Space Charge Effects at the KEK PS Main Ring
Space Charge Effects at the KEK PS Main Ring
S. Igarashi, K. Koseki, E. Nakamura, Y. Shimosaki, M. Shirakata, K. Takayama and
S. Igarashi, K. Koseki, E. Nakamura,T.Y.Toyama
Shimosaki, M. Shirakata, K. Takayama and
T. Toyama
KEK 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan
KEK 1-1 Oho, Tsukubajbaraki 305-0801, Japan
Abstract. Space charge effects during the injection period of the 12 GeV main ring of the KEK proton
synchrotron have been studied. Measurement of the transverse beam profiles using flying wires has revealed
Abstract. Space charge effects during the injection period of the 12 GeV main ring of the KEK proton
a characteristic temporal change of the beam profile within a few milliseconds after the injection. Horizontal
synchrotron have been studied. Measurement of the transverse beam profiles using flying wires has revealed
emittance growth was observed when the horizontal tune was close to the integer. The effect was more enhanced
a characteristic temporal change of the beam profile within a few milliseconds after the injection. Horizontal
for higher beam intensity. Resonance created by the space charge field was the cause of the emittance growth.
emittance growth was observed when the horizontal tune was close to the integer. The effect was more enhanced
A multiparticle tracking simulation program, ACCSIM, taking account of space charge effects has successfully
for higher beam intensity. Resonance created by the space charge field was the cause of the emittance growth.
reproduced the beam profiles.
A multiparticle tracking simulation program, ACCSIM, taking account of space charge effects has successfully
reproduced the beam profiles.
INTRODUCTION
INTRODUCTION
Horizontal Beam Profiles, \)
υXx=7.05
=7.05
11
Beam Intensity 8.0×10
S.OxlO11 protons
The
The beam
beam intensity
intensity of
of the
the KEK
KEK PS 12
12 GeV
GeV main ring
has
has significantly
significantly increased
increased since
since the
the K2K
K2K neutrino oscillation
lation experiment
experiment started.
started. Efforts
Efforts to
to minimize
minimize beam loss
have
have been
been continuously
continuously made.
made. One
One of
of the
the issues
issues is
is to
to rereduce
ducethe
theloss
loss during
duringthe
the injection
injection period.
period. Nine bunches of
protons
protons with
with the
the kinetic
kinetic energy
energy of
of 500
500 MeV
MeV are
are injected
injected
with
with the
the interval
interval of
of 50
50 ms.
ms. About
About 10
10 %
% of
of protons
protons are
are
lost
lost during
during the
the injection
injection period
period of
of 510
510 ms.
ms. The
The highest
highest
12
operating
protons
operating intensity
intensity of
of the
the main
main ring
ring is
is 1.4×10
1.4x 1012
per
per bunch
bunch at
at the
the injection.
injection. The
The nominal
nominal operational
operational tune
has
has been
been optimized
optimized to
to be
be 7.15
7.15 and
and 5.25
5.25 for the horizontal
and
and vertical
vertical tune
tune respectively.
respectively. The
The main
main ring
ring has
has aa circumference of
of 340
340 m
m and
and four-fold
four-fold symmetry.
symmetry. A
A super
super
cumference
period consists
consists of
of seven
seven FODO
FODO cells.
cells.
period
The incoherent
incoherent tune
tune shift
shift is
is estimated
estimated to
to be 0.5 for
for
The
the highest
highest operating
operating intensity
intensity without
without considering
considering the
the
effect of
of the
the image
image field
field or
or dispersion.
dispersion. The
The large value
effect
of the
the space
space charge
charge tune
tune shift
shift is
is partly
partly due
due to
to aa small
small
of
emittance of
of the
the injection
injection beam.
beam. Emittance
Emittance dilution and
emittance
particle loss
loss would
would occur
occur under
under these
these circumstances.
circumstances. It
particle
empirically known
known that
that emittance
emittance dilution
dilution observed
observed
isis empirically
after the
the injection
injection to
to the
the main
main ring
ring depends
depends on the beam
after
intensity and
and tune.
tune.
intensity
PROFILE MEASUREMENTS
MEASUREMENTS
PROFILE
Flying wire
wire transverse
transverse beam
beam profile
profile monitors
monitors have
have been
Flying
operated at
at the
the main
main ring
ring and
and have
have demonstrated
demonstrated a wide
operated
dynamicrange
rangeof
of more
morethan
thantwo
two orders
orders of
of magnitude
magnitude and
and
dynamic
position accuracy
accuracyof
of0.4
0.4mm
mm[1].
