Radiation Handling in the Slow Extraction
RadiationofHandling
the JHF in
50 the
GeVSlow
RingExtraction
of the JHF 50 GeV Ring
Takeichiro Yokoi and Masahito Tomizawa
Takeichiro Yokoi and Masahito Tomizawa
KEKAccelerator
Accelerator Laboratory
Laboratory
KEK
Abstract.
the
lis expected
expected to
tohit
hitthe
theESS(Electro
ESS(ElectroStatic
StaticSeptum).
Septum).
Abstract.InIn
theslow
slowextraction
extractionofofthe
theJHF
JHF50GeV
50GeVring,
ring, about
about 1is
The
beam
loss
beam power
powerof
of7.5kW.
7.5kW.Considering
Consideringthe
thetolerable
tolerable
The
beam
lossininthe
thescattering
scatteringisisabout
about1%
1%corresponding
corresponding to
to the
the beam
beam
loss(0.5~lW/m),
scattering beam
beam isisindispensable.
indispensable.ToToevaluate
evaluatethethe
beam
loss(0.5∼1W/m),careful
carefulstudy
studyof
ofthe
the beam
beam loss
loss of the scattering
radiation
14(00), was
was carried
carried out.
out.InInaddition,
addition,the
thebeam
beamloss
loss
radiationlevel
levelaround
aroundESS,
ESS,simulation
simulation study
study with
with MARS
MARS14(00),
distribution
14(00) and single
single particle
particle tracking.
tracking.The
Theresult
resultshows
showsthat
that
distributionininthe
thering
ringwas
wasstudied
studiedcombining
combining MARS
MARS14(00)
thethe
radiation
In addition,
addition,ititwas
wasfound
foundthat
thatthe
theactual
actualbeam
beam
radiationlevel
levelaround
aroundESS
ESSisissuppressed
suppressedto
to the
the tolerable
tolerable level. In
loss
is is
much
loss
muchsmaller
smallerthan
thanthe
theloss
lossofof1%
1%which
whichhit
hit the
the ESS
ESS wire .
INTRODUCTION
INTRODUCTION
$ l! m w :;i
:M .1. J:.aLi:;.l«;
slowextraction
extractionofofthe
theJHF
JHF50GeV
50GeV synchrotron,
synchrotron,
In In
thetheslow
whose
beam
power
is
750kW(15
µ
A,
50GeV),
the beam
beam
whose beam power is 750kW(15juA, 50GeV), the
hit
rate
on
the
ESS
wire
is
expected
to
be
suppressed
hit rate on the ESS wire is expected to be suppressed
down
about1%
1%[2].
[2].Though
Thoughthe
theloss
lossrate
rateisissuppressed
suppressed
down
to to
about
low,
absolutebeam
beampower
powerisis7.5kW.
7.5kW.Considering
Considering
so so
low,
thetheabsolute
tolerablebeam
beamloss
lossfrom
fromthe
thepoint
pointofofview
view machine
machine
thethe
tolerable
maintenance,
∼1W/m,
the
loss
is
quite
large.
Thus,
demaintenance, ~lW/m, the loss is quite large. Thus, aa detailed study using computer simulation is indispensable.
tailed study using computer simulation is indispensable.
In following sections, the radiation level and loss rate in
In following sections, the radiation level and loss rate in
the ring are to be discussed.
the ring are to be discussed.
SLOW EXTRACTION CHANNEL OF
SLOW EXTRACTION CHANNEL OF
JHF MAIN RING
JHF MAIN RING
The instruments for the slow extraction system, such as
The
instruments
for the slow
extraction
system,
as
ESS,
septum magnets,
are to
be installed
in a such
straight
ESS,
septum
magnets,
are
to
be
installed
in
a
straight
section of 116m long. The layout of the slow extraction
section
116m
Theand
layout
of theenvelope
slow extraction
line ofofthe
ESS long.
channel
the beam
is shown
line
of
the
ESS
channel
and
the
beam
envelope
shown
in Fig. 1. In the slow extraction section, longis straight
in sections
Fig. 1. In
slow extraction
section,
long straight
arethe
prepared
for the beam
collimation
system
sections
are prepared
the beam collimation system
of the slow
extractionfor
scattering.
of the slow extraction scattering.
