The Production and Acceleration of RIBs at ISAC-I and
Future Plans for ISAC-II
R.E. Laxdal
TRIUMF, 4004 Wesbrook Mall, Vancouver, BC, Canada, V6T2A3
Abstract. ISAC-I at TRIUMF is now delivering intense beams of both low energy and accelerated radioactive ion beams
(RIBs) for experiments. The post-accelerator for ISAC-I includes a room temperature RFQ and DTL operating cw to accelerate
ions of A < 30 to a final energy fully variable from 0.153 to 1.53MeV/u. The design concept, machine status and early
operating experience of the ISAC-I linear accelerator complex will be summarized.
TRIUMF has received funding through to 2005 to proceed with an extension to the ISAC facility, ISAC-II, to permit
acceleration of radio-active ion beams above the Coulomb Barrier for masses up to 150. Central to the addition are a ECR
charge state booster before the ISAC RFQ and a superconducting heavy ion linac. The accelerator design and present status
of the project including superconducting rf developments will be presented.
INTRODUCTION
There is an intense interest world-wide in the use of Radioactive Ion Beams (RIBS) for experiment. By virtue
of a strong driver beam and with the completion of the
ISAC-I post-accelerator, TRIUMF is now poised to become the leading facility for ISOL based systems, delivering intense beams of both low energy and accelerated RIBs for experiments. In brief, the facility includes
a 500 MeV proton beam (I < 100 jU A) from the TRIUMF
cyclotron impinging on a thick target, an on-line source
to ionize the radioactive products, a mass-separator, an
accelerator complex and experimental areas.
The accelerator chain includes a 35.4 MHz RFQ[1], to
accelerate beams of A/q < 30 from 2keV/u to 153 keV/u
and a post stripper, 106 MHz variable energy drift tube
linac (DTL)[2] to accelerate ions of 3 < A/q < 6 to a
final energy between 0.153 MeV/u to 1.53 MeV/u.
TRIUMF is now constructing an extension to the
ISAC facility, ISAC-II, to permit acceleration of radioactive ion beams up to energies of at least 6.5 MeV/u for
masses up to 150. In brief the proposed acceleration
scheme would use the existing RFQ with the addition
of an ECR charge state booster to achieve the required
mass to charge ratio (A/q < 30) for masses up to 150.
A new room temperature IH-DTL would accelerate the
beam from the RFQ to 400 keV/u followed by a poststripper heavy ion superconducting linac designed to accelerate ions of A/q < 7 to the final energy. A new building will be ready for occupancy in Jan. 2003. An initial
installation of 25 MV of superconducting linac will be
completed in 2005 with a further 18 MV added two to
three years later. Present studies are concentrating on design and development for the first stage installation.
BEAM PRODUCTION
Present licensing permits continuous operation at
100 jUA proton intensity for targets with Z < 82. Thus
far 40 jUA have been run onto Nb, TiC and Ta targets
and 15 juA onto a SiC target with beam production from
a surface ion source. Beams of E < 60 keV and A < 238
have been delivered to the low energy experimental area
since 1998. Sample yields are 2.2 x 104pps nLi from
a Ta target, 1.4 x 104pps 74Rb from a Nb target and
3 x 109pps 21Na from a SiC target. Presently beams are
run to six experimental stations in the low energy area
and two experimental stations in the high energy area.
Past production has been limited to a single 'West' target station. A second 'East' target station has now been
commissioned with a new surface source target module.
A second target module outfitted with a 2.45 GHz ECR
source for the production of singly charged gaseous and
volatile species is now installed in the 'East' target station. The new source has been commissioned with stable
beams. First radioactive beams from the ECR are scheduled in the new year. Operation of the 'West' target continues with the installation of a TaC target for potassium
beams. A target storage facility has recently been completed. An off-line conditioning box, complete with stable beam analysis station, is now in operation for target
testing and bake-out prior to on-line use. Development is
underway on a laser ion source initially for the production of aluminum beams. Finally an evaporator is being
CP680, Application of Accelerators in Research and Industry: 17th Int'l. Conference, edited by J. L. Duggan and I. L. Morgan
© 2003 American Institute of Physics 0-7354-0149-7/03/$20.00
249
converted
for high
high beam
beam
converted to
to allow
allow development
development of
of targets
targets for
power.
power.
ISAC-I
ISAC-I ACCELERATOR
ACCELERATOR
A
(LEBT) delivers
delivers stable
stable
A low
low energy
energy beam
beam transport
transport (LEBT)
beams
from
the
off-line
source
(OLIS)
or
exotic
beams
beams from the off-line source (OLIS) or exotic beams
from
A switchyard
switchyard can
can
from the
the mass-separator
mass-separator to
to the
the RFQ.
RFQ. A
send
the
stable
beams
to
the
low
energy
area
while
sisend the stable beams to the low energy area while simultaneously
high energy
energy area,
area,
multaneously delivering
delivering RIBs to the high
or
electrostatic and
and
or vice
vice versa.
versa. The LEBT is completely electrostatic
houses
5.7 m
m
houses an
an 11.8
11.8 MHz multi-harmonic pre-buncher 5.7
upstream
post-accelerator for
for
upstream of
of the
the RFQ. A layout of the post-accelerator
IS
AC is
ISAC
is shown in Fig. 1.
DTL (106MHz)
HEBT
Low j0 Buncher
(11.8MHz)
FIGURE2.2. The
TheISAC
ISAC35.4
35.4MHz
MHzRFQ.
RFQ.
FIGURE
MEBT ,
ing cavities
cavities before
before Tanks
Tanks2,3,4
2,3,4providing
providingtransverse
transverseand
and
ing
longitudinalfocussing
focussingrespectively.
respectively.To
Toachieve
achieveaareduced
reduced
longitudinal
final energy
energythe
thehigher
higherenergy
energyIH
IHtanks
tanksare
areturned
turnedoff
offand
and
final
the
the voltage
voltage and
and phase
phaseininthe
thelast
lastoperating
operatingtank
tankare
arevarvaried.
ied.