[1].ItIttakes
takesabout
about44ms
msfor
for
aaposition
the wire
wire to
to scan
scan aa typical
typical size
size of
of the
the injection beam. The
the
wirescanning
scanning can
can be
be initiated
initiated once
once in
in an
an acceleration
acceleration cywire
cle
of
the
main
ring
at
an
arbitrary
timing
using aa delayed
delayed
cle of the main ring at an arbitrary timing using
trigger
with
respect
to
the
injection
kicker
timing
signals
trigger with respect to the injection kicker timing signals
or
the
acceleration
cycle
timing
signals.
A
new
stroboor the acceleration cycle timing signals. A new strobo-
—
—
—
—
—
0.07
0.06
0.05
™~~~
———
——-
•-•- +2.2 ms
••-- +2.4 ms
+2.6 ms
••-- +2.8 ms
—
-10
0
+0.2 ms
+0.3 ms
+0.4 ms
+0.5 ms
+0.6 ms
+0.7 ms
ms
+0.8 ms
ms
+0.9 ms
+1.0 ms
+1.2 ms
+1.4 ms
+1.6 ms
+1.8 ms
ms
+2.0 ms
10
(mm)
Position (mm)
profi les 0.2 ∼
~ 2.8 ms after
after the
FIGURE 1. Horizontal beam profiles
injection when the horizontal tune was 7.05 and the
the injection
injection
11
8.Ox 1011
.
beam intensity was 8.0×10
scopic procedure has recently
recently been established
established to reconreconstruct the beam profile that quickly changes with a time
scale of 11 ms or less. A series of profile data are acquired
by changing the trigger setting with an increment
increment of 0.2
0.2
ms. They are then rearranged to reconstruct the simultaneous profiles.
11
x 1011
When the injection beam intensity was set to 8.0
8.0×10
after the inprotons, the beam profile 0.2 ms to 2.8 ms after
jection were reconstructed as in figure 1. The horizontal
horizontal
tune in this case was 7.05 which was not the
the nominal
nominal opoperational value. The vertical tune was 5.22.
5.22. A significant
significant
beam loss was observed within 1 ms after
after the
the injection
injection
under the condition. The reconstructed profile
profile shows a
notable change of the distribution. The profile
profile at 0.2 ms
after the injection consists of a narrow peak and a broad
broad
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
300
Horizontal
υi)Xx=7.11
HorizontalBeam
Beam Profiles,
Profiles,
=7,11
11
Beam
protons
Beam Intensity
Intensity 8.0×10
8.0x10°
protons
Horizontal Beam Profiles, 4 ms after the Injection
Injection
11
Beam Intensity 4.3×10
4.3x10° protons
υ
1^=7.10
0,06 υDXx=7.06
=7,06
X=7.10
0,09
—
—
—
—
—
0,08
0,07
0,06
0.03
—
——
—....
....
—
0,02
—
— +2.2
+2.2 ms
ms
"-»- +2.4
+2.4 ms
ms
-"• +2.6
+2.6 ms
ms
,„.„., +2.8
+2.8 ms
ms
-40
-30
-20
-10
0
10
20
+0.2
+0.2 ms
ms
+0.3
+0.3 ms
ms
+0.4 ms
ms
+0.4
+0.5 ms
ms
+0.5
+0.6 ms
ms
+0.6
+0.7 ms
ms
+0.7
+0.8 ms
ms
+0.8
+0.9 ms
ms
+0.9
+1.0 ms
ms
+1.0
+1.2 ms
ms
+1.2
+1,4 ms
ms
+1.4
+1.6 ms
ms
+1.6
+1.8ms
+1.8
ms
+2.0 ms
ms
+2.0
30
0,04
0,04
0,02
0,02
-40
0,06
20
40
-40
0,04
0,02
0,02
0,06
-20
0
20
Position(mm)
40
υX=7.24
-40
0,06
0,04
0,04
0,02
0,02
0
-40
40
-20
-20
0
20
40
0
20
40
0
20
40
Position(mm)
υ
=7.19
BxX=7.19
0,04
Position (mm)
(mm)
Position
0
20
Position(mm)
40
-20
Position(mm)
DXY=7.28
=7,28
υ
-40
-20
Position(mm)
FIGURE3.3. Horizontal
Horizontalbeam
beamprofiles
profi les44ms
msafter
after the
theinjection
injection
FIGURE
whenthe
theinjection
injection beam
beamintensity
intensity was
was4.3×10
4.3 x 101111..
when
HorizontalEmittance
Emittance
Horizontal
BeamIntensity
Intensityatatthe
theInjection
Injection
Beam
11 protons
8,3x10°
8.3×10 protons
11 protons
4,3x10°
4.3×10
protons
11 protons
2,4x10°
2.4×10
protons
Horizontal Emittance (π mmmrad)
distribution.The
Thenarrow
narrow peak
peak diminishes
diminishes inin 22 ms
ms and
and
distribution.
only
the
broad
distribution
remains.
only the broad distribution remains.