SCATTERING AT ESS
SCATTERING AT ESS
Beam loss at ESS is caused by direct hit of proton beam
on the
wire.is In
such by
a case,
process
and
Beam
lossESS
at ESS
caused
directthe
hitloss
of proton
beam
are well
In addition,
onthe
theamount
ESS wire.
In defined
such a and
case,understood.
the loss process
and
diameter
of thedefined
ESS wire
is 80µ m. In In
such
a thin
thethe
amount
are well
and understood.
addition,
target,
most
of
the
scattered
particle
go
out
with
Moliere
the diameter of the ESS wire is SOjUm. In such a thin
scattering.
target,
most of the scattered particle go out with Moliere
In such a case, a detailed computer simulation of beam
scattering.
loss
process
is aindispensable
and possible
withofabeam
good
In such
a case,
detailed computer
simulation
accuracy.
loss process is indispensable and possible with a good
To study the beam loss at the ESS wire, a simulaaccuracy.
tion study with MARS14(00)[1] was carried out. The
To study the beam loss at the ESS wire, a simulation study with MARS14(00)[1] was carried out. The
FIGURE 1.
Layout of beam extraction devices and beam
FIGURE
envelope 1. Layout of beam extraction devices and beam
envelope
setup of the simulation is shown in Fig. 2. In the sim-
setup
simulation
shownbeam
in Fig.
In size
the simulationofa the
uniform
50GeVisproton
with2.the
of
ulation
a uniform
50GeV
beam
× 10mm(V)
hits proton
the ESS
wirewith
fromthe
thesize
up-of
80µ m(H)
80
stream.
jum(H) x 10mm(V) hits the ESS wire from the upstream.
Fig 3 shows the particle distribution at the exit of
FigIt3indicates
shows the
at proton
the exitgoof
ESS.
thatparticle
most ofdistribution
the scattered
ESS.
It indicates
thatlosses,
most and
of the
proton
out with
small energy
thatscattered
half of them
keepgo
circulating
in the
ring losses,
for turns.
what
we have
out
with small
energy
and Then,
that half
of them
keep
to evaluate in
arethe
the ring
radiation
level Then,
aroundwhat
ESS we
duehave
to
circulating
for turns.
theevaluate
prompt scattering,
and the loss
in theESS
ring due
withto
to
are the radiation
levelmap
around
multi-turn
the
prompttracking.
scattering, and the loss map in the ring with
multi-turn tracking.
RADIATION AROUND ESS
RADIATION AROUND ESS
Using the setup shown in Fig. 2, radiation level around
ESS was
usingin
MARS.
the point
view
Using
theestimated
setup shown
Fig. 2,From
radiation
levelof around
of
maintainability
of
the
ring,
life
time
of
the
elements
ESS was estimated using MARS. From the point of view
andmaintainability
the residual dose
are crucial
problems.
the
of
of the
ring, life
time of Among
the elements
element of the slow extraction channel, the quadrupole
and the residual dose are crucial problems. Among the
element of the slow extraction channel, the quadrupole
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
177
300
siide view 300
siide view
55
300
300
55
55
Beam
15mSV/hour in maximum. However, for the duct be15mSV/hour
in maximum.
maximum.
However,
for the
the duct
duct
between ESS and
QFP,whichHowever,
is madefor
of
SUS,
theberesid15mSV/hour
in
15mSV/hour
in
maximum.
