Present Status of Development of Thick Long-Lived Hybrid
Carbon Stripper Foils for the 3 GeV Proton Booster Ring
I. Sugai1*, Y. Takeda1, M. Oyaizu1, H. Kawakami1, Y. Me^Y. Arakida1,
1
9
9
I. Yamane , I. Sakai, M. Kinsho and K. Kuramochi
1) High Energy Accelerator Research Organization
2) Japan Atomic Energy Research Institute
Abstract. JAERI -KEK joint accelerator as a typified high power proton beam requires thick carbon stripper foils from 300
to 500 jig/cm2 to stripe electrons from the H" beam. In such high energy and high intensity beam bombardment, the foil
lifetime is very short due to the radiation damage. Consequently, this short lifetime makes a great low operation efficiency of
accelerator and highly hazardous work for the foil exchanger personal. Therefore, it is essentially important to make a
breakthrough of the preparation method for long-lived carbon stripper foils. For this purpose, we have been performing
systematic research, development and production with high reproducibility using a controlled ACDDC arc-discharge
method.
INTRODUCTION
JKJ (JAERI-KEK joint) accelerator requires thick
carbon stripper foils (300 to 500|ig/cm2) to strip the
electrons from the H- beam, supplied by the Linac,
before injecting into the RCS ( Rapid Cyclic
Synchrotron). The 400 MeV H- beam from Linac has
a pulse length of 0.5 ms with a repetition 25 Hz and an
average current of 0.333 mA. Table 1 is the list of the
injection beam properties of the joint accelerator. As
mentioned below, long-lived thick carbon stripper foils
are indispensable to the accelerator of the next
generation.
Table 1. Injection beam properties of JKJ 3 GeV ring.
Kinetic energy
Beam pulse length
Repetition rate
Average beam current
Beam size
400 MeV
0.5ms
25 Hz
0. 333 mA
10 mm x 10 mm
is high (>1500K), the ablating evaporation involving
the sputtering effect becomes to dominate and the foil
thickness will be rapidly reduced with increasing
temperature, and the lifetime of the foil results in
shortening.
The results of the short lifetime of stripper foils
make following great problems. Namely, stripper foil
replacement is one of the most dose-intensive
activities and radiation hazardous work that
maintenance personnel is concerned with, and the
accelerator operational efficiency becomes very low.
As a matter of fact, in the carbon stripper foils of
300 and 500|ig/cm2 thickness cases, maximum
temperatures of foil by beam injection, as listed in
Table 1 are approximately 1200K to 2000K. The
carbon stripper foils with temperature of 2000K will
be rapidly evaporated by beam irradiation. For high
temperature of 2000K, diamond foil is a very attractive
candidate for a thick stripper foil, because of
drastically high thermal conductivity. However, the
diamond foil is not so easy to obtain as a selfsupporting foil without Si substrate and also not yet so
much creditable for practical use, according to test
performance by high energy and high intensity ion
beam accelerator so far.
Lifetime of the stripper carbon foils depends very
sensitive and strongly on the beam current intensity.
Due to energy loss of H" beam in the carbon foil and
hitting by recirculated particles, the foil temperature
Therefore, it is very difficult to obtain such stripper
will go up to high temperature. The foil rupture may
foils
in the world.
be categorized mainly by the following two processes,
depending on the foil temperature. Firstly, when the
Consequently, the development of a long-lived
foil temperature is relatively low (<1000K), the foil
carbon stripper foil with high durability for 2000K is
ruptures will happen mainly due to the radiation
one of the key technologies for 3 GeV RCS, JKJ high
damage on such slackening, thickening and shrinkage
power accelerator.
during irradiation. Secondly, when the foil temperature
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
346
FOIL
FOILPREPARATION
PREPARATION AND
AND
DEVELOPMENT
DEVELOPMENT
The
The carbon
carbon foils
foils prepared
prepared by
by conventional
conventional
methods,
methods,for
forexample,
example, 1)
1) electron
electron beam
beam evaporationevaporationcondensation,
condensation,2)2)glow
glowdischarge,
discharge, 3)
3) thermal
thermal cracking
cracking
and
and4)4)arc-discharge
arc-dischargemethods
methodshave
havebeen
beenused
used [1~3].
[1~3].
