JAERI-Conf 95-021

3p1-1
OUTLINE OF JHP SYNCHROTRON DESIGN
Yoshiharu MORI and JHP Synchrotron Design Group

Institute for Nuclear Study, University of Tokyo
Midori-cho, Tanashi-shi, Tokyo 188 JAPANAbstract
An outline of the JHP synchrotron design is described.

1. Introduction
The Japanese Hadron Project (JHP) wasrevised very recently.[l] The revised JHP consists of the following three accelerators;(1) injector: 200 MeV proton linear accelerator(2) booster: 3 GeV proton synchrotron(3) main ring: 50 GeV proton synchrotron
The accelerators will be constructed at the northsite of the KEK and the whole plan view of theaccelerator complex is shown in Fig.1.
The first stage of beam acceleration of theJHP is provided by the linac. The -linac accelerates H- ions up to 200MeV. The expected peakbeam current in the Injector linac is at least
20mA and the pulse duration and the repetition
rate of the beam is more than 400 IJ.Sec and25Hz(50Hz in future), respectively.
The H · beam is injected into the booster bycharge-exchange multi-turn injection and accelerated up to 3 GeV. The 3 GeV booster will be
constructed in the exiting tunnel for the present
KEK-PS main ring.
All of the components ofthe KEK-PS main ring such as dipole magnets,
quadrupole magnets, vacuum chambers and others will be removed. The booster is a rapid cycling proton synchrotron and its repetition rate is25Hz.
The expected beam intensity in thebooster is 5xlo13 ppp (protons per pulse), therefore, the average beam current becomes 200.UA.
The total power of the extracted beam from thebooster reaches 0.6MW. The accelerated 3 GeV
protons are supplied into three experimental facilities; a pulsed spallation neutron source
facility(N-arena ), a meson facility(M-arena) andan unstable nuclei facility(E-arena), and into the50 GeV main ring.
Protons from the booster are injected into
the main ring and accelerated up to 50 GeV.
The e4-:ected beam intensity in the main ring is4x101 ppp and the repetition rate is about 1/6Hz, respectively. Thus, the average accelerated beam current reaches 10 11A in the 50 GeV
main ring. The 50 GeV protons are extracted bya slow and fast extraction schemes for two experimental areas, respectively; one is for the experiments using secondary beams(K,p, p) andprimary beams by slow extraction, and the otherfor the neutrino oscillation experiment by fastextraction.
In addition to acceleration of high intensity protons, heavy ion and polarized proton
beams are also requested. Using the 500 MeV
booster of the KEK-PS as an injector ofthe3 GeV
booster, it becomes feasible to accelerate theseparticles.

2. Outline ofthe ring design

0100

200500m

Fig.l Whole plan view of the JHP accelerator complex.

The 3 Ge V booster is a rapid cycling pro ten
synchrotron where the repetition rate of the acceleration is 25Hz. (This repetition rate will beamended up to 50 Hz in future by adding more rf
acceleration system.) In order to accomplish thishigh repetition rate, the maximum magnetic
field strength of the dipole magnets has to beless than 1T . The power supply for each groupof the magnets is operated with an independent
resonance circuit system.
The lattice design of the booster is pre--454-

JAERI-Conf 95-021

sented in detail in this proceedings.[2] Thebooster ring comprises 48 bending magnets andParameters of the48 quadrupole magnets.
booster ring are presented in Table 1. Since thering should be placed in the present KEK-PStunnel, the superperiodici ty of the ring is chosen
to be four. There is no transition energy during
beam acceleration.
In the 50Hz operation, about 800kV rfvoltage is needed for beam acceleration. Thus, alarge number of straight sections is necessary forthe rfcavity stations. The rfparameters ofthis
ring will be presented in the proceedings.[3] In
the present design, there are 24 straight sections
and the length of each one is 6.57m.
The requested apertures for each component of the 3GeV booster are summarized inIn this estimation, the beam emitTable 2.
tance of 320 1t.mm.mrad at the beam injection forboth horizontal and vertical directions, and themomentum spread of +-0.5% and the COD of5mm are assumed.
Table 1. Parameters of the 3 Ge V Booster

Injection enegy
Maximum energy
Beam intensity
Repetition rate
Circumference
Magnetic rigidity
Lattice configuration
Tune
Transition energy:yt
Total number of cells
Number of B-magnets
Number of Q-magnets
B-magnet length
Q-magnet length
Maximum magnetic fieldstrength of B-magnet
Maximum magnetic field
gradient of Q-magnet
Natural chromaticity
Hamonic number
RF frequency
RF voltage
Beam emittance (injection)
Beam emittance (extraction)

0.2GeV
3GeV
5 X 10 13 PPP
25Hz
339.36 m
2.15-12.76 Tm
FODO(7 .3,4.3)
724
48
48
1.75 m
0.5m
0.95T
5.4 T/m ·-6.77,-5.84
4
1.99- 3.43 MHz
389 kV
320 1tmm.mrad
53.9 1tmm.mrad

Table 2.

Apertures of the 3 GeV booster.

