The JKJ
JKJ Lattice
Lattice
The
.j.* _
.j*.
*.fc
#H
Kenta Shigaki
Shigaki ,, FumiakiNoda
Fumiaki Noda ,, Kazami
Kazami Yamamoto
, Shinji Machida
Kenta
Machida ,,
# Yamamoto , Shinji
@
Alexander Molodojentsev
Molodojentsev#,, Yoshihiro
Alexander
Yoshihiro Ishi
Ishi®
*
Japan Atomic Energy Research Institute, Tokai, Ibaraki 319-1195, Japan
* Japan Atomic Energy Research Institute, Tokai, Ibaraki 319-1195, Japan
# High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan
High Energy Accelerator
Research Organization (KEK), Tsukuba, Ibaraki 305-0801, Japan
@
@ Mitsubishi Electric Corporation, Kobe, Hyogo 652-8555, Japan
Mitsubishi Electric Corporation, Kobe, Hyogo 652-8555, Japan
#
Abstract. The JKJ high-intensity proton accelerator facility consists of a 400-MeV linac, a 3-GeV 1-MW rapid-cycling
Abstract.
The
JKJ
high-intensity
proton
acceleratorThe
facility
consists
of a 400-MeV
linac, aof3-GeV
1-MW
rapid-cycling
synchrotron
and
a 50-GeV
0.75-MW
synchrotron.
lattice
and beam
dynamics design
the two
synchrotrons
are
synchrotron
reported. and a 50-GeV 0.75-MW synchrotron. The lattice and beam dynamics design of the two synchrotrons are
reported.
INTRODUCTION
INTRODUCTION
The
TheJKJ
JKJisis aajoint
joint project
project of
of Japan
Japan Atomic
Atomic Energy
Energy
Research
intensity proton
ResearchInstitute
Instituteand
andKEK
KEK for
for aa highhigh-intensity
proton
accelerator
accelerator facility
facility [1-3].
[1-3]. Its
Its accelerator
accelerator complex
1
consists
consists of
of aa 400-MeV
400-MeV1 linac,
linac, aa 3-GeV
3-GeV rapid-cycling
synchrotron
synchrotron (RCS)
(RCS) and
and aa 50-GeV
50-GeV synchrotron
synchrotron (MR).
The
TheRCS
RCSand
andMR
MR are
are characterized
characterized with
with their
their design
output
output power
power as
as large
large as
as 1 MW
MW and
and 0.75
0.75 MW,
respectively.
respectively.
3-GEV RCS
RCS
3-GEV
The3-GeV
3-GeVRCS
RCSreceives
receives aa 400-MeV
400-MeV proton
proton beam
The
from the
the linac
linac and
and accelerates
accelerates itit to
to 3 GeV with a
from
repetition rate
rate of
of 25
25 Hz.
Hz. The
The design
design output beam
repetition
powerisis11MW
MWwith
with 8.3
8.3 x× 101313 ppp.
ppp. Its output beam is
power
time-sharedbetween
between the
thepulsed
pulsed spallation
spallation neutron
neutron and
time-shared
muon
sources
(95
%)
and
the
MR
(5
%).
muon sources (95 %) and the MR (5 %).
circumference of
of 348.333
348.333 m.
m. The
The FODO
FODO structure
structure
circumference
eases requirements
requirements for
for the
the strength
strength ofof the
the quadrupole
quadrupole
eases
magnets and
and also
also allows
allows an
an effective
effective arrangement
arrangement ofof
magnets
the secondary beam
beam collimators
collimators (halo
(halo collectors)
collectors)with
with
the large and
and smooth
smooth phase
phase advance.
advance.
QFN QRC QFN
extraction kicker and septum maq
QFN
QFL
QFL;
Design Concepts
Concepts
Design
The design
design of
of the
the RCS
RCS primarily
primarily focuses
focuses on
on
The
achieving the
the 1-MW
1-MW output
output beam
beam power.
power. The
The ring
ring
achieving
acceptanceisisas
as large
large as
as 486
486 nπ mm
mm mrad
mrad transversely
transversely
acceptance
and
±
1
%
in
momentum,
to
circulate
the
beam up
up to
to
and ± 1 % in momentum, to circulate the beam
324
π
mm
mrad
and
reduce
the
beam
loss
due
to
intra324 n mm mrad and reduce the beam loss due to intrabeamscattering.
scattering.The
The expected
expected incoherent
incoherent tune
tune shift
shift is
is
beam
–0.16
at
the
injection
energy
with
the
design
bunching
-0.16 at the injection energy with the design bunching
factorofof0.41.
