Towards a Common Proton Driver for a Neutrino Factory and a Spallation Neutron Source based on ISIS upgrade J. Pasternak, Imperial College, London / RAL STFC 08.04.10, IDS Meeting, Fermilab J. Pasternak

Introduction and ISS recommendations. Outline of the talk Introduction and ISS recommendations. Current options for NF proton driver. Towards proton driver compatible with neutron production (ISIS MW upgrade). Research on proton FFAGs. Summary 08.04.10, IDS Meeting, Fermilab J. Pasternak

Reference IDS Neutrino Factory Design nsFFAG 08.04.10, IDS Meeting, Fermilab J. Pasternak

ISS recommendations 08.04.10, IDS Meeting, Fermilab J. Pasternak

Updates to ISS recommendations Recently based on MERIT results, 100 μs delay time beetwen the bunches (200 μs total pulse duration) was propsed. HARP results suggest a possibility of lowering the proton energy down to even 3-4 GeV. J. Strait, NuFact’09 08.04.10, IDS Meeting, Fermilab J. Pasternak

Current options for NF proton driver Linac based (SPL) proton driver at CERN – the most advanced. Synchrotron(s)/FFAG based proton driver (green field solution) – under study at RAL. Project X based solution at Fermilab. Solution based on synergy between neutron spallation source (MW ISIS upgrade) and NF – idea shared by many people. Other solutions (multiple FFAGs, NS-FFAGs, etc.) – in the state of ideas. 08.04.10, IDS Meeting, Fermilab J. Pasternak

ISIS Upgrade Options (J. Thomason) Comments Beam Power (MW) Neutron Yield 1(a) Add 180 MeV Linac Technical Issues ~ 0.4 1.7 1(b) Add 800 MeV RCS Operational Issues ~ 0.5 2.0 1(c) Upgrades 1(a) + 1(b) Technical/Operational Issues ~ 0.9 3.8 2 Add ~ 3 GeV RCS Recommended 1st Upgrade 1 3.2 3 Add ~ 6 GeV RCS Technical/Cost Issues 5.6 4 Upgrades 1+2 or 1+3 ~ 2 – 6 ~ 6.4 – 16.8 5 400 – 800 MeV Linac + 3 GeV RCS Recommended 2nd Upgrade 2 – 5 6.4 – 16.0 6 1.334 GeV Linac + Accumulator Ring Good “Green Field” Option 18.8 08.04.10, IDS Meeting, Fermilab J. Pasternak

Possible RCS Rings (Chris Warsop, Grahame Rees, Dean Adams, Ben Pine, Bryan Jones, Rob Williamson) 08.04.10, IDS Meeting, Fermilab J. Pasternak

5SP RCS Ring Energy 0.8 – 3.2 GeV Rep Rate 50 Hz C, R/R0 367.6 m, 9/4 Gamma-T 7.2 h 9 frf sweep 6.1-7.1 MHz Peak Vrf ~ 750 kV Peak Ksc ~ 0.1 εl per bunch ~ 1.5 eV s B[t] sinusoidal 08.04.10, IDS Meeting, Fermilab J. Pasternak

Synergy with ISIS Upgrade Basic idea is to take 1-3 bunches at 3.2 GeV (1-2 MW) and accelerate it to achieve 4 MW in another RCS Fundamental question – is bunch compression possible? I believe, the answer is yes, but we need to work out the details! ISIS Upgrade work plan : collimation activation beam dump stripping space charge simulations Now mostly focused on a new linac at ~ 180 MeV. 08.04.10, IDS Meeting, Fermilab J. Pasternak

Common Proton Driver for the Neutron Source and the Neutrino Factory Based on MW ISIS upgrade with 0.8 GeV linac and 3.2 GeV RCS. Assumes a sharing of the beam power at 3.2 GeV between the two facilities Requires additional RCS machine in order to meet the power and energy needs of the Neutrino Factory Both facilities can have the same ion source, RFQ, chopper, linac, H- injection, accumulation and acceleration to 3.2 GeV Additional RCS ISIS MW upgrade 08.04.10, IDS Meeting, Fermilab J. Pasternak