However,
for
the
duct
be1
tween
ESS
and
QFP,which
is
made
of
SUS,
the
residual dose
150mSv/hour
!! Therefore,
theresidmaintetween
ESSreaches
and QFP,which
is made
of SUS, the
1made of SUS, the residtween
andwould
QFP,which
ual
doseESS
reaches
ISOmSv/hour
!! Therefore,
themaintemaintenance
ofreaches
ESS
requireis1special
treatment.
ual
dose
150mSv/hour
the
1!! Therefore,
ual dose
reaches
150mSv/hour
!! Therefore,
the maintenance
of ESS
ESS
would
require
special
treatment.
However,
in most
of the
ESS treatment.
channel,
the radiation
nance
of
would
require
special
nance
of
ESS
would
require
special
treatment.
However,
in most
most of
of the
the ESS
ESS channel,
channel,the
theradiation
radiation
However,
in
level
is tolerable.
However,
in most of the ESS channel, the radiation
level
tolerable.
level
isis tolerable.
level is tolerable.
front view
siide view
550
300
300 550
150
550
550
150
150550
Beam
Beam
front view
front view
550wire
ESS
ESS wire 100kV/cm
(~230gauss)
ESS wire100kV/cm
1500
2300
1500
1500
Proton beam 2300
2300
Proton
Proton beam*
beam
Proton
——»
•beam
• •
BEAM LOSS ESTIMATION OF ESS
BEAM LOSS
LOSS
ESTIMATION OFESS
ESS
BEAM
ESTIMATION
SCATTERING
BEAM LOSS
ESTIMATION OF
OF ESS
SCATTERING
SCATTERING
SCATTERING
100kV/cm
(~230gauss)
(~230gauss)
80µm
Tungsten
80µm
Tungsten
1200 wires(=1.5m)
80µm
1.25mm Total
Tungsten
1.25mm Total
TotalTungsten
1200 wires(=1.5m)
wires(=1.5m)
1200
1.25mm
Total
1200 wires(=1.5m)
1.25mm
replaced by low density bulk
5
•••
I
Q T
From the initial distribution of scattered particle(Fig. 3),
From
the initial
initial
distribution
ofscattered
scattered
particle(Fig.
3),
From
distribution
of
half the
of
scattered
particle
go outparticle(Fig.
in the first3),
turn.
From
thethe
initial
distribution
of scattered
particle(Fig.
3),
half
of
the
scattered
particle
go
out
in
the
first
turn.
half
of
the
scattered
particle
go
out
in
the
first
turn.
Then,
problemgois out
the in
lossthedistribution
half
of the
the remaining
scattered particle
first turn. in
Then, the
the remaining
remaining problem
problem isisthe
theloss
lossdistribution
distributioninin
Then,
the ring
many problem
turns. Inisorder
to distribution
study the issue,
Then,
the for
remaining
the loss
in
the ring
ring for
for many
many turns.
turns. In
In order
order toto study
study the
the issue,
issue,
the
simulation
the result
fromthe
MARS
the
ring forstudy
manycombining
turns. In order
to study
issue,and
simulation study
study combining
combiningthe
theresult
resultfrom
fromMARS
MARSand
and
simulation
simulation
studytracking(SAD)
combining thewas
result
from out.
MARS and
single particle
carried
single particle
particletracking(SAD)
tracking(SAD)was
wascarried
carriedout.
out.
single
single
particle
wasmagnet,
carried out.
From
ESS tracking(SAD)
to the 1st septum
all the scattered
From
ESS to
to
the
1st septum
septummagnet,
magnet,all
allthe
thescattered
scattered
From
ESS
the
1st
From ESS
tothrough
the 1st the
septum
magnet,
all the scattered
particles
pass
same
field
configuration.
Thus,
particles
pass
through
the
same
field
configuration.
Thus,
particles
pass
through
the
same
field
configuration.
Thus,
particles
pass
through
the
same
field
configuration.
Thus,
at
first,
the
beam
loss
up
to
the
1st
septum
was
examined.
at
first,
the
beam loss
up
to
the 1st
at
first,
the
loss
up
to
1stseptum
septumwas
wasexamined.
examined.
at
first,
the beam
beam
loss
upmap
to the
the
1st
septum
was
examined.