Rebuncher (35.4MHz)
^Stripping Foii
Chopper (5.9/11.8MHz)
Bunch Rotator (106MHz)
RFQ
(35.4MHz)
Pre-buncher (11.8MHz)
LEBT
Switchyard
OLIS
FIGURE 1.
1. The
The ISAC-I
ISAC-I accelerator.
FIGURE
accelerator.
The medium
medium energy
energy beam
beam transport
transport (MEBT)
The
(MEBT) is
is comcomposed
of
a
matching
section
to
the
stripping
posed of a matching section to the stripping foil,
foil, aa
charge selection
selection section
section and
and aa matching
matching section
charge
section to
to the
the
DTL.
A
two
frequency
chopperprovides
a
clean
separaDTL. A two frequency chopperprovides a clean separation between
between pulses
pulses selectable
selectable between
between 85
tion
85 and
and 170
170 ns
ns
and aa 106
106 MHz
MHz bunch
and
bunch rotator
rotator produces
produces aa time
time focus
focus
on the
the stripper
stripper foil.
foil. The
The DTL
DTL matching
matching section
on
section utilizes
utilizes
a
35.4
MHz
spiral
rebuncher.
The
high
a 35.4 MHz spiral rebuncher. The high energy
energy beam
beam
transport (HEBT)
(HEBT) delivers
delivers the
the beam
beam from
transport
from the
the DTL
DTL to
to
the experimental
experimental stations.
stations. A
A bunching
bunching station
the
station consisting
consisting
of aa low-/3
low-β 11.8
11.8 MHz
MHz triple
triple gap
gap structure
structure and
β
of
and aa highhigh-/3
35.4
MHz
spiral
resonator
are
incorporated
to
maintain
35.4 MHz spiral resonator are incorporated to maintain
the good
good longitudinal
longitudinal emittance
emittance to
to the
the target.
the
target.
The RFQ
RFQ [1],
[1], aa four
four vane
vane split-ring
The
split-ring structure
structure (Fig.
(Fig. 2),
2),
has
no
bunching
section;
instead
the
beam
is
pre-bunched
has no bunching section; instead the beam is pre-bunched
at 11.8
11.8MHz.This
MHz.This not
not only
only shortens
shortens the
the linac
at
linac but
but rereduces
the
longitudinal
emittance
at
a
small
expense
duces the longitudinal emittance at a small expense in
in
the beam capture. The variable energy DTL (Fig. 3) is
the
beam capture. The variable energy DTL (Fig. 3) is
based on a separated function approach with five indebased on a separated function approach with five independent interdigital H-mode (IH) structures, each with
pendent
interdigital H-mode (IH) structures, each with
0◦ synchronous phase, providing the acceleration with
0° synchronous phase, providing the acceleration with
quadrupole triplets between tanks and three-gap bunchquadrupole triplets between tanks and three-gap bunch-
FIGURE
FIGURE3.3. The
TheISAC
ISAC106.1
106.1MHz
MHzDTL.
DTL.
Commissioning
Commissioningand
andBeam
BeamDelivery
Delivery
Beam
Beam commissioning
commissioning with
with stable
stablebeams
beamsconfirm
confirmthe
the
design
aims
of
the
accelerators.
The
steps
taken
design aims of the accelerators. The steps takentotorereduce
duce the
the longitudinal
longitudinal emittance
emittanceproved
provedsuccessful
successfulwith
with
aa measured
keV/u-ns ininagreement
measured value
value of
of 0.5
0.5 π7rkeV/u-ns
agreementwith
with
calculations.
The
RFQ
capture
efficiency
calculations. The RFQ capture efficiencyatatthe
thenominal
nominal
voltage
voltageisis75-80%
75-80%ininthe
thebunched
bunchedcase
case(three
(threeharmonics)
harmonics)
and
25%
for
the
unbunched
case
in
reasonable
and 25% for the unbunched case in reasonableagreement
agreement
with
with predictions.
predictions.DTL
DTLrfrfparameters
parametersand
andbeam
beamoptics
opticssetsettings were established for over twenty different energy
tings were established for over twenty different energy
set-points covering the whole specified operating range.
set-points covering the whole specified operating range.
The transmission through the DTL was over 95% with
The transmission through the DTL was over 95% with
good beam quality over the whole energy range. Energy
good beam quality over the whole energy range. Energy
The Production and Acceleration of RIBs at ISAC-I and Future Plans for ISAC-II
250
November 11, 2002
2
TABLE 1. Experimental results from
TABLE 1. collaboration
Experimental results
from
ISN/TRIUMF
ECR Charge
TABLE
1. Experimental onresults
from
ISN/TRIUMF
collaboration on ECR Charge
Breeder
at
Grenoble.
ISN/TRIUMF collaboration on ECR Charge
Breeder at Grenoble._______________
Breeder
at Grenoble.
Isotope
Q
Eff.(%) I (pnA) A/q
Isotope
Q
Eff.(%) I(pnA) A/q
Isotope
Q
Eff.(%)
I (pnA)
A/q
115 In
18+
3.3
130
5.8
spread and pulse width measurements after the DTL are
spread
and
pulse
measurements
after
the DTL are
consistent
with
an width
emittance
of 1π keV/u-ns.
spread and
pulse
width measurements
after the DTL are
consistent
with
an
emittance
of
l7rkeV/u-ns.
Stable accelerated
beams ofhave
been delivered to
consistent
with an emittance
1π keV/u-ns.
accelerated
beams
been
to
Stable
accelerated
beams
have
been delivered
delivered
to
two Stable
experimental
stations,
the have
DRAGON
recoil mass
two
experimental
stations,
the
DRAGON
recoil
mass
two experimental
stations,
DRAGON
recoil
mass
spectrometer
and the
TUDAthegeneral
purpose
scatterspectrometer and
the
general
purpose 4scatterscatterand April
the TUDA
TUDA
general
ingspectrometer
chamber, since
1, 2001.
They purpose
include 4He1+
1+,
1,
2001.
include
1+,,
13ing
3+chamber,
14,15 N4+since
16 OApril
4+
20,21
4,5+ They
24include
6+ . 4He
ing
chamber,
since
April
1,
2001.
They
He
C
,
,
,
Ne
and
Mg
13
4+
Mg +.
