: The RCNP 2200-ton 400-MeV ring cyclotron.

Figure 18: Fixed-field accelerators - the cyclotron family.
Figure 16: The RIKEN Superconducting Ring Cyclotron
and staff. Inset: Yasushige Yano.
Japanese industry played a major role in building thecomponents of these impressive research cyclotrons, andhas applied the expertise acquired to becoming a successful international supplier of small cyclotrons for medicine
and industry. The Japan Steel Works models include a
17-MeV cyclotron for making PET isotopes. Sumitomo
also produces a range of cyclotrons for isotope production,
two of which, installed at the National Institute for Radiological Science (NIRS) at Chiba are shown in Figure 17.

They were first proposed independently (presumably byvirtue of location and language) by Ohkawa [5] in Japan
in 1953, by Kolomensky [19] in Moscow in the same year,
and by Symon [20, 21] in the United States in 1954.
Donald Kerst [22] added the idea of spiral edge focusing.
The most intensive studies of FFAGs were carried out at
MURA in Wisconsin in the 1950s and 60s. Several
electron models were built and operated, but no proton
FFAG until Mori’s at KEK in 2000.
Now there is a great deal more interest. Six are in
operation for protons, electrons and alpha particles, andtwo more for electrons are under construction. Also many
designs are under study for a variety of particles, including some novel “non-scaling” designs, with diverse
applications in view, including cancer therapy, industrial
irradiation, driving reactors, providing intense highenergy proton beams and producing neutrinos.

Tihiro Ohkawa

Figure 17: The Sumitumo HM-18 (18-MeV H) andSHI-930 (89-MeV proton) cyclotrons at NIRS.

FFAG ACCELERATORSAs Figure 18 indicates, FFAGs are the least constrained
members of the cyclotron (fixed-magnetic-field accelerator) family, offering a wide variety of operating conditions.
Like synchrocyclotrons they are frequency-modulated andrun in pulsed mode, but, unlike them, benefit from strong
focusing produced by alternating radial field gradients.
The fixed magnetic fields of FFAGs make their orbits
spiral outwards, so that they need wider magnets, rf
cavities and vacuum chambers than synchrotrons. But
their repetition rates can be much faster (up to kilohertz)
as there’s no need to cycle the magnetic field. Also they
have very large horizontal and momentum acceptances.
For these two reasons they can deliver much higher beam
currents than synchrotrons – a consideration that has
fuelled interest in FFAGs for nearly 60 years.

As mentioned above, the first suggestion for FFAGs
came from Tihiro Ohkawa (Figure 19), someone who,
interestingly enough, though not a direct student of Dr.
Nishina, may well have been inspired to take up physics
as a career through exposure to him at the age of 16 as ahigh-school student helping in a RIKEN lab. I contacted
Dr. Ohkawa a couple of weeks ago and he explained:“Incidentally, I met Professor Nishina during war time.
Because of the air raid danger, RIKEN was dispersing

Figure 19: L-R: Ernest Courant, Tihiro Ohkawa, David
Judd, Nils Vogt-Nilsen, Kent Terwilliger, Felix Adler andOtto Frisch at the 1955 MURA Summer Study.

some of divisions away from Tokyo. The cosmic raygroup came to my hometown Kanazawa. Several of thestudents of the Gymnasium were recruited to help reestablishing the lab. Professor Nishina paid a visit oncea month and he would tell us about the time he spent in
Bohr’s laboratory.”
Anyhow, after graduating from Tokyo University,
Ohkawa conceived the idea of applying the newlydiscovered alternating-gradient focusing to fixed-field
accelerators by alternating positive-bending magnets withshorter reverse-bending ones (Figure 20). As the fieldstrength B increases outwards in each of the magnets,
the gradient dB/dr alternates in sign between the positive–
and reverse-bending magnets, providing AG focusing.

Scaling FFAGS
A major concern in the 1950s was to avoid exciting
resonances between the transverse betatron oscillations
and the magnetic field harmonics, as these could lead toloss of beam quality or intensity. The general resonancecondition may be written:l r ± m z = nwhere r , z denote the betatron tunes (the number of transverse oscillations per turn) and , m and n are integers. To
avoid crossing any resonances, FFAGs therefore followed
so-called scaling designs in which the orbit shape, optics
and tunes were kept constant throughout acceleration.
To first order the tunes are given by the same equations
as those for imperfectly isochronous cyclotrons:(radial)r2  1 + kz2  -k + F 2(1 + 2tan2 ),
r  Bz ,
where the field index k (r )  Bz  r(vertical)

the magnetic flutter

F 2  [Bz ( )   Bz  ]2

 Bz  2 ,and  is the spiral angle.

