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FFAG Concepts and Studies

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Not isochronous. 11. JNF- FFAGs lattice design. Lattices are 'scaling' radial-sector FFAGs ... Motion is not very isochronous. h = 1 and h = 2 accelerations are OK; 17 ... – PowerPoint PPT presentation

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Title: FFAG Concepts and Studies


1
FFAG Concepts and Studies
  • David Neuffer
  • Fermilab

2
Outline
  • Introduction
  • Feasibility studies use Linacs and recirculating
    linacs
  • Need to develop cheaper acceleration
  • FFAG Acceleration ??
  • Fixed-field permits fast-acceleration
  • 10 turns possible .
  • FFAG Lattice styles (DIMAD simulations)
  • scaling FFAG Machida Mori
  • non-scaling FFAG Johnstone
  • FMC-like Dejan Trbojevic
  • Longitudinal Motion Constraints
  • simulations

3
Study 2 Costs .
  • Study I, II ?-Factory feasible but too
    expensive
  • Biggest cost item acceleration (600M)

4
FFAG Acceleration?
  • Linacs/RLAs require a lot of rf
  • RLA multiple-pass transports spreader/recombiner
    s complicated and expensive
  • Muons decay too quickly for fast-cycling magnets
  • Need Fixed-field lattice that can accept beam
    over large energy spread (6?20 GeV ?) for
    multipass return transports FFAG
    lattice ?
  • With same transport for all turns can accelerate
    over more turns less rf.
  • FFAG lattice can have large momentum acceptance
    large transverse acceptance need less cooling

5
POP-first Proton FFAG
  • First Proton FFAG built and operated
  • All systems verified
  • (magnet, rf, injection)

6
FFAG magnet- 150 MeV FFAG
  • Figure shows yoke-free FFAG triplet used for 150
    MeV proton FFAG
  • 150 MeV FFAG is under construction (magnets done)

7
PRISM low-energy muon ring
  • Low-energy muon source
  • ??e experiments

8
Japan Neutrino Factory Scenario
9
JNF Scenario
  • Use 50 GeV p-bunch to produce pions
  • Capture beam in 20-T ? 5-T transport channel
  • Short decay line inject beam directly into
    low-energy FFAG
  • Capture beam in low-frequency rf bucket
  • Accelerate up chain of FFAGs to 20GeV
  • Inject into 20GeV storage ring

10
Scaling FFAGS
  • Lattice
  • Advantages
  • Naturally Zero chromaticity
  • Disadvantages
  • Large negative bends (large circumference )
  • Nonlinear fields (from rk expansion)
  • Not isochronous

11
JNF- FFAGs lattice design
  • Lattices are scaling radial-sector FFAGs
  • Triplet focusing with reverse-bend D-quads
  • Low to high energy orbit width is 0.5m
  • 0.3 ? 1.0 GeV,
  • 1 ? 3.0 GeV
  • 3.0?10 GeV
  • 10? 20 GeV FFAGs
  • Lattices have been generated using SAD, DIMAD

12
Parameters for JNF FFAG lattices
13
Acceleration and Decay
  • Acceleration must avoid muon decay
  • Need 1MV/m to avoid decay (2 MV/m gradient in
    cavities)

14
Acceleration Parameters
  • For acceleration, use superconducting
    (smaller-radius) FFAGs
  • At 1MV/m, 10 turns acceleration / FFAG
  • Assume harmonic h 1 on lowest-energy FFAG keep
    frequency constant
  • h 1 ? 4.75 MHz rf (???)
  • Initial beam from decay
  • 300?150MeV/c ?10ns

 
15
Scenario requires 2MV/m rf
  • Harmonic1 (for lowest energy FFAG) implies 4.75
    MHz
  • Harmonic2 implies 9.5 MHz works OK in 1-D
    simulation
  • Experience indicates 26MHz cavity is more
    realistic (Iwashita)
  • Use 26 MHz 3rd harmonic ?

16
Longitudinal Motion in FFAG
  • Equations of motion
  • Motion is not very isochronous
  • h 1 and h 2 accelerations are OK

17
Injection and Extraction
  • Requires fast, large-aperture kickers
    particularly for low-energy FFAGs
  • Risetime for 1GeV FFAG must be less than 200ns
    20 GeV FFAG can be gt 1?s
  • Example 150MeV FFAG will need 500g, 0.6m,
    150ns
  • 1GeV FFAG needs 0.53 T-m

18
Non-scaling FFAG (Johnstone)
  • 6?20 GeV lattice C2100m
  • Basic lattice unit is FODO cell 7m long
  • Primary bending magnet is D
  • Lattice is more isochronous
  • (transition at 13 GeV)
  • B? constant (tune varies with energy)
  • Good linear behavior
  • (but large chromaticity )

F
D
19
Dejan Trbojevic Lattice
  • 10?20 GeV
  • 270m circumference
  • Strong focusing to very small dispersion
    ?? 6cm
  • No negative bends at central energy
  • Chromaticity corrected Tune (E) more nearly
    constant (but does cross integers)

20
(No Transcript)
21
Summary
  • FFAG accelerators have been built and operated at
    KEK
  • POP FFAG
  • 150 MeV FFAG (under construction)
  • PRISM (proposed)
  • RIKEN radioactive ion FFAG
  • FFAG accelerators could be used in neutrino
    factory
  • Need magnet, rf , injection/extraction RD
  • Muon production and cooling options to be
    explored
  • Comparisons with other design approaches are not
    completed
  • FFAG or RLA or linac or ???
  • Cost estimates ???
  • Integration into complete neutrino factory
    scenario is also required
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