13 C3+
3+ ,14,15
14,15 N4+
4+ 16
16 O
4+ ,20,21^4,5+
20,21 Ne4,5+and
6+ .
and 24
Mg2001
RIB beams
have, been
accelerated
since
July
with
RIB
beams
have
been
accelerated
since
July
2001 with
with
7 pps
8 Li
2+ delivered
RIB
2001
2 × 10
to the since
TOJAJuly
experiment.
7beams
8 have
2+ been accelerated
22 x× 10
pps
Li
delivered
to
the
TOJA
experiment.
7
8
2+
21 NaLi
5+ hasdelivered
to the to
TOJA
Since 10
thenpps
been delivered
bothexperiment.
DRAGON
21
5+
21Na
5+ has
Since
then
been
delivered
to
both
DRAGON
8
Since
then
Na
has
been
delivered
to
bothPilot
DRAGON
and
TUDA
with
intensities
up
to
6×10
beams
8 pps.
8
and
TUDA
with
intensities
up
to
6
x
10
pps.
Pilot
beams
16 TUDA
4+
21 intensities
5+
and
with
up
to
6×10
pps.
Pilot
beams
ofof 1616
OO4+
and
21Ne 5+ respectively were used for pre4+ and 21Ne 5+ respectively were used for preof O
and Ne The
respectively
were pilot
used beam
for pretuning
the
accelerator.
switch
from
tuning
the
switch
from
pilot
beam to
to
tuning
the accelerator.
accelerator.InThe
The
switch
from
pilotare
beam
to
RIB
is
straightforward.
general
beam
tunes
RIB
isis straightforward.
In
general
beam
tunes
are estabestabRIB
straightforward.
In
general
beam
tunes
are
established
by a aphysicist
with
delivery
monitored
and
lished
with
delivery
monitored
and opoplished by
by operations
a physicist
physicist staff
with 24
delivery
monitored
and
optimized
by
hours/day
seven
days
a
timized
by
operations
staff
24
hours/day
seven
days
timized by operations staff 24 hours/day seven days aa
week.
A
plot
of
various
beams
and
energies
accelerated
week.
accelerated
week. A
A plot
plot of
of various
various beams
beams and
and energies
energies accelerated
totoexperiment
are
given
ininFig.
4.4.
experiment
are
given
Fig.
to experiment are given in Fig. 4.
24
C
?
N
?
Q
115
115 In
109
InAg
Ag
109
109
64Ag
64Zn
Zn
64 Zn
120
120 Sn
Sn
120
88Sn
88Sr
Sr
88
69Sr
69Ga
Ga
6990Ga
6
?
Y
90y
90
208
YPb
208p
208 Pbb
18+
18+
17+
17+
17+
10+
10+
10+
19+
19+
19+
14+
14+
14+
11+
11+
11+
14+
14+
14+
25+
25+
25+
3.3
3.3
3.0
3.0
3.0
2.8
2.8
2.8
4.1
4.1
4.1
3.7
3.7
3.7
2.0
2.0
2.0
3.3
3.3
3.3
2.0
2.0
2.0
130
130
175
175
175
42
42
42
167
167
167
470
470
470
460
460
460
178
178
178
700(2+)
700(2+)
700(2+)
5.8
5.8
6.4
6.4
6.4
6.4
6.4
6.4
6.3
6.3
6.3
6.3
6.3
6.3
6.3
6.3
6.3
6.4
6.4
6.4
8.3
8.3
8.3
E=6.5MeV/u (A/q=7)
Stage 2
MEBT2jl^
25 20 -
* M£8T1
n o
I
15
1H-DTL1
aa
~
FIGURE
5. Stage
Stage111and
andStage
Stage222of
ofthe
theISAC-II
ISAC-II
expansion.
FIGURE 5.
5.
Stage
and
Stage
of
the
IS
AC-IIexpansion.
expansion.
FIGURE
10 5-
0
0.0
0.2
0.4
0.6
0.8
1.0
Energy (MeV/u)
1.2
1.6
FIGURE
FIGURE
Stable
and
radioactive
beams accelerated
accelerated to
exFIGURE4.4.4. Stable
Stableand
andradioactive
radioactivebeams
to experiment.
periment.
periment.
ISAC-II
ISAC-II
ECRCharge
ECR
ChargeBreeder
Breeder
ECR
TRIUMFisisiscollaborating
collaboratingwith
Grenoble on
on the
the
TRIUMF
collaborating
with ISN
ISN Grenoble
TRIUMF
developmentofof
ofan
anECR
ECRbased
state booster.
booster. A
A
development
an
ECR
based charge
charge state
development
14
GHzPhoenix
Phoenixsource
and will
will soon
soon
GHz
Phoenix
sourcehas
hasbeen
beenordered
ordered and
1414
GHz
be
assembledon
onaaatest
teststand
standatatTRIUMF.
TRIUMF.Results
Results of
of iniiniassembled
on
test
stand
bebe
assembled
tial
studies
measuring
1+/n+
conversion
efficiency
pertialstudies
studiesmeasuring
measuring1+/n+
l+/n+ conversion efficiency
efficiency pertial
formedon
onthe
theISN
ISNtest
teststand
standare
are given
given in
in Table
Table 1[3].
1[3].
formed
on
the
ISN
test
stand
are
given
in
Table
1[3].
formed
These
‘fasting
tuning’
results
can
be
improved
by
a
facThese‘fasting
'fastingtuning’
tuning'results
resultscan
canbe
beimproved
improved by
by aa facfacThese
tor
of
two
by
careful
optimization
of
the
particular
charge
tor
of
two
by
careful
optimization
of
the
particular
charge
tor of two by careful optimization of the particular charge
state.
state.
state.
Superconducting Linac
Linac
Superconducting
Superconducting
Linac
The two
two stages
stages of
of the
the ISAC-II
ISAC-II installation
installation are
are shown
The
shown
The
two
stages
of the
ISAC-II
shown
in
Fig.
5. A
A comprehensive
comprehensive
first installation
order design
designare
study[4],
in
Fig.