Energy difference between bunches 2nd bunch s 1st bunch 3rd bunch GeV 200 us RCS keeps ramping unless dedicated „flat top” is created. Without this „flat top” ramp will creat ∆p/p of 1.3x10-4 between bunches. This needs to be taken into account. 08.04.10, IDS Meeting, Fermilab J. Pasternak

A possible solution for the common proton driver compatible with the ISIS MW upgrade 4-fold symmetry 3.2 GeV RCS is assumed here. Longitudinal emittance is larger, than in the „green field” solution. In order to deliver the beam for NF another RCS with bunch compression capability is needed. 3.2 GeV RCS Number of superperiods 4 Circumference 408.4 m Harmonic number RF frequency 2.4717-2.8597 MHz Betatron tunes ( QH, QV) (6.38, 6.3) Gamma transition 6.6202 Beam power at 3.2 GeV 5 MW for 4 bunches Bunch area 1.8 eVs Δp/p at 3.2 GeV 5.3 10-3 Injection / extraction energy 0.8 / 3.2 GeV Repetition rate 50 Hz Parameters of 3.2 GeV RCS (G. Rees) 08.04.10, IDS Meeting, Fermilab J. Pasternak

Preliminary design of the second RCS Number of superperiods 6 Circumference 708.788 m Harmonic number RF frequency 2.4717-2.5289 MHz Betatron tunes ( QH, QV) (7.81, 7.78) Gamma transition 7.9056 Beam power at 6.4 GeV 4 MW for 2 bunches Bunch area 1.8 eVs Δp/p at 3.2 GeV 5.3 10-3 Injection / extraction energy 3.2 / 6.4 [10.3] GeV Repetition rate 50 Hz Max B field in dipoles 1.2 T ( at 10.3 GeV) Length of long drift 12 m Lattice may allow for flexibility in gamma transition choice (even with beam). Ring is overdesigned in order to allow for 10.3 GeV. Optimised solution for 6.4 GeV is in preparation! Parameters of 6.4 (10.3) GeV RCS 08.04.10, IDS Meeting, Fermilab J. Pasternak

Assumptions for the common proton driver compatible with ISIS upgrade 3 bunches will be transfered from the booster RCS at 3.2 GeV and 2 MW. Acceleration by a factor of 2 is needed to get the necessary 4 MW (to 6.4 GeV). Some beam parameters at injection: - longitudinal emittance 1.8 eVs, - total bunch length 110 ns, - intensity 2.6x1013 protons/bunch, - 3 bunches, Options for the bunch compression to ± 2 ns rms bunch length (9 ns total assuming parabolic distribution): - adiabatic compression in the RCS, - „fast” phase rotation” in the RCS. - fast phase rotation in the dedicated compressor ring, 08.04.10, IDS Meeting, Fermilab J. Pasternak

Bunch compression scenarios Adiabatic compression requires a large voltage (33 MV if RF with h=6 is used). This calls for multiple RF systems with different harmonic numbers. Fast rotation may allow for smaller voltage, but fast change in voltage is needed (this requires low Q RF cavities). The „fast rotation” in the RCS takes several hundreds of turns. It is order of magnitude slower than it could be in the compressor ring. Is it too slow? Simulations are in progress! To keep the bunch rotated at top energy in the RCS for 200 us still 1.7 MV is needed at h=120. The scenario with fast rotation in the dedicated ring is most economic from the voltage poin of view. The final decision, which scenario to use, should be based on cost optimisation. 08.04.10, IDS Meeting, Fermilab J. Pasternak

Alternative Proton Driver layout 800 MeV H- linac NF target, 4 MW, 3 bunches RCS 3.2 GeV, 50 Hz RCS 6.4 GeV, 50 Hz Small Compressor Ring Neutron target, 2.6 MW Fast phase rotation in the dedicated compressor ring (most economic from the RF point of view, but another ring is needed). Bunches will be extracted one by one from the RCS. Compressor ring works above transition, but the rotation is very fast. The bunches in the RCS will wait uncompressed for 200 us, but they will come with different energies. We do not have a design for the compressor ring at the moment, but CERN design can be adopted. 08.04.10, IDS Meeting, Fermilab J. Pasternak

