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The SPL* at CERN
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  1. The SPL* at CERN OUTLINE • Why ? • How ? • Roadmap • Summary * SPL = Superconducting Proton Linac A concept for improving the performance of the proton beams at CERN, ultimately based on a high-energy Superconducting Linear Accelerator 1

  2. The SPL Working Group REFERENCES - Conceptual Design of the SPL, a High Power Superconducting Proton Linac at CERN, ed. M. Vretenar, CERN 2000-012 - SPL web site: http://cern.web.cern.ch/CERN/Divisions/PS/SPL_SG/ 2

  3. Period of interest… Long–term Scientific Programme at CERN (from CERN/SPC/811) LHC SPS Fixed target PSB & PS 3

  4. Why ? For the approved physics programmes: • To consolidate the injectors’complex and be ready to provide enough protons to all users PS supercycle for LHC PS supercycle for CNGS Remaining PSB & PS pulses to be shared between nTOF, AD, ISOLDE, East Hall, Machine studies… 4

  5. Why ? For the approved physics programmes: • Because higher beam performance (brightness*) will be first, welcome, and later, necessary to: • Reliably deliver the ultimate beam actually foreseen for LHC, • Reduce the LHC filling time, • Increase the proton flux onto the CNGS target, • Increase the proton flux to ISOLDE, • Prepare for further upgrades of the LHC performance beyond the present ultimate. * For protons, brightness can only degrade along a cascade of accelerators Þ Any improvement has to begin at the low energy (linac) end 5

  6. Why ? For possible new physics programmes: • Neutrino Physics with a successive set of instruments of increasing complexity: • Super-Beam (= conventional but very intense proton beam) generating an intense neutrino flux towards a remote (~ 150 km) underground experiment • “beta” beams generating electron neutrinos and anti-neutrinos towards the same underground experiment • Neutrino Factory sending neutrinos to very remote (up to 3000 km) underground experiment(s) • Nuclear Physics with a Radio-Active Ion Beam Facility of the second generation ? 6

  7. Why a high energy linac ? • For improvements of the present accelerator complex, the energy of the linac injecting into the first synchrotron has to be increased (50 MeV today) • Comparing a Linac + fixed energy rings set-up with a 2-3 GeV Rapid Cycling Synchrotron (RCS) : • The linac set-up can accommodate more users since its beam power can be increased, • Some users prefer the long beam pulse delivered by a linac, • The RCS construction cost could be smaller, but this is moderated by the availability of the LEP RF equipment which a linac will re-use • Linac maintenance is likely to require less manpower 7

  8. A large inventory of LEP RF equipment is available (SC cavities, cryostats, klystrons, waveguides, circulators, etc.) which can drastically reduce the cost of construction LEP cavity modules in storage Stored LEP klystrons 8

  9. SPL lay-out 9

  10. SPL cross section 10

  11. SPL design parameters For neutrino physics, it has to be compressed with an Accumulator and a Compressor ring into 140 bunches, 3 ns long, forming a burst of 3.3 ms 11

  12. Accumulator and Compressor Rings (“PDAC”) 2 synchrotron rings in the ex-ISR tunnel 12

  13. SPL design 55 cryostats, 33 from LEP, 22 using components (68 total available) 49 klystrons (44 used in LEP) 13

  14. Superconducting cavities in the LEP tunnel 14

  15. Roadmap (1) 1) 3 MeV pre-injector 2006 at CERN On-going collaboration with CEA (Saclay-F) and CNRS (Orsay-F) to build, test and install at CERN a 3 MeV pre-injector based on the “IPHI” RFQ (Injecteur de Protons de Haute Intensité) 15

  16. Roadmap (2) 2) Linac 4 in the South Hall of the CERN PS E.U. support for R. & D. on crucial components is being requested in the frame of a Joint Research Activity on “High Intensity Pulsed Proton Injectors” (HIPPI). • Goal: improved performance of the proton beam for the approved physics programme (LHC, CNGS, ISOLDE, AD,…) at a minimal cost • Principles: • normal conducting linac (120 – 160 MeV / H-) which can later serve as the low energy part of the SPL • replace (and improve upon) the present linac 2 (50 MeV / protons) as the proton source at CERN • minimise cost by re-using buildings and LEP RF equipment Main characteristics • Energy: originally 120 MeV. Now increased to 160 MeV for the needs of the PSB (= factor 2 inbg2 ) • Intensity goal: 5x1013 in the PSB (CNGS, ultimate LHC in one PSB pulse) • Emittance: 0.4pmm mrad (rms, norm.) – (3 times smaller) 16

