1. ISIS Accelerator Division
Upgrades to the
ISIS Facility
John Thomason
ISIS Accelerator Division

2. ISIS Accelerators H ion source (17 kV) 665 kV H RFQ 70 MeV H linac
800 MeV proton
synchrotron
Extracted proton
beam lines
The accelerator produces a
pulsed beam of 800 MeV
(84% speed of light) protons
at 50 Hz, average beam current
is 230 A (2.9× 1013 ppp) therefore
184 kW on target (148 kW to TS-1 at 40 pps, 36 kW to TS-2 at 10 pps).

3. ISIS Upgrades Present operations for two target stations
Operational Intensities: 220 – 230 μA (185 kW)
Experimental Intensities of 31013 ppp (equiv. 240 μA)
DHRF operating well: High Intensity & Low Loss
Now looking at overall high intensity optimisation
Study ISIS upgrade scenarios
0) Linac and TS1 refurbishment
1) Linac upgrade leading to ~0.5 MW operations on TS1
2) ~3.3 GeV booster synchrotron: MW Target
3) 800 MeV direct injections to booster synchrotron: 2 – 5 MW Target
4) Upgrade 3) + long pulse mode option

4. ISIS MW Upgrade Scenarios
1) Replace ISIS linac with
a new ≈ 180 MeV linac
(≈ 0.5MW)
2) Based on a ≈ 3.3 GeV RCS fed by bucket-to-bucket transfer from ISIS 800 MeV synchrotron (1MW, perhaps more)
3) RCS design also accommodates multi-turn charge exchange injection to facilitate a further upgrade path where the RCS is fed directly from an 800 MeV linac (2 – 5 MW)

6. Power / Benefit / Cost Neutrons £ + Risk Power Upgraded TS1 TS2
Existing TS1
Power

7. ISIS Upgrades, Developments and R&D Work
We have on-going research and studies to
develop and fully exploit the machine
map out the best development routes
define principle upgrades
undertake basic R&D into physics of high intensity beams
Main focus presently ~180 MeV Injector Upgrade
summarised in the following pages
holistic optimisation including targets, neutronics, … “at the user”
Next steps
Exploring the possibilities for optimistic & less optimistic funding scenarios
Mapping out the best options for a 1-2 MW short pulse neutron source
Development and research on present machine

8. ISIS Injection Upgrade
New 180 MeV Linac
ISIS Injection Upgrade
70 MeV Linac
A New 180 MeV Injector
Update old linac
Increase beam power ~0.5 MW
Advantages
Reduces Space Charge (factor 2.6)
Chopped, Optimised Injection & Trapping
Challenges
Injection straight
Activation (180 MeV)
Space charge, beam stability, ....
MICE
800 MeV Synchrotron
TS1
TS2

9. ISIS Injection Upgrade Ring Physics Study
Snapshots of the work: challenges of getting 0.5 MW in the ISIS Ring
Injection
Longitudinal Dynamics
Injection Straight Modelling
Injection Straight
Analytical Work
Simulation Results
Test Distribution
Evolution of bunch
Foil temperatures
Injected distributions in (x,x’),(y,y’),(,dE)
RF Bucket
Variation of key parameters
Transverse & Full Cycle 3D Dynamics
Other Essentials: Activation, Diagnostics
Predicted Space Charge Limit
Single particle tune shift distributions at 0.5 MW
Activation vs Energy
Activation Measurements
Coherent Tune Shift and Resonance
Electron Cloud Monitor
Strip-line Monitor/Kicker
Accelerated distributions in (x,x’),(y,y’),(,dE)

10. Possible ≈ 3.3 GeV RCS Rings

11. Bucket-to-Bucket Transfer

12. 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

13. Accelerating Structures DTL/SC Elliptical Cavities Frequency
Grahame Rees,
Ciprian Plostinar ( )
800 MeV, Hˉ Linac Design Parameters
Ion Species H-
Output Energy
800 MeV
Accelerating Structures
DTL/SC Elliptical Cavities
Frequency
324/648 MHz
Beam Current
43 mA
Repetition Rate
30 Hz (Upgradeable to 50 )
Pulse Length
0.75 ms
Duty Cycle
2.25 %
Average Beam Power
0.5 MW
Total Linac Length
243 m

14. Design Options

15. Capacity upgrade scenarios
“Traditional” 3-stage MW upgrade scenario could be extended so 3.2 GeV RCS includes multiple extraction straights (or switchyard in EPB), with or without 800 MeV linac.
Stacked rings (as at CERN PSB) could be implemented as part of AC magnet replacement programme. Would require increased linac performance, but otherwise it is an engineering challenge to minimise off time during installation rather than an accelerator physics challenge, and would be a very predictable upgrade.

16. One synchrotron with several extraction straights?
Target station #1
Target station #2
“Efficient” footprint
Maximises total number of neutron beam lines
Flexible
Easy extraction of proton beams of different energies, intensities and repetition rates to suit wide range of neutron experiments
Linac
Synchrotron
Would need to drive trim quads. and steerers differently for different energies and intensities, but trim quads. and steerers are pulsed anyway, and so changing trim magnet current profiles from acceleration cycle to acceleration cycle should raise no fundamental complications.
Target station #4
Target station #3

17. Ring High Intensity Beam Studies on ISIS
Some of our R&D Studies
Half-integer intensity limit in proton rings
Using the ISIS ring to study halo formation
New simulation code: Set 3Di
Model losses, benchmark on ISIS
Simulation
Simulation
Measurement
(Y,Y)
Y profile
Y profile
Higher order loss effects and images
Investigating complex loss mechanisms
Head-tail instability
Key for high intensity proton rings
Image driven resonance
Vertical dipole motion along bunch on successive turns
Vertical difference signal
(along bunch, many turns)
Loss vs Q measurement
Samples along bunch
Turn 

18. Necessary Hardware R&D
High power front end (FETS)
RF Systems
Stripping Foils
Diagnostics
Targets
Kickers
etc.
To realise ISIS upgrades and generic high power proton driver development, common hardware R&D will be necessary in key areas:
In the neutron factory context SNS and J-PARC are currently dealing with
many of these issues during facility commissioning and we have a watching
brief for all of these
Active programmes in some specific areas