Bending magnet
quadrupole magnet

horizontal vertical
95.3 mm
92.9 mm
106.0 mm 106.6 mm

Magnets are divided into three groups
such as bending, focusing and the defocusing.
Each group is excited using an independent resonant circuit. The design of the magnets andtheir power supplies are summarized in this proceedings. [4]There are several design constraints forthe 50 GeV main ring as shown below.
(1) Max. field of bending magnets :<1.8 T (fornormal conducting magnet)(2) Max. field gradient of quadrupole magnets:<25T/m(3) No transition energy:Less than 1% beam loss
during beam acceleration
Eminence at beam in(4) Small beam size:
jection - 54 1t.mm.mrad(5) No dispersion at straight section: Internal gas
target experiment and Siberian snakes for polarized beam(6) Numbers and length of a long straight section: 4, >40m
The circumference of the ring is almost
four times larger than that of the KEK-PS ring
because of the site limitation. Superconducting
magnets are very attractive from the point ofview of the site limitation described above, however, there are several problems, such as beam
induced quenching, to be overcome. In thepresent lattice design, we assume to use normal
conducting magnets. Thus, the maximum magnetic field strength of bending magnets and themaximum magnetic field gradient of quadrupole
magnets are set to less than 25 T/m, respectively.
In an ordinary FODO lattice, the nroughly equals the horizontal tune. Thus, using
an ordinary FODO lattice, it is inevitable to havetransition energy during beam acceleration up toOne of the features in the main ring
• 50 GeV.
design is that an imaginary rt lattice is employed.[2] Therefore, no transition energy crossing exists during beam acceleration. When thetotal integral of the dispersion function in thebending magnets is negative, the momentum
compaction factor is negative and rt becomes
imaginary. In order to realize imaginary ')t, thearc section of the ring comprises a series of cellunits. Each cell unit consists of three DOFO
normal cells where the central cell has no bending magnets. To accommodate the dispersion
free straight sections, total horizontal phase advance, ll'arc. in the arc is set to integer times 2lt.
In this design, we set that li'arc=5x2lt. With thisoptics, n becomes 27i. In order to avoid a seri--455-JAERI-Conf 95-021

ous radioactivation problem in high intensity
mode acceleration, the beam loss should be kept
small, therefore, small beam size is desired;bmax should be made small and flat as much as
possible. The high intensity mode lattice wasalso designed from this point of view. Details of
the lattice design are presented in this proceedings.[2]The requested apertures of the 50 GeV
ring are summarized in Table 3.
In this estimation, the beam emittance of 54 mnmmrad at
the beam injection for both horizontal and vertical directions, and the momentum spread of +0.5% and the COD of 5mm are assumed, respectively.
Table 3. Apertures ofthe 50 GeV mainring.
Bending magnet
Quadrupole magnet

horizontal vertical
46.1 mm43.8 mm52.6 mm
44.5 mmSpace charge effects for the beams in the 3
GeVbooster and the 50 GeVmain ring are anticipated to be very large.[5]Using Laslett tune
shift formula, the space charge effects are estimated.
The incoherent and coherent spacecharge limits for both rings are summarized inTable 4. In this estimation, the Laslett tune shift
is -0.25.
Table 4. Space charge limit
3 GeV Booster
50 GeV Main Ring

Incoherent Coherent
5.6 X 1013 1.2 X 1014
4.7 X 1014 4.2 X 1014

The general parameters of the 50 GeV
main ring are summarized in Table 5.

3. Summary
The outline of the JHP circular accelerators are described.
In parallel with optimization of the beam optics and dynamics in the bothrings, some R&D's for hardwares have alreadystarted.
(1) R&D of the rf acceleration system which canstand for heavy beam loading in both rings.
(2) R&D of the magnet power supply with a resonant network for the 3 Ge V booster.
(3) R&D of the ceramic beam duct and rf shield
for the 3 GeV booster.
References(1] Y. Akaishi et at., "Physics with 50 GeV highintensity proton accelerator"(in Japanese), 1995.
[2]Y.Ishi et al., "Lattice design of JHP circularaccelerators", in this proceedings.

[3]C.Oomori et al.,"RF systems of synchrotrons
for the Japanese Hadron Project", in this proceedings.
[4)T. Adachi et al.,"Design of magnets and power
supplies of 3 GeV booster for Japan HadronProject", in this proceedings.
[5]S.Machida et al.,"Beam dynamics issues inJHP circular accelerators", in this proceedings.
Table 5 Parameters of 50 Ge V Main Ring.
Injection enegy

3GeV

Maximum energy

50GeV

Beam intensity

4 X 1Ql4ppp

Repetition rate

-1/6 HzCircumference

1442m

Average radius
Magnetic rigidity

229.5 m12.76- 170 Tm

Lattice configuration

3- cell DOFO
x 6 module+4 - straight cellTune(24.25, 20.7)

Transition energy:yt

27 i ( imaginary )Total number of cells

88

Number of B-magnets

96

Number of Q-magnets

176

B-magnet length

6.2m

Q-magnetlength

1.5 m & 2m

Maximum magnetic fieldstrength of B-magnet

1.8 T

Maximum magnetic field
gradient of Q-magnet
Hamonic number

25T/m
34

RF frequency

6.83-7.03 MHzRF voltage

200kV

Beam emittance (injection)

53.9 7tmm.mrad

Beam emittance (extraction)

4.17tmm.mrad-456-