100 MeV

1 GeV Proton Synchrotron
for
Indian Spallation Neutron Source
Gurnam Singh
Beam Dynamics Section
CAT, Indore
CAT

KEK

Sokendai School on Spallation Neutron Sources, 2004
BASIC LAYOUT OF INDIAN
SPALLATION NEUTRON SOURCE
100
MeV
Linac
Linac to PS
Transfer Line
PS to Target
Transfer Line
100 MeV
–
1 GeV
PROTON
SYNCHROTRON (PS)
T
a
r
g
e
t
H

Source
RFQ
4.5
MeV
Outline:
1.
Preliminary
design
aspects
of
Rapid
Cycling
Proton
Synchrotron
2.
Linac
to
Synchrotron
Transfer
Line
Preliminary
design aspects
Of
Rapid Cycling
Proton Synchrotron
Key parameter in a spallation source
Beam Power
P
beam
= q.N
p
.E .R
=
I.E
•
P
beam
:Beam power (W) at target
•
q
:Charge on proton (C)
•
N
p
:No. of protons in ring
•
E
:Final proton energy (eV)
•
R
:Repetition rate (Hz)
•
I
:Average current at target (A)
To increase the beam power
Two Ways
Increase beam energy
Large machine, big cost
Increase beam Current
Severe space charge
Collective beam instabilities
Choose optimum energy & current
Accelerator choice
Full Energy Linac
&
Accumulator Ring
Linac
&
RCS
•
High
power
achievable
but
high
cost
•
High
injection
energy
means
very
tight
beam
loss
control
at
injection
•
High
injection
energy,
so
more
heating
of
injection
foil
•
Low
injection
energy,
thus
more
space
charge
problem
•
Rapid
acceleration,
means
powerful
RF
systems
•
Ceramic
chamber
Indian Spallation Neutron Source
•
100 MeV Linac & RCS based
•
Beam power
:100 kW
•
Final energy of the beam
: 1 GeV
•
Average current
: 100
䄠
[@ 25 Hz Repetition Rate]
2.4
13
protons in synchrotron
Design Considerations
1
.
Injection
energy
100
MeV
The
first
estimation
of
current
in
the
synchrotron
is
made
by
space
charge
tune
shift
.
x
y
y
f
y
p
y
a
a
a
B
R
Nr
3
2
=>
For
the
required
N,
the
tune
should
not
cross
any
dangerous
resonances
.
Thus
tune
should
have
sufficient
room
for
movement
.
In
our
design,
allowable
tune
shift
taken
as
0
.
2
.
For
decreasing
the
tune
shift
(for
enhancing
the
average
current
handling
capability
of
the
synchrotron)
*
Increase
the
injection
energy
=>
Increase
the
cost
of
Linac
.
*
Decrease
the
N
and
increase
the
repetition
rate,
so
that
average
current
remains
same
=>
Constraints
from
technology
and
frame
overlap
in
time
of
flight
type
experiments
.
*Increase
the
bunching
factor
at
injection
=>
Deciding
factor
of
RF
programme
of
the
machine
.
2
.
Beam
loss
control
Beam
loss
control
is
of
major
concern
in
the
high
intensity
machines
.
1
W/m
is
the
allowable
limit
of
uncontrolled
loss
for
hands
on
maintenance
.
=>
@
injection,
average
beam
power
10
kW
Uniform
loss
on
whole
length
of
ring
gives
the
upper
most
limit
:
2
%
allowed
uncontrolled
loss
.
=>
Thus
for
controlled
loss,
betatron
and
momentum
collimators
needed
.
3. Sufficient space
Large
dispersion
free
straight
sections
are
needed
for
1
)
RF
systems
.
2
)
Betatron
collimators
3
)
Injection
systems
4
)
Extraction
system
Apart
from
these,
other
systems
which
should
be
accommodated
in
the
ring
are
diagnostic
devices,
vacuum
pumps,
correctors
etc
.
4.
High tune for working well below the
瑲t湳楴楯n
Options for the lattices
Many
lattice
configurations
can
fulfill
these
requirements
:
For
making
an
arc
with
achromatic
conditions
1
.
FODO
with
Missing
dipole
scheme
(IPNS,
KEK