5.
first
order
study[4],
innow
Fig. complete,
5. A comprehensive
first
order
design
study[4],
set the
the parameters
parameters of
of the
the floor
layout
nowcomplete,
complete, set
set
floor layout
layout
now
the parameters
of the
floor
prior
to
building
construction.
Designs
are
compatible
prior
to
building
construction.
Designs
are
compatible
prior
building construction.
compatible
withtomulti-charge
multi-charge
accelerationDesigns
to Ag/g
∆Q/Qare
≤
±8
to
prewith
acceleration
to
< ±8
±8 to
to preprewith
multi-charge
acceleration
to
∆Q/Q
≤
serve
beam
intensity
and/or
allow
the
possibility
of
a
serve
beam
intensity
and/or
allow
the
possibility
of
serve beam intensity and/or allow the possibility of aa
second
optionalstripping
strippingstage
stagetoto
toboost
boostthe
thefinal
finalion
ionenensecond optional
stripping
stage
boost
the
final
ion
ensecond
ergy. The
The superconducting
superconducting
linacisisiscomposed
composedofof
oftwo-gap,
two-gap,
superconductinglinac
linac
composed
two-gap,
ergy.
niobium, quarter
quarterwave
waverfrfrfcavities,
cavities,for
foracceleration,
acceleration,
bulk niobium,
quarter
wave
cavities,
for
acceleration,
bulk
superconducting
solenoids,for
forperiodic
periodictransverse
transverse
and superconducting
superconducting solenoids,
solenoids,
for
periodic
transverse
and
focussing, housed
severalvacuum
vacuuminsulated
insulatedcryomodcryomodhoused in
inseveral
several
vacuum
insulated
cryomodfocussing,
The linac
linac has
beengrouped
groupedinto
intolow,
low,medium
mediumand
and
ules.
ules. The
has been
been
grouped
into
low,
medium
and
high
high beta
corresponding
cavities
with
design
beta sections
sectionscorresponding
correspondingtoto
tocavities
cavitieswith
withdesign
design
velocities
=4.2%,
4.2%,
5.7,7.1%
and
10.4%
velocities of
of βft,
βoo =
βoo==
4.2%,βft,
=5.7,
5.7,7.1%
7.1%and
andβft,
=10.4%
10.4%
oβ=
o=
respectively.
The two
two cavity
cavity
types
the
mid
beta
secrespectively. The
cavitytypes
typesinin
inthe
themid
midbeta
betasecsection
tion (Fig.
(Fig. 6),
6), composed
composed
of
eight
5.7%
and
twelve
βo o===5.7%
composedof
ofeight
eightβft?
5.7%and
andtwelve
twelve
βPooo =
= 7.1%
7.1% cavities,
cavities, are
are
now
being
fabricated
indusarenow
nowbeing
beingfabricated
fabricatedinininindusindustry.
of the
the
7.1%
cavity[5]
has
been
deβoo===7.1%
try. A
A prototype
prototypeof
theβft?
7.1%cavity[5]
cavity[5]has
hasbeen
beendedesigned
signed in
collaborationwith
with
INFN-LNL,
and
fabricated
signed
in aacollaboration
collaboration
withINFN-LNL,
INFN-LNL,and
andfabricated
fabricated
in
cavity, recently
recently
added
the
design
for
in Italy.
Italy. The
The flat
flat cavity,
recentlyadded
addedtoto
tothe
thedesign
designfor
for
improved
beam dynamics
dynamics
(see
below),
borrows
from
the
improved beam
dynamics(see
(seebelow),
below),borrows
borrowsfrom
fromthe
the
geometry
geometry of
of the
the
low
cavities
on
the
Piave
accelerator
geometry
of
the low
lowβ/3
β cavities
cavitieson
onthe
thePiave
Piaveaccelerator
accelerator
at
INFN-LNL[6].
atINFN-LNL[6].
at
INFN-LNL[6].
The
The linac
linac has
has
been
designed
assuming
design
gradiThe
linac
has been
beendesigned
designedassuming
assumingdesign
designgradigradients
of
5
MV/m
in
the
low
beta
section
and
ents
of
5
MV/m
in
the
low
beta
section
and
MV/m
ents of 5 MV/m in the low beta section and666MV/m
MV/mininin
the
high beta
sections respectively.
These
the medium
medium and
and
the
medium
and high
high beta
beta sections
sections respectively.
respectively.These
These
correspond
to
rather
aggressive
peak
surface
fields
of
correspond
to
rather
aggressive
peak
surface
fields
correspond to rather aggressive peak surface fields ofof
∼25
and
∼30
MV/m
respectively.
The
prototype
cavity
~25
and
~30
MV/m
respectively.
The
prototype
cavity
∼25 and ∼30 MV/m respectively. The prototype cavity
performance
the ISAC-II
requirements
with
an
performance exceeds
exceeds
ISAC-II
requirements
with
an
performance
exceedsofthe
the
ISAC-II
requirements
withat
an
accelerating
gradient
6.7
MV/m
for
7
W
dissipated
accelerating
gradient
of
6.7
MV/m
for
7
W
dissipated
atat
accelerating
gradient
of
6.7
MV/m
for
7
W
dissipated
◦
44°K.
K. A
gradient of
11 MV/m
(E pp ==55
MV/m) has
A peak
peak
4◦ K. achieved.
A
peak gradient
gradient of
of 11
11 MV/m
MV/m (E
(E p =55
55MV/m)
MV/m)has
has
been
been
achieved.
been
achieved.
The
beta
cavities are
housed
in one
long
The eight
eight low
low
beta
are
housed
one
The
eight
low three
beta cavities
cavities
are
housed in
in between
one long
long
cryomodule
with
solenoids
interspersed
cryomodule
with
three
solenoids
interspersed
between
cryomodule
with
three
solenoids
interspersed
between
cavities.
The
twenty
medium
beta
cavities
are
installed
cavities. The
The twenty
cavities.
twenty medium
medium beta
beta cavities
cavities are
are installed
installed
The Production and Acceleration of RIBs at ISAC-I and Future Plans for ISAC-II
The Production and Acceleration of RIBs at ISAC-I and Future Plans for ISAC-II
251
November 11, 2002
November 11, 2002
3
3
(a) N o m i n a l (£-7.1%)
(b) Fiat (0=5.7%)
FIGURE
6.
