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A 10 GeV, 4 MW, FFAG, Proton Driver at 50 Hz

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A 10 GeV, 4 MW, FFAG, Proton Driver at 50 Hz G H Rees, RAL Non-scaling, Non-linear FFAGs Categories for FFAG Lattice Cells of Five Magnets: 1. – PowerPoint PPT presentation

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Title: A 10 GeV, 4 MW, FFAG, Proton Driver at 50 Hz


1
A 10 GeV, 4 MW, FFAG,Proton Driver at 50 Hz
  • G H Rees, RAL

2
Non-scaling, Non-linear FFAGs
  • Categories for FFAG Lattice Cells of Five
    Magnets
  • 1. IFFAG isochronous, no Qvn and 2Qvn crossing
  • 2. IFFAGI IFFAG with combined function
    insertions
  • 3. NFFAG non-isochronous, high/imag ?-t, no Q
    varn
  • 4. NFFAGI NFFAG with insertions, some Qh
    variation
  • 1 and 2 rapid acceleration of muons or
    electrons
  • 3 and 4 high power proton drivers or medical
    rings

3
4 MW Proton Driver Arrangement
  • Muon yields optimal for 6 - 10 GeV (S Brooks,
    RAL)
  • Choose 10 GeV, 50 Hz to reduce target shock
  • 3 GeV booster for 3 10 GeV
    NFFAGI
  • 2, 25 Hz or 1, 25 Hz booster (R
    2.2 Rb)
  • 0.18 GeV H? linac for low bunch
    areas
  • 5 bunches at h 5 for RCS
    booster(s)
  • Transfer 5 (1013 protons/bunch) to the NFFAGI
  • Bunch to 1 ns (rms) adiabatically (h 33 198)

4
Longitudinal bunch area
  • The longitudinal bunch area (in eV sec) is
  • A (8Ra/(ch)) ((2 V(I-?sc)Eo?) / (h??))½
  • For a small longitudinal bunch area, choose
  • a low value of injection energy and ring radius
  • Choose Eo (? - 1) 0.18 GeV and Rb ? 50.0 m
  • Choose the bunch harmonic number (h) 5
  • Compressed bunch area needed ? 0.66 eV sec

5
4 MW, Proton Driver Layout
0.18 GeV H ? Linac
0.18 GeV H ? Achromat
3 GeV, 50 Hz, h 5, RCS (1 at 50 Hz, or 2 at 25
Hz)
10 GeV, 50 Hz, N 5, NFFAGI with 1013 protons
per bunch
6
NFFAGI Design Criteria
  • For compression of the 5 bunches at 10 GeV
  • Design for a gamma-t value at 10 GeV ? 20
  • Design for longitudinal bunch areas ? 0.66 eV s
  • Adiabatic acceleration comp. with h 33, 198
  • Design the NFFAG ring with lattice insertions, to
  • ease injection, ejection beam loss collection
  • Use two insertions to allow most flexibility, eg
  • 21 normal and 13 insertion cells per insertion

7
Acceleration and Compression Systems
  • Driver-booster circumference ratio 2.2 to 1
  • Booster rf range (h5) 2.6164 to 4.670 MHz
  • Driver rf range (h33) 14.011 to 14.370 MHz
  • Compression frequency (h198) 86.222 MHz
  • Peak accelerating voltage per turn 1.0 MV
  • Peak compression voltage per turn 2.56 MV

8
Lattice Cell Options
  • Normal cell Insertion cell
    Magnet types
  • Doublet D D1 T0 D2
    2 7
  • Triplet T T1 T2 T1
    2 4
  • Pumplet P1 P2
    3 3
  • Easiest solution is to match P1 and P2 pumplet
    cells
  • P1 has a smaller ß-range than either D or T
  • The insertion has only one type of cell, P2
  • P2 has the smallest closed orbit lever arm
  • No 2? dispersion suppressors, as too many are
    needed

9
10 GeV, Normal Insertion Cell Layouts
  • bd(-) BF() BD ()
    BF() bd(-)
  • O 0.5 0.5
    0.5 0.5 O
  • 0.60 1.25 1.9
    1.25 0.60
  • 0.651 Normal cell (5.294º, 8.902
    m) 0.651
  • 2.2 Insertion cell (5.294º,
    12.00 m) 2.2
  • There are two superperiods of 21 normal 13
    insertion cells
  • At 10 GeV Qv 13.72, Qh 19.36, ? -t
    20.4, R 109.17 m

10
NFFAGI Lattice Design
  • Use equal bend, normal and insertion, pumplet
    cells
  • Arrange matching for a normal and insertion
    cell
  • Arrange integer, insertion tunes eg Qh 4 Qv
    3
  • The normal cells in an insertion are then matched
  • Seek unchanged closed orbits on adding insertions
  • by varying the normal cell field gradients and
    tunes
  • Then, dispersion match is almost exact for
    insertions
  • Small ripple remains in ßh and ßv (max) in
    insertions

11
Non-Linearity Compensation
  • Crossing of the 3rd order resonance 3Qh
    58
  • Insertion and arc 3(Qh ) values 3Qh
    3(4, 5? )
  • Hence, no 3rd order excitation for 3Qh
    58
  • Crossing of 4th order resonance 2Qh 2Qv 66
  • Insertion and arc values for 2(Qh Qv )
    2(7, 9½ )
  • So, no 4th order excitation for 2Qh 2Qv 66
  • Crossing of the 4th order resonance 4Qh
    77
  • Insertion and arc 4(Qh ) values 4Qh
    4(4, 5? )
  • Some small 4th order excitation for 4Qh 77

12
NFFAGI Lattice Results
  • Satisfactory matching at the 24 reference
    energies
  • 10.0..6.8, 6.5..5.0, 4.75..4.0, 3.8..3.0 GeV.
  • Qv 13.72 throughout the 3 to 10 GeV energy
    range.
  • Dispersion match is found by varying K(bd) and
    ?h
  • T 10.06.8, 6.5. 5.0, 4.75..4.0, 3.83.0
    GeV
  • Qh19.36, 19.31, 19.3, 19.29, 19.2, 19.2, 19.2,
    19.2
  • Gamma-t becomes imaginary for the low energies

13
Combined Function Magnet Fields (T)
  • Magnets Insertion
    Normal cell
  • bd -1.70 to -1.18
    -1.70 to -0.98
  • BF 1.75 to -0.15
    1.75 to -0.27
  • BD 0.54 to 1.55
    0.54 to 1.59
  • Tmax bending ratios bd BF BD - 0.47 1.0
    0.23
  • (Ratios in muon ring bd BF BD - 1.0
    1.0 1.0)

14
Beam Loss Collimators
  • Vertical
  • Locate in 4, adjacent, long, insertion straights
  • Use 1, primary and 3, secondary, 5 kW collimators
  • Use tapered units for lower, high energy
    acceptance
  • Horizontal
  • Locate in the first three, vertical, collimator
    straights
  • Use 1, primary and 3, secondary, 5 kW collimators
  • Use angled units for collimation at 3 and 10 GeV

15
10 GeV NFFAGI versus RCS
  • Pros Allows acceleration over more of the cycle,
  • No need for ac magnet p/s or ceramic chamber,
  • Gives more flexibility for the holding of
    bunches,
  • Required is one NFFAGI ring, but two RCS(s),
  • Allows operation at 50 Hz instead of at 25 Hz,
  • with 5 1013 ppp at target, instead of 1014 ppp.
  • Thus, there is half the target shock per pulse.
  • Cons needs a larger ( 0.33 m) radial aperture
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