Pulsed Ion Linac for EIC
January 27, 2010
Content



Pulsed linac
Short Normal Conducting section: RFQ and IH structure
Stripper for heavy ions at 12 MeV/u
2
Basic parameters of the linac

Linac layout
Ion Sources
RFQ
IH
MEBT
Normal conducting
QWR
QWR
HWR
Stripper
Superconducting
Parameter
1
2
3
4
5
6
7
8
9
DSR
Ion species
Ion species for the reference design
Kinetic energy of lead ions
Maximum beam current averaged over the pulse
Pulse repetition rate
Pulse length
Maximum beam pulsed power
Fundamental frequency
Total length
Value
From Hydrogen to Lead
Pb
100 MeV/u
2 mA
10 Hz
0.25 msec
680 kW
115 MHz
150 m
208
3
Radio Frequency Quadrupole
A Segment of the RFQ
Basic RFQ Parameters
Frequency
115 MHz
Total length
3.6 m
Voltage
85 kV
Average radius
7 mm
Number of segments
4
Input energy
25 KeV
Output energy
500 keV/u
4
Example of a short MEBT
Q1
Q2 Q3 Q4
Buncher
L= 995 mm
Basic Quadrupoles
Parameters
Eff. Length
(mm)
Gradient
(T/m)
Q1
20.0
23.0
Q2
50.0
-22.0
Q3
50.0
32.75
Q4
50.0
-16.5
Basic Buncher
Parameters
Cavity
Quarter Wave
Voltage
0.8 MV
Frequency
117.3 MHz
Length
340 mm
5
Normal Conducting IH cavities


TRIUMF Separated DTL
Courtesy Bob Laxdal
6
Normal Conducting IH structure

U. Ratzinger (Frankfurt) Group has built it for the BNL EBIS injector project
7
Stripping energy
Lead ions
440
430
Linac total voltage (MV)

420
410
400
390
380
0
5
10
15
20
25
30
Stripping energy (MeV/u)
8
Superconducting cavities


119 cavities
21 cryostats
QWR
HWR
DSR
Heavy-Ion Linac - SC Resonator Configuration
Beta
0.151
Type
QWR
Freq
Length
at 1 MV/m
(MHz)
(cm)
Epeak
115.0
25.0
3.2
57
R/Q
G
509 42
Esurf
Eacc
30
9.46
STRIPPER
#
Phase Cav
20
Subtotal
0.151
QWR
115.0
25.0
3.2
57
509 42
0.263
HWR
230.0
22.5
2.9
78
0.393 2SPOKE 345.0
38.1
3.0
69
28
28
30
9.46
20
14
241 58
30
10.31
30
28
444 71
30.0
10.00
Subtotal
30
63
91
Total Cavity Count
=
119
9
Voltage gain per cavity for lead ions
4
3.5
Voltage (MV)
3
2.5
2
1.5
1
0.5
0
0.1
0.2
0.3
0.4
0.5
b
10
Voltage gain per cavity for protons
4
3.5
Voltage (MV)
3
2.5
2
1.5
1
0.5
0
0.1
0.2
0.3
0.4
0.5
0.6
b
11
Energies of different ion beams
Proton
Dueteron
40
Ar
132
Xe
208
Pb
Q ion source Energy at the stripper
MeV/u
1
55
1
32.8
12
22.4
26
16.5
30
13.2
Q after the stripper
1
1
18
48
67
Total energy
MeV/u
285
169
150
120
102
12
Accelerated Beam Parameters
 Transverse normalized emittance (5rms) ~ 1  mm mrad
 Longitudinal emittance (5rms) <10  keV/u nsec
 Momentum spread can be controlled by the rebuncher and can be as low
as ~0.05%.
13
Proton Beam
Linac Pulse Length (s) =
2.50E-04
Frequency (MHz) =
115
Number of Bunches in Pulse=
28750
Average current per pulse, P (A)=
2.00E-03
Charge per pulse (C)=
5.00E-07
Number of protons per pulse =
3.13E+12
Injection Efficiency=
0.9
Transverse cooling time (s) =
0.130
Longitudinal cooling time (s) =
0.067
RF acceleration time (s) =
0.080
Injection
Extraction
Cycle
β N_total MeV/n γ
β N_total Pulses Time(s)
Ion A Q I (A) S (m) MeV/n γ
P 1 1 1 300
200 1.21 0.57 1.10E+13 3000 4.22 0.97 6.43E+12 4
0.70
P 1 1 1 250
200 1.21 0.57 9.17E+12 3000 4.22 0.97 5.36E+12 3
0.61
P 1 1 1 200
200 1.21 0.57 7.34E+12 3000 4.22 0.97 4.29E+12 3
0.52
P 1 1 1 150
200 1.21 0.57 5.50E+12 3000 4.22 0.97 3.22E+12 2
0.43
14
Lead Beam
Linac Pulse Length (s) =
Frequency (MHz) =
Number of Bunches in Pulse=
Average current per pulse, Pb
(A)=
Charge per pulse (C)=
Average charge state of lead ion=
Number of lead ions per pulse =
Injection Efficiency=
Transverse cooling time (s) =
Longitudinal cooling time (s) =
RF acceleration time (s) =
Ion
Pb
Pb
Pb
Pb
A
207
207
207
207
Q I (A)
67 1
67 1
67 1
67 1
2.50E-04
115
28750
5.00E-04
1.25E-07
67
1.17E+10
0.5
0.130
0.067
0.080
Injection
S (m) MeV/n γ
300
70 1.08
250
70 1.08
200
70 1.08
150
70 1.08
β
0.37
0.37
0.37
0.37
N_total
2.54E+11
2.12E+11
1.69E+11
1.27E+11
Extraction
MeV/n γ
1180 2.27
1180 2.27
1180 2.27
1180 2.27
β
0.90
0.90
0.90
0.90
N_total
1.04E+11
8.66E+10
6.93E+10
5.20E+10
Cycle
Pulses Time(s)
18
2.48
15
2.10
12
1.71
9
1.32
15
Spin tracking in the LINAC (first segment of the linac)
Linac with solenoids
Initial
Polarization
Direction
Linac with doublets
Final Polarization in Linac with
Solenoids
(Direction of polarization changes)
Emittance
5*Emittance
Final Polarization in Linac with Doublets
(Direction remains same as initial)
Emittance
5*Emittance
(%)
Spread
(%)
Spread
(%)
Spread
(%)
Spread
X
99
3x10-2
98
2x10-1
99
1x10-2
99
5x10-2
Y
99
3 x10-2
98
2x10-1
99
1x10-2
99
5x10-2
Z
99
4x10-2
96
3x10-1
99
1x10-2
99
7x10-2
16
QWR and HWR production at ANL