The two
two medium
medium beta
beta cavities.
cavities.
FIGURE
6. The
FIGURE 6. The two medium beta cavities.
four
per
cryomodule
in a total
of five
modules.
Twenty
four
perper
four
cryomodule in atotal
totalofoffive
fivemodules.
modules.Twenty
Twenty
high
beta
cavities
are
divided
into
two
modules
six
high
beta
divided
into
two
modules
high beta cavities are divided into two modulesofof
ofsix
six
cavities
and
one
of
eight
cavities.
Each
of
the
cavities
and
module
of
eight
cavities.
Each
of
the
cavities and one module of eight cavities. Each of the
medium
and
high
beta
cryomodules
are
equiped
with
one
medium
and
medium
and
high
betacryomodules
cryomodulesare
areequiped
equipedwith
withone
one
solenoid.
boxes
are
positioned
at
waists
solenoid.
Thin
diagnostic
boxes
are
positioned
at
waists
solenoid. Thin diagnostic boxes are positioned at waists
in in
thethe
transverse
in
the
transverse
envelopes
between
cryomodules.
transverse
envelopesbetween
betweencryomodules.
cryomodules.
Beam
Dynamics
Studies
BeamDynamics
DynamicsStudies
Studies
investigationofofmisalignment
misalignment
tolerances
‘realisInInananinvestigation
tolerances
'realisInfields
an investigation
ofgenerate
misalignment
tolerances
‘realistic’
are
used
to
velocity
dependent
linear
tic' fields are used to generate velocity dependent linear
tic’ fields
are usedThe
to generate
velocity is
dependent
linear
matrix
elements.
beam
centroid
tracked
through
matrix elements. The beam centroid is tracked through
matrix
elements.
The beam
ismisalignments.
tracked through
the
linac
formultiple
multiple
seedsofcentroid
oflinac
linac
the
linac
for
seeds
misalignments.
ForFor
the
linac
for
multiple
seeds
of
linac
misalignments.
Forare
eachseed
seedlinac
linacelement
elementpositions
positionsatat
entrance
and
exit
each
entrance
and
exit
are
each
seed
linac
element
positions
at
entrance
and
exit
are a
displacedrandomly
randomlywithin
withina aGaussian
Gaussiandistribution
distribution
displaced
of of
a
displaced
randomly within a Gaussian distribution of a
given
width.
given width.
given
Thewidth.
studiesshow
showthat
thatthe
thesolenoid
solenoid
least
times
The
studies
is is
at at
least
sixsix
times
Thesensitive
studies show
that the solenoid
isthe
at cavities,
least six times
more
to
misalignment
than
assummore sensitive to misalignment than the cavities, assummorethat
sensitive
to misalignment
than the cavities,
assuming
thecavity
cavity
errorsare
arerandomized
randomized
within
the
error
ing
that
the
errors
within
the
error
ing
that
the
cavity
errors
are
randomized
within
the
error is
margin.
Since
the
difficulty
of
aligning
any
element
margin.
margin.Since
Since the
the difficulty
difficulty of
of aligning
aligning any
any element
element is
is
aboutthe
thesame
samewe
wecan
canrelax
relaxthe
thealignment
alignmentofofthethecavcavabout
about the same we can relax the alignment of the cavityby
by a factorofoftwo
two withrespect
respect tothethesolenoid
solenoid while
ity
ity byaafactor
factor of twowith
with respect to
to the solenoid while
while
notimpacting
impactingthe
theoverall
overallperformance.
performance.
We
set the
tolernot
We
not impacting the overall performance. We set
set the
the tolertolerance
on
the
beam
centroid
variation
and
hence
solenoid
ance
on
the
beam
centroid
variation
and
hence
solenoid
ance on the beam centroid variation and hence solenoid
and
cavitymisalignment
misalignmentto
limitthe
thereduction
reductionin
and
and cavity
cavity
misalignment
totolimit
limit
the
reduction
in indydy-dynamic
aperture
by
no
more
than
20%.
The
dynamic
apernamic
aperture
by
no
more
than
20%.
The
dynamic
apernamic aperture by no more than 20%. The dynamic aperture
of
the
mid
beta
section
based
on
LANA
simulations
ture
of
the
mid
beta
section
based
on
LANA
simulations
ture of the mid beta section based on LANA simulations
through
In
Fig.
77 7
through
realisticfields
fieldsisisis/3e
2.2
mm-mrad.
Fig.
throughrealistic
realistic
fields
ββε ε===2.27rmm-mrad.
2.2
ππ
mm-mrad.
InIn
Fig.
the
beam
centroid
shift
for
a
randomized
solenoid
shift
the
beam
centroid
shift
for
a
randomized
solenoid
shift
the beam centroid shift for a randomized solenoid shift
ofof
400jU
is
superimσ==
=200jU
200µµand
andcavity
cavityshift
shiftof
2σ===
400
superimof2(7
22σ
200
and
cavity
shift
ofof2cr
2σ
400
µµ
is is
superimposed
with
aa 20%
posedon
onthe
theenvelope
envelopedifference
differenceassociated
associated
with
a 20%
on
the
envelope
difference
associated
with
20%
and
Results
for
100
and40%
40%reduction
reductionininindynamic
dynamicaperture.
aperture.
Results
100
40%
reduction
dynamic
aperture.
Results
forfor
100
seeds
the
individseedsare
aregiven
givenwith
witheach
eachdot
dotrepresenting
representing
individare
given
with
each
dot
representing
thethe
individual
line
shows
the
rms
seed
displacements
and
the
solid
line
shows
thethe
rms
ualseed
seeddisplacements
displacementsand
andthe
thesolid
solid
line
shows
rms
displacement
of
the
beam
centroid.
The
rms
beam
center
displacement of
center
displacement
ofthe
thebeam
beamcentroid.
centroid.The
Therms
rmsbeam
beam
center
shift
In
the
plot
steerers
after
shiftisis
within
the
20%
envelope.
