Intensity Dependent Emittance-Exchangein a High
Intensity Proton Synchrotron
I. Sakai, S. Machida, T. Adachi, Y. Arakida, Y. Me, K. Kitakawa, Y. Mori,
Y. Shimosaki, H. Someya, M. Yoshimoto
KEK, 1-1 Oho, Tsukuba-shi, Ibaraki-ken, 305-0801, Japan
Abstract. The normalized acceptance of the KEK booster has large value in horizontal plane (80 n mm mrad in the
horizontal plane and 1871 mm mrad in the vertical plane). To increase the beam intensity we have been trying to achieve
painting injection in the horizontal plane. The intensity-dependent emittance-exchanges in the horizontal and vertical
plane were measured by a method using a scraper and bump magnets and extracted beam profiles measured by multiwire profile monitor.
machine. However, regarding high-intensity mode
operation (>1.8xl012 ppp), the horizontal emittance of
the extracted beams dose not exceed the half value of
the designed acceptance and only the vertical
emittance grows; nevertheless, the injected beams of
the booster were extended to the full acceptance by
off-center injection in the horizontal plane.
This strange, but interesting, phenomenon has been
carefully examined and studied from various angles.
The beam envelopes were measured through an
accelerating process, and it has been known that the
shrinking of the horizontal emittance and the blow-up
of the vertical emittance both occur in the bunching
process just after injection, where the line-charge
density increases in the RF bucket. In this paper we
discuss the space-charge effects of flat beams in a
high-intensity proton synchrotron based on the
experimental results.
INTRODUCTION
The 500-MeV KEK booster has characteristics of
rapid cycling (20Hz), being very compact and
combined-function magnets. It supplies proton beams
to both the 12-GeV main ring (MR) and the neutron
and meson science laboratory (NML). The MR
demands control of the extracted beam emittance of
the booster for optimum injection, and the NML
demands high-intensity beams that are as high as
possible.
The features of the KEK booster are a wide
horizontal aperture and a rather narrow vertical
aperture, because of its initial design of septum-type
multi-turn injection. The normalized value of the
designed acceptance of the KEK booster is SOrc mm
mrad in the horizontal plane and ISrc mm mrad in the
vertical plane. The injection system was converted to
one using a charge-exchanging method, and the
injection energy has been upgraded to 40MeV to
increase the beam intensity. The incoherent spacecharge limit of the booster was calculated to be
3.2xl012 ppp assuming the full designed acceptance of
the machine. Until now, a beam intensity of 2.2xl012
ppp was constantly obtained by normal H" injection
without painting. At this beam intensity, the emittance
of the extracted beam is 40n mm mrad in the
horizontal plane and 24n mm mrad in the vertical
plane. An increase of the vertical beam size would
seem to restrict the beam intensity. But the horizontal
emittance of the extracted beams is half the value of
the full acceptance.
To increase the beam intensity, painting injection in
the horizontal plaine has been tried [1]. It had been
expected that the beam intensity increases by 25%, if
the horizontal emittance is extended to the full
acceptance of the machine by painting injection. In the
case of a low-intensity beam (<lx!012 ppp), the
extracted beam emittance is well controlled by
painting injection, and fills the full acceptance of the
INJECTION SCHEME AND PAINTING
DEVICE
The injection scheme of the KEK Booster is shown
in Fig.l. The injection system consist of four closedorbit bump magnets for charge-exchange injection and
two orbit-shift bump magnets for phase-space
painting. The position and angle of the injection point
for charge-exchange injection are fixed by the closedorbit bump magnets, and the center of the closed orbit
45
(Wain bump magnets)
Bunjp t
45"
Bump 2 Butrip 3 Bump 4
FIGURE 1. Charge-Exchange Injection System for Phase
Space Painting
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
303
the situation of the off-center painting injection. In
the
situationplane,
of thetheoff-center
injection.beam
In
horizontal
width ofpainting
the extracted
horizontal
plane,
the
width
of
the
extracted
beam
the situation
of the
off-center
injection. mode
In
profile
shrinks
compared
withpainting
low intensity
profile
shrinks
compared
with
intensity
mode
horizontal
plane,
the
width
of the
extracted
beam
operation.
