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Status and recent progress on muon IDS-FFAG J. Pasternak, Imperial College, London / RAL STFC

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on muon IDS-FFAG

J. Pasternak, Imperial College, London / RAL STFC

Work in collaboration and with contributions from:

M. Aslaninejad (IC), J. Scott Berg (BNL), D. Kelliher (ASTeC/STFC/RAL),

S. Machida (ASTeC/STFC/RAL), H. Witte (JAI)

J. Pasternak

- Current baseline IDS FFAG design and alternative
- (J. Scott Berg, S. Machida).
- Studies of injection/extraction for IDS muon FFAG
- (D. Kelliher, J.P., M. Aslaninejad, H. Witte).
- Injection/extraction hardware design studies
- (M. Aslaninejad, H. Witte, J.P.).
- Summary and future plans.

J. Pasternak

- Non-scaling FFAG is preferred for muon acceleration from 12.6 to the final 25 GeV attheNeutrino Factory. Advantages include:
- Allows very fast acceleration (~8-16 turns).
- Large dynamic aperture due to linear magnets + high degree of symmetry
- More turns than in RLA – more efficient use of rf
- Quasi-isochronous – allows fixed frequency rf
- Orbit excursion and hence magnet aperture smaller than in the case of a scaling FFAG
- Principles of NS-FFAG will be soon tested during EMMA commissioning.

J. Pasternak

- Lattice choice triplet with long drift:
- due to longest drift injection/extraction
- seems to be most feasible comparing
- to other lattices
- allows for symmetric injection/extraction,
- good performance
- but less cost-effective than the short drift
- triplet,
- lattice needs to be further studied and
- optimised.
- chromaticity correction can be added
- in order to correct the final energy spread
- due to ToF

Scott’s lattice parameters.

J. Pasternak

Introduction to injection/extraction

- Working assumptions:
- Try to distribute kickers to reduce their strengths.
- Apply mirror symmetric solution to reuse kickers for both signs of muons.

Positive

Muons

Negative

Muons

F

D

F

D

F

D

F

Septum

Septum

Kickers

J. Pasternak

Injection/Extraction in the Long Drift Triplet, D. Kelliher

Injection

geometry

Extraction

geometry

- Large beam excursion
- near the septum requires
- special magnets with
- large aperture.
- Those magnets may
- introduce orbit and optics
- distortions (correction can
- be possible).

J. Pasternak

Orbit shift due to extended fringe fields, J. P.

m

- There are 3 curves on the plot:
- -orbit with the hard edge model,
- - with the soft edge model,
- - with shifted magnets

Zoom to see the difference

between hard edge and soft edge

results with shifted magnets.

This study suggest, that just by

shifting the magnets we can correct

the effect of special magnets

on orbit distortion in the

injection/extraction regions.

GeV

J. Pasternak

Preliminary study of IDS kickers (H.W., J.P.)

- Due to the proton beam time structure, at least 3 independent Pulse Forming Networks
- (PFNs) and switches are needed for every muon train.
- Termination is very important to avoid reflections back to magnet (for injection).
- Current is most likely to high for a single thyratron, but we can connect them
- in paralell.

PFN

switch

PS

Kicker

PFN

switch

Transmission line

Termination

PFN

switch

J. Pasternak

Layout of the kicker system, H. Witte

Magnet

Transmission line

made of RG220

Termination

Switches for 3 muon

bunch trains (Thyratrons CX1925)

PFN-Pulse Forming Network

J. Pasternak

Travelling wave kicker solution

- PFN impedance is 1 Ohm in order
- to lower the voltage to 60 kV.
- 1 Ohm impedance is kept all along
- the system till termination resistor
- in order to avoid reflections.
- In order to keep small inductance
- and matched impedance, capacitance
- needs to be added to the magnet.
- Magnet inductance is 3 uH.
- Voltage is limited by the switch.
- Current needed for 0.1 T is 30 kA.
- 2. 4 m long magnet is subdivided
- into 12 sections (6 „positive” and
- 6 „negative” ones).
- Each PFN powers 3 sections.
- This gives total of 12 PFNs for
- every kicker for 3 bunch trains.
- Real hardware components tests with
- high voltage and high current is needed!

J. Pasternak

IDS Kicker

Kicker geometry

EM simulations, M. Aslaninejad.

- Geometry
- Aperture: 0.3x0.3 m2
- Yoke: 120 mm
- Length: 2.4 m
- Field: 100 mT
- Current: 29 kA
- Magnetic energy: 500 J
- Inductance (single turn): 2.8 uH
- Impedance matching
- Add 5 plate capacitors (40 mm available)

J. Pasternak

Recent progress on kicker circuit, H. Witte

3 Ohm

PFN 1

Tfire=0 us

PFN 2

Lmag

PFN 3

PFN 4

1 Ohm

Rterm

PFN 5

Tfire=100 us

PFN 6

The assumed impedance was changed:

Each PFN: Z= 3 Ohms

Voltage: 60 kV

Peak current: 30 kA

Peak current thyratron: 10 kA

Kicker: subdivided into 3 smaller kickers

Each kicker: Travelling wave, 20 sections

PFN 7

Tfire=200 us

PFN 8

PFN 9

J. Pasternak

- Injection/extraction schemes in the NS-FFAG lattices
- were evaluated. The triplet lattice with long drift was chosen as the baseline.
- Alternative Nonlinear NS lattice with insertions and partial chromaticity
- correction was proposed.
- More beam dynamics studies are needed
- (chromaticity correction, errors, insertion).
- Substantial progress on the injection/extraction kicker design was achieved!
- Work focuses on the design of the superconducting extraction septum!

J. Pasternak

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