InIn
the
plot
after
iswithin
withinthe
the20%
20%envelope.
envelope.
the
plot
steerers
after
each
have
been
used
to
minimize
the
beam
eachcryomodule
cryomodule
have
been
used
to
minimize
cryomodule have been used to minimize the beam
divergence.
divergence.
divergence.
Detailed
Detailed
beam
dynamics
studies
have
concentrated
on
Detailed
beam
dynamicsstudies
studieshave
haveconcentrated
concentratedon
on
thethe
first
stage
SCSClinac
linac
first
stageSC
linacinstallation,
installation,and
andin
particularon
on
the
first
stage
installation,
and
ininparticular
particular
on
thethe
medium
beta
section.
medium
betasection.
section.Two
Twomain
mainasymmetries
asymmetriesinin
inthe
the
the
medium
beta
Two
main
asymmetries
the
medium
beta
cavity
fields
medium
beta
cavityfields
fieldsare
areresponsible
responsiblefor
fordifferences
differences
medium
beta
cavity
are
responsible
for
differences
between
'simple
betweenaa a‘simple
‘simplecavity
cavitymodel'
model’and
and 'realistic
‘realistic field'
field’
between
cavity
model’
and
‘realistic
field’
simulations.
Inherent
simulations.
Inherentin
quarterwave
wavecavities
cavitiesare
areboth
bothaaa
simulations.
Inherent
ininquarter
quarter
wave
cavities
are
both
vertical
electric
dipole
vertical
electricdipole
dipolefield
fieldand
andaaaradial
radialmagnetic
magneticfield
field
2o=400,200 M
vertical
electric
field
and
radial
magnetic
field
that
give
velocity
and
phase
dependent
vertical
that
give
velocity
and
phase
dependent
verticalkicks
kicks
that give velocity and phase dependent vertical
kicks
to to
thethebeam[7].
beam[7].
beam[7].The
Thevertical
verticalsteering
steeringcan
canlead
leadtoto
toloss
loss
to
the
The
vertical
steering
can
lead
loss
of
dynamic
aperture
and
transverse
emittance
growth
of
dynamic
aperture
and
transverse
emittance
growth
of dynamic aperture and transverse emittance growth
especially
forformulti-charge
especially
multi-chargebeams.
beams.The
Thesteering
steeringcan
canbe
be
especially
for
multi-charge
beams.
The
steering
can
be
largely
cancelled
by
displacing
the
cavity
vertically
so
largely
cancelled
by
displacing
the
cavity
vertically
so
largely cancelled by displacing the cavity vertically so
the
electric
focussingfield
fieldcompensates
compensatesfor
forthe
themagnetic
magnetic
the
electric
focussing
the electric focussing field compensates for the magnetic
kick[8].
kick[8].
kick[8].
Thecylindrical
cylindricalstem
stemwhile
whilesimplifying
simplifyingconstruction
construction
The
The cylindrical
stem while
simplifying electric
construction
produces
asymmetry
thetransverse
transverserfrfelectric
fields.
produces
anan
asymmetry
ininthe
fields.
produces
an asymmetry
in the
transverse
rf electric
fields.
The
asymmetry
leadstoto
mismatch
between
horizontal
The
asymmetry
leads
a amismatch
between
horizontal
L (m)
The
asymmetry
leads toInaamismatch
between
horizontal
and
verticalmotion.
motion.
solenoidallattice
latticethe
the
beamisis
and
vertical
In a solenoidal
beam
and
vertical
motion.
In
a
solenoidal
lattice
the
beam
is
rotated
periodicallyand
anda amismatch
mismatchbetween
betweentransverse
transverse
rotated
periodically
rotated
periodically
and
a mismatch
between
transverse
planes
canlead
leadtototransverse
transverse
emittance
growth
oncethe
the
planes
can
emittance
growth
once
FIGURE7.7. The
Thesingle
single charge
charge state
state beam
beam centroid
centroid shift
shift with
planes
lead tototransverse
emittance
growth
once the FIGURE
with
beam
is
delivered
toa aquadrupole
quadrupole
transport
system.
beam
iscan
delivered
transport
system.
FIGURE
7. Thefor
single
charge statesolenoid
beam centroid
with
=
steeringcorrection
correction
for aa randomized
randomized
solenoid
shift of
ofshift
2σ =
steering
shift
2a
beam
is
delivered
to
a
quadrupole
transport
system.
To
reduce
the
effects
of
the
focussing
asymmetry
we
To reduce the effects of the focussing asymmetry we
σ =
steering
for
shift of
200µ and
andcorrection
cavity shift
shift
ofa2cr
2randomized
σ == 400jU
400µ isissolenoid
superimposed
on 2the
the
200jU
cavity
of
superimposed
on
To the
reduce
the effects
focussing
asymmetry
we
alter
theoriginal
original
designof
adding
newcavity
cavitygeomegeomealter
design
bybythe
adding
a anew
envelope
difference
associated
with
20%
and 40%
40% reduction
reduction
200
µ and
cavity shift
of 2σ with
=
400
is superimposed
on the
envelope
difference
associated
aa µ
20%
and
alter
the
original
design
by
adding
a
new
cavity
geometry.
In
the
‘flat’
cavity
(Fig.
6(b))
the
inner
conductor
indynamic
dynamicdifference
aperture. associated with a 20% and 40% reduction
try. In the 'flat' cavity (Fig. 6(b)) the inner conductor isis inenvelope
aperture.
try.
In the to
‘flat’
cavity
(Fig.
6(b))
the
inner
conductor
is
squeezed
to4040mm
mmfrom
from
mmin
inthe
thebeam
beam
direction
in dynamic aperture.
squeezed
6060
mm
direction
squeezed
to
40 mm
fromports
60
mm
the beam
direction
andthethegrounded
grounded
beam
ports
arein
extended
maintain
and
beam
are
extended
totomaintain
gap.Studies
Studies
show
that
smallto
but
worthand
theoriginal
grounded
beam
ports
are
extended
maintain
thetheoriginal
gap.
show
that
a asmall
but
worthHardware
Hardware
while
improvement
in
dynamic
aperture
is
gained
for
the
original
gap.