On the
other
hand,
inlowvertical
plane,
the
operation.
On the
otherblow-up
hand,
plane,
the
profile shrinks
compared
with in
low
mode
extracted
beam
profiles
in vertical
theintensity
vertical
plane.
extracted
profiles
the vertical
plane.
operation.beam
On the
otherblow-up
hand, inin vertical
plane,
the
at the injection point can be shifted by two orbit bump
at the injection
can be shifted
two orbitand
bump
magnets
which point
are placed
at the by
upstream
the
magnets
which
are
placed
at
the
upstream
and
the
at the injection
point can
two orbit
downstream
positions.
At be
theshifted
each by
position
of bump
orbit
downstream
positions.
Atphase
theateach
position
ofand
orbit
magnets
which
arethe
placed
upstream
the
shift
bump magnets,
ofthe
betatron
oscillation
shift
bump magnets,
the phase
ofeach
betatron
oscillation
downstream
positions.
At
the
position
of
orbit
leads and lags by π/2 from the injection point. Beams
shift
bump
magnets,
the phase
of betatron
oscillation
leads
and
lags
by n/2 from
the
Beams
are
injected
gradually
from
the injection
center
ofpoint.
phase
space
are
injected
gradually
from
the
center
of
phase
space
leads
and
lags
by
π/2
from
the
injection
point.
Beams
to the outside by a shift of the closed orbit, which
is
gradually
from
centerorbit,
of phase
space
to are
the injected
outside
by
a shiftpattern
of thethe
which
is
controlled
by the
decay
ofclosed
the magnetic
field of
to the outside
by
a shift
of the
closed
orbit, which
controlled
by themagnets.
decay
pattern
of the
magnetic
field ofis
these
two bump
controlled
by
the
decay
pattern
of
the
magnetic
field of
these two bump magnets.
extracted
beam profiles
blow-up in Beam
the vertical
plane.
The Change
of Extracted
Emittance
The Change of Extracted Beam Emittance
with
the Width
of Off-Center
Injection
The
Change
of Extracted
Beam Emittance
with
the Width
of Off-Center
Injection
with
the Width
Off-Center
Injection
The extracted
beamofemittance
with the
width of offThe extracted beam emittance with the width of offcenter
injection
in
the
horizontal
plane
asoff-the
The extracted
with theplane
width ofas
center
injection beam
in emittance
the horizontal
the
parameter
of
the
beam
intensity
is
shown
in
Fig.3.
center injection
in the
horizontal
planein Fig.3.
as theInIn
parameter
of the beam
intensity
is shown
the
low-intensity
mode,
the shown
increments
of the
parameter
of the beam
intensity
in Fig.3.
the
low-intensity
mode,
the is increments
of In
the
horizontal
emittance
give
good
agreement
with
the
the low-intensity
the increments
horizontal
emittancemode,
give good
agreement of
withthethe
calculated
values
by
the
width
of
the
off-center
horizontal emittance
the
calculated
values bygive
the good
widthagreement
of the with
off-center
injection,
thebyvertical
emittance
only little
calculated and
values
the width
of theis off-center
injection, and the vertical emittance is only little
injection,byand
vertical expansion
emittance ofisthe
only
little
affected
the the
horizontal
emittance.
affected by the horizontal expansion of the emittance.
affected
by
the
horizontal
expansion
of
the
emittance.
It can be considered that the emittnce is conserving
It can be considered that the emittnce is conserving
It can bethe
considered
thatprocess.
the emittnce is conserving
through
accelerating
through
the
accelerating
process.
through
the
accelerating
process.
On the other hand, in the high-intensity mode,
On
other hand,
hand, inin the
the high-intensitymode,
mode,
On the
the the
other
although
injected beams
beams high-intensity
of the
the booster
booster were
were
although
the
injected
of
although the
injected
beams
of the booster
were
expanded
by
off-center
injection,
the
horizontal
expanded
by off-center
off-center injection,
injection, the
the horizontal
horizontal
expanded dose
by
emittance
not increase
increase with
with the
the extended
extended offoffemittance
dose
not
emittance
dose not
increase
with the
extended
offcenter
injection.
