1. Status of the JLEIC Injector Linac Design
B. Mustapha
Physics Division,
Argonne National Laboratory
JLEIC R&D Weekly Meeting, March 2nd, 2017
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2. Outline Current Injector Linac Design
Two RFQs: One for light ions & one for heavy ions
IH-DTL: No frequency jump & FODO lattice instead of triplets
Two LEBTs designed for light & heavy ion beams
We have it in pieces: The Different Linac Sections
LEBTs
RFQs
IH-FODO
SRF Linac
Putting it all together: End-to-end Simulations …
Important Issue: H-/D- charge-exchange injection or H+/D+ injection?
Summary
B. Mustapha Progress on the Multi-Ion Injector Linac Design JLEIC Collaboration Meeting, October 5, 2016

3. Current Linac Design ²⁰⁸Pb ³⁰⁺ ²⁰⁸Pb ⁶²⁺ Normal conducting
0.5 MeV/u
10 keV/u
Stripper (¹²C)
100 MHz
100 MHz
200 MHz
0.5 mA
(Pb) IS
RFQ
IH-FODO
QWR
QWR
QWR
HWR
HWR
2 mA
(H¯, D¯) IS
RFQ
5 MeV/u
8.7 MeV/u
44 MeV/u
5 MeV/u
135 MeV
(H¯, D¯)
0.5 MeV/u
15 keV/u
Normal conducting
Superconducting
Two RFQs: For light ions (q/A ~ 1/2) and for heavy ions (q/A ~ 1/7)
Different emittances and voltage requirements for polarized light ions and heavy ions
Selected RT Structure: IH-DTL with FODO Lattice instead of Triplets
No Frequency jump & FODO focusing  Significantly better beam dynamics
Separate LEBTs and MEBTs for light and heavy ions
Stripper and SRF section are the same
B. Mustapha Progress on the Multi-Ion Injector Linac Design JLEIC Collaboration Meeting, October 5, 2016

4. The Different Linac Sections
B. Mustapha Progress on the Multi-Ion Injector Linac Design JLEIC Collaboration Meeting, October 5, 2016

5. LEBTs: From Ion Sources to the RFQs
Similar to CERN Linac3 LEBT Similar to BNL LEBT
B. Mustapha Progress on the Multi-Ion Injector Linac Design JLEIC Collaboration Meeting, October 5, 2016

6. Two Separate RFQs for Light Ions and Heavy Ions
2 m
Light-Ion RFQ is designed for polarized beams with 2 π mm mrad normalized transverse emittance
Heavy-Ion RFQ is designed for ion with Z/A ≤ 7 with 0.5 π mm mrad normalized transverse emittance
A/Z ≤ 2, 15 keV/u
Light-I-RFQ
A/Z ≤ 7, 10 keV/u
Heavy-Ion-RFQ
5 m
0.5 MeV/u
Parameter
Heavy ion
Light ion
Units
Frequency
100
MHz
Energy range
keV/u
Highest - A/Q 7 2
Length
5.6
2.0 m
Average radius
3.7
7.0 mm
Voltage 70
103 kV
Transmission 99 %
Quality factor
6600
7200
RF power consumption (structure with windows)
210
120 kW
Output longitudinal
emittance (Norm., 90%)
4.5
4.9
π keV/u ns
B. Mustapha Progress on the Multi-Ion Injector Linac Design JLEIC Collaboration Meeting, October 5, 2016

7. IH-DTL with FODO Focusing Lattice
3 Tanks – 20 Quadrupoles in FODO arrangements
Energy gain: 0.5 – 4.9 MeV/u = 30.5 MeV
Total length: m = 11.2 m
Real-estate accelerating gradient: 2.72 MV/m
RF Power losses: = 1.3 MW
B. Mustapha Progress on the Multi-Ion Injector Linac Design JLEIC Collaboration Meeting, October 5, 2016