0.41.The
Theloss
loss isis controlled
controlled and
and localized
localized with
with
factor
transverse
and
longitudinal
beam
collimators
in
the
transverse and longitudinal beam collimators in the
ring.
The
uncontrolled
beam
loss
is
suppressed
to
a
ring. The uncontrolled beam loss is suppressed to a 11
W/m level
level except
except inin the
the injection,
injection, collimation
collimation and
and
W/m
extraction regions.
extraction regions.
RingLayout
Layout and
and Lattice
Lattice Functions
Functions
Ring
The RCS has 27 FODO cells with three-fold and
The RCS has 27 FODO cells with three-fold and
mirror symmetries, as shown in Figure 1, over its
FIGURE
FIGURE 1.
1. The
The ring
ring layout
layoutofofthe
the3-GeV
3-GeVRCS.
RCS.
Figure
Figure 22 shows
shows main
main lattice
lattice functions
functions ofofaasupersuperperiod
of
the
RCS.
The
arc
sections
period of the RCS. The arc sections have
have so-called
so-called
missing
missing bends
bends where
where the
the horizontal
horizontal momentum
momentum
dispersion
function
peaks.
The
dispersion function peaks. The raised
raised transition
transition γyatat
9.14
9.14 makes
makes the
the RF
RF operation
operation easier.
easier. The
Themissing-bend
missing-bend
sections are suitably used for longitudinal beam
sections are suitably used for longitudinal beam
collimation and chromaticity correction. The three
collimation and chromaticity correction. The three
long dispersion-free insertions are utilized for injection
long dispersion-free insertions are utilized for injection
and beam collimation, RF acceleration and fast
and beam collimation, RF acceleration and fast
extraction, respectively.
extraction, respectively.
mirror symmetries, as shown in Figure 1, over its
11
futureextension
extensionto
to 600
600 MeV
MeV is planned
planned for the linac.
AAfuture
CP642, High Intensity and High Brightness Hadron Beams: 20th ICFA Advanced Beam Dynamics Workshop on
High Intensity and High Brightness Hadron Beams, edited by W. Chou, Y. Mori, D. Neuffer, and J.-F. Ostiguy
© 2002 American Institute of Physics 0-7354-0097-0/02/$ 19.00
140
13:15:14 Wednesday 04/3/2002
stripping foil is at the center of the system
symmetrically sandwiched by four closed-orbit bump
magnets. The system is designed to support multiple
injection schemes, from center injection for
commissioning to precise transverse painting injection
for optimum operation. Four horizontal painting
magnets in the ring and two vertical painting magnets
on the injection line at a phase n upstream of the
injection point are used for the two-dimensional
painting. Specific schemes of transverse painting, e.g.
correlated or anti-correlated in horizontal and vertical
directions, are under study in terms of emittance
deformation during the injection. The system is
capable to adjust the painting area on the pulse-bypulse basis.
FIGURE 2. Lattice functions of a super-period of the
3-GeVRCS.
Beam Collimation
Transverse and longitudinal beam collimators are
in the RCS to control and localize the beam loss. The
system consists of two primary collimators to scatter
the halo particles and five secondary collimators to
collect them. The secondary collimators are located in
the second half of the injection insertion to collect halo
particles directly after the injection without spreading
them over the ring. The acceptance ratio between the
collimators and the rest of the ring is adjustable with
the movable collimator jaws and designed at 1.5 for
the halo collection efficiency of 98 % in the collimator
region.
Working Point and Tunability
The nominal working point of the RCS is chosen at
(vx, vy) = (6.72, 635) to avoid structure resonance and
for small emittance blowup due to intra-beam
scattering and P modulation with the injection bump
orbit on. The lattice is flexible in the betatron tune
space for alternate working points and stable enough
to cover the expected incoherent tune shift and
possible tune excursions during the acceleration.
Dynamic Aperture
The dynamic aperture of the RCS is designed to
cover the physical aperture of 486 n mm mrad with ±
1 % momentum spread. Effects of field imperfection,
e.g. higher order fringe field, on the dynamic aperture
have been studied [4]. The dynamic aperture is
comparable to the physical aperture even with the full
chromaticity correction.
Extraction
The RCS is equipped with a fast extraction system
consisting of eight kicker and four septum magnets.