Fig.
shows
the
loss
in
the
straight
section.
Fig.
444shows
the
loss
map
in
the
straight
section.
Fig.
shows
the
loss
map
in
the
straight
section.
Fig. 4 shows the loss map in the straight section.
replaced
replaced by low density bulk
replaced by low density bulk
Proton beam
Proton
Proton beam
beam
Proton beam
θ
θ
θ
loss(W/7.5kW)
loss(W/7.5kW)
loss(W/7.5kW)
FIGURE 2. Simulation model of ESS
FIGURE 2. Simulation model of ESS
FIGURE
FIGURE 2. Simulation model of ESS
i
llsM
*.:•••
,j
i-sa
I
, ,
:
! •,,,
•P
^
^
(»'-••••••
$
*ml M
:
:-
f
:.
-J
. • • • • - • •f.-
--
's
L|**
loss(W/7.5kW)
loss(W/7.5kW)
loss(W/7.5kW)
i:;
:
--
"
•^"f""^
i'YVrli*, K
S
'- £•'
'•?
f- ' '•*&
!•'"•,- ».
:.-
':•-
* • .,*'•" :-i
FIGURE
3. Distribution
Distribution
ofofScattered
exit of
FIGURE
Scattered
particle
at
the
FIGURE
Distributionof
Scatteredparticle
particleat
atthe
of
FIGURE
3.3.3. Distribution
particle
at
the exit
exit of
of
ESS
(a)Momentum
distribution,(b)phase
ESS
(a)Momentum
distribution,(b)phase
space
distribution
of
ESS
(a)Momentumdistribution,(b)phase
distribution,(b)phasespace
spacedistribution
distributionof
of
ESS
(a)Momentum
space
distribution
of
high
energy
region(>50GeV/c),(c)angle
high
energy
region(>50GeV/c),(c)angle
distribution
high
energy
region(>50GeV/c),(c)angledistribution
distribution
high
energy
region(>50GeV/c),(c)angle
distribution
magnet
installed
atatthe
the
downstream
magnet
installedat
thedownstream
downstreamof
ofESS(QFP)
ESS(QFP)is
isexexmagnet
installed
at
downstream
of
ESS(QFP)
isis
exmagnet
installed
the
of
ESS(QFP)
expected
to
suffer
from
the
most
serious
radiation
dampected
to
suffer
from
the
most
serious
radiation
dampected
to
suffer
from
the
most
serious
radiation
dampected
to
suffer
from
the
most
serious
radiation
damage.
Thus,
by
modeling
the
quadrupole
age.
Thus,
by
modelingthe
thequadrupole
quadrupolemagnet,
magnet,radiation
radiation
age.
Thus,
by
modeling
the
quadrupole
magnet,
radiation
age.
Thus,
by
modeling
magnet,
radiation
level
there
was
estimated.
level
there
was
estimated.
level
there
was
estimated.
levelFirst,
therethewas
estimated.
absorption
dose
in the
coil
First,the
theabsorption
absorptiondose
dosein
thecoil
coilinsulator
insulatorwas
wasestiestiFirst,
insulator
was
estiFirst,
the
absorption
dose
ininthe
the
coil
insulator
was
estimated.
The
result
indicates
that
assuming
5000
hour
mated.
The
result
indicates
that
assuming
5000
houropopmated.
The
result
indicates
that
assuming
5000
hour
mated.
The
result
indicates
that dose
assuming
5000
houropoperation
per
one
year,
absorption
reaches
∼16MGy/y
eration
per
one
year,
absorption
dose
reaches
∼16MGy/y
erationper
perone
oneyear,
year, absorption
absorption dose
dose reaches
~16MGy/y
eration
reaches
∼16MGy/y
ininmaximum.
Using
polyimide
film(Kapton)
as
the
coil
maximum.Using
Usingpolyimide
polyimidefilm(Kapton)
film(Kapton) as
as the
the coil
coil
in maximum.
ininsulator,
maximum.