The
distributions
of
injected
beams
center
The distributions
distributions ofofinjected
injectedbeams
beams
center injection.
injection. The
are
no longer
longer
conserved
theextraction.
extraction.
are
no
conserved
atatthe
these two bump magnets.
INTESITY
THE
INTESITY DEPENDENCE
DEPENDENCE OF
OF THE
EXTRACTED
BEAM
EMITTANCE
INTESITY DEPENDENCE
OF THE
EXTRACTED
BEAM EMITTANCE
EXTRACTED BEAM EMITTANCE
Observation
Profiles
Observation of
of Extracted
Extracted Beam
Beam Profiles
Observation
of Extracted
Beam
Profiles
under
the
Fixed
Off-Center
Injection
under the Fixed Off-Center Injection
under the Fixed Off-Center Injection
1.2
1
(98.6.7 #201-#205)
(98.6.7 #201-#205)
5.7e11ppp
2.1e12ppp
5.7e11ppp
1 0.8 2.1e12ppp
I *
0.8 0.6
10.8
I0.6
0.6 0.4
I0.4
0.4 0.2
0.22
|0.
0
> 00 -0.2-30
-20
-0.2
1-o.z
-30
-10
-20
-10
0
10
x (mm)
0
10
x (mm)
20
20
30
30
40
40
Outout Voltage (Normalized by peak value)
Horizontal Beam Profiles
Horizontal
Horizontal Beam
Beam Profiles
Profiles
1.2
Outout Voltage (Normalized by peak value)
Output Voltage (Normalized by peak value)
Output Voltage (Normalized by peak value)
1.2
are no longer conserved at the extraction.
100
....
100
Normalized
) )
Normalized ε εx,x, εzε(mm
(mmmrad
mrad
5|808080
6
z
The projection of the extracted beam distribution is
The projection of the extracted beam distribution is
The projection
of the extracted
distribution
measured
by multi-wire
profile beam
monitors
at theis
measured
by multi-wire
profile
monitors atat the
measured bypoints
multi-wire
profile monitors
the
dispersion-free
on
the
extracted
beam
line.
dispersion-free
points
ononthe
extracted
beam
line.
dispersion-free
points
the
extracted
beam
line.
In
low-intensity
mode
operation,
lower than
than
In In12
low-intensity
mode
operation,
lower
low-intensity
mode
operation,
lower
than
12 ppp,
1.0x10
the
profiles
of
the
extracted
beams
are
l.OxlO
ppp,
thetheprofiles
ofofthe
beams
are
1.0x1012
ppp,
profiles
theextracted
extracted
beams
are
controllable
by
adjusting
the
injection
devices
[1].
A
controllable
bybyadjusting
thetheinjection
devices
[1].
A
controllable
adjusting
injection
devices
[1].by
A
uniform
distribution
of
charged
particles
is
realized
uniform
distribution
ofofcharged
particles
isisrealized
by
uniform
distribution
charged
particles
realized
by
the
precise
orbit
shift
painting, which
is performed by
by
thethe
precise
orbit
shift
precise
orbit
shiftpainting,
painting,which
whichisisperformed
performed by
two
orbit
shift
bump
magnets
in
the
ring.
The
simple
twotwo
orbit
shift
bump
orbit
shift
bumpmagnets
magnetsininthe
thering.
ring.The
The simple
simple
off-center
injection, without
two orbit
shift bump
bump
off-center
off-centerinjection,
injection,without
withouttwo
two orbit
orbit shift
shift bump
magnets,
forms
a
hollow
distribution
by
adjusting
the
magnets,
forms
a hollow
magnets,
forms
a hollowdistribution
distributionbybyadjusting
adjustingthe
the
two
steering
magnets
on
the
injection
beam
line.