The first half of the extraction insertion is allocated for
the system. The system is designed to have the
minimum acceptance of 324 n mm mrad, the
collimator acceptance, for the one-pass extraction line
and 1.5 times more for the circulating beam, at the
nominal working point and for the momentum spread
of ± 1 %. Note that the beam core at the extraction
energy is 81 n mm mrad.
Closed-Orbit Distortion and Its Correction
The closed orbit will be distorted by up to 10 mm
with expected magnetic and alignment errors without a
correction. A beam position monitor and a correction
dipole magnet are placed in each half-cell to correct
the distortion. The expected residual closed-orbit
distortion after correction is within ± 1 mm with the
design resolution of the beam position monitor of 0.2
mm.
50-GEVMR
The 50-GeV MR accelerates protons from 3 GeV
to 50 GeV. The design output beam power is 0.75 MW
with 3.3 x 1014 ppp and a 0.3-Hz repetition rate. The
MR is equipped with fast and slow extraction channels
for particle and nuclear physics facilities [2].
Injection
The RCS has a charge-exchange injection system
with carbon stripping foils, located in the first half of
the injection insertion. Approximately 300 pulses are
injected from the linac in 500 jLtsec. The primary
Design Concepts
The design concept of the MR is basically on the
same line as that of the RCS. The missing-bend
141
technique further pushes the transition y of the lattice
to the imaginary region to avoid crossing it during the
acceleration process. The achromatic arc sections are
realized by setting the horizontal phase advance at 2nn,
where n is an integer (6).
Slow Extraction
A major difference in the design of the MR from
that of the RCS is the existence of the slow extraction
channel. See Reference [5] for its design and
discussions on the system.
Ring Layout and Lattice Functions
Reference for Other Issues
The MR has a circumference of 1567.5 m with a
three-fold symmetry. Each super-period consists of an
achromatic arc section (24 FODO cells), a dispersionfree insertion (3 FODO cells) and two matching
sections (2 cells each). Main lattice functions of a
super-period are shown in Figure 3. The missing-bend
structure of the arc sections makes the momentum
compaction factor flexible, with its nominal setting
below zero leading to an imaginary transition y. One of
the three long dispersion-free insertions is dedicated
for slow extraction. Another is for injection, beam
abort at the injection energy and beam collimation, and
the last for RF acceleration and fast extraction. A halfcell in the matching section has a relatively large P and
a small a function for the slow extraction system.
See Reference [1] for other beam dynamics issues
of the MR, such as the dynamic aperture, the closedorbit distortion and its correction and the injection,
beam collimation and fast extraction systems.
SUMMARY AND OUTLOOK
The lattice design of the 3-GeV RCS and 50-GeV
MR of the JKJ high-intensity proton accelerator
facility is basically completed, while it may still need
minor final-stage tuning as the hardware R&D
progresses. Most of the key issues and concerns with
their beam dynamics design have been examined and
cleared. See Reference [1] for further details. With the
construction of the facility starting in 2002, the RCS
expects its first beam in fall of 2006, and the MR in
spring of 2007. Studies of their operation modes are
under way on specific topics, e.g. the transverse
injection painting of the RCS, halo formation and
beam loss control and the commissioning scenarios.
14:23:28 Thursday 04/4/2002
ACKNOWLEDGMENTS
The project is supported by the Ministry of
Education, Calture, Sport, Science and Technology of
Japan.
300
REFERENCES
400
FIGURE 3. Lattice functions of a super-period of the
50-GeV MR.
Working Point and Tuning Knobs
The nominal working point of the MR is at (vx, vy)
= (22.33, 22.28), with the horizontal tune constrained
for the slow extraction. The integer part of the vertical
tune is adjustable in the range from 17 to 22. The
momentum compaction factor is another tuning knob
of the lattice, adjustable from -0.0022 (transition y at
21/) to +0.0022 (transition y at 21).
142
1.
Accelerator Technical Design Report for High-Intensity
Proton Accelerator Facility Project, edited by
Y.Yamazaki et al.
2.
Lnazato, J., "JHF Physics", in these proceedings.
3.
Mori, Y., "Accelerator Complex of Joint Project in
Japan", in these proceedings.
4.
Molodojentsev, A., "Tracking Studies for the JKJ
Lattice", in these proceedings.
5.
Tomizawa, M., and Yokoi, T., "Radiation Handling in
the Slow Extraction of the JHF 50 GeV Ring", in these
proceedings.