The same
same procedure
procedure was
was applied
applied for
for the
the horizontal
horizontal
The
tune
of
7.11
and
the
vertical
tune
of
5.21
which
was
tune of 7.11 and the vertical tune of 5.21 which was
near the
the nominal
nominal operational
operational value.
value. The
The reconstructed
reconstructed
near
profilesare
areshown
shownininfigure
figure2.2.The
Theprofile
profileatat0.2
0.2ms
msafter
after
profiles
the
injection
still
consists
of
a
narrow
peak
and
a
broad
the injection still consists of a narrow peak and a broad
distribution.The
Thenarrow
narrowpeak
peakdiminishes
diminishes inin11ms,
ms,and
and
distribution.
only
the
broad
distribution
remains
as
in
the
case
of
the
only the broad distribution remains as in the case of the
tune
of
7.05.
The
narrow
peak
of
this
case
is,
however,
tune of 7.05. The narrow peak of this case is, however,
lesssignificant
significant than
than that
that ofof the
the previous
previous tune,
tune, and
and the
the
less
beam
loss
is
not
either
significant
in
this
case.
beam loss is not either significant in this case.
Horizontalbeam
beamprofiles
profilesafter
afterthe
theinjection
injectionwere
weremeameaHorizontal
sured
for
the
injection
beam
intensity
of
2.4,
4.3
and
sured for11the injection beam intensity of 2.4, 4.3 and
8.3
xlO
protons.
The
measurements
were
performed
11
8.3×10 protons. The measurements were performed
foraarange
rangeofofthe
thehorizontal
horizontaltune
tunefrom
from 7.05
7.05to
to 7.3.
7.3.The
The
for
vertical
tune
was
maintained
to
be
between
5.2
and
5.25.
vertical tune was maintained to be between 5.2 and 5.25.
Thetrigger
triggerwas
wasset
settotoinitiate
initiatethe
thewire
wirescanning
scanningtototake
take
The
beam
profiles
of
about
4
ms
after
the
injection
when
the
beam profiles of about 4 ms after the injection when the
rapid
change
of
the
profile
was
settled.
The
profiles
for
rapid change of the profile
11 was settled. The profiles for
the
intensity
of
4.3x
10
protons
are
shown
in
figure
11
the intensity of 4.3×10 protons are shown in figure 3.3.
wasobserved
observedtotobe
bewide
widewhen
whenthe
thehorizontal
horizontaltune
tunewas
was
ItItwas
7.06,
and
became
narrower
as
the
tune
was
away
from
7.06, and became narrower as the tune was away from
theinteger.
integer.ItItisisalso
alsonoted
notedthat
thatthe
theprofile
profile of
ofthe
thetune
tuneof
of
the
7.28
has
tails
unlike
any
other
profile.
7.28 has tails unlike any other profile.
threshold was
was set
set toto cut
cut baseline
baseline noises
noises and
and the
the
AA threshold
full
beam
widths
were
measured
from
the
profiles.
Beam
full beam widths were measured from the profiles. Beam
emittanceswere
wereestimated
estimatedwith
withthe
thefull
full widths
widthsand
andplotplotemittances
ted
in
figure
4.