QWR, f=109 MHz, b=0.15
HWR, f=172 MHz, b=0.26
17
Advanced EM Optimization of New Cavities

Advanced EM optimization : outer conductor:
form cylinder to conical shape


Drift tubes are highly optimized to reduce EPEAK
2.5 deg drift tube face tilt to compensate beam
steering effect
Frequency
109.125 72.75
MHz
beta
0.14
0.077
U0 at 1 MV/m
0.4
0.39
J
bl
39
32
cm
EPEAK at 1 MV/m
5.0
4.6
MV/m
BPEAK at 1 MV/m
92
76
Gs
G
40
26
Ohm
Rsh/Q
548
575
Ohm
Voltage per cavity
2.1
2.5
MV
Dynamic LHe load
6
11.4
W
109 MHz
72.75 MHz
30 cm
18
Cryomodule assembly at ANL
beam
19
Cavity subsystems

4 kW capacitive coupler
– Adjustable
– 1 cold and 1 warm windows


Piezoelectric tuner (PZT)
– ~90 Hz window
– 35 m displacement
Pneumatic slow tuner
LN in
beam
Ceramic disk
LN out
PZT has been tested with
excellent performance
RF Coupler
20
Recently developed and built QWR, 72.75 MHz
21
Remaining tasks for the linac pre-conceptual design

Status of the injectors
– 2 mA is available for polarized light ion beams
– 2 mA is not available yet for lead ions
• ~0.5 mA is realistic number
• Can be increased by using 56 GHz ECRs –expensive device

Update the linac design on the base of recent (3-4 years) progress in performance
of TEM class cavities
– Introduce better optimization of EM parameters to reduce Epeak/Eacc and Bpeak/Eacc
– Peak magnetic field can be as high as ~90 mT for the pulsed operation
– Peak electric field ~40 MV/m

Optimal injection energy to the pre-booster
– Do we need 100 MeV/u lead ions and 280 MeV H-minus?

Focusing system
– In SC environment, focusing by SC solenoids is cost effective
– Spin dynamics studies to avoid depolarization effects: compare quadrupole and solenoid
focusing
22