, IDS Meeting, Fermilab J. Pasternak Challenges of muon FFAG: injection/extraction, beam dynamics and injection/extraction hardware design studies 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)

, IDS Meeting, Fermilab J. Pasternak 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). Injection/extraction hardware design studies (M. Aslaninejad, H. Witte, J.P.). Recent beam dynamics studies (J.P). Summary and future plans.

, IDS Meeting, Fermilab J. Pasternak Reference IDS Neutrino Factory Design nsFFAG

, IDS Meeting, Fermilab J. Pasternak 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

, IDS Meeting, Fermilab J. Pasternak It will be tested in EMMA soon, 2010!

, IDS Meeting, Fermilab J. Pasternak 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 chromaticity Corrected chromaticity

, IDS Meeting, Fermilab J. Pasternak Alternative solution - Nonliner NS-FFAG, S. Machida (2) Layout of FFAG with insertions

, IDS Meeting, Fermilab 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. FDFFFDD Septum Positive Muons Negative Muons Septum Kickers

, IDS Meeting, Fermilab J. Pasternak Injection – Triplet, D. Kelliher Kickers Septum Horizontal scheme is feasible in triplet. Scheme is less demanding with respect to special magnet needs. It uses m long kickers at T and the 2.4 m long septum at 2 T.

, IDS Meeting, Fermilab J. Pasternak D. Kelliher

, IDS Meeting, Fermilab J. Pasternak 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.

, IDS Meeting, Fermilab J. Pasternak Preliminary ideas for kicker R&D PS PFN 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 a single thyratron, but we can connect them in paralell. 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 (~ x~0.026 m), field T, I~ 9 kA, V~50 kV rise time 100 ns length 1 m Work in collaboration with H. Witte.

, IDS Meeting, Fermilab J. Pasternak Layout of the kicker system, H. Witte PFN-Pulse Forming Network Switches for 3 muon bunch trains (Thyratrons CX1925) Transmission line made of RG220 Magnet Termination

, IDS Meeting, Fermilab J. Pasternak Travelling wave kicker solution, H. Witte 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 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!

, IDS Meeting, Fermilab J. Pasternak Current pulses in 3 kicker sections – „travelling wave” using PSPice

, IDS Meeting, Fermilab J. Pasternak Pulses for 3 muon buch trainsseparated by 100 us.

, IDS Meeting, Fermilab J. Pasternak Kicker geometry, M. Aslaninejad Kicker apertures were checked recently! It seems, we still have margins

, IDS Meeting, Fermilab J. Pasternak J=4.4e7 A/m^2 I=26400 A Kicker magnet simulations in COMSOL 2D simulation to estimate the current, which is needed. Ferrite 3c11 is assumed for the yoke. Field quality is OK and it can still be improved.

, IDS Meeting, Fermilab J. Pasternak 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. This depends on the achievable thickness. HTS design is most likely needed to have higher quench limit. We need to work out losses at the septum. HTS screening may be added. Superconducting part is needed anyhow!

, IDS Meeting, Fermilab J. Pasternak Preliminary geometry of the normal conducting septum

, IDS Meeting, Fermilab J. Pasternak 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?

, IDS Meeting, Fermilab J. Pasternak What needs to be done: 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).

, IDS Meeting, Fermilab J. Pasternak Recent beam dynamics studies New soft edge model based on Enge function (up to 3rd order) was implemented into BeamOptics. Tunes in long drift triplet QHQH QVQV Almost no change of tunes between hard edge and soft edge models (fringe field length 0.1 m ). GeV Tune per cell

, IDS Meeting, Fermilab J. Pasternak Orbit shift due to extended fringe fields GeV 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.

, IDS Meeting, Fermilab J. Pasternak 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?). More beam dynamics studies are needed (chromaticity correction, errors, insertion). Substantial progress on the injection/extraction hardware design was achieved! In order to have a real design for the kicker system hardware tests are needed! Summary