The
The lifetime
lifetime measurements
measurements of
of the
the foils
foils made
made by
by
different
differentmethods
methodsdescribed
describedabove
abovewere
wereperformed
performed for
for
high
highenergy
energy800
800MeV
MeVproton
proton beam
beam of
of up
up to
to 85|iA
85µA in
in
PSR
PSRofofLos
LosAlamos
AlamosNational
National Laboratory
Laboratory [4],
[4], and
and also
also
for
forlow
lowenergy
energy3.2
3.2MeV
MeVNe
Ne++beam
beamof
of3-4|iA
3-4µAfrom
from Van
Van
Graaffaccelerator
acceleratorofofTokyo
TokyoInstitute
Institute of
of Technology
Technology
dedeGraaff
[3].However,
However,the
theboth
bothresults
results showed
showed short
short lifetime.
lifetime.
[3].
We consider
consider that
that these
these foils
foils ruptured
ruptured by
by the
the first
first
We
processofofthe
theradiation
radiationdamage.
damage.In
Inorder
order to
toovercome
overcome
process
these short
short lifetimes,
lifetimes, we
we have
have developed
developed following
following
these
mainlythree
three carbon
carbon foil
foil preparation
preparation methods
methods of
of 1)
1)
mainly
Modified Controlled
Controlled AC
AC and
and DC
DC arc-Discharge
arc-Discharge
Modified
(mCADAD) method
method [5],
[5], 2)
2) Heavy
Heavy Ion
Ion Beam
Beam
(mCADAD)
Sputtering (HIBS)
(HIBS) and
and Mixed
Mixed Ion
Ion Beam
Beam Sputtering
Sputtering
Sputtering
(MIBS)methods
methodsand
and3)3)Ion
Ion Beam
Beam Sputtering
Sputtering method
method
(MIBS)
with Reactive
Reactive Nitrogen
Nitrogen gas
gas (IBSRN).
(IBSRN). Among
Among them,
them,
with
thefflBIS
HIBISand
andthe
theMIBS,
MIBS,the
theIBSRN
IBSRNmethods
methods and
and the
the
the
Laserplasma
plasmadeposition
deposition(Lp-foil)
(Lp-foil)method
method are
areavailable
available
Laser
forthin
thinfoil
foilofof55toto30|ig/cm
30µg/cm22ininthickness,
thickness, but
but not
not for
for
for
22 due to its low sputtering
thicker
than
about
50µg/cm
thicker than about 50|ig/cm due to its low sputtering
rateofofthe
thecarbon
carbon element,
element, especially
especially for
for the
the HIBS,
HIBS,
rate
MIBS
and
the
IBSRN.
On
the
Lp-foil
method,
foil
MIBS and the IBSRN. On the
Lp-foil method, aa foil
22 is not reported yet, but
with
thicker
than
~10µg/cm
with thicker than ~10|ig/cm is not reported yet, but
veryattractive
attractiveinin the
the future
future development
development for
for its
its long
long
very
lifetime.
From
these
point
of
views,
in
practical
foil
lifetime. From these point of views, in practical2 foil
2 can
preparation,
the
foils
with
thicker
than
100µg/cm
preparation, the foils with thicker than 100|ig/cm can
produced only
only by
by the
the mCADAD
mCADAD method.
method. This
This
bebe produced
method,ininprinciple,
principle,isisunique
unique and
and simple
simple method
method for
for
method,
long-livedcarbon
carbonfoil
foilpreparation.
preparation.Namely,
Namely, the
the carbon
carbon
long-lived
foilformed
formedby
byablation
ablationfrom
fromcathode
cathode electrode
electrode in
in DC
DC
foil
arc-discharge
is
very
strong
against
high
intensity
ion
arc-discharge is very strong against high intensity ion
beam
iraradiation,
but
very
fragile
for
mechanical
beam iraradiation, but very fragile for mechanical
stress.On
Onthe
theother
otherhand,
hand, the
the carbon
carbon foil
foil by
by ablation
ablation
stress.
from
both
electrodes
in
AC
arc–discharge
very
from both electrodes in AC arc-discharge isis very
fragile
for
ion
beam
one,
but
very
strong
for
fragile for ion beam one, but very strong for
mechanical
stress.
Therefore,
by
combining
both
mechanical stress. Therefore, by combining both
positive merits, we can make long-lived carbon
positive
merits, we can make long-lived carbon
stripper foils. As stated in ref [6], the lifetime of the
stripper foils. As stated in ref [6], the lifetime of the
foil depends on the ratio R=Wc/(Wc+Wa)(%), where
foil depends on the ratio R=Wc/(Wc+Wa)(%), where
Wc and Wa are the carbon source weight losses due to
We and Wa are the carbon source weight losses due to
ablation from the DC and AC arc discharge,
ablation from the DC and AC arc discharge,
respectively.
respectively.