JAERI
etc
.
)
2
.
Achromat
design
(eg
.
SNS)
Obtaining
the
long
straight
dispersion
free
sections
1
.
FODO
2
.
Doublet/
Triplet
structures
Lattice for the ISNS
FODO
structure
:
Simple,
smooth
variation
of
beta
function
means
less
prone
to
errors
.
Missing
dipole
for
the
dispersion
matching
Four
superperiods
The
four
long
straight
sections
will
be
used
for
the
injection
system,
collimators
(beam
collimatoss),
RF

system
and
extraction
system
respectively
.
Four
superperiods
have
better
stability
for
structure
resonance
than
the
three
period
structure
.
M
HALF UNIT CELL
One period
0
5
10
15
20
25
30
35
40
45
50
2
0
2
4
6
8
10
12
14
16
18
Qf2
Qd2
Qf1
Qd1
Qf1
Qd1
Qf3
ARC SECTION
•
Half

cell length of FODO:
4.425 m
•
Total cells in arc:
4 (one period)
•
Total straight section cells:
2 (one period)
•
Quadrupole families:
5 (3f & 2d)
•
Length of the period:
53.1 m
•
Length of long straight:
4
3.875=15.5 m
Choice of tune
90
phase
advance
per
cell
requires
a
tune
of
6
.
0
,
so
the
tune
of
the
machine
is
kept
near
6
.
0
.
In
horizontal
plane,
it
is
higher
than
the
6
.
0
and
in
vertical
plane
it
is
on
the
lower
side
.
But
it
has
wide
tunability
range
and
it
can
be
operated
at
split
and
un

split
working
points
.
Structure & half integer resonance diagram
( upto 4
th
order)
Shaded region is the space for different tune options
y
x
5
6
7
8
4
5
6
7
3
X
=20
X
+2
y
=20
X
+2
y
=16
2
X
+2
y
=24
2
X

y
=8
3
X

y
=12
3
X
+
y
=28
X
+3
y
=24
5.5
6.5
(6.88, 5.88)
X

y
=1
X

y
=0
•
•
•
(7.3, 6.3)
(6.3, 6.3)
* Further selection depends on imperfection
resonance
The
lattice
can
have
various
tune
points
in
these
regions
.
Primarily
selected
tune
is
6
.
88
and
5
.
88
[other
options
are
6
.
3
,
6
.
3
and
7
.
3
,
6
.
3
(higher
tunes)]
.
Tune
is
far
away
from
resonance
up
to
3
rd
order
.
Tune
drift
of
–
0
.
2
(due
to
space
charge)
does
not
hit
any
resonance
up
to
3
rd
order
.
Lattice parameters
0
5
10
15
20
25
30
35
40
45
50
2
0
2
4
6
8
10
12
14
16
18
Bx
Bz
Eta
Fx
Fz
Preliminary tracking results with sextupoles
(without error)
Horizontal phase space, 5000 turns
Vertical phase space, 5000 turns
Initial co

ordinates are chosen corresponding to maximum
displaced particle in both the planes with 1%
p/p.
Further optimization needed in sextupoles for vertical plane.
H

Injection
500
s
(
300
turns
)
pulse
length
of
H

ions
from
100
MeV
linac
to
be
injected
through
a
stripping
foil
.
Constraints
imposed
by
Liouville’s
theorem
on
conventional
multi

turn
injection
†
摯
湯n
慰灬y
楮
瑨楳
捡獥
.
possible
to
inject
a
large
number
of
turns
.
Goals Of Injection
To fill transverse acceptances (
x
=
y
= 300
mm
mrad) in K

V distribution
uniform filling
avoid excessive space charge forces
牥晥牲敤e慳湪散瑩潮灡楮瑩t
Injection Paintings
Horizontal Phase Space : Variable Bump by four
bump
magnets located in a long straight section
Angle of Injection
Peak of the bump at the stripping foil
Minimum number of traversal of beam
through the foil
Partially
stripped
particles
H
0
do
not
pass
through
high
magnetic
field
(
centre
of
QD
)
Sripped
H