Dream machine, 100 Hz Proton Driver 100 Hz FFAG proton driver can deliver beam to 2 50 Hz facilities. Such machine can supply with beam the Neutrino Factory, PRISM and may be also Muon Collider (with some downstream accelerator). Advanced FFAG concept was recently introduced by Y. Mori in the context of muon acceleration and it should allow the room for H- injection. Y. Mori, FFAG’09 08.04.10, IDS Meeting, Fermilab J. Pasternak

Proton driver based on FFAGs Alternative 1) RCS or FFAG, 5.2 GeV, 50 Hz 440 MeV H- Linac Neutrino factory target, 4 MW, 50 Hz 2.6 GeV, 4 MW FFAG, 100 Hz Neutron production target, 2 MW, 50 Hz Needs 2 rings 100 – 200 Hz for booster FFAG operation should be possible 08.04.10, IDS Meeting, Fermilab J. Pasternak

RACCAM Machine Parameters k 5.15 Spiral angle 53.5° Rmax 3.46 m Rmin 2.8 m (Qx, Qy) (2.77, 1.64) Bmax 1.7 T pf 0.34 Injection energy 6-15 MeV Extraction energy 75-180 MeV h 1 RF frequency 1.9 – 7.5 MHz Bunch intensity 3109 protons Scaling size to 0.440-2.6 GeV: Rmax 19.4 m Rmin 15.9 m 08.04.10, IDS Meeting, Fermilab J. Pasternak

Spiral scaling superferric FFAG option (preliminary) k 11 Spiral angle 57.8° Rmax 11.09 m Rmin 10.02 m (Qx, Qy) (3.76, 1.12) Bmax 3 T pf 0.34 Injection energy 440 MeV Extraction energy 2600 MeV h 1 RF frequency 3.49 – 4.15 MHz RF voltage 117 kV/turn Rep rate 100 Hz Acceleration time 9 ms 08.04.10, IDS Meeting, Fermilab J. Pasternak

Radial scaling FFAG option –normal conducting (preliminary) k 191 Lattice type radial DFD triplet Rmax 95.49 m orbit excursion 0.6 m (Qx, Qy) (20.7, 7.58) Bmax 1.7 T pf 0.55 Drift length 3.2 m Injection energy 440 MeV Extraction energy 2600 MeV h 10 RF frequency 3.68 – 4.82 MHz RF voltage 1020 kV/turn Rep rate 100 Hz Acceleration time 9 ms 08.04.10, IDS Meeting, Fermilab J. Pasternak

Radial scaling FFAG option -superferric (preliminary) k 85 Lattice type radial DFD triplet Rmax 47.7 m orbit excursion 0.68 m (Qx, Qy) (12.18, 3.6) Bmax 3 T pf 0.45 Drift length 3.3 m Injection energy 440 MeV Extraction energy 2600 MeV h 5 RF frequency 3.71 – 4.81 MHz RF voltage 510 kV/turn Rep rate 100 Hz Acceleration time 9 ms 08.04.10, IDS Meeting, Fermilab J. Pasternak

NS-FFAG option (Preliminary design parameters) N of cells 64 Lattice type dublet R 34.6 m (Qx, Qy)/cell (0.269, 0.19) Bmax 1.7 T Magnet packing factor 0.4 E 0.3 - 2.5 GeV h 5 RF swing 4.5– 6.5 MHz Drift length 1.9 m T 37.6 Machine type Nonlinear Nonscaling FFAG Orbit excursion 0.2 m RF voltage 380 kV/turn Rep rate 100 Hz Acceleration time 9 ms More work is needed on this type of machines! Chromaticity correction is an issue! 08.04.10, IDS Meeting, Fermilab J. Pasternak

Summary and future plans Parameters needed for the Neutrino Factory Proton Driver are still evolving (pulse length, energy ?), but this will not chane to much in the design. Several solutions are advancing well to be able to meet the goal. In particular SPL based PD at CERN is the most advanced option! ISIS upgrade may be an interesting option for the UK to create a multiuser facility (for neutron production and NF). More work is needed on the bunch compression scenarios. Simulation work is now starting. Proton driver based on FFAG is very promising option, but still a lot of work is needed on this technology. 08.04.10, IDS Meeting, Fermilab J. Pasternak