ISIS Accelerator Division ISIS Upgrade Options John Thomason ISIS Accelerator Division

0.24 MW ISIS • Assumes an optimised 2RF system giving 300 µA in the synchrotron • 4/5 pulse pairs to TS-1 (192 kW) and 1/5 pulse pairs to TS-2 (48 kW) • Must keep beam to TS-2 for the foreseeable future

Upgrade Options Option 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 • Upgrade routes for ISIS are summarised in the table above. All designs are to be developed primarily for an optimised neutron facility, and should provide provision of an appropriate proton beam to the newly built TS-2. The list here is not exhaustive, but presents the main, reasonable routes that would provide a major boost in beam power. Primary considerations are the cost relative to a new facility and the impact on ISIS operations.

Linac Upgrade • Replaces oldest and probably most vulnerable part of ISIS accelerators • Increased energy (up to 180 MeV) gives increased intensity in synchrotron and more beam to target • Similar designs are already available e.g. CERN Linac4, J-PARC • Would require a new building and reconfiguration of the TS-1 neutron and muon targets

(Steve Jago, Stuart Birch, Adrian McFarland) 180 MeV Injection (Steve Jago, Stuart Birch, Adrian McFarland) HEDS Line - DC Dipoles and Quadrupoles Vertical “Sweeper” - Pulsed Dipole Injection Septum - High Current DC Dipole Injection Dipoles - 4 Pulsed Dipoles - Closed Orbit Bump Stripping Foil - Beam rigidity - Aperture - Increased field/current/voltage - Stripping efficiency - Lifetime Single Turn / Ferrite Core 155 mm Aperture Peak Field ~ 0.11 T for 70 MeV Peak Current ~ 12200 A Rise / Fall Time ~ 80 µs Flat-top ~ 400 µs

70 MeV Magnetic Model Calculated current - 12195 A Actual current – 12200 A Calculated voltage - 175 V Actual voltage ~ 250 – 300 V

180 MeV Magnetic Model Peak field ~ 0.18 T for 180 MeV Calculated current - 20725 A Calculated voltage - 290 V

Power Supply I > 21000 A Rise/fall ~ 80 µs Flat-top ~ 400 µs Possibility of tuneable gradient on “flat-top” Current waveform Voltage waveform

180 - 800 MeV Acceleration (Chris Prior) Initial calculations (done in 2003) show that 180 MeV injected beam should be cleanly accelerated to 800 MeV in the ISIS ring at intensity levels giving 0.5 MW on target There should already be enough RF acceleration available in the ISIS ring to accommodate this (calculations were better optimised for fundamental only rather than dual harmonic acceleration) Did not include transverse effects Requires beam chopping

Recommended MW Upgrades • Based on a ~ 3 GeV RCS fed by bucket-to-bucket transfer from ISIS 800 MeV synchrotron (1MW) • RCS design also accommodates multi-turn charge exchange injection to facilitate a further upgrade path where the RCS is fed directly from a 800 MeV linac (2 – 5 MW)

RCS Rings (Chris Warsop, Grahame Rees, Dean Adams, Ben Pine, Bryan Jones, Rob Williamson)

Outline Work Plan Main topics to cover Pull work together: comparisons Longitudinal Calculations/Simulations for candidate FI Rings, then MTI Build up MTI simulation 2D to 3D, then acceleration Model Injection Magnet and Region (CST based, as profile monitors) Transverse Space Charge and Working Point, Correction Schemes Lattice Optimisation, Analysis, Correction Instabilities: standard checks, e-p work Collimation: outline designs, full simulations with activation Review all main systems Pull work together: comparisons Best lattice and ring size; RF and MMPS combinations Estimated losses and activation Started Next Uncertain Cover

Simulation Hardware SCARF: Linux only: Red Hat Enterprise 4.4 GNU, Intel, PGI compilers for Fortran, C, java AMD, Intel, ATLAS, Goto BLAS, BLACS, ScaLAPACK, FFTW libraries MPI is the parallel framework 3 main sections of cluster Can choose section or just submit Access by grid certificate Obtained from e-Science locally ORBIT MPI installed as a module Synchrotron Physics and Intense Beams Groups have purchased 17 nodes = 136 processors Will be available soon after 16th February Larger jobs possible using normal SCARF queues Will still maintain access to 16 processor development rig

Simulation Codes ORBIT MPI: Strip-foil injection, including painting and foil scattering RF focusing and acceleration Transport through various magnetic elements Longitudinal and transverse impedances Longitudinal, transverse, and three-dimensional space charge forces Collimation and limiting apertures Calculation of many useful diagnostic quantities Parallel version of ORBIT available on SCARF Set Development (Ben Pine): Parallel version of Set running on SCARF Currently 2D with space charge Work advancing on adding 2.5D Main goals this year: - Benchmarking against standards - Adding new 2D boundary conditions - Starting to think about full 3D And: Add other software Add other accelerator codes

Visualization e-Science Application Development Group Parallel visualization cluster Expertise in data mining, computational steering Could use existing tools if data put into nexus data format http://www.nexusformat.org/Main_Page Simulation hardware, code and visualization resources on site to do the world-class accelerator physics required for ISIS upgrades

(Grahame Rees, Ciprian Plostinar) 800 MeV H- Linac (Grahame Rees, Ciprian Plostinar) Design Parameters: Beam power for 2 MW, 30 Hz, 3.2 GeV RCS: 0.5 MW Beam pulse current before MEBT chopping: 43.0 mA Beam pulse current after MEBT chopping: 30.0 mA Number of injected turns for 370 m RCS: ~500 turns Beam pulse duration at the 30 Hz rep rate; ~700.0 μs Duty cycle for the extent of the beam pulse; ~2.1 % MEBT(in) normalised rms emittances: 0.25, 0.375 (π) mm mr MEBT(out) normalised rms emittances: 0.292, 0.42 (π) mm mr Cell equipartition transv/long phase shift ratios: 1.40

All options have the same 324 MHz, 74.8 MeV stage 1: Design Options All options have the same 324 MHz, 74.8 MeV stage 1: IEBT DTL MEBT RFQ 74.8 MeV Options F (MHz) Stage 2 Stage 3 Stage 4 1 648 ScL 1 ScL 2 ScL 3 2 648 CCL ScL 2 ScL 3 3 972 ScL d ScL e ScL c 4 324-?-972 ScL a ScL b ScL c ~200 MeV 800 MeV

Beam Envelopes for Option 2 DTL CCL (193 MeV) ScL (800 MeV)

800 MeV H- Linac Studies Still Needed MEBT comparisons Selection of option ScLa/b spoke cavities? Refine stage matchings Linac error effect study Effect of failed cavities Ring collimation line