(Magnetic
field)
畮睡湴敤
桡汯
景牭慴楯i
慲潵湤
捩牣畬慴楮
灡牴p捬敳
Layout of the injection system of ISNS
Time Dependence of Four Kick Bump Angles
Orbit
Bump
and
its
Slope
at
the
Location
of
Stripping
Foil
(Injection
Point)
vs
Injection
Turn
Number
Bending Angle with Injection Turn Number
0
50
100
150
200
250
300
350
0
10
20
30
40
50
60
70
Y  Amplitude
X  Amplitude
Amplitude of Betatron Oscillations (mm)
Injected Turn Number (N)
Amplitude of Betatron Oscillations of Injected Particles
with Turn Number During Injection
Painting in vertical normalized phase space
Spatial distribution of nearly 350 injected turns
Striping Foil
•
Thickness of the foil:
(High stripping efficiency )
At 100MeV 60
朠捭

2
is adequate
• Foil materials:
Polyparaxylene,carbon
or
Aluminium oxide
Beam loss and Collimators
The
lattice
should
accommodate
the
collimators
(betatron
and
momentum)
for
controlled
loss
.
At
injection
only
2
%
particle
loss
is
allowed
(if
distributed
uniformly
all
over
the
length)
in
the
ring
.
Key parameter in collimator design:
Phase advance between primary and secondary
collimators and their apertures
Collimators
remove
the
Halo
from
the
beam
at
the
predefined
locations
.
The
first
collimator
scatters
the
halo
particles,
with
low
impact
parameter
.
Due
to
scattering,
the
amplitude
increases
and
these
are
collected
at
secondary
collimator,
which
is
placed
at
a
proper
phase
advance
.
Proper phase and critical kick is given by
2
1
cos
n
n
opt
n
1
and
n
2
are
the
apertures
of
primary
and
secondary
in
terms
of
beam
size
.
The
critical
kick
is
2
1
2
2
n
n
K
c
Phase difference between primary and secondary collimator
X
–
Plane: 158
and n
2
/n
1
=1.08
Y
–
Plane: 144
and n
2
/n
1
=1.20
Material choice in collimators
Two Effects:
When a proton traverse through a primary collimator, it
loses energy. If this loss is high, particle may be out of
bucket or longitudinal acceptance. (Acceptance of ring
1%)
The primary collimator has to give a large kick, so
protons hit the secondary collimator with large impact
parameter. This kick is largely imparted through the
multiple Coulomb scattering.
The
first
effect
demands
a
very
thin
collimator,
which
does
not
cause
the
much
energy
loss
.
The
second
effect
demands
a
high
Z
material
.
Thus
choices
are
among
Pt,
W
etc
.
Other
requirements
are
good
thermal
conductivity,
high
melting
point,
good
polishing
capability,
radiation
damage
.
As
high
Z
has
the
shower
effects,
which
is
drawback
.
Therefore,
for
proper
choice
of
material
and
optimization
of
its
thickness,
simulation
studies
are
essential
.
Tentative
locations
of
betatron
collimators
In
next
period
to
injection
.
44
46
48
50
52
54
56
58
60
62
2
0
2
4
6
8
10
12
14
16
18
Bx
Bz
Eta
Fx
Fz
y

plane
x

plane
Phase difference between primary and secondary collimator
X
–
Plane: 158
and n
2
/n
1
=1.08, beam sizes at the collimators: 4.2cm, 3.8 cm, 3.2 cm
Y
–
Plane: 144
and n
2
/n
1
=1.20, beam sizes at the collimators: 3.8cm, 5.6 cm, 3.6 cm
10
12
14
16
18
20
22
24
26
28
30
32
34
36
38
40
42
44
2
0
2
4
6
8
10
12
14
16
18
x
y
D
x
x
y
Lattice parameters (m)
Path length (m)
Tentative locations of momentum collimators
Phase difference between primary and secondary collimator
X
–
Plane: 150
and n
2
/n
1
=1.15
In arc next to injection system.
Preliminary beam diagnostic
requirements
48 Beam position monitors ( one @ each quadrupole).
Beam loss monitors distributed all over the ring.
Beam profile monitors.
Current monitors (Average and Pulse).
Parameter
Value
Beam power
100 kW
Energy
0.1
–
1.0 GeV
Repetition Rate
25 Hz
Circumference (m)
212.4
Periodicity
4
No. of bending magnets
24
Bending angle
15
per magnet
Bending Magnet Field
0.207