In
the
twotwo
steering
magnets
ononthetheinjection
steering
magnets
injectionbeam
beamline.
line.InInthe
the
case
of
the
the
center
of
the
case
hollowdistribution,
distribution,the
the center
center of
of the
the
case
of of
thethehollow
hollow
distribution,
projection
of
charged-particle
beams
is
22%
lower
projection
of
charged-particle
beams
is
22%
lower
projection of charged-particle beams is 22% lower
than
the
bybyprecise
precise
orbit
sift
than
uniformdistribution
distributionby
precise orbit
orbit sift
sift
than
thetheuniform
uniform
distribution
painting.
The
precise
orbit
replaceable
painting.
The
precise
orbitshift
shiftpainting
paintingis
replaceable
painting.
The
precise
orbit
shift
painting
isisreplaceable
by
simple
off-center
the
convenience
in
simple
off-centerinjection
injectionfor
forthe
theconvenience
convenience in
in
by by
simple
off-center
injection
for
experiments.
experiments.
experiments.
Horizontal
profiles
under
the
Horizontaland
andvertical
verticalbeam
beamprofiles
profiles under
under the
the
Horizontal
and
vertical
beam
15mm
off-center
injection
in
the
horizontal
plane
as
15mm
off-center
injection
in
the
horizontal
plane
as
15mm off-center injection in the horizontal plane as
parameters
of
the
beam
intensity
are
shown
in
Fig.2.
parameters
of
the
beam
intensity
are
shown
in
Fig.2.
parameters of the beam intensity are shown in Fig.2.
low-intensitymode,
mode, the
the extracted
extracted beam
beam
In
the
extracted
beam
In Inthe
thethelow-intensity
low-intensity
mode,
profile
in
the
horizontal
plane
indicate
the
hollow
profile
in
the
horizontal
plane
indicate
the
hollow
profile in the horizontal plane indicate the hollow
distribution
in the
real
spacebybythe
theoff-center
off-centerinjection.
injection.
distribution
in
space
distribution
in the
the real
real
space
by the
off-center
injection.
The
vertical
profile
indicate
the
Gaussian
distribution
The
distribution
The vertical
vertical profile
profile indicate
indicate the
the Gaussian
Gaussian distribution
by the
center
injection
withoutpainting.
painting.
by
injection
without
by the
theIncenter
center
injection
without
painting.
12
12 ppp,
the
high-intensity
modeoperation,
operation,2.0x10
2.0x1012
In
the
high-intensity
mode
ppp,
In
the
high-intensity
mode
operation,
2.0xl0
ppp,
extracted beam profiles are not directly reflected
by
extracted
reflected by
extracted beam
beam profiles are not directly reflected
Vertical
Beam Profiles
Profiles
Vertical Beam
1
1 0.8
5.7e11ppp
2.1e12ppp
000 -5
-5
-5
(99.6.13 #4 #7 #9)
(99.6.13 #4 #7 #9)
0.6 0.4
0.4 0.2
0
-0.2
-20
-10
-10
0
00
10
20
z (mm)
20
10
20
30
30
30
I^ X
^^£>^
ojjpW&i«««,,«oi,,<«|
A
_ - — -., r - —— --*
2
00
0
55
1010
5
10
Off-Center
(mm)
Off-Center
(mm)
15 15
15
20 20
20
FIGURE 3.
3.
the
width
ofofof
FIGURE
3. The
Theextracted
extractedbeam
beamemittance
emittancewith
with
the
width
FIGURE
The
extracted
beam
emittance
with
the
width
off-center
injection
as
the
parameter
of
the
beam
intensity.
off-center
injection
as
the
parameter
of
the
beam
intensity.
off-center injection as the parameter of the beam intensity.
5.7e11ppp
2.1e12ppp
0-0.2-20
^
j#r
Off-Center (mm)
0.8 0.6
0.2
εz (7.5x1011n ppp)
—*- εz
ez(7.5x10
(7.5x10 ppp)
ppp)
12
εx (2.0x1012 ppp)
ppp)
—*~ εx
EX (2.0x10
(2.0x10 "ppp
12
εz(2.0x1012 ppp)
—*' εz(2.0x10
ez(2.0xl012ppp)
ppp)
40
40
6 20
20
o 20
1
,^:
εx (7.5x10 11ppp)
13
Vertical Beam Profiles
1.2
60
60
w -60
εx (calculated)
- — - εx
ex(calculated)
(calculated)
11
εx (7.5x1011 ppp)
40
40
40
FIGURE 2. Projection of The Extracted Beam
z (mm) Profiles as
z(mm)
Parameter
the Beam of
Intensity
(Normalized
byProfiles
peak value)
FIGURE
2.
