Challenges and Progress on the SB Horn Design NuFact 08 Valencia-Spain, June 30 - July 5 2008 Marcos DRACOS IN2P3/CNRS Strasbourg 30 June 2008 M. Dracos, NuFact08

Super-Beam Studies in Europe Super Proton Driver at CERN (SPL) Target and collector integration Hadron Collector Pulser Conclusion 30 June 2008 M. Dracos, NuFact08

Conventional Neutrino Beams proton beam Decay tunnel physics hadrons p p n target hadron collector (focusing) Detector 30 June 2008 M. Dracos, NuFact08

SPL Super-Beam Project H- linac 2.2, 3.5 or 5 GeV, 4 MW Accumulator ring + bunch compressor p proton driver Magnetic horn capture (collector) p Target hadrons n, m decay tunnel ~300 MeV nm beam to far detector to be studied in EURO WP2 30 June 2008 M. Dracos, NuFact08

Super Proton Linac at CERN SPL (http://doc.cern.ch/yellowrep/2006/2006-006/full_document.pdf) 30 June 2008 M. Dracos, NuFact08

SPL (CDR2) main characteristics Ion species H- Kinetic energy 3.5 GeV Mean current during the pulse 40 mA Mean beam power 4 MW Pulse repetition rate 50 Hz Pulse duration 0.57 ms Bunch frequency 352.2 MHz Duty cycle during the pulse 62 (5/8) % rms transverse emittances 0.4 p mm mrad Longitudinal rms emittance 0.3 p deg MeV Length 430 m butch compressor to go down to 3.2 s (important parameter for hadron collector pulsing system) (possible energy upgrade to 5 GeV could be the subject of a 3rd CDR) 30 June 2008 M. Dracos, NuFact08

Proton Target 300-1000 J cm-3/pulse Severe problems from : sudden heating, stress, activation Safety issues ! Baseline for Super-Beam is solid target, mercury is optional (baseline for NF) Extremely difficult problem : need to pursue two approaches : Liquid metal target (Merit experiment) Solid target (extensive R/D program at CCLRC and BNL) Envisage alternative solutions very challenging task 30 June 2008 M. Dracos, NuFact08

Proposed collection system proton beam horn 3.7 cm 8.5° 300 kA 4 cm target 16.6 cm 40 cm 80 cm taking into account the proton energy and collection efficiency, the target must be inside the horn 30 June 2008 M. Dracos, NuFact08

Proton Target some ideas cooling is a main issue… CC target Horn He IN He OUT Proposed rotating tantalum target ring (realistic?) Horn Helium cooling of target fluidised jet of particles Liquid Mercury (MERIT) Work at BNL and RAL Experience on T2K target (750 kW) very useful cooling is a main issue… 30 June 2008 M. Dracos, NuFact08

Hadron production Particles coming out of the target 2.2 GeV protons pT distribution not the same for all targets  the choice of the target could influence the hadron collection system (horn shape) pT From now on Hg will be considered 30 June 2008 M. Dracos, NuFact08

Hadron production uncertainties 2.2 GeV protons disagreement between models (Monte Carlo production, interaction and transport codes) p+ momentum more development is needed (simulation, measurements) 30 June 2008 M. Dracos, NuFact08

Proton Energy and Pion Spectra pions per proton on target. Kinetic energy spectrum 2.2 GeV: <Ek>=300MeV 3.5 GeV: <Ek>=378MeV interesting region for SPL SB Ekine (GeV) 1GeV 2GeV cos q hadrons boosted forward -1 1 30 June 2008 M. Dracos, NuFact08

Proposed design for SPL for pions coming out of the target 500 < pp < 700 MeV/c p+ angle p+ momentum horn region for a Hg target, 30 cm length, 15 mm (x1016/sec) relatively better collection when pproton the target must be inside the horn 30 June 2008 M. Dracos, NuFact08

Horn geometry 2.2 GeV proton beam : I = 300 kAmp I = 300 kAmp r(m) <pp> = 492 MeV/c <qp> = 55° 2.2 GeV proton beam : <pp> = 405 MeV/c <qp> = 60° I = 300 kAmp I = 300 kAmp r(m) r(m) B~1/r B~1/r B must be 0 B must be 0 4 cm 4 cm target target 30 cm z(m) 30 cm z(m) 30 June 2008 M. Dracos, NuFact08

Proposed design for SPL reflector Hg target proton beam horn 8.5° 40 cm 16.6 cm 4 cm 3.7 cm 20.3 cm 12.9° 80 cm 70 cm 600 kA 300 kA very high current inducing severe problems 30 June 2008 M. Dracos, NuFact08

Focusing Power 20% more p+ with reflector p+ transverse momentum (2.2 GeV option) p- are deflected 20% more p+ with reflector 30 June 2008 M. Dracos, NuFact08