Using
polyimide
film(Kapton)
as the
coil
the
life
time
is more
than
25
isissufinsulator,
thelife
lifetime
time
morethan
than
25year,
year,which
which
sufinsulator,
the
isismore
25
year,
which
is sufinsulator,
the
life
time
is
more
than
25
year,
which
is
sufficiently
long.
ficientlylong.
long.
ficiently
Next,
the
residual
dose
rate
was
ficiently
Next,long.
theresidual
residualdose
doserate
rate was
was estimated.
estimated. AssumAssumNext,
the
estimated.
Assuming
the
operation
day
run
and
coolNext,
the
residualwith
dose30
rate
was
estimated.
Assuming
the
operation
with
30
day
run
and 111 day
day
cooling the operation with 30 day run and
day
cooling,
for
the
side
ofof
ESS
and
QFP,
the
residual
dose
is
ing
the
operation
with
30
day
run
and
1
day
cooling,
for
the
side
ESS
and
QFP,
the
residual
dose
ing, for the side of ESS and QFP, the residual dose isis
ing, for the side of ESS and QFP, the residual dose is
178
4
4
1010
10 4 3
3
1010
10 3 2
10
10 22
10
1010
10
1 1
1-1 -1
1010-1
10
0 0
0
Q-mag.
scraper
Q-mag.
(a) (a)
w/ow/o
scraper
Q-mag.
(a) w/o scraper
5 5
5
4 4
1010
10 4
3 3
1010
10 3
2 2
1010
10 2
1010
10
1 1
1-1
-1-1
10
10
10
10
0
00
10 10
10
15 15
15
scraper
scraper
scraper
5
55
10
1010
20 20 25 25 30 30
20
25
30
ielmielm
ielm
(b) (b)
wt scraper
scraper
(b) wtwt
scraper
15
15 15
20
25
30
20 20 25 25 30 30
ielm
ielmielm
FIGURE
4.
loss
distribution
of
scattering
event
FIGURE
4.4. Beam
Beam
loss
distribution
ofESS
ESS
scattering
event
FIGURE
of
ESS
scattering
event
FIGURE
Beamline;
lossdistribution
distribution
of
ESS
scattering
event
in
the
slow
extraction
(a)without
scraper,
(b)
with
scraper
in
the
slow
extraction
line;
scraper,
(b)
with
scraper
in
the
slow
(a)without
scraper,
(b)
with
scraper
in the slow extraction line; (a)without scraper, (b) with scraper
In
the
study, the
case with
scraper
was
also
examined.
In
the
scraper
was
also
examined.
In
the
the
with
was
also
examined.
In
thestudy,
study,
thecase
case
with
scraper
was
also
examined.
The
scraper
aperture
was
set
to
match
the
extraction
orThe
was
set
to
match
the
extraction
orThe
scraper
aperture
match
the
extraction
or-orThe
scraper
aperture
was
set
to
match
the
extraction
bit
and
injection
orbit(acceptance:81
π
mm·mrad.).
It
inbit
and
injection
orbit(acceptance:81
π
mm·mrad.).
It
inbit
and
injection
orbit(acceptance:8l7rmm-mrad.).
It
inbit andthat
injection
orbit(acceptance:81
π mm·mrad.).
It indicates
without
scrapers,
the
next
quadrupole
magdicates
that
scrapers,
the
next
quadrupole
magdicates
that
without
next
quadrupole
magdicates
that
without
scrapers,
the
next
quadrupole
magnet
suffers
beam
loss
of
150W.
netof
ofQFP
suffersfrom
fromsevere
beam
loss
of
about
150W.
net
suffers
severe
beam
loss
ofabout
about
150W.
netof
ofQFP
QFP
suffers
fromsevere
severe
beam
loss
of
about
150W.