The Extracted
Beam
FIGURE
2. ofProjection
Projection
of
Profiles
as
Parameter
Parameter of
of the
the Beam
Beam Intensity
Intensity (Normalized
(Normalized by peak value)
Intensity
Intensity Dependence
Dependenceofof
ofthe
theExtracted
Extracted
Intensity
Dependence
the
Extracted
Beam
Emittance
under
the
Fixed
Beam Emittance
Emittance under
under the
the Fixed
FixedOffOffBeam
OffCenter
Injection
Center
Injection
Center Injection
The intensity dependence of the extracted beam
The
intensity dependence
dependence of the
the extracted
extracted beam
beam
The
intensity
emittance
in the case of 15mmofoff-center
injection is
emittance in
in the
the case
case of
of 15mm
15mm off-center
off-center injection
injectionisis
emittance
shown in Fig.4.
shown
in Fig.4.
Fig.4. beam emittance is measured by multishown
in
The extracted
The
extracted
beamatemittance
emittance
measured
bymultimultiThe
extracted
beam
isismeasured
by
wire profile monitors
the dispersion-free
points
on
wire
profile monitors
monitors
at the
theThe
dispersion-free
points on
on
wire
profile
at
dispersion-free
points
the extracted
beam line.
off-center painting
the
extracted
beam
line.
The
off-center
painting
the
extracted
line.
off-center
injection
is triedbeam
only in
the The
horizontal
plane. painting
In the
injection
triedthe
only
in the
the horizontal
horizontal
plane.
the
injection
isis tried
only
in
the
vertical plane,
injection
point andplane.
angle InIn
are
vertical
plane,
the
injection
point
and
angle
are
vertical
plane,
the
injection
point
and
angle
are
adjusted to the center of the phase space to obtain the
adjusted
toemittance
the center
center
of the
the
phase
spacetotoobtain
obtainthe
the
adjusted
the
phase
space
minimumto
in of
the
vertical
plane.
minimum
emittance
in the
thevertical
vertical
plane.
The horizontal
emittance
decreases
with the beam
minimum
emittance
in
plane.
The
horizontal
emittance
decreases
the beam
beam
intensity
nevertheless
the injected
beam with
iswith
expanded
to
The
horizontal
emittance
decreases
the
intensity nevertheless
nevertheless the
the injected
injectedbeam
beamisisexpanded
expandedtoto
intensity
304
Ex,Ez
Ex,Ez(pi
(pimm
mmmrad,
mrad,Normalized)
Normalized)
thefull
fullacceptance
acceptancebybythe
the15mm
15mmoff-center
off-centerinjection.
injection.
the
15mm
Onthe
theother
otherhand,
hand,vertical
verticalemittance
emittanceincreases
increaseswith
with
On
emittance
increases
with
thebeam
beamintensity.
intensity.The
Theresults
resultscoincide
coincidewith
withthose
thoseof
of
the
coincide
with
those
of
Fig.
2
and
Figf.3.
Fig. 2 and Figf.3.
o
Ev, Eh (pi mm mrad:Normalized)
Ev, Eh (pi mm mrad:Normalized)
100
100
100
Ex(15mm H. Off-Cent. Inj.)
Ex(15mm H. Off-Cent. Inj.)
Ez3(15mm H. Off-Cent. Inj.)
Ez3(15mm H. Off-Cent. Inj.)