0.789 T
Bending radius (m)
7.1626
No. of quadrupoles
48
Maximum gradient (T/m)
4.5
Nominal tune point
6.88, 5.88
x,max
,
y,max
(m)
16.4, 16.4
No. of sextupoles
16 (two families 8F and 8D)
Parameters of Synchrotron
Parameter
Value
D
max
(m)
2.4896
Chromaticity

8.954,

7.640
Momentum compaction
0.031989

transition
5.591
Dispersion free straights
4
3.874=15.5 m / period
Straight with dispersion
2
3.875=7.75 m / period
RF
(MHz)
1.21
–
2.47 for h = 2
Revolution Time
1.65
–
0.81
µs
Peak energy gain per turn
60 keV
Beam size (max)
9.6 cm @ 1%
p/p @ Qf1
Emittance after painting
300
mm.mrad after injection
in both planes
Peak RF voltage
120 kV
•
Parameters of Linac (injector)
Parameter
Value
Energy
100 MeV
Pulse length
500
s
Pulse current
25 mA
Energy spread
0.3 %
Emittance (normalized)
0.23
mm mrad
Magnet apertures
Magnet
Max
(m)
Max D
(m)
Strength
(m

2
)
Good
field
radius
(mm)
Qf1
16.4
2.6

0.67
120
Qd1
16.1
2.5
0.56
100
Qf2
16.1
0.0

0.64
100
Qd2
16.4
0.0
0.61
100
Qf3
13.2
2.5

0.67
120
BM
~8
~2
0.8 T
100, 100
Linac to Synchrotron
Transfer Line
•
Design Philosophy
•
To match the beam parameters from the linac output
to synchrotron injection point.
•
To provide the adequate space for installation of
various components, as
1.RF cavity for energy jitter correction.
2.Diagnostic elements
(Profile monitors,
Current monitors, Beam position monitors
and Beam loss monitors).
3.Dump line.
4.Bumpers for injection painting.
•
To install collimators for control of beam loss.
10
0
10
20
30
40
50
60
70
15
10
5
0
5
10
15
20
25
30
x
y
x
Optics parameters (m)
Path length (m)
Optics parameters of Transfer Line
Matching section
4 Quads
2 FODO
Achromat
1 FODO
Matching section
4 Quads
10
0
10
20
30
40
50
60
70
15
10
5
0
5
10
15
20
25
30
x
y
x
Optics parameters (m)
Path length (m)
Primary collimator
Secondary collimator X
Secondary collimator Y
RF Cavity
Parameter
Value
Length
62.95 m
No. of quadrupoles
21 (11 F & 10 D)
Maximum strength (m

2
)
6.1
No. of dipoles
2
Bending field (T)
0.65
x,max
,
y,max
(m)
27.6, 15.8
x,inj
,
y,inj
, D
inj
(m)
0.99, 1.95, 0.00
x,ext
,
y,ext
, D
ext
(m)
13.0, 2.5, 0.0
Conclusions
Only
preliminary
linear
studies
have
been
carried
out
.
•
Studies
to
be
carried
out
1
.
Non

linear
behavior
and
sextupole
scheme
2
.
Detailed
studies
of
Longitudinal
dynamics
with
space
charge
and
deciding
the
RF
program
3
.
Space
charge
issues
and
beam
loss
control
4
.
Detailed
studies
of
injection
and
extraction
5
.
Design
of
transfer
lines
5
.
Transverse
and
Longitudinal
instabilities
2
2
2
2
1
2
2
2
2
g
b
B
a
a
a
B
Nr
y
y
f
x
y
y
f
y
p
y
Exact formulation of Tune Shift
(including the image terms)
y
x
5
6
7
8
4
5
6
7
3
X
=20
X
+2
y
=20
X
+2
y
=16
2
X
+2
y
=24
2
X

y
=8
3
X

y
=12
3
X
+
y
=28
X
+3
y
=24
5.5
6.5
(6.88, 5.88)
X

y
=1
X

y
=0
•
•
•
(7.3, 6.3)
(6.3, 6.3)
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