However,
once
the
scraper
is
installed,
the
beam
losses
of
However, once the scraper is installed,
the
beam
losses
of
However,
installed,
the
beam
losses
of of
However,
once
the
scraper
is
installed,
the
beam
losses
the
magnets
except
QFP
are
reduced
to
less
than
10W.
the
magnets
except
QFP
are
reduced
to
less
than
10W.
the
magnets
to
less
than
10W.
the
magnets
except QFP are
reduced
to less than
10W.
The
multi-turn
tracking
The next
next step
step isis toto carry
carry out
out the
the
The
next
the multi-turn
multi-turn tracking
tracking
The
next
step
is
to
carry
out
the
multi-turn
tracking
and
make
the
loss
map
in
the
whole
ring.
Fig.5
shows
the
and make
make the loss map in the whole ring.
and
ring. Fig.5
Fig.5 shows
showsthe
the
and
make
the
loss
map
in
the
whole
ring.
Fig.5
shows
the
beam
loss
map
up
to
12
turns.
In
the
study,
the
injection
beam loss
loss map
map up
up to
to 12
turns. In
beam
12 turns.
In the
the study,
study, the
the injection
injection
beam loss map up to 12 turns. In the study, the injection
1 If the duct material is replaced to Ti, the residual dose is reduced to
11 If the duct material is replaced to Ti, the residual dose is reduced to
If the duct material is replaced to Ti, the residual dose is reduced to
1/3
1 If the duct material is replaced to Ti, the residual dose is reduced to
1/3
1/3
1/3
scraper
scraper is
is also
also installed.
installed. Without scrapers,
scrapers, beam power of
15W
15W isis expected
expected to
to dissipated
dissipated in
in aa element
element in
in maximum.
maximum.
However,
However, with
with scrapers,
scrapers, it drops to 2W.
2W. It is acceptance
level
level considering
considering the length of the elements(3∼5m).
elements(3~5m).
5 1010
5 1i-1
6 1010
00
(a)
(a) w/o
w/o scraper
scraper
10 r-\
S10
33 •
W/7.5kW
2
nilllllHinillUllHIIlilHIIIMIllllllluUlilJlll^^
200
200
4
10
;sio
liiKpiiiiiiiiiiifiiiiiiiiii^
400
400
(b)
(b) wt
wt scraper
scraper
600
800
injection scraper
loss(W/7.5kW)
10 2 liiiiiiiiiiiiiiiiiiiiiiiMiiiiiiiiiiiiiiiiiiiiiiiiiMiiiiiiiiiiiiiiiiiiiiiiiiiMiiiiiiiiNUiliiiiiiiiiiiNiiiiiiiiiiiiiiiiiiiiiiiiiNiiiii
10
1-1
^ 10
10
ilMSMMMiMllllim^
200
400
1000
0
200
400
600
800
1000
Element
&
IT
FIGURE 5.
5. Beam
Beam loss
loss distribution
distribution of ESS scattering
scattering event
event
FIGURE
in the
the JHF
JHF 50GeV
50GeV ring; (a)without
(a)without scraper,(b) with scraper
in
Fig. 66 shows
shows the horizontal phase space distribuFig.
tion at
at ESS
ESS for
for the first 3turns.
Sturns. It indicates that certain
tion
amount of
of scattered
scattered beam
beam is
is extracted
extracted eventually; 0turn:
Oturn:
amount
~ 50%,2turn:∼
50%,2turn:~ 2%,3turn:23%.
2%,3turn:23%.
∼
10
i
2
10
1000
1000
Element
11
-1
10
10 "
in
10
W/7.5kW
loss(W/7.5kW)
£• 10
extraction
ESS wire is extracted eventually. It means the extraction
efficiency
extraction is
is quite
quite high.
high.
efficiency of the slow extraction
said that
that as long
long as
as the
the
From these results, it can be said
scattering at the ESS wire is concerned, the loss in the
scrapers.
ring can be controlled by employing the scrapers.
