WP2 (SuperBeam) Targets Status of Work Programme Chris Densham

SB Targets Talk Outline Outline of issues for target + horn + integration Proposed baseline Graphite target (Longhin / Zito) Implementation of T2K graphite target Powder jet study Possible study path: target technology progression

SPL-SB Initial baseline Schematic: Neutrino Factory Baseline Schematic: Initial SPL-SB baseline used same liquid mercury jet target as NF/MC baseline

Pulsed beam interactions with mercury Contained mercury Free mercury jet MERIT experiment: Beam-induced splashing of mercury jet (c.200 J/cc) Damping of splashes due to magnetic field observed as predicted - Analysis of MERIT data ongoing Cavitation damage in wall of Hg target container after 100 pulses of 19 J/cc proton beam (WNR facility at LANL)

Can a free mercury jet be combined with a magnetic horn? Magnetic horns are typically manufactured from aluminium alloy Mercury is commonly known to cause severe and rapid erosion of aluminum and its alloys Is it possible to protect a horn with a material compatible with liquid mercury? If so, would the jet be ‘open’ or ‘contained’? Corrosion problem is in addition to the shock wave problem B=0 inside horn, ie no magnetic damping of mercury jet as in MERIT experiment Combination of a mercury jet with a magnetic horn would appear to be extremely difficult – not proposed to study this any further within this WP

If not mercury, how about graphite? Graphite is conventional(!) for conventional neutrino beams Easier to combine with a magnetic horn (e.g. T2K target) Questions include: How does pion production for C compare with Hg? Can a static graphite target dissipate heat from a 4 MW beam? What is the expected lifetime for a graphite target in a 4 MW beam?

Target itself is not the only difficulty – consider magnetic horn Magnetic horn collector system requires a major step in performance beyond current state-of-the-art Challenges include: 50 Hz operation Secondary particles from target interacting with inner conductor

Comparison of SPL horn with existing examples (Dracos) In operation (120 GeV) In operation (8 GeV) completed (12 GeV) CERN horn prototype for SPL Super-Beam (3.5 GeV) In operation (400 GeV) MiniBooNE 17 Dec. 2008 M. Dracos, EUROnu-WP2 NUMI CNGS K2K

New ideas (Dracos/ ref. Sievers) 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 (only one pulser): send at the same time 1 MW per target/horn system send 4 MW/system every 50/4 Hz possibility to use solid target?

Proposed SB baseline (as of 16 Dec 2008): The parallel 4-horn and 4-target system Potential solution to difficulties with both target and horn NB Horn operation at 12 Hz only factor of ≈ 2.5 x MiniBoone 4 static, solid (graphite) targets operating with 1 MW beam power each may be feasible (C.f. T2K at 0.75 MW beam power)

New investigation of graphite target (Longhin) 120 (140) cm 190 (220) cm 80 cm 40.6 cm 7.4 cm Study of 2λ Hg target performance by A. Cazes / M. Zito 140 cm 220 cm 80 cm New study of 2λ C target by A. Longhin / M. Zito

Pion multiplicities vs Energy (Longhin): C and Hg normalized to 4 MW fixed power pi+ 1.13 × 1016 pot/s at 2.2 GeV 0.71 × 1016 pot/s at 3.5 GeV 0.55 × 1016 pot/s at 4.5 GeV 0.31 × 1016 pot/s at 8.0 GeV More pi+ from carbon at low energy, gets ~ equal at about 8 GeV pi- yield similar (a bit better with Hg)‏ for carbon r=1 looks preferable pi-

Pion multiplicities vs Energy (Longhin): C and Hg restrict to pions producing neutrinos around the oscillation maximum 500 < p < 