Figure 20: Radial-sector FFAG magnets and orbits.
On alerting Kerst to his earlier work Ohkawa wasinvited to join the MURA group and spent a couple ofyears there. Among his most notable contributions was
the idea of the two-way FFAG collider [23], where thepositive- and reverse-bending magnets are of equal length(Figure 21). The orbits nevertheless close, as the arcs inthe positive bends are longer and in stronger field regions
than those in the reverse bends. Such a device can therefore support counter-rotating beams of the same charged
particle. This was one of the first schemes for a particle
collider and formed the basis of the MURA 50-MeV
electron model.

Figure 21: (Left) The two-way collider. (Right) The
MURA 50-MeV electron model.
After MURA, Ohkawa moved to CERN and then joined Kerst, who had gone to General Atomics to work on
fusion plasmas. There and at UC San Diego he pursued adistinguished career in plasma physics with over 150
publications and over 100 patents. In 1979 he was awarded the Maxwell Prize of the American Physical Society.

Clearly, achieving constant r requires
k = constant,
implying magnetic field and momentum profiles of theform:Bz  = B0(r/r0)k p = p0(r/r0)k+1.
Constant k also means that to achieve constant z we needF 2(1 + 2tan2 ) = constant.
This quantity must also be given a high value, since
usually k >> 0 in order to minimize the radial aperture.
MURA’s recipe was to keep the flutter
F2(r) = constant,by using a constant field profile Bz()/Bz and: for spiral sectors: choosing constant , so the sector axis
is a logarithmic spiral:
R = R0ecot; for radial sectors: boosting the flutter F2 by alternating
positive-bending magnets (usually with positive k andso radially focusing (F)) with shorter reverse-bending
defocusing (D) magnets, usually with:
BD = -BF.
Of course, reverse fields increase the mean radius: its
ratio to the local radius of curvature, the “circumference
factor”, is 4.45 in the absence of straights [21], but
smaller in their presence. The radial-sector design isshown schematically in Figure 20 above.
MURA built several successful electron models, including 400-keV radial-sector, 120-keV spiral-sector, and
50-MeV two-way machines. They also pioneered much of
the basic theory of high-energy synchronous accelerators,
particularly rf acceleration and beam stacking. But noneof the MURA proposals for proton FFAGs of 10, 15, or
20 GeV were funded. It was not until Yoshiharu Mori andhis team [7] built the Proof-of-Principle (PoP) 1-MeV

radial-sector machine at KEK about 10 years ago that
protons were accelerated in an FFAG (Figure 22). They
then went on to build a 150-MeV FFAG ring [24] with 12
cells and a small cyclotron as injector.

Boron Neutron Capture Therapy (BNCT), a form ofcancer therapy. The ring stores a 70-mA beam of 11-MeV
protons, which then produces a very intense neutron beamfor patient treatment via a (p,n) reaction on an internal Be
target. This enormously intense beam can be maintained
over more than 1,000 passages through the target byionization cooling, using a 250-kV rf cavity, and taking
advantage of the huge acceptance of an FFAG [25].

Figure 22: KEK 1-MeV PoP FFAG. Inset: Y. Mori.
Protons pose a greater technical challenge than electrons, because of the need to modulate the radiofrequency
rapidly over a wide range. In synchrocyclotrons this had
been accomplished using rotary or vibratory capacitors mechanical devices notorious for their unreliability.
Mori introduced two important innovations. One was
Finemet alloy loading of the rf cavities, allowing reliablefrequency modulation at up to 250 Hz, and correspondingly high beam pulse repetition rates. Moreover the highpermeability of this metallic glass alloy allows quite shortcavities to produce high fields, while their low Q–value(1) permits broadband operation. His second innovation
was to build the magnets as combined-function DFD
triplets powered as a single unit where the reverse-bend
Ds also act as yoke for the central F.
Mori then moved to Kyoto to build a three-ring FFAG
complex for ADSR studies (Figure 23): a 2.5-MeV spiralsector injector, a 20-MeV radial-sector booster, and the150-MeV 12-cell main ring (similar to that at KEK). This
is installed at the Kyoto University Research Reactor
Institute (KURRI), and is on the itinerary of one of next
Saturday’s tours. The world’s first experimental demonstration of ADSR was performed here last year [8].

Figure 24: The 8-FDF-cell ERIT storage ring for BNCT.
Another example of an FFAG storage ring is PRISM, a10-cell ring for muons being built in Osaka for eventual
installation at J-PARC. This will collect muon bunches at
68 MeV/c and rotate them in phase space, reducing their
momentum spread from ±30% to ±3%. With its large
acceptance and high repetition rate, the beam intensity
will be high enough to allow ultrasensitive studies of raremuon decays. An initial version using six of the cells has
been used to store 0.8-MeV alpha particles (Figure 25)
and demonstrate the feasibility of this technique [26].

