Status and Recent Progressin the Muon FFAG Designs

for the NF

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), Y. Mori (Kyoto University),T. Planche (Kyoto University), H. Witte (JAI)

Outline of the talk

• Status of baseline IDS FFAG design (S. Berg, S. Machida).

• Studies of injection/extraction for IDS muon FFAG (D. Kelliher, J.P., M. Aslaninejad, H. Witte).

• Scaling FFAG options for low energy acceleration (Y. Mori, T. Planche).

• Summary and future plans.

Reference IDS Neutrino Factory Design

nsFFAG

Introduction

Motivations for Non Scaling FFAGs:• quasi-isochronous –enables high frequency RF• linear fields – gives huge DA and allows for simple magnets• small orbit excursion – cost effective

Main problems:• TOF with amplitude• injection/extraction

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

It will be tested in EMMA soon, 2010!

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Alternative solution Nonliner NS-FFAG, S. Machida (1)

•Due to natural chromaticity time of flight depends on amplitude, which introduces longitudinal blow-up and limits acceptance.• The lattice with chromaticity correction is proposed to correct for this effect.

Natural chromaticityCorrected chromaticity,

study by S. Machida

Alternative solution - Nonliner NS-FFAG, S. Machida (2)

Layout of FFAG with insertions

Please see S. Machida’s talk for updates.

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.

F D FFF DD

Septum

PositiveMuons Negative

Muons

Septum

Kickers

Injection – Triplet, D. Kelliher

Kickers Septum

• Horizontal scheme is feasible in trilet.• Scheme is less demanding with respect to special magnet needs.• It uses 3 2.4 m long kickers at 0.0855 T and the 2.4 m long septum at 2 T.

Please see D. Kelliher’s talk for updates.

D. Kelliher

Effects of special magnets

• Beams close to septum push the magnet aperture.• Special magnets with higher aperture is needed in injection/extraction regions.• Those magnets introduce the ring lattice symmetry breaking, which can cause accelerated orbit distortion.• Current studies show that the effect is not dramatic, but more simulations are needed.

Preliminary ideas for kicker R&D

PS

PFN

PFN

PFN

switch

switch

switch

Transmission line Kicker Termination

• 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 thyratrons, but IGBTs should be OK.• We want to push conventional kickers, but may also look at new ideas.• Kicker R&D are just starting for FFAG accelerators within IDS!

FFAG IDS kicker:• size HxV (~ 0.3 x~ 0.3 m), • field 0.1 T, •I~ 30 kA, •V~60 kV,• rise time 1.5 us• length 1.4 m

PAMELA-FFAG kicker:• size HxV (~ 0.185 x~0.026 m), • field 0.063 T, •I~ 9 kA, •V~50 kV • rise time 100 ns• length 1 m

Work in collaboration with H. Witte.

Current pulse, H. Witte

3 Current pulses for 3 bunches, H. Witte

Kicker magnet simulations, M. Aslaninejad

• We need to update the aperture requirements for kickers!

What about the septum?

• Superconducting septum of similar parameters was designed and constructed for Jefferson Lab Hall A• The very similar septum is needed for medical FFAG for carbon treatment• We may need to subdivide the septum into normal and superconducting part. • HTS screening may be applied.• We are just starting the study in collaboration with JAI, Oxford.

Some thougths, which need to be discussed and challenged soon!

• Long drift triplet may work without insertion• Short drift triplet seems to be more cost

effective, but injection/extraction is more difficult. Insertion may be beneficial here, and only modest additional drift space could be OK (3-4 m).

• What is the effect of chromaticity correction on the injection/extraction scheme?

What needs to be done:• Update of the aperture requirements for kickers.

• Update of kicker and pulse generator parameters.

• Effect of chromaticity correction on injection/extraction.

• Address the level of chromaticity correction versus DA.

• Insertion study for the short drift triplet (or other configuration ?).

• Error study (including the effect of injection/extraction special magnets and possibly insertion).

Updated Scaling FFAG Lattice, T. Planche

Beam dynamics studies, T. Planche

Preliminary horizontal injection

Rad

• The injection was studied as extraction.• 2 kickers 0.19 T, 0.96 m (0.3 m space between the kicker and the magnet)• Beam separation ąbout 1 cm• Septum 0.96 m, 4 T, beam separation of about 25 cm at the magnet.

4.6 GeVbeam, 3 cm normalizedacceptance

3.6 GeV, beam, 3 cm normalizedacceptance

beam, 3 cm normalizedacceptance

Preliminary horizontal extraction

Rad

• 2 kickers 0.39 T, 0.96 m (0.3 m space between the kicker and the magnet)• Beam separation ąbout 1 cm• Septum 0.96 m, 4 T, beam separation of about 8 cm at the magnet.

12.6 GeVbeam, 3 cm normalizedacceptance

11.6 GeV, beam, 3 cm normalizedacceptance

Rad

Current status of scaling FFAG option

• The scaling FFAG ring has a good DA.

• 6D Beam dynamics studies are very promising!

• Horizontal injection requires 2 0.19 T kickers and 4 T septum.

• Extraction requires 2 0.39 T for the current geometry.

• Fast betatron decoherence makes options with more than 2 kickers questionable.

• The effect of decoherence needs to be studied.

• At extraction 4 T septum gives only 8 cm beam separation.

• We need to study the vertical injection/extraction schemes.

• More drift length would be beneficial!

• Baseline NS linear FFAG lattices have been optimised.

• Alternative Nonlinear NS lattice with insertions and partial chromaticity correction was proposed. • Injection/extraction schemes in the baseline lattices (FODO and triplet) were evaluated. The current results suggest triplet lattice with long drift to be most promising (the baseline?).

• Scaling FFAG option for low energy muon acceleration (3.6-12.6 GeV) compatible with 200 MHz RF was proposed.

• Work in progress on all aspects of muon FFAG towards the Fermilab IDS meeting (beam dynamics and injection/extraction including kicker R&D)!

Summary