Status of the JLEIC Injector Linac Design B. Mustapha Physics Division, Argonne National Laboratory JLEIC R&D Weekly Meeting, March 2nd, 2017 Go to "View | Header and Footer" to add your organization, sponsor, meeting name here; then, click "Apply to All"

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

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

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

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

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 10 - 500 15 - 500 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

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: 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

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 @ 8.7 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

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

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

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

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

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