Studies
show
that
a
small
but
worthwhile improvement in dynamic aperture is gained for
Hardware
lightbeams
beamsbybyreplacing
replacing
thefirst
first
eight'nominal'
‘nominal’
caviwhile
improvement
in dynamic
aperture
is gained
for
Work isis ongoing
ongoing on
on several
several fronts
fronts with
with the
the goal
goal of
of
light
the
eight
caviWork
ties
in
medium
betasection
section
with
the'flat'
‘flat’
cavities[9].
light
by replacing
the first
eight
‘nominal’
cavi- realizing
realizing
beam
delivery
inseveral
2005The
first major
major
milestone
ties
inbeams
thethe
medium
beta
with
the
cavities[9].
Workbeam
is ongoing
onin
fronts
with milestone
the goal of
delivery
2005The
first
Adding
more
than
eight
‘flat’cavities
cavities
reduces
linacperperties
in themore
medium
beta
section
with
the
‘flat’ cavities[9].
isthe
thefabrication
fabrication
and cold
cold
test of
of aa completed
completed
medium
Adding
than
eight
'flat'
reduces
linac
beam delivery
in test
2005The
first majormedium
milestone
isrealizing
and
formance
because
of
the
reduced
.
β
o
Adding
more
than
eight
‘flat’
cavities
reduces
linac
performance because of the reduced f}0.
is the fabrication and cold test of a completed medium
formance because of the reduced βo .
The Production and Acceleration of RIBs at ISAC-I and Future Plans for ISAC-II
November 11, 2002
4
m
cavso!
The Production and Acceleration of RIBs at ISAC-I and Future Plans for ISAC-II
252
™
November 11, 2002
4
beta
betacryomodule
cryomodulein
in mid
mid 2003.
2003. A
A summary
summary of
of the
the present
developments
developmentsare
are given
given below.
below.
Cryomodule
Cryomodule Design.
Design. A
A prototype
prototype of
of the medium
beta
beta cryomodule
cryomodule isis now
now in
in the
the design
design phase. The vacuum tank
tank consists
consists of
of aa stainless
stainless steel
steel rectangular box
uum
andlid.
lid.All
All services
services and
and feedthroughs
feedthroughs are
are located on the
and
lid.Copper
Coppersheet
sheet cooled
cooled with
with LN2
LN2 piping serve as a heat
lid.
shield.Cavities
Cavitiesand
andsolenoids
solenoids are
are suspended
suspended from
from a comshield.
mon support
support frame.Pre-cool
frame.Pre-cool of
of components
components is done by
mon
deliveringcold
cold helium
helium vapour
vapour to
to the
the bottom
bottom of each madelivering
jor component.
component. Magnetic
Magnetic shielding
shielding in the form of high µ
jU
jor
sheet isis suspended
suspended between
between the
the warm
warm wall
wall and the cold
sheet
shield.
shield.
Solenoids. Focusing
Focusing in
in the
the SC
SC LINAC
LINAC is
is provided
Solenoids.
by 99Tesla
Tesla 26
26 mm
mm diameter
diameter bore
bore SC
SC solenoids
solenoids of lengths
by
16,34
34and
and 45
45 cm
cm corresponding
corresponding to the low, medium and
16,
high beta
beta cryomodules
cryomodules respectively.
respectively. An order for five
high
medium beta
beta and
and two
two high
high beta
beta solenoids
solenoids is now placed
medium
in
industry.
A
prototype
of
a
medium
solenoid is
in industry. A prototype of a medium beta solenoid
expected
early
next
year.
expected early next year.
SCRF Developments.
Developments. A
A temporary
temporary superconducting
superconducting
SCRF
2
2
rf
test
lab
of
~
100
m
is
set-up
in
a
space rented
rented by
by
rf test lab of ∼ 100 m is set-up in a space
TRIUMF
in
a
neighbouring
laboratory
complex.
The
TRIUMF in a neighbouring laboratory complex. The
laboratory includes
includes aa test
test area
area with
with aa sunken
sunken cryostat
cryostat
laboratory
pit for
for high
high field
field rf
rf testing,
testing, and
and clean
clean areas
areas for
for cavity
pit
cavity
assembly (Class
(Class 1000)
1000) and
and high
high pressure
pressure water
water rinsing
rinsing
assembly
(Class 100).
100). In
In the
the high
high pressure
pressure rinse
rinse area
area an
an on-line
on-line
(Class
treatment system
system delivers
delivers 20
20 ltr/min
Itr/min of
of 18
18 MΩ
MQ water
water at
at
treatment
2000psi
psi to
to aa manual
manual rinse
rinse unit.
unit. A
A prototype
prototype rf
rf controls
controls
2000
system using
using aaself-excited
self-excited loop
loop architecture
architecture with
with digital
digital
system
signal
processors
is
in
development
and
has
been
used
to
signal processors is in development and has been used to
successfully
lock
a
cold
cavity
in
both
self-excited
and
successfully lock a cold cavity in both self-excited and
fixed frequency
frequency operation.
operation. Cold
Cold tests
tests of
of the
the prototype
prototype
fixed
cavity
are
ongoing
at
the
rate
of
one
a
month.
cavity are ongoing at the rate of one a month.
prototype mechanical
mechanical tuner
tuner is
is now
now being
being tested.
tested. It
It
AA prototype
consistsof
ofaalever
lever mechanism
mechanism acting
acting directly
directly on
on the
the cencenconsists
terof
ofthe
thecavity
cavity tuner
tunerplate
plate through
through aa zero
zero backlash
backlash hinge
hinge
ter
and
stiff
rod
connected
through
a
bellows
to
a
precision
and stiff rod connected through a bellows to a precision
linearmotor
motorlocated
located on
on the
the top
top of
of the
the cryostat.
cryostat. The
The tuner
tuner
linear
is
capable
of
both
coarse
(20
kHz)
and
fine
(few
Hz)
freis capable of both coarse (20 kHz) and fine (few Hz) frequency
adjustments
Initial
tests
are
promising.