-2
r
M
r
..................I•
4
10
3
10
2
t
!_.. . > :survive
:survi ve
rlossiintt-tlthe ring
:P i 1 :loss
i ,,, i,,J,
0
10
10
. ,>
1
1
'
2
•
(a) w/o Scrape
Scraper
(a)
•
, , J , ,
4
6
j
•"•••r"-""-V-, J , , , J , ,
8
10
10
,
J
,
12
12
Turn
Turn
-r-----"|-------r----"-r---^D7ipei
(b) wi
wt sera
Scraper
-[--•'--•f---*--^---0--!---*--1
• ! * j
A
j
•
<»
!
;
£
i A
•
1 i 4
)
:sui
vive
I
I
I
:survive
-1
rlos in the ring
10 r 11 :loss
-2
k , :loss
:los s^^rpeifs,
at scarpers , , j , , , j , , , j , , , j ,
10 " - , 4
10
2
4
6
8
10
12
0
Turn
Turn
FIGURE 7. Beam loss summary of ESS scattering event(up
event(up
to 12 turn) (a)without
(a) without scraper, (b)with scraper
SUMMARY
FIGURE 6.
6. Horizontal
Horizontal phase
phase space
space distribution
distribution of
of the
the scatscatFIGURE
tered particle
particle at
at ESS
ESS
tered
In the slow extraction of JHF 50GeV
50GeV main
main ring,
ring, about
about
1% of beam hit the ESS
ESS wire,
wire, which
which corresponds
corresponds to
to the
the
beam power of 7.5kW. For the beam loss, the
the simulasimulation combining MARS
14(00) and single particle
MARS14(00)
particle tracktracking(SAD) was carried out.
out. From
From the
the radiation
radiation level
level estiestimation, the radiation level around
around ESS is tolerable level.
level.
Multi-turn tracking of scattered particle off the
the ESS
ESS wire
wire
shows that the scraper is effective
effective to reduce the
the unconuncontrolled beam loss in the ring, and that most of the
the scatscattered beam was extracted eventually
eventually without
without losing
losing in
in the
the
ring. Thus, as long as the scattering at the ESS wire is the
main source of the primary
primary beam
beam loss in
in the
the slow
slow extracextraction, the extraction efficiency
is
quite
high.
efficiency
REFERENCES
REFERENCES
Multi-turn tracking
tracking shows
shows that
that such
such tendency
tendency lasts
lasts for
for
Multi-turn
turns. Fig.
Fig. 77 summarizes
summarizes the
the beam
beam loss
loss of
of the
the scattered
scattered
turns.
particles. From
From the
the figure,
figure, the
the following
following features
features can
can be
be
particles.
seen. (1)
(1) After
After 8turns,
Sturns, actually
actually no
no beam
beam loss
loss occurs
occurs in
in the
the
seen.
ring. (2)
(2) In
In every
every 3turns,
Sturns, 20∼
20~ 30%
30% of
of circulating
circulating beam
beam is
is
ring.
in the
the side
side of
of extracted
extracted beam
beam at
at the
the ESS
ESS wire.
wire. Thus,
Thus, if
in
if the
the
tendency lasts
lasts furthermore,
furthermore, after
after 60turns,
60turns, the
the remaining
remaining
tendency
scattered
particle
in
the
ring
is
expected
to
reduced
to
scattered particle in the ring is expected to reduced to
1/1000.
Thus
more
than
90%
of
scattered
beam
off
the
1/1000. Thus more than 90% of scattered beam off the
1.
1.
2.
2.
179
N.Mokhov, MARS13(98)
MARS13(98) code
code system
system User's
N.Mokhov,
User’s guide
guide
"Design of
small-beam loss
”Design
of small-beam
loss slow
slow extraction
extraction in
in aa high
high
intensity
intensity 50-GeV
50-GeV proton
proton synchrotron",
synchrotron”, Masahito
Masahito Tomizawa
Tomizawa
et
al. Proc.
et al.
Proc. of
of EPAC'02,
EPAC’02, p2267~2269
p2267∼2269