  17. Linac4 layout source Basic layout: 120 MeV, 80 m, 16 LEP klystrons Costing exercise still in progress (finished in fall?) First estimates at 60 MCHF 17

  18. Linac4 parameters Note: Linac4 is designed to be the first part of a future SPL  for 14% duty cycle & very low loss 18

  19. Linac4 layout in South Hall to inflector & PSB 19

  20. Linac4 R&D (low energy part of SPL) Construction of a hot model of CCDTL (Cell-Coupled Drift Tube Linac H- source, 25 mA 14% duty CCDTL prototype • Design and construction of a chopping line to be tested with beam in 2006: • chopper structure • chopper pulser • 3 bunching cavities Collaboration with IPHI (CEA-IN2P3), building an RFQ that will come to CERN in 2006 (chopping=removing at low energy the linac bunches that would fall outside of the PSB bucket) Chopper prototype 20

  21. An example of R&D: the CCDTL CCDTL = Cell Coupled Drift Tube Linac, a simpler and cheaper alternative to DTL for energy > 40 MeV coupling cell quadrupole DTL-like accelerating cell (2 or 3 drift tubes) CCDTL prototype 21

  22. Roadmap (3) 3) Full performance / high power proton injector / driver • Preliminary step: • Design optimisation / successful hardware prototyping • Next steps: • Positive decision for a physics programme needing such a driver • Attribution of resources for machines, targets and experiments • Authorisation of construction (INB procedure etc.) 22

  23. SPL R&D (high energy part) H- source, 25 mA 14% duty cycle Normal conducting (NC) cavities Fast chopper (2 ns transition time) Superconducting (SC) cavities: b=0.52, 0.7, 0.8 Beam dynamics studies aiming at minimising losses (activation!) RF system: 352 MHz (LEP klystrons) Vibrations of SC cavities: analysis, compensation schemes. 23

  24. R&D topics – low b SC cavities • CERN technique of Nb/Cu sputtering • excellent thermal and mechanical stability (important for pulsed systems) • lower material cost, large apertures, released tolerances, 4.5 K operation with Q = 109  Bulk Nb or mixed technique for b=0.52 (one 100 kW tetrode per cavity) (E. Chiaveri, R. Losito) The b=0.7 4-cell prototype 24

  25. R&D topics - vibrations + possible chaotic effects (J. Tückmantel) Effect on the beam Effect on field regulation • vector sum feedback can compensate only for vibration amplitudes below 40 Hz • possible remedies: piezos and/or high power phase and amplitude modulators (prototype ordered - H. Frischholz) 25

  26. R&D topics – loss management For hands-on maintenance, the generally accepted figure is a particle loss < 1 W/m For the SPL, 10 nA/m (10-6/m) @ 100 MeV, 0.5 nA/m (10-7/m) @ 2 GeV Present Linac2 loss level (transfer line):  25W/80m = 0.3 W/m (but hot spots at > 1 W/m !) • Mechanism of beam loss in the SPL: • H- stripping  < 0.01 W/m in quads for an off-axis beam • Residual gas  < 0.03 W/m @ 10-8 mbar, 2 GeV (but 0.25 W/m @ 10-7) • Halo scraping  more delicate, requires: • large apertures (SC is good!) •  careful beam dynamics design 26

  27. Summary At CERN: • High intensity protons beams will remain a strong asset beyond 2010. Improving their performance is a logical and necessary path for the approved physics programme. • The SPL would be a high potential upgrade, preparing for the addition of new physics goals. 27

  28. Conclusion / Recommendation A large effort in R. & D. is required, with very similar goals and technologies than for EURISOL ß Close coordination between teams is absolutely necessary to share the effort and present a coherent set of requests to the E.U.. 28