8. Stripper and SRF Linac Section
Stripping Energy & Charge
²⁰⁸Pb ³⁰⁺
²⁰⁸Pb ⁶²⁺
Stripper (¹²C)
100 MHz
200 MHz
QWR
QWR
QWR
HWR
HWR
Pb, 5 MeV/u
8.7 MeV/u
44 MeV/u
p, 5 MeV/u
135 MeV
QWR Module
HWR Module
@ MeV/u: 30+ → 62+  44 MeV/u
@ 13.3 MeV/u: 30+ → 67+  40 MeV/u
Horizonal orientation of cavities
Parameter
QWR
HWR
Units
βopt
0.15
0.30
Frequency
100
200
MHz
Length (β) 45 cm
EPEAK/EACC
5.5
4.9
BPEAK/EACC
8.2
6.9
mT/(MV/m)
R/Q
475
256  G 42 84
EPEAK in operation
57.8
51.5
MV/m
BPEAK in operation
86.1
72.5 mT
EACC
10.5
Phase (Pb)
-20
-30
deg
Phase (p/H⁻)
-10
No. of cavities 21 14
QWR Design
HWR Design
B. Mustapha Progress on the Multi-Ion Injector Linac Design JLEIC Collaboration Meeting, October 5, 2016

9. First Attempt to End-to-end Simulations
B. Mustapha Progress on the Multi-Ion Injector Linac Design JLEIC Collaboration Meeting, October 5, 2016

10. Simulation of 2 mA Deuteron Beam in the RT Section
Issues: 15% emittance growth in the RFQ and Beam loss in the IH-DTL
B. Mustapha Progress on the Multi-Ion Injector Linac Design JLEIC Collaboration Meeting, October 5, 2016

11. Problems and Possible Solutions
The main difficulty in the design of the light-ion injector is the large emittances of polarized H-/D- beams from ABPIS type source. (Ref. V. Dudnikov’s talk at the last JLEIC meeting, it’s ~ 2*π mm.mrad for 90% of the beam)
Because of this, we have a much larger beam than typical ion injector beams  two separate injectors for light and heavy ions
Possible solutions
Increase the injection energy to 20 keV/u, this should reduce the beam size in the LEBT and better control space charge in the RFQ.
We may need a different RFQ energy and separate DTL for the light ions  Completely separate RT sections for the light and heavy ion beams up to 5 MeV/u.
Or??? Consider using polarized H+/D+ instead of H-/D-, H+/D+ sources can deliver higher current in smaller emittance, Ref. V Dudnikov, BUT this will complicate the injection into the Booster  see next slide …
B. Mustapha Progress on the Multi-Ion Injector Linac Design JLEIC Collaboration Meeting, October 5, 2016

12. H+/D+ versus H-/D- Injection
H+/D H-/D-
High source current > 10 mA
Emittance ~ 1 π mm.mrad
Less challenging Linac design
High current  less injection turns, but higher Linac power
Less efficient injection to Booster, more injection loss
Larger emittance in Booster, but cooling should help
Your comments…
Current limited to 3-4 mA
Emittance ~ 2 π mm.mrad
Completely separate RT section for light ions
Multi-turn charge-exchange injection, lower current OK
More efficient injection
Smaller Booster emittance
Your comments …
B. Mustapha Progress on the Multi-Ion Injector Linac Design JLEIC Collaboration Meeting, October 5, 2016

13. Summary Current injector design is adequate for heavy-ions
We need to revise the design for light ions, to reduce emittance growth in the RFQ and avoid beam loss in the DTL  Solutions:
Increase the injection energy from 15 keV/u to 20 keV/u to reduce beam size in the LEBT and control space charge in the RFQ
A longer higher energy RFQ may be required, injecting to a separate DTL or if possible to the second tank of the heavy-ion DTL
A completely different approach for discussion: Inject H+/D+ instead of H-/D- because H+/D+ sources offer higher current with smaller emittance …
This will push the Linac problems to the Booster, BUT will cooling in the Booster help?
We still think charge-exchange injection of H-/D- still wins despite the larger emittance at the Source and Linac, Comments?
B. Mustapha Progress on the Multi-Ion Injector Linac Design JLEIC Collaboration Meeting, October 5, 2016