The
injected
beam
95
%
emittance
was
ted in figure 4. The injected beam 95 % emittance was
measured
at
the
beam
transfer
line
to
be
15.9±0.2,
measured at the beam transfer line to be 15.9±0.2,
17.8±0.1 and 18.6±0.2 Trmmmrad for the intensity of
π mmmrad for the intensity of
17.8±0.1 and 18.6±0.2
2.4,
4.3 and 8.3 xlO 11 protons respectively. Emittance
2.4, 4.3 and 8.3×1011 protons respectively. Emittance
0
Position(mm)
υuXx=7.15
=7.15
-40
FIGURE2.2. Horizontal
Horizontalbeam
beamprofiles
profi les0.2
0.2∼~2.8
2.8ms
msafter
afterthe
the
FIGURE
injectionwhen
whenthe
thehorizontal
horizontaltune
tunewas
was7.11
7.11and
andthe
theinjection
injection
injection
11
11 . .
beamintensity
intensitywas
was8.0×10
8.Ox 10
beam
-20
7
7,05
7,1
7,15
Horizontal Tune
Horizontal Tune
FIGURE 4.4. Horizontal
Horizontal emittance
emittance as
as aa function
function of
of the
the horhorFIGURE
izontal tune.
tune. About
About 0.3
0.3 %
% of
of the
the tail
tail isis ignored
ignored in
in case
case of
of aa
izontal
Gaussiandistribution.
distribution.
Gaussian
growth was
was observed
observed when
when the
the tune
tune isis close
close to
to the
the inteintegrowth
ger
for
all
the
measured
intensity
settings.
A
tune
range
ger for all the measured intensity settings. A tune range
that emittance
emittance growth
growth occurs,
occurs, however,
however, depends
depends on
on the
the
that
intensity.
The
ranges
are
0.1
and
0.15
for
the
intensity
of
intensity. The ranges
are 0.1 and 0.15 for the intensity of
11
2.4
and
4.3
x
10
protons
respectively.
Emittance
growth
11
2.4 and 4.3×10 protons respectively. Emittance growth
was observed
observed for
for all
all the
the measured
measured tune
tune range
range for
for the
the ininwas
11
tensity
of
8.3
x
10
protons.
The
tune
range
of
the
emit11
tensity of 8.3×10 protons. The tune range of the emittance growth
growth corresponds
corresponds to
to naive
naive estimate
estimate of
of the
the incoincotance
herent
tune
shift.
It
is
inferred
that
the
emittance
growth
herent tune shift. It is inferred that the emittance growth
is due to resonance created by the space charge.
is due to resonance created by the space charge.
301
ACCSIM
ACCSIM Simulations,
Simulations, υi)Xx=7.04
Horizontal
Horizontal Beam
Beam Profiles
Profiles
ACCSIM
ACCSIMsimulations
simulations
(7.04,
5.21), Beam
(7.04,5.21),
BeamIntensity
Intensity8×10
SxlO1111protons
protons
+0.15 ms
+0.30 ms
+0.45 ms
+0.60 ms
pPxo
X
x
(mm)
Position (mm)
FIGURE 5.5. ACCSIM
ACCSIM simulation
simulation of
of the
the x-p
x-pxx phase
phase space
space
FIGURE
1thehorizontal
plotsofof20
20test
testparticles
particlesFigure
whenthe
horizontaltune
tunewas
was7.04
7.04and
and
plots
when
theinjection
injectionbeam
beamintensity
intensitywas
was8.0×10
8.0x 101111..
the
FIGURE 6.
6. ACCSIM
ACCSIM simulation
simulation of
of the
the Horizontal
Horizontal beam
beam
FIGURE
profiles 0.15
0.15 ∼
~ 0.6
0.6 ms
ms after
after the
the injection
injection when
when the
the horizontal
horizontal
profiles
11
tunewas
was7.04
7.04 and
and the
the injection
injection beam
beam intensity
intensity was
was 8.0×10
8.0x 1011
tune
..
ACCSIMSIMULATIONS
SIMULATIONS
ACCSIM
CONCLUSIONS
CONCLUSIONS
multiparticletracking
tracking simulation
simulation program,
program, ACCSIM
ACCSIM
AAmultiparticle
[2],taking
takingaccount
accountof
ofspace
spacecharge
chargeeffects
effects has
has been
been perper[2],
formed toto understand
understand the
the observed
observed phenomena.
phenomena. TransTransformed
versespace
spacecharge
chargeforces
forceshave
havebeen
beencalculated
calculatedfor
for10000
10000
verse
macro particles
particles with
with aa hybrid
hybrid fast-multipole
fast-multipole technique
technique
macro
andgrids
gridsofof11mm
mm×x 11mm
mmevery
every 0.76
0.76m
m step.
step. Thin
Thin lens
lens
and
kicks
have
been
applied
to
simulate
sextupole
and
ockicks have been applied to simulate sextupole and octupole
magnets.
A
fringing
field
from
an
injection
septupole magnets. A fringing field from an injection septummagnets
magnetswas
was suspected
suspected as
as one
one source
source of
of closed
closed orortum
bit
distortion
and
included
in
simulations
for
some
cases.
bit distortion and included in simulations for some cases.