FIGURE 1. Relationship between the ratio
FIGURE
ratio R
R and
and the
the
lifetime (Lifetime
(Lifetime measurements were performed with
lifetime
with aa 3.2
3.2
MeV, Ne
Ne++ at 3.0±0.5uA
3.0±0.5µA of 3.5mmφ
MeV,
3.5mm(|) beam spot).
spot). Error
Error bars
bars
represent mean
mean square errors and the numbers attached to
represent
to the
the
points are measured
measured sample numbers ..
points
The lifetime
lifetime is defined as integrated ion current
The
current
(mC) per
per unit area (cm22) until foil rupturing occurs.
(mC)
occurs.
The foils
foils are
are mounted on a stainless steel holder of
The
of 0.3
0.3
mm
thick
with
a
10
mm
diameter
aperture.
Figure
mm thick
aperture. Figure 11
shows the
the relationship
relationship between
between the
shows
the ratio
ratio R
R and
and the
the
lifetime. The
The data
data of
of fig.
lifetime.
fig. 11 shows
shows the
the very
very long
long
lifetime corresponding
corresponding 65
lifetime
65 times,
times, in
in maximum,
maximum, of
of the
the
best commercially
commercially available
available foil
best
foil made
made by
by the
the
evaporation-condensation method.
evaporation-condensation
method. We
We believe
believe that
that
this
characteristic
data
of
the
lifetime
versus
this characteristic data of the lifetime versus R
R will
will be
be
fruitful for
for lifetime
lifetime estimations
estimations of
the
thick
carbon
fruitful
of
the
thick
carbon
stripper foil
foil (>100|ig/cm
(>100µg/cm22),
), although
stripper
although the
the 2tested
tested foils
foils
shown
in
fig.
1
were
thin,
10
to
15µg/cm
shown in fig. 1 were thin, 10 to 15|ig/cm2.. The
The foils
foils
made by
by the
the mCADAD
mCADAD method
method have
have been
made
been widely
widely used
used
not only
only for
for low
low energy
energy heavy
heavy ion
ion beams
not
beams (thin
(thin ;; 10102
2 ) , but also for high energies such as 800
15µg/cm
15|ig/cm+ ) , but also for high2 energies such as 800
MeV IT
H (thick;
(thick; 100-300µg/cm
MeV
100-300|ig/cm2)[5].
)[5].
REFERENCES
REFERENCES
1. P.Maier-Komor, Nucl .Instr. and Meth. 102(1972)485-487
1. P.Maier-Komor, Nucl .Instr. andMeth. 102(1972)485-487
2. D.W.L. Tolfree, D.S. Whitmeel et al., Nucl. Instr. and
2. D.W.L. Tolfree, D.S. Whitmeel et al., Nucl. Instr. and
Meth.158(1979)333-336
M^.158(1979)333-336
3. I.Sugai, T. Fujino, K. Yamazaki and T. Hattori, Nucl.
3. LSugai, T. Fujino, K. Yamazaki and T. Hattori, Nucl.
Instr. and Meth. A236(1985)576-589
Instr. andMeth. A236( 1985)576-589
4. M.J.Borden, G.E.Adamson, R.N.Johnson and W.F.Nicase,
4. MJ.Borden,
G.E.Adamson, R.NJohnson and W.F.Nicase,
Nucl. Instr. and Meth .A303(1991)63-67
Nucl. Instr. andMeth .A303(1991)63-67
5. I.Sugai, M.Oyaizu, H.Kawakami, C.Ohmori, T.Hattori,
5. LSugai,
M.Oyaizu,
H.Kawakami,
C.Ohmori,Nucl.
T.Hattori,
K.Kawasaki,
M.J.Borden
and R.J.Macek,
Instr.
K.Kawasaki,
MJ.Borden
and
RJ.Macek,
Nucl.
Instr.
and Meth. A362(1995)70-76
andMeth. A362( 1995)70-76
6. I . Sugai, T.Hattori, K.Yamazaki et al., Nucl. Instr. and
6. I Meth.
. Sugai,
T.Hattori, K.Yamazaki et al., Nucl. Instr. and
A265(1988)376-382
Meth. A265(1988)376-382
347