8080
o
1
E
>
60
60
40
40
W
0
00
0
11
5 10
11
5510
10 11
12
1 10
12
1110
1012
12
1.5 10
1.5
10 1212
1.510
Beam Intensity (ppp)
Beam
Beam Intensity
Intensity (ppp)
(ppp)
8080
60
60
60
40
40
40
20
20
20
0
00 0
0
0.5
0.5
0.5
1
11
1.5
1.5
1.5
After Injection(ms)
(ms)
After
After Injection
Injection (ms)
2
22
FIGURE 5. NormalizedEx,
Ex, EzThrough
Through Accelerating
FIGURE
FIGURE5.5. Normalized
Normalized Ex,Ez
Ez ThroughAccelerating
Accelerating
Process
Just
After
Injection
as
a
Parameter
of High &
& Low
Process
Process Just
Just After
After Injection
Injection as
asaaParameter
ParameterofofHigh
High &Low
Low
Beam
Intensity
under
the
Horizontal
Off
Center
Injection.
Beam
Beam Intensity
Intensityunder
underthe
theHorizontal
HorizontalOff
OffCenter
CenterInjection.
Injection.
20
20
0
Ex(26.0e11ppp)
—@-Ex(26.0e11ppp)
Ex(26.0elippp)
Ex(5.3e11-5.9e11ppp)
(5.3e11-5.9e11ppp)
—a—Ex
Ex (5.3e! l-5.9el Ippp)
Ez (17.1e11-19.6e11ppp)
Ez
—tto - Ez(17.1e11-19.6e11ppp)
(17.1el l-19.6el Ippp)
Ez (5.3e11-5.9e11ppp)
Ez (5.3e11-5.9e11ppp)
—A--Ez
(5.3ell-5.9ellppp)
100
100
100
12
2 10
2210
10 1212
intensity mode
mode operation
operation from
from the
the absolute
absolute value
value of
of
intensity
intensity
mode beam
operation
from the
absolute
value of
the
extracted
emittance
in
the
low
intensity
the
extracted
beam emittance in the low intensity
the
extracted
mode
operation.beam emittance in the low intensity
mode
operation.
mode
operation.
As shownFig.5,
Fig.5, ininhigh-intensity
high-intensity mode
mode operation,
operation, aa
As
As shown
shown
Fig.5,
in high-intensity
operation,
decrease
in the
horizontal
emittancemode
and the
increasea
decrease
in
the
horizontal
emittance
and
the
increase
decrease
in
the
horizontal
emittance
and
the
increase
in the vertical emittance take place simultaneously
in
the
vertical
emittance
take
place
simultaneously
in
the
vertical
emittance
take
place
simultaneously
during the period from 0.06ms (or faster) to 1.5ms
during
the
from 0.06ms
(or
toto 1.5ms
during
the period
period
(or faster)
faster)
1.5ms
after injection
hasfrom
been0.06ms
completed.
The emittance
after
injection
has
been
completed.
The
emittance
after
injection
has
been
completed.
The
emittance
changes saturate until 2.0ms and the values of the
changes
saturate
until
and the
values ofof the
changes
saturate
until 2.0ms
2.0ms
the
circulating
beam emittance
areand
closetheto values
the extracted
circulating
beam
emittance
are
close
to
extracted
circulating
beam emittance
close
to the
the emittance
extracted
beam emittance
in Fig. 2.areThe
vertical
beam
emittance in
Fig. 2.2. The
vertical
emittance
beam
Thelimit
vertical
growthemittance
reaches tointheFig.
acceptance
of theemittance
vertical
growth
reaches
to
the
acceptance
limit
of
the
vertical
growth
reaches
to
the
acceptance
limit
of
the
vertical
plane. The experimental results suggest the existence
plane.
The
experimental
results
suggest
the
existence
plane.
The
experimental
results
suggest
the
existence
of an X-Y coupling resonance by space-charge effects.
of
of an
an X-Y
X-Ycoupling
couplingresonance
resonanceby
byspace-charge
space-chargeeffects.
effects.
FIGURE 4. Intensity Dependence of the Extracted Beam
FIGURE
4. Intensity
Dependence of
Beam
FIGURE
Intensity
of the
the Extracted
Extracted
Emittance4. under
the Dependence
15mm Off center
Injection Beam
in the
Emittance
under
the
15mm
Off
center
Injection
in
the
Emittance
under
the
15mm
Off
center
Injection
in
the
Horizontal Plain.