Present Collectors In operation In operation completed (120 GeV) In operation (8 GeV) completed (12 GeV) CERN horn prototype for SPL Super-Beam (3.5 GeV) In operation (400 GeV) MiniBooNE NUMI CNGS K2K 30 June 2008 M. Dracos, NuFact08

Decay Tunnel Flux vs decay tunnel length (2.2 GeV option) short decay tunnel 30 June 2008 M. Dracos, NuFact08

More about previous studies S. Gilardoni: Horn for Neutrino Factory and comparison with a solenoid http://doc.cern.ch/archive/electronic/cern/preprints/thesis/thesis-2004-046.pdf http://newbeams.in2p3.fr/talks/gilardoni.ppt A. Cazes: Horn for SPL http://tel.ccsd.cnrs.fr/tel-00008775/en/ http://slap.web.cern.ch/slap/NuFact/NuFact/nf142.pdf http://slap.web.cern.ch/slap/NuFact/NuFact/nf-138.pdf 30 June 2008 M. Dracos, NuFact08

Main Technical Challenges Horn : as thin as possible (3 mm) to minimize energy deposition, Longevity in a high power beam (currently estimated to be 6 weeks!), 50 Hz (vs a few Hz up to now), Large electromagnetic wave, thermo-mechanical stress, vibrations, fatigue, radiation damage, Currents: 300 kA (horn) and 600 kA (reflector) design of a high current pulsed power supply (300 kA/100 μs/50 Hz), cooling system in order to maintain the integrity of the horn despite of the heat amount generated by the energy deposition of the secondary particles provided by the impact of the primary proton beam onto the target, definition of the radiation tolerance, integration of the target. 30 June 2008 M. Dracos, NuFact08

CERN horn prototype cooling system Current of 300 kA p Protons To decay channel B = 0 Hg Target B1/R initial design satisfying both, neutrino factory and super-beam 30 June 2008 M. Dracos, NuFact08

Energy deposition in the conductors MARS 48.2 kW 67kW 14.9kW 78.7kW +8kW from Joule effect 4MW, 2.2GeV proton beam (1MeV = 1.82 kW) 30 June 2008 M. Dracos, NuFact08

Localization of the energy deposition P (kW) target z (cm) z position of the particles coming out of the target z (cm) power deposited in the inner conductor as a function of z 30 June 2008 M. Dracos, NuFact08

Horn prototype …but Al not compatible with Mercury! For the horn skin AA 6082-T6 / (AlMgSi1) is an acceptable compromise between the 4 main characteristics: Mechanical properties Welding abilities Electrical properties Resistance to corrosion Same for CNGS …but Al not compatible with Mercury! tests done with: 30 kA and 1 Hz, pulse 100 ms long new tests to be done with 50 Hz Electrical and water connections 30 June 2008 M. Dracos, NuFact08

Power Supply for horn pulsing (major issue) values considered by CERN 30 June 2008 M. Dracos, NuFact08

3 Solutions proposed by ABB schematic versions at the capacitors ends option 1 at the capacitors ends option 2 in the charge option 3 s 30 June 2008 M. Dracos, NuFact08

Pulser simulation parameters magnetic field with electrical excitation (pulses 100 μs, 50 Hz) induced current distributions magnetic forces temperature and expansion distributions mechanical constraints and deformations (static+ dynamical), vibration modes non-linear magnetic and thermal effects in the calculation of mechanical constraints fatigue (and constraints from radiations if any) studies are needed to make the right choice, increase the system lifetime, reduce the cost 30 June 2008 M. Dracos, NuFact08

New ideas minimize power dissipation and radiation problems (pulser problems remain as before) use the advantage of the small horn size 2.5 m protons protons 2.5 m same decay tunnel Ø 3 m protons protons to be studied in EURO 2 options: send at the same time 1 MW per target/horn system send 4 MW/system every 50/4 Hz possibility to use solid target? 30 June 2008 M. Dracos, NuFact08

New (crazy) ideas to be studied in EURO superconducting wire (1 mm Ø) in superfluid He, DC power supply use a cryogenic horn (toroidal coil) blow gas He to avoid quenching problems No problem with power supply (pulser no more needed) Proton compressor no more needed to be studied in EURO 30 June 2008 M. Dracos, NuFact08

Conclusions Proton driver characteristics and target have to be fixed before horn design. Preliminary studies about horn focusing performance for SPL already exist. Collector studies are necessary to increase the system lifetime. Target/horn integration to be considered since the beginning. Multi-physics simulations would be very useful. New studies will start soon in the framework of EURO FP7 project. 30 June 2008 M. Dracos, NuFact08

End 30 June 2008 M. Dracos, NuFact08