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Proton driver front end test stand Update / UKNF Meeting / Sep-04

Proton driver front end test stand Update / UKNF Meeting / Sep-04 David Findlay ISIS Accelerator Division. STVLTVS EST QVI ACCELERATORIBVS CVRANDIS VICTVM QVAERIT. Why a front end test stand? Prove key elements of high power proton accelerators

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Proton driver front end test stand Update / UKNF Meeting / Sep-04

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  1. Proton driver front end test standUpdate / UKNF Meeting / Sep-04 David FindlayISIS Accelerator Division STVLTVS EST QVI ACCELERATORIBVS CVRANDIS VICTVM QVAERIT

  2. Why a front end test stand? • Prove key elements of high power proton accelerators • Applications Generic Spallation neutron sources Neutrino factories Transmutation machines Tritium generators Energy amplifiers Training / Young people / Real hardware Specific ISIS upgrades UKNF UK academic accelerator community

  3. ISIS • World’s leading spallation neutron source • Natural wish to stay at or near front • Upgrade strategies important • UK Neutrino Factory • Strong drive from UKNF community • PPARC support for proton driver R&D • Synergies with possible ISIS upgrades • UK academic community • Imperial-CCLRC joint appointment • Extend university accelerator centres to protons

  4. Alternatively • Condensed matter studies • High energy physics • Reintroducing accelerators into UK universities

  5. High energy physics in a nutshell?

  6. What’s in a front end? • Ion source, LEBT, RFQ and beam chopper • Why does it matter? • Where beam quality set for entire machine • But suitable front ends not yet demonstrated • ISIS 0.16/0.24 MW Now • PSI 0.75 MW Now, but CWSNS 1 MW Near future • JPARC 1 MW Near future • NF 4 MW — a big step! Further away • [ISIS 1, 2, 5 MW Plans]

  7. Proton driver front end test stand at RAL • ISIS Accelerator Division CCLRC/ASTeC • Imperial College PPARC • Warwick University PPARC • EU support • Ion sources HPRI-CT-2001-50021 • Beam chopper HIPPI/CARE/ESGARD

  8. 75 keV 2½ – 3 MeV H– ion source 60 mA2 ms RFQ234 MHz Bunch + accel-erate Chopper Switch in 2 ns for~0.1 ms LEBT Match ion source to RFQ Beam stop Diagnostics Transverse emittances,energy & energy spectra,bunch widths, halo, ... Block diagram of RAL front end test stand

  9. Building R8 5 6 Site Services workshop and offices 7 27½ Vacuum lab. 12 Lab. / Old test stand control room Old RFQ test stand area 5 m 12 1½ 4½ Corridor 7 7 Synchrotron RF test area 5½ 10 Present state of R8 — with old RFQ test stand area

  10. Building R8 5 6 Site Services workshop and offices 7 27½ Mag. spectr. 12 5 m Ion source LEBT RFQ Chopper Diagnostics 12 1½ 4½ 7 RF driver area 7 Synchrotron RF test area 5½ 10 Proposed reconfigured R8 for new test stand

  11. RFQ 0.7 MeV Linac 70 MeV First beam through new ISIS front end and linac8 September 2004

  12. Building R8 5 6 Site Services workshop and offices 7 27½ Mag. spectr. 12 5 m Ion source LEBT RFQ Chopper Diagnostics 12 1½ 4½ 7 RF driver area 7 Synchrotron RF test area 5½ 10 ~20 metres Front end test stand in R8

  13. Building R8 Building R9 Mag. spectr. Ion source LEBT RFQ Chopper Diagnostics Linac Possibility of extension into R9

  14. Infrastructure issues • Optimum compromise amongst expenditure, progress, infrastructure specification, and provision for future • E.g. “Rolls-Royce” electricity & water infrastructures would prejudice progress • Purpose of front end test stand? • Generic • For demonstrating production of suitable beams • Not necessarily front end of actual HPPA • Get as far as can as economically as possible while not blocking future up-rating