The
tuner
quency adjustments Initial tests are promising. The tuner
plateposition
positionhas
has been
been modulated
modulated at
at drive
drive frequencies
frequencies of
of
plate
0.1
Hz
to
10
Hz
and
amplitudes
of
IjU
to
6/1
correspond0.1 Hz to 10 Hz and amplitudes of 1µ to 6µ corresponding to
to cavity
cavity frequncy
frequncy variations
variations of
of ±5Hz
=L5Hz and
and ±30Hz
=L30Hz
ing
respectively.
The
self
excited
frequency
response
follows
respectively. The self excited frequency response follows
thedriving
drivingsignal
signalwith
with no
no significant
significant induced
induced microphonmicrophonthe
ics.
Fig.8
shows
both
tuner
position
and
cavity
frequency
ics. Fig.8 shows both tuner position and cavity frequency
for
a
5
Hz,
±1.5
jum
tuner
variation.
In
another
study the
the
for a 5 Hz, ±1.5 µ m tuner variation. In another study
cavity
was
phase
locked
while
over
coupled,
generating
cavity was phase locked while over coupled, generating
a 20 Hz rf bandwidth, and the plate was dithered with a
a 20 Hz rf bandwidth, and the plate was dithered with a
frequency of 8 Hz at ±ljU without losing phase lock.
frequency of 8 Hz at ±1µ without losing phase lock.
TUner position
t
3jjm
vwv
Cavity Frequency
600msec-
FIGURE 8. The tuner position and cavity
cavity frequency
frequency with
with
tuner driven at 5 Hz and amplitude of ±1.5 jum.
µ m. The
The cavity
cavity
frequency is modulated by ±7
frequency
±7 Hz.
Hz.
Refrigerator.
Refrigerator. An order for the
the Stage
Stage 1 LHe
LHe refrigerarefrigera◦
tor with a 500 W capacity at 4.2°K
is
soon
out for
4.2 K
for tender.
tender.
ACKNOWLEDGEMENTS
ACKNOWLEDGEMENTS
The author
author is
The
is representing
representing aa strong
strong and
and talented
talented acceleraccelerator group
group at
at TRIUMF/ISAC
ator
TRIUMF/ISAC whose
whose many
many accomplishaccomplishments are
are summarized
summarized here.
AC-I/IS AC-II
ments
here. Further,
Further, the
the IS
ISAC-I/ISAC-II
project has
project
has benefited
benefited over
over the
the years
years from
from many
many outside
outside
collaborations. In
collaborations.
In our
our most
most recent
recent adventures
adventures in
in supersuperconducting rf
conducting
rf we
we are
are guided
guided by
by our
our collegues
collegues and
andfriends
friends
at Argonne
Argonne and
at
and Legnaro.
Legnaro.
REFERENCES
REFERENCES
i. R.
R. Poirier,
1.
Poirier, et
et al,
al, "CW
“CW Performance
Performance of
of the
the TRIUMF
TRIUMF 88Meter
Meter
Long
RFQ
for
Exotic
Ions",
Proc.
of
the
XXth
Long RFQ for Exotic Ions”, Proc. of the XXthLinac
LinacConf.
Conf.
(LINAC2000), Monterey,
(LINAC2000),
Monterey, USA,
USA, Aug.
Aug. 2000,
2000, p.
p. 1023.
1023.
2. R.E.
R.E. Laxdal,
2.
Laxdal, et
et al,
al, "Beam
“Beam Commissioning
Commissioning and
and First
First
Operation of
Operation
of the
the ISAC
ISAC DTL
DTL at
at TRIUMF",
TRIUMF”, Proc.
Proc. of
of the
the
2001
Part.
Ace.
Conf.,
Chicago,
2001.
2001 Part. Acc. Conf., Chicago, 2001.
3. T.
T. Lamy,
Lamy, et
et al,
3.
al, "Charge
“Charge Breeding
Breeding Method
Method Results
Results with
with the
the
PHOENIX
Booster
ECR
ION
Source",
EPAC2002,
PHOENIX Booster ECR ION Source”, EPAC2002, Paris
Paris
2002.
2002.
4.
R.
4. R. E.
E. Laxdal,
Laxdal, M.
M. Pasini,
Pasini, http://www.triumf.ca/lax/ISAC5.ps
http://www.triumf.ca/lax/ISAC5.ps
5. A.
A. Facco,
5.
Facco, et
et al,
al, 'The
‘The Superconducting
Superconducting Medium
Medium ]8β Prototype
Prototype
for
Radioactive
Beam
Acceleration
at
TRIUMF',
for Radioactive Beam Acceleration at TRIUMF’,PAC2001,
PAC2001,
Chicago, June
Chicago,
June 2001.
2001.
6.
A.
Facco,
6. A. Facco, et
et al,
al, "The
“The Non-RFQ
Non-RFQ Resonators
Resonators of
of the
the PIAVE
PIAVE
Linac", Proc.
Linac”,
Proc. of
of HIAT98,
HIAT98, Argonne
Argonne 1998,
1998, p.
p. 185.
185. June
June 2001.
2001.
7. A. Facco, et al, "Study on Beam Steering in Intermediate-]8
7. A. Facco, et al, “Study on Beam Steering in Intermediate-β
Superconducting Quarter Wave Resonators", PAC2001,
Superconducting Quarter Wave Resonators”, PAC2001,
Chicago, June 2001.
Chicago, June 2001.
8. P.N. Ostroumov, K.W. Shepard, "Correction of Beam
8. P.N. Ostroumov, K.W. Shepard, “Correction of Beam
Steering Effects in Low Velocity Superconducting QuarterSteering Effects in Low Velocity Superconducting QuarterWave Cavities", Phys. Rev. ST. Accel. Beams 11, 030101
Wave Cavities”, Phys. Rev. ST. Accel. Beams 11, 030101
(2001).
(2001).
9. M. Pasini, et al, "Beam Dynamics Studies on the ISAC-II
9. M. Pasini, et al, “Beam Dynamics Studies on the ISAC-II
Post-Accelerator at TRIUMF", EPAC2002, Paris 2002.
Post-Accelerator at TRIUMF”, EPAC2002, Paris 2002.
The Production and Acceleration of RIBs at ISAC-I and Future Plans for ISAC-II
253
November 11, 2002
5