1 Multipass Droplet Arc Design Guimei WANG Muons

1 Multi-pass Droplet Arc Design Guimei WANG (Muons Inc. /ODU) Dejan Trbojevic (BNL) Alex Bogacz (JLAB) MCDW 2008, JLAB, Dec 8 -12, 2008

2 Outline Requirements of Muon collider acceleration Baseline design Prototype design Proposed new lattice design Ongoing… MCDW 2008, JLAB, Dec 8 -12, 2008

Requirements of Muon collider acceleration Economical system with multi pass acceleration 1. Single Accelerator 2. Single arc Short life time 1. High gradient accelerator 2. Short circumference MCDW 2008, JLAB, Dec 8 -12, 2008 3

Baseline design—— 4 Separate droplet arc for different energies Alex Bogacz and Rol Johnson: single linac (with Pulsed linac Optics)+ multi droplet Arcs to accommodate multi pass beam acceleration 3 Ge. V m+ m- 35 Ge. V 4 Ge. V/pass Ramped Quads field gradient with time Reference: RECIRCULATING LINEAR MUON ACCELERATOR WITH RAMPED QUADRUPOLES, S. A Bogacz, R. P. Johnson, EPAC, 2629 -2631 MCDW 2008, JLAB, Dec 8 -12, 2008

5 Baseline design — Linac Optics Pulsed linac Optics Fixed linac Optics 1 -pass 8 -pass Increase from 8 -pass (Fixed Optics) to 12 -pass (Pulsed Optics) for 500 m long 4 Ge. V pass 12 -pass MCDW 2008, JLAB, Dec 8 -12, 2008

Baseline design — 6 Mirror-symmetric ‘Droplet’ Arc Optics 2 cells 16 cells dipole spreader 5 Ge. V 13 Ge. V 21 Ge. V 29 Ge. V septum Different energy beams coming out of a linac are directed into different ‘droplet’ arcs for recirculation. Cost moves from accelerator to arcs. MCDW 2008, JLAB, Dec 8 -12, 2008

Prototype design—— 7 NS-FFAG (Non-Scaling Fixed Field Alternating Gradient) Dejan Trbojevic: Double linac + two 180 degree Arcs to accommodate large momentum spread (~60%) 1. 2. 3. 4. Large energy acceptance Very small orbit offsets Reduce number of arcs Very compact structure Basic cell structure in ARC (combined function magnet with extremely strong focusing ) Reference: FLEXIBLE MOMENTUM COMPACTION RETURN ARCS FOR RLAS, D. Trbojevic, R. P. Johnson, EPAC, 2578 -2580 MCDW 2008, JLAB, Dec 8 -12, 2008

8 Proposed new lattice design Single Linac (pulsed linac optics) + Single Droplet arc (NS-FFAG) for two or more passes acceleration Or Single Linac +Single Droplet arc (pulsed linac optics + pulsed arc optics) for two or more passes acceleration m+ m- m- mm+ m- m+ Basic arc design requirements: 1. Mirror symmetry arc structure for muon +/- acceleration 2. Large momentum acceptance 3. Path length control to match beam phase in the linac MCDW 2008, JLAB, Dec 8 -12, 2008

9 New lattice design Tools： Optim, Madx-PTC, Cosy-Infinity… Linac: use Alex’s design Arc: Combine the droplet design and idea of NS-FFAG basic cell design. Mirror Symmetric droplet Arc with large momentum acceptance Basic cell of Large momentum acceptance with combined bending magnet: Extremely strong focusing to suppress dispersion function MCDW 2008, JLAB, Dec 8 -12, 2008

Flexible Momentum Compaction Symmetric Cells Inward bending cell 10 Outward bending cell , Strong focusing yields very small beta functions and dispersion (Gr/B ~50, optics dominated by quads) The maximum betatron in x and y plane are 4. 9 m and 3. 4 m. The maximum dispersion are 7. 21 cm and -7. 21 cm. MCDW 2008, JLAB, Dec 8 -12, 2008

11 NS-FFAG multi-pass ‘Droplet’ Arc , 600 outward 3000 inward 600 outward The total length is 199 m, with 74 m long and 27 m wide. MCDW 2008, JLAB, Dec 8 -12, 2008

Cells for different energy spread—— 12 Beta function Inward bending cell Outward bending cell For different energy spread, ~the same beta function in opposite bending cell. With MADX- Polymorphic Tracking Code. Energy spread changes from -30% to 90% MCDW 2008, JLAB, Dec 8 -12, 2008

13 Cells for different beam energy — orbit offset and dispersion Inward bending cell Outward bending cell For different energy spread, opposite offset and dispersion in opposite bending cell. Beam offset <10 cm, dispersion < 0. 1 m. Possible solution: (1) Matching cell with –I matrix in x plane, and +/- I matrix in y plane. MCDW 2008, JLAB, Dec 8 -12, 2008

Analysis with multipoles components 14 Same bending raduis, same optics, same chromaticity Beam offset VS energy spread MCDW 2008, JLAB, Dec 8 -12, 2008

15 Ongoing More optimizations on the basic cell design, such as use multipoles Dispersion and opposite bending cells match study Pathlength difference and adjustment study Orbit offset Optics match between Linac and Arc and Optics mismatch sensitivity Error sensitivity study, beam dynamics study… Pulsed droplet arc optics study MCDW 2008, JLAB, Dec 8 -12, 2008

16 MCDW 2008, JLAB, Dec 8 -12, 2008

17 ‘Pulsed’ vs ‘Fixed’ Dogbone RLA (1 -pass) Pulsed 1 -pass, 3 -7 Ge. V Fixed MCDW 2008, JLAB, Dec 8 -12, 2008

18 ‘Pulsed’ vs ‘Fixed’ Dogbone RLA (8 -pass) Pulsed 8 -pass, 28 -32 Ge. V Fixed phase adv. diminishes down to 1800 MCDW 2008, JLAB, Dec 8 -12, 2008

19 ‘Pulsed’ vs ‘Fixed’ Dogbone RLA (12 -pass) Pulsed phase adv. diminishes down to 1800 12 -pass, 47 -51 Ge. V Fixed no phase adv. across the linacbeam envelopes not confined MCDW 2008, JLAB, Dec 8 -12, 2008