  15. Example: RF for RFQ • 75 keV  2.5 MeV needs 1–2 MW RF driver • 2 ms, 50 pps 10% duty factor • 100–200 kW RF mean power • anode dissipation also ~100–200 kW • TH116 RF valve (ISIS linac) Panode 70 kW max. • TH628 (Diacrode) necessary — largely unknown • 2 ms, 10 pps 2% duty factor • 20–40 kW mean power •  Can use existing ISIS linac RF systems (buying ahead key components of ~50 TH116s) ~400 kW PSU

  16. Elements of front end test stand • H– ion source — Development requiredBased on ISIS H– ion source • LEBT — Revision of new ISIS LEBT sufficient • RFQ — Base on ISIS & ESS 4-rod RFQsMost expensive item: ~1–2 MW RF driver • Beam chopper — Development requiredBased on ESS concept

  17. The ISIS Ion Source Penning H– ion source Surface plasma source (SPS) 35 mA through 0.6 × 10 mm aperture, ~600 mA/cm2 200–250 s, 50 Hz,~1% duty cycle 20 ml/min H2 3 g/month Cs ~0.17  mm-mrad (rms)

  18. Development goals • Double output current, 35 mA  70 mA • Increase pulse length 200 µs  1–2 ms • Improve emittance • Maximise lifetime • Dedicated Ion Source Development Rig (ISDR) constructed • ISDR “duplicates” equipment on the ISIS, and allows ion source development work without affecting ISIS operations

  19. Experimental “top loading” ion source

  20. Thermal Modelling 3D Finite Element Model of the Ion Source using ALGOR software Experimental test rig set up on the ISDR to measure radiation functions and convection coefficients to be applied to the surfaces of the model Computational fluid dynamic modelling of the cooling channels was conducted by Oxford University to validate the cooling system

  21. 600 520 440 360 280 200 Comparison of calculated steady state temperatures with measurements ISIS Model Diff. thermo- thermo- max. couple couple surface Anode 400–600°C 458°C 488°C 30°C Cathode 440–530°C 496°C 593°C 97°C Source 390–460°C 428°C 446°C 27°C body

  22. Transient results for present ion source Cathode Surface T= 51 ºC Head HTC 250 Wm-2C-1 (1.5ms-1 Air Flow) Flange HTC 450 Wm-2C-1 ( 0.08Lmin-1 Water) Anode Surface T= 30 ºC 500 μs duty

  23. Transient results for present ion source — double duty Cathode Surface T= 73 ºC Head HTC 1200 Wm-2C-1 (7.2ms-1 Air Flow) Flange HTC 500 Wm-2C-1 ( 0.09Lmin-1 Water) Mica Removed Anode Surface T= 39 ºC 1000 μs duty

  24. Double size ion source — quadruple duty Cathode Surface T= 51 ºC Head HTC 600Wm-2C-1 (3.6ms-1 Air Flow) Flange HTC 250 Wm-2C-1 ( 0.04Lmin-1 Water) Mica Removed Anode Surface T= 28 ºC 2000 μs duty

  25. Recent results — lengthening duty cyclepresent ion sourcekeeping cooling constant Measured on development rig Model predictions

  26. Electromagnetic modelling — MAFIAExtraction region and 90° sector magnet

  27. 17 keV normalised Hrms= 0.03  mm mrad Vrms= 0.16  mm mrad 0T 0.5T 0T 0.5T 17 keV normalised Hrms= 0.04  mm mrad Vrms= 0.16  mm mrad Inadequately terminated sector magnet field— present arrangement Correctly terminated sector magnet field

  28. Terminated Extract Terminated Pierce Extract 17 keV normalised Hrms= 0.07  mm mrad Vrms= 0.05  mm mrad 17 keV normalised Hrms= 0.04  mm mrad Vrms= 0.16  mm mrad 17 keV normalised Hrms= 0.03  mm mrad Vrms= 0.03  mm mrad Extract Geometry Modifications Existing Extract

  29. New pole pieces, cold box insert, and extract electrodes manufactured

  30. Emittance measurements on ISDR Standard extract geometry H = 0.97  mm mrad V = 0.94  mm mrad Pierce extract geometry H = 0.62  mm mrad V = 0.73  mm mrad

  31. Future ion source work • Increase extraction potential to 25 kV • Variable Penning field studies • Deal with hydrogen demand issues • ×2 size source • Lifetime studies • [End]

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