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Multi-pass Droplet Arc Design. Guimei WANG (Muons Inc./ODU) Dejan Trbojevic (BNL) Alex Bogacz (JLAB). Outline. Requirements of Muon collider acceleration Baseline design Prototype design Proposed new lattice design Ongoing…. Requirements of Muon collider acceleration.

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Multi pass droplet arc design

Multi-pass Droplet Arc Design

Guimei WANG (Muons Inc./ODU)

Dejan Trbojevic (BNL)

Alex Bogacz (JLAB)

MCDW 2008, JLAB, Dec 8-12, 2008


Outline
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
Requirements of Muon collider acceleration

  • Economical system with multi pass acceleration

  • Single Accelerator

  • Single arc

  • Short life time

  • High gradient accelerator

  • Short circumference

MCDW 2008, JLAB, Dec 8-12, 2008


Baseline design separate droplet arc for different energies

3 GeV

m-

m+

35 GeV

4 GeV/pass

Baseline design——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

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


Baseline design linac optics
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 GeV pass

12-pass

MCDW 2008, JLAB, Dec 8-12, 2008


Baseline design mirror symmetric droplet arc optics

dipole

dipole

spreader

5 GeV

21 GeV

septum

13 GeV

2 cells

2 cells

16 cells

29 GeV

Baseline design—Mirror-symmetric ‘Droplet’ Arc Optics

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 ns ffag non scaling fixed field alternating gradient
Prototype design——NS-FFAG (Non-Scaling Fixed Field Alternating Gradient)

  • Dejan Trbojevic: Double linac + two 180 degree Arcs to accommodate large momentum spread (~60%)

  • 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


Proposed new lattice design

m+

m-

m-

m+

m+

m-

m-

m-

m-

m+

m+

m+

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

Basic arc design requirements:

  • Mirror symmetry arc structure for muon +/- acceleration

  • Large momentum acceptance

  • Path length control to match beam phase in the linac

MCDW 2008, JLAB, Dec 8-12, 2008


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
Flexible Momentum Compaction Symmetric Cells

  • 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 4.9m and 3.4m. The maximum dispersion are 7.21cm and -7.21cm.

Inward bending cell

Outward bending cell

,

MCDW 2008, JLAB, Dec 8-12, 2008


Ns ffag multi pass droplet arc

600 outward

600 outward

3000 inward

NS-FFAG multi-pass ‘Droplet’ Arc

,

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——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


Cells for different beam energy orbit offset and dispersion
Cells for different beam energy —orbit offset and dispersion

For different energy spread, opposite offset and dispersion in opposite bending cell.

Beam offset <10cm, dispersion < 0.1 m.

Inward bending cell

Outward bending cell

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
Analysis with multipoles components

Same bending raduis, same optics, same chromaticity

  • Beam offset VS energy spread

MCDW 2008, JLAB, Dec 8-12, 2008


Ongoing
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



‘Pulsed’ vs ‘Fixed’ Dogbone RLA (1-pass)

Pulsed

1-pass, 3-7 GeV

Fixed

MCDW 2008, JLAB, Dec 8-12, 2008


‘Pulsed’ vs ‘Fixed’ Dogbone RLA (8-pass)

Pulsed

8-pass, 28-32 GeV

Fixed

phase adv. diminishes down to 1800

MCDW 2008, JLAB, Dec 8-12, 2008


‘Pulsed’ vs ‘Fixed’ Dogbone RLA (12-pass)

Pulsed

phase adv. diminishes down to 1800

12-pass, 47-51 GeV

Fixed

no phase adv. across the linac- beam envelopes not confined

MCDW 2008, JLAB, Dec 8-12, 2008


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