1. 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
, IDS Meeting,
Fermilab
J. Pasternak

2. 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
, IDS Meeting,
Fermilab
J. Pasternak

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

4. ISS recommendations
, IDS Meeting,
Fermilab
J. Pasternak

5. 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
, IDS Meeting,
Fermilab
J. Pasternak

6. 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.
, IDS Meeting,
Fermilab
J. Pasternak

7. 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
, IDS Meeting,
Fermilab
J. Pasternak

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

9. 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
MHz
Peak Vrf
~ 750 kV
Peak Ksc
~ 0.1
εl per bunch
~ 1.5 eV s
B[t]
sinusoidal
, IDS Meeting,
Fermilab
J. Pasternak

10. 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.
, IDS Meeting,
Fermilab
J. Pasternak

11. 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
, IDS Meeting,
Fermilab
J. Pasternak

12. 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.
, IDS Meeting,
Fermilab
J. Pasternak

13. 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
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
Injection / extraction energy
0.8 / 3.2 GeV
Repetition rate
50 Hz
Parameters of 3.2 GeV RCS (G. Rees)
, IDS Meeting,
Fermilab
J. Pasternak

14. Preliminary design of the second RCS
Number of superperiods 6
Circumference m
Harmonic number
RF frequency
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
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
, IDS Meeting,
Fermilab
J. Pasternak

15. 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,
, IDS Meeting,
Fermilab
J. Pasternak

16. 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.
, IDS Meeting,
Fermilab
J. Pasternak

17. 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.
, IDS Meeting,
Fermilab
J. Pasternak

18. 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
, IDS Meeting,
Fermilab
J. Pasternak

19. 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
, IDS Meeting,
Fermilab
J. Pasternak

20. RACCAM Machine Parametersk
Spiral angle °
Rmax m
Rmin m
(Qx, Qy) (2.77, 1.64)
Bmax T pf
Injection energy MeV
Extraction energy MeV h
RF frequency – 7.5 MHz
Bunch intensity 109 protons
Scaling size to GeV:
Rmax m
Rmin m
, IDS Meeting,
Fermilab
J. Pasternak

21. Spiral scaling superferric FFAG option (preliminary)k
Spiral angle °
Rmax m
Rmin m
(Qx, Qy) (3.76, 1.12)
Bmax T pf
Injection energy MeV
Extraction energy MeV h
RF frequency – 4.15 MHz
RF voltage kV/turn
Rep rate Hz
Acceleration time ms
, IDS Meeting,
Fermilab
J. Pasternak

22. Radial scaling FFAG option –normal conducting (preliminary)k
Lattice type radial DFD triplet
Rmax m
orbit excursion m
(Qx, Qy) (20.7, 7.58)
Bmax T pf
Drift length m
Injection energy MeV
Extraction energy MeV h
RF frequency – 4.82 MHz
RF voltage kV/turn
Rep rate Hz
Acceleration time ms
, IDS Meeting,
Fermilab
J. Pasternak

23. Radial scaling FFAG option -superferric (preliminary)k
Lattice type radial DFD triplet
Rmax m
orbit excursion m
(Qx, Qy) (12.18, 3.6)
Bmax T pf
Drift length m
Injection energy MeV
Extraction energy MeV h
RF frequency – 4.81 MHz
RF voltage kV/turn
Rep rate Hz
Acceleration time ms
, IDS Meeting,
Fermilab
J. Pasternak

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

25. 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.
, IDS Meeting,
Fermilab
J. Pasternak