Upgrades to the ISIS Facility

ISIS Accelerator Division

John Thomason

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 apulsed beam of 800 MeV(84% speed of light) protonsat 50 Hz, average beam currentis 230 A (2.9× 1013 ppp) therefore184 kW on target (148 kW to TS-1 at 40 pps, 36 kW to TS-2 at 10 pps).

ISIS Upgrades

• Present operations for two target stationsOperational Intensities: 220 – 230 μA (185 kW)Experimental Intensities of 31013 ppp (equiv. 240 μA)DHRF operating well: High Intensity & Low LossNow looking at overall high intensity optimisation

• Study ISIS upgrade scenarios

4) Upgrade 3) + long pulse mode option

0) Linac and TS1 refurbishment1) Linac upgrade leading to ~0.5 MW operations on TS12) ~3.3 GeV booster synchrotron: MW Target3) 800 MeV direct injections to booster synchrotron: 2 – 5 MW Target

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)

1) Replace ISIS linac witha new ≈ 180 MeV linac(≈ 0.5MW)

ISIS MW Upgrade Scenarios

Power / Benefit / Cost£

+ Ri

skN

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ons

Power

TS2

Existing TS1

Upgraded TS1

ISIS Upgrades, Developments and R&D Work

• We have on-going research and studies todevelop and fully exploit the machinemap out the best development routesdefine principle upgradesundertake basic R&D into physics of high intensity beams

• Main focus presently ~180 MeV Injector Upgradesummarised in the following pagesholistic optimisation including targets, neutronics, … “at the user”

• Next stepsExploring the possibilities for optimistic & less optimistic funding scenariosMapping out the best options for a 1-2 MW short pulse neutron sourceDevelopment and research on present machine

ISIS Injection Upgrade

• A New 180 MeV Injector Update old linacIncrease beam power ~0.5 MW

• AdvantagesReduces Space Charge (factor 2.6)

Chopped, Optimised Injection & Trapping

• ChallengesInjection straightActivation (180 MeV)Space charge, beam stability, ....

New 180 MeV Linac

70 MeV Linac

800 MeV Synchrotron

TS1

TS2

MICE

2 3

1

2

pinc

r NQ

B

• Snapshots of the work: challenges of getting 0.5 MW in the ISIS Ring

Longitudinal Dynamics

Transverse & Full Cycle 3D Dynamics

Injection

Other Essentials: Activation, Diagnostics

Analytical Work Simulation Results

Test

Dis

trib

utio

n

RF Bucket Variation of key parameters

Evolution of bunch

Accelerated distributions in (x,x’),(y,y’),(,dE)

Predicted Space Charge Limit

Coherent Tune Shift and Resonance

Single particle tune shift distributions at 0.5 MW

Injected distributions in (x,x’),(y,y’),(,dE)Foil temperatures

Injection Straight

Injection Straight Modelling

Activation vs Energy Activation Measurements

Electron Cloud Monitor Strip-line Monitor/Kicker

ISIS Injection Upgrade Ring Physics Study

Possible ≈ 3.3 GeV RCS Rings

Bucket-to-Bucket Transfer

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

5SP RCS Ring

800 MeV, Hˉ Linac Design ParametersGrahame Rees,Ciprian Plostinar ( )

Ion Species H-

Output Energy 800 MeVAccelerating Structures DTL/SC Elliptical CavitiesFrequency 324/648 MHzBeam Current 43 mARepetition Rate 30 Hz (Upgradeable to 50 )Pulse Length 0.75 msDuty Cycle 2.25 %Average Beam Power 0.5 MWTotal Linac Length 243 m

Design Options

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.

One synchrotron with several extraction straights?

Flexible

Easy extraction of proton beams of different energies, intensities and repetition rates to suit wide range of neutron experiments

Linac

Synchrotron

Target station #1 Target station #2

Target station #4 Target station #3

“Efficient” footprint

Maximises total number of neutron

beam lines

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.

Head-tail instability Key for high intensity proton rings

New simulation code: Set 3DiModel losses, benchmark on ISIS

Ring High Intensity Beam Studies on ISIS

Half-integer intensity limit in proton ringsUsing the ISIS ring to study halo formation

(Y,Y)

Higher order loss effects and imagesInvestigating complex loss mechanisms

Image driven resonanceLoss vs Q measurement

Vertical dipole motion along bunch on successive turns

Simulation Simulation Measurement

Y profile

• Some of our R&D Studies

Y profile

Turn

Sam

ples

alo

ng b

unch

Vertical difference signal(along bunch, many turns)

• 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

Necessary Hardware R&D