Parametersfor
forthe
theinjection
injection beam
beam emittance
emittance were
were based
based
Parameters
onthe
thetransfer
transferline
lineprofile
profilemeasurements.
measurements.
on
Figure55isis the
the x-p
x-pxx phase
phase space
space plot
plot of
of 20
20 test
test parparFigure
ticlesfor
for400
400 turns
turns when
when the
the horizontal
horizontal tune
tune isis 7.04.
7.04. ItIt
ticles
showspatterns
patternsof
ofresonance
resonancethat
thatwas
wascreated
createdby
bythe
thespace
space
shows
charge
force.
Octupole
type
space
charge
field
would
crecharge force. Octupole type space charge field would create
the
resonance.
The
resonant
tune
is
7/4
for
a
super
ate the resonance. The resonant tune is 7/4 for a super
period,because
becausethe
themain
mainring
ringhas
hasfour-fold
four-fold symmetry.
symmetry.
period,
Beam
profiles
at
the
tune
of
7.28
has
tails
asin
infigure
figure
Beam profiles at the tune of 7.28 has tails as
3.
The
tails
may
also
be
due
to
resonance
by
the
space
3. The tails may also be due to resonance by the space
chargefield.
field. The
The resonant
resonant tune
tune isis 7.25
7.25 inin this
this case,
case, asascharge
sumingsome
someimperfection
imperfectionininthe
thefour-fold
four-fold symmetry.
symmetry.
suming
Horizontalprofiles
profiles from
from the
the ACCSIM
ACCSIM simulation
simulation up
up
Horizontal
to
400
turns
which
corresponds
to
0.6
ms
is
plotted
to 400 turns which corresponds to 0.6 ms is plotted
for the
the horizontal
horizontal tune
tune of
of 7.04
7.04 in
in figure
figure 6.
6. ItIt shows
shows aa
for
good
agreement
with
the
measurement.
Another
tracking
good agreement with the measurement. Another tracking
simulation
code,
PATRASH
[3],
has
also
been
applied
simulation code, PATRASH [3], has also been applied
and
the
results
agreed
with
the
ACCSIM
results.
and the results agreed with the ACCSIM results.
Measurement of
of the
the transverse
transverse beam
beam profiles
profiles using
using flyflyMeasurement
ing wires
wires has
has revealed
revealed aa characteristic
characteristic temporal
temporal change
change
ing
ofthe
thebeam
beamprofile
profile within
withinaafew
fewmilliseconds
milliseconds after
after the
the ininof
jection.Horizontal
Horizontalemittance
emittance growth
growth was
was observed
observed when
when
jection.
the horizontal
horizontal tune
tune was
was close
close to
to the
the integer.
integer. The
The effect
effect
the
was
more
enhanced
for
higher
beam
intensity.
Resonance
was more enhanced for higher beam intensity. Resonance
created by
by the
the space
space charge
charge field
field was
was the
the cause
cause of
of the
the
created
emittance
growth.
A
multiparticle
tracking
simulation
emittance growth. A multiparticle tracking simulation
program, ACCSIM,
ACCSIM, taking
taking account
account of
of space
space charge
charge efefprogram,
fects
has
successfully
reproduced
the
beam
profiles.
fects has successfully reproduced the beam profiles.
ACKNOWLEDGMENTS
ACKNOWLEDGMENTS
We thank
thank F.
F. Jones
Jones for
for valuable
valuable advices
advices and
and installation
installation
We
of
ACCSIM
in
our
computer.
We
also
thank
H.
Sato and
and
of ACCSIM in our computer. We also thank H. Sato
K.
Sato
for
useful
comments.
K. Sato for useful comments.
REFERENCES
REFERENCES
Igarashi, S.,
S., Arakawa,
Arakawa, D.,
D., Koba,
Koba, K.,
K., Sato,
Sato, H.,
H., Toyama,
Toyama,
1.1. Igarashi,
T., and
andYoshii,
Yoshii,M.,
M.,Nuclear
Nuclear Instruments
Instruments and
and Methods
Methods in
in
T.,
Physics Research
Research A,
A,482/1-2,
482/1-2, 32–41
32-41 (2002).
(2002).
Physics
2. Jones,
Jones, F.,
F., Accsim
Accsim Reference
Reference Guide
Guide Version
Version 3.5s,
3.5s, pp.
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