Horizontal
Horizontal Plain.
Plain.
EMITTANCEEXCHANGE
EXCHANGE THROUGH
EMITTANCE
EXCHANGE THROUGH
THROUGH
ACCERERATINGPROCESS
PROCESS
ACCERERATING
ACCELERATING PROCESS
To obtain information about shrinkage of the
To
information
about shrinkage
To obtain
obtain
information
shrinkage of
of the
the
extracted
beam
emittance inabout
the accelerating
process,
extracted
beam
emittance
in
the
accelerating
process,
extracted
beam
emittance
in
the
accelerating
process,
the beam size was measured using a system
the
beam
was
using
the
beam size
wasandmeasured
measured
using[3].aa system
system
composing
asize
scraper
bump magnets
composing
a
scraper
and
bump
magnets
[3].
composing
a scraper
andboth
bump
[3].and vertical
The beam
sizes in
themagnets
horizontal
The
sizes in
the horizontal
and
The beam
beam
in both
both
horizontal
and vertical
vertical
planes
were sizes
measured
overthea period
of 0.06ms
to 2.0
planes
were
measured
over
aa period
of
0.06ms
to
planes
were
measured
over
period
of
0.06ms
to 2.0
2.0
ms after injection, where the charge-exchange
ms
after
where
the
charge-exchange
msinjection
after isinjection,
injection,
where
the
charge-exchange
completely finished and after which the
injection
completely
and
which
injection
is
completely
finished
and after
after
which
the
injected is
coasting
beamsfinished
are gradually
captured
in athe
RF
injected
coasting
beams
are
gradually
captured
in
injected
are gradually
in aa RF
RF
bucket.coasting
In thisbeams
bunching
process, captured
the momentum
bucket.
In
bunching
the
bucket.
In this
this
bunching
process,increases
the momentum
momentum
spread and
the linecharge process,
density
in the RF
spread
and
the
linecharge
density
increases
the
spread
and
thebunching
line- charge
density
increases
in
the
RF
bucket.
The
factor
decreases
fromin
1.0
toRF
0.4
bucket.
The
bunching
factor
decreases
from
1.0
to
0.4
bucket.
decreasestofrom
0.4
duringThe
thisbunching
period factor
from 0.06ms
1.5 1.0
mstoafter
during
this
during
this period
period from
from 0.06ms
0.06ms to
to 1.5
1.5 ms
ms after
after
injection.
injection.
injection.
The experimental results are shown in Fig.5. Here,
The
experimental
results
shown
in
Here,
Thevalues
experimental
results
are
shown
in Fig.5.
Fig.5.
Here,
the
of the beam
sizeare
at 95%
beam
intensity
are
the
values
of
the
beam
size
at
95%
beam
intensity
are
the
values oftothe
at normalized
95% beam intensity
areIn
converted
thebeam
value size
of the
emittance.
converted
to
of
normalized
In
the horizontal
plane,
theemittance.
momentum
converted
to the
the value
value
of the
thebecause
normalized
emittance.
In
the
horizontal
plane,
because
the
momentum
dispersion
of the plane,
KEK booster
is not the
zero (1.4m)
at the
the
horizontal
because
momentum
dispersion
of
booster
zero
at
scraper position,
the momentum
spread
not constant
dispersion
of the
the KEK
KEK
booster is
is not
not
zerois(1.4m)
(1.4m)
at the
the
scraper
position,
the
momentum
spread
is
not
constant
throughout
the
accelerating
process;
we
cannot
scraper position, the momentum spread is not constant
throughout
the
process;
we
cannot
directly calculate
the horizontal
emittance
the
throughout
the accelerating
accelerating
process;
we from
cannot
directly
calculate
horizontal
from
whole beam
size. the
However,
underemittance
the assumption
that
directly
calculate
the
horizontal
emittance
from the
the
whole
beam
However,
under
the momentum
is constant
the same that
time
whole
beam size.
