R.G. – 17/03/2003 MORIOND Workshop 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

R.G. – 17/03/2003 MORIOND Workshop The SPL Working Group - Conceptual Design of the SPL, a High Power Superconducting Proton Linac at CERN, ed. M. Vretenar, CERN SPL web site: REFERENCES

R.G. – 17/03/2003 MORIOND Workshop (from CERN/SPC/811) Period of interest… LHC SPS Fixed target PSB & PS Long–term Scientific Programme at CERN

R.G. – 17/03/2003 MORIOND Workshop  To consolidate the injectors’complex and be ready to provide enough protons to all users Why ? For the approved physics programmes: PS supercycle for LHC PS supercycle for CNGS Remaining PSB & PS pulses to be shared between nTOF, AD, ISOLDE, East Hall, Machine studies…

R.G. – 17/03/2003 MORIOND Workshop  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. Why ? * For protons, brightness can only degrade along a cascade of accelerators  Any improvement has to begin at the low energy (linac) end For the approved physics programmes:

R.G. – 17/03/2003 MORIOND Workshop  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 ? Why ? For possible new physics programmes:

R.G. – 17/03/2003 MORIOND Workshop  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 Why a high energy linac ?

R.G. – 17/03/2003 MORIOND Workshop 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

R.G. – 17/03/2003 MORIOND Workshop SPL lay-out

R.G. – 17/03/2003 MORIOND Workshop SPL cross section

R.G. – 17/03/2003 MORIOND Workshop 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  s

R.G. – 17/03/2003 MORIOND Workshop Accumulator and Compressor Rings (“PDAC”) 2 synchrotron rings in the ex-ISR tunnel

R.G. – 17/03/2003 MORIOND Workshop SPL design 55 cryostats, 33 from LEP, 22 using components (68 total available) 49 klystrons (44 used in LEP)

R.G. – 17/03/2003 MORIOND Workshop Superconducting cavities in the LEP tunnel

R.G. – 17/03/2003 MORIOND Workshop Roadmap (1) 1) 3 MeV pre-injector2006 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)

R.G. – 17/03/2003 MORIOND Workshop 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 in  2 ) Intensity goal: 5x10 13 in the PSB (CNGS, ultimate LHC in one PSB pulse) Emittance: 0.4  mm mrad (rms, norm.) – (3 times smaller)

R.G. – 17/03/2003 MORIOND Workshop Linac4 layout Basic layout: 120 MeV, 80 m, 16 LEP klystrons Costing exercise still in progress (finished in fall?) First estimates at 60 MCHF source

R.G. – 17/03/2003 MORIOND Workshop Linac4 parameters Note: Linac4 is designed to be the first part of a future SPL  for 14% duty cycle & very low loss

R.G. – 17/03/2003 MORIOND Workshop Linac4 layout in South Hall to inflector & PSB

R.G. – 17/03/2003 MORIOND Workshop Linac4 R&D (low energy part of SPL) H- source, 25 mA 14% duty Collaboration with IPHI (CEA-IN2P3), building an RFQ that will come to CERN in 2006 Design and construction of a chopping line to be tested with beam in 2006 : - chopper structure - chopper pulser - 3 bunching cavities Construction of a hot model of CCDTL (Cell- Coupled Drift Tube Linac Chopper prototype CCDTL prototype (chopping=removing at low energy the linac bunches that would fall outside of the PSB bucket)

R.G. – 17/03/2003 MORIOND Workshop An example of R&D: the CCDTL CCDTL = Cell Coupled Drift Tube Linac, a simpler and cheaper alternative to DTL for energy > 40 MeV quadrupole coupling cell DTL-like accelerating cell (2 or 3 drift tubes) CCDTL prototype

R.G. – 17/03/2003 MORIOND Workshop 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.)

R.G. – 17/03/2003 MORIOND Workshop H- source, 25 mA 14% duty cycle Fast chopper (2 ns transition time) Normal conducting (NC) cavities Superconducting (SC) cavities:  =0.52, 0.7, 0.8 Beam dynamics studies aiming at minimising losses (activation!) Vibrations of SC cavities: analysis, compensation schemes. RF system: 352 MHz (LEP klystrons) SPL R&D (high energy part)

R.G. – 17/03/2003 MORIOND Workshop R&D topics – low  SC cavities The  =0.7 4-cell prototype  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 = 10 9  Bulk Nb or mixed technique for  =0.52 (one 100 kW tetrode per cavity) (E. Chiaveri, R. Losito)

R.G. – 17/03/2003 MORIOND Workshop R&D topics - vibrations Effect on field regulation Effect on the beam  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) + possible chaotic effects (J. Tückmantel)

R.G. – 17/03/2003 MORIOND Workshop 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 ( MeV, 0.5 nA/m ( 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: 1.H- stripping  < 0.01 W/m in quads for an off-axis beam 2.Residual gas  < mbar, 2 GeV (but ) 3.Halo scraping  more delicate, requires: large apertures (SC is good!) careful beam dynamics design

R.G. – 17/03/2003 MORIOND Workshop Summary At CERN:  High intensity protons beams will remain a strong asset beyond 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.

R.G. – 17/03/2003 MORIOND Workshop Conclusion / Recommendation A large effort in R. & D. is required, with very similar goals and technologies than for EURISOL  Close coordination between teams is absolutely necessary to share the effort and present a coherent set of requests to the E.U..