Status of the JLEIC Injector Linac Design B

Status of the JLEIC Injector Linac Design B. Mustapha Physics Division, Argonne National Laboratory JLEIC R&D Weekly Meeting, March 2 nd, 2017

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

Current Linac Design ²⁰⁸Pb ⁶²⁺ ²⁰⁸Pb ³⁰⁺ (Pb) 0. 5 Me. V/u 10 ke. V/u 0. 5 m. A (Pb) IS RFQ 2 m. A (H¯, D¯) IS RFQ 15 ke. V/u Stripper (¹²C) 100 MHz IH-FODO (H¯, D¯) 0. 5 Me. V/u QWR 5 Me. V/u Normal conducting 200 MHz 100 MHz QWR HWR 8. 7 Me. V/u HWR 44 Me. V/u 135 Me. V Superconducting q Two RFQs: For light ions (q/A ~ 1/2) and for heavy ions (q/A ~ 1/7) q Different emittances and voltage requirements for polarized light ions and heavy ions q Selected RT Structure: IH-DTL with FODO Lattice instead of Triplets q No Frequency jump & FODO focusing Significantly better beam dynamics q Separate LEBTs and MEBTs for light and heavy ions q Stripper and SRF section are the same B. Mustapha Progress on the Multi-Ion Injector Linac Design JLEIC Collaboration Meeting, October 5, 2016 3

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

LEBTs: From Ion Sources to the RFQs Similar to CERN Linac 3 LEBT B. Mustapha Progress on the Multi-Ion Injector Linac Design Similar to BNL LEBT JLEIC Collaboration Meeting, October 5, 2016 5

Two Separate RFQs for Light Ions and Heavy Ions 2 m A/Z ≤ 2, 15 ke. V/u A/Z ≤ 7, 10 ke. V/u ü Light-Ion RFQ is designed for polarized Light-I-RFQ beams with 2 π mm mrad normalized transverse emittance ü Heavy-Ion RFQ is designed for ion with Heavy-Ion-RFQ Z/A ≤ 7 with 0. 5 π mm mrad normalized 5 m 0. 5 Me. V/u transverse emittance Parameter Frequency Energy range Highest - A/Q Length Average radius Voltage Transmission Quality factor RF power consumption (structure with windows) Output longitudinal emittance (Norm. , 90%) B. Mustapha Heavy ion Light ion 100 10 - 500 15 - 500 7 2 5. 6 2. 0 3. 7 7. 0 70 103 99 99 6600 7200 Units MHz ke. V/u m mm k. V % 210 120 k. W 4. 5 4. 9 π ke. V/u ns Progress on the Multi-Ion Injector Linac Design JLEIC Collaboration Meeting, October 5, 2016 6

IH-DTL with FODO Focusing Lattice ü 3 Tanks – 20 Quadrupoles in FODO arrangements ü ü Energy gain: 0. 5 – 4. 9 Me. V/u = 30. 5 Me. V Total length: 4. 3 + 3. 5 + 3. 4 m = 11. 2 m Real-estate accelerating gradient: 2. 72 MV/m RF Power losses: 280 + 400 + 620 = 1. 3 MW B. Mustapha Progress on the Multi-Ion Injector Linac Design JLEIC Collaboration Meeting, October 5, 2016 7

Stripper and SRF Linac Section ²⁰⁸Pb ³⁰⁺ Stripper (¹²C) QWR Pb, 5 Me. V/u p, 5 Me. V/u Stripping Energy & Charge ²⁰⁸Pb ⁶²⁺ 200 MHz 100 MHz QWR HWR 8. 7 Me. V/u QWR Module 44 Me. V/u 135 Me. V HWR Module Horizonal orientation of cavities QWR Design B. Mustapha HWR Design Progress on the Multi-Ion Injector Linac Design @ 8. 7 Me. V/u: 30+ → 62+ 44 Me. V/u @ 13. 3 Me. V/u: 30+ → 67+ 40 Me. V/u Parameter βopt Frequency Length (β ) EPEAK/EACC BPEAK/EACC R/Q G EPEAK in operation BPEAK in operation EACC Phase (Pb) Phase (p/H⁻) No. of cavities QWR 0. 15 100 45 5. 5 8. 2 475 42 57. 8 86. 1 10. 5 -20 -10 21 HWR 0. 30 200 45 4. 9 6. 9 256 84 51. 5 72. 5 10. 5 -30 -10 14 Units MHz cm m. T/(MV/m) MV/m m. T MV/m deg JLEIC Collaboration Meeting, October 5, 2016 8

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

Simulation of 2 m. A 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 10

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 ke. V/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 Me. V/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 11

H+/D+ versus H-/D- Injection H+/D+ H-/D- § High source current > 10 m. A § 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… B. Mustapha § Current limited to 3 -4 m. A § 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 … Progress on the Multi-Ion Injector Linac Design JLEIC Collaboration Meeting, October 5, 2016 12

Summary q Current injector design is adequate for heavy-ions q We need to revise the design for light ions, to reduce emittance growth in the RFQ and avoid beam loss in the DTL Solutions: q Increase the injection energy from 15 ke. V/u to 20 ke. V/u to reduce beam size in the LEBT and control space charge in the RFQ q 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 q A completely different approach for discussion: Inject H+/D+ instead of H-/D- because H+/D+ sources offer higher current with smaller emittance … q This will push the Linac problems to the Booster, BUT will cooling in the Booster help? q 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 13