Figure 25: The 6-cell -particle test ring for PRISM.

Figure 23: The FFAG complex at KURRI. Note the
combined-function DFD triplets built as single entities.
But that’s not the only innovative machine at KURRI.
Mori has also built the ERIT storage ring (Figure 24) for

In addition to all these, two commercial companies
have been building electron machines for industrial irradiation. NHV in Japan has built and operated a 0.5-MeV
FFAG with 6 spiral-sectors, and RadiaBeam in California
is building a 12-cell 5-MeV radial-sector FFAG.
There have also been more than a dozen design studies
for scaling FFAGs over the last five years or so, most ofthese in Japan. They cover a wide range of particles (electrons, protons, heavy ions, muons), energies (1 MeV to
20 GeV), diameters (5 cm 400 m), and applications (irradiation, cancer therapy, neutrino production). The smallestof these, Mitsubishi Electric’s “Laptop” can be held com-fortably in one hand, while the largest, a 10-20 GeV muonring for a neutrino factory, would spread across the whole
J-PARC site (Figure 26). The latter would be the last in achain of four FFAGs, Mori’s most ambitious project [27],feeding muons into a racetrack decay ring, from which
neutrinos would be sent off to Super-Kamiokande.

Figure 26: An FFAG-based neutrino factory for J-PARC.

Non-Scaling FFAGs
FFAGs are attractive for accelerating muons because of
their very large acceptances. But the muon’s 2.2-μs mean
lifetime demands very rapid acceleration if it is to survive,
and in this case crossing a betatron resonance occurs too
rapidly to damage the beam. The rationale for scaling
therefore disappears (Mills [28], Johnstone [29]), and lessrestrictive non-scaling designs may be considered in which
the tunes are allowed to vary. In particular Johnstone et al.
[30] proposed using constant-gradient FDF triplets, which
would provide greater momentum compaction than comparable scaling FFAGs, allowing fixed-frequency operation, and would be simpler to build than magnets withconstant high k.
A demonstration model of such a linear non-scaling(LNS) FFAG is currently under construction at Daresbury
in the UK, and will come into operation later this year.
EMMA is a 42-cell, 2.64-m radius, 10-20 MeV electron
model of a 10-20 GeV muon FFAG [31] (Figure 27).

The funding for EMMA also has an allocation for conceptual design of a non-scaling FFAG for cancer therapy.
This would require 250-MeV protons or 400-MeV/u
carbon ions, and is being studied by a team led by theJohn Adams Institute in Oxford. The rf equipment
required for rapid acceleration would be too expensive forhospitals, especially as the frequency has to be varied
over a wide range for these non-relativistic particles.
Resonance crossing is therefore again a concern, so
designers have searched for non-scaling solutions thatnevertheless maintain constant tune. A Fermilab team[32], working on a similar project, has achieved this byangling the magnet edges to provide edge focusing.
The Oxford accelerator design, though, due to twoformer members of Prof. Mori’s group, Shinji Machida
and Takeichiro Yokoi, is less radical, but neverthelessquite novel – what might be termed a quasi-scaling lattice.
They aim to approximate a scaling magnetic field over the
narrow orbit region by overlaying 2-, 4-, 6- and 8-polefields in suitable proportions. To minimize the machine
diameter, 4-T superconducting magnets are used, and inthese such a superposition is straightforward to implement,with the various multipole coils being wound concentrically on a cylindrical former. The lattice consists of 12
FDF cells, and tracking studies confirm that it provides
tunes that vary little with energy, and that it provides
good dynamic apertures [33]. Figure 28 shows the overalllayout, with the proton ring (radius 6.25 m) and carbon
ring (radius 9.2 m) arranged concentrically. The proton
injector is a 31-MeV cyclotron, the carbon ion injector an
RFQ linac.

Figure 28: PAMELA layout, showing the proton andcarbon ion treatment rooms.

THE NISHINA LEGACY

Figure 27: The Linear Non-Scaling FFAG EMMA.

Dr. Nishina pioneered the construction of accelerators
in Japan with instruments whose specifications were asadvanced as any in the world at that time. His students
and those he inspired have continued to keep Japan in theforefront of cyclotron and FFAG development. He would
surely be proud to know that Japanese accelerator
physicists are not only renowned for their achievements athome but sought out for their expertise by other countries.

ACKNOWLEDGEMENTS
I would like to express my thanks to all those who
made this talk possible by answering my importunate
requests for old photographs: Drs. Honma, Kamigaito,
Murakami, Noda, Tanabe and Yano, and especially Dr.
Hirao. I’m also indebted to the organizers for making
available a transcript of the talk.

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