size. spread
However,
under the
theatassumption
assumption
that
the
momentum
spread
is
constant
at
the
same
time
after
injection,spread
irrespective
of the
beam
intensity
the
momentum
is constant
at the
same
time
after
injection,
(neglecting
the irrespective
beam loadingof
RF beam
acceleration
and
after
injection,
irrespective
ofinthe
the
beam intensity
intensity
(neglecting
the
beam
loading
in
RF
acceleration
and
space
charge
effect
on
the
RF
bucket),
the difference
(neglecting the beam loading in RF acceleration
and
space
the
the
difference
in thecharge
beam effect
size ison
considered
to be the
space
charge
effect
on
the RF
RF bucket),
bucket),
thedifference
differencein
in
the
beam
size
is
considered
to
be
the
difference
the
emittance
due
to
the
beam
intensity.
in the beam size is considered to be the difference in
in
the
due
the
beam
intensity.
We can deduce
of the injected beam
the emittance
emittance
due to
tothe
theinitial
beamvalue
intensity.
We
the
value
of
emittance
(at 0.06ms
after
injection)
in the beam
highWe can
can deduce
deduce
the initial
initial
value
of the
the injected
injected
beam
emittance
(at
0.06ms
after
injection)
in
emittance (at 0.06ms after injection) in the
the highhigh-
DISCUSSION AND SUMMARY
DISCUSSION
DISCUSSION AND
ANDSUMMARY
SUMMARY
From the experimental results, the emittance
From
the
emittance
From the
the
experimental
results,
theinduced
emittance
exchange
due experimental
to
the couplingresults,
resonance
by
exchange
due
to
the
coupling
resonance
induced
by
exchange
due to effects
the coupling
resonanceThe
induced
by
space charge
is observed.
tricky
space
charge
The
tricky
space
charge ofeffects
effects
is observed.
observed.
Thethat
tricky
measurement
beam is
envelopes
reveals
the
measurement
of
reveals
that
measurement
of beam
beam
envelopes
revealswhen
that the
the
exchange occurs
right envelopes
after injection
the
exchange
occurs
right
after
when
exchange
occurs
rightproceeds
after injection
injection
when the
the
longitudinal
bunching
and correspondingly
longitudinal
bunching
proceeds
and
longitudinal
bunching
proceeds
and correspondingly
correspondingly
the line density
increase.
The simulation
results well
the
line
density
increase.
The
simulation
the
line the
density
increase.results
The simulation
results well
well
support
experimental
[3] [4]. results
support
the
experimental
results
[3]
[4].
support the experimental results [3] [4].
1.
1.1.
2.
2.
2.
3.
3.
3.
4.
4.
4.
305
REFERENCES
REFERENCES
REFERENCES
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Sakai,
ofofEPAC98,
Chargein the KEKPainting
Booster”,
Sakai, etInjection
et al,
al, “Phase-space
"Phase-space
Painting
Chargeexchange
Injection
inin the
Stockholm,
June 1998.
exchange
Injection
the KEK
KEK Booster”,
Booster", EPAC98,
EPAC98,
Stockholm,
1998.
I. Sakai, et.June
al.,“Observation
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Stockholm,
June
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I.I.inSakai,
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al.,“Observation
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the KEK
EPAC2000,
Vienna, June 2000
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EPAC2000,
Vienna,
June
2000
S.
Machida,
et.
al.,
"Simulation
of
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S.
Machida,
et.
Space
Effects
in a Synchrotron
"AIP Conf.ofofProc.
448,Charge
p. 73,
S.
Machida,
et. al.,
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"Simulation
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"AIP
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448,
May
1998I.
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May
1998I.
Sakai,
et. al., ”Intensity Dependent EmittanceMay
19981.
Sakai,
et. inal.,a High
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EmittanceExchange
Intensity
Proton Synchrotron”
Sakai,
et. al., ”Intensity
"Intensity
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EmittanceExchange
inChicago,
a HighJune
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Proton Synchrotron”
PAC
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2001
Exchange in a High Intensity Proton Synchrotron"
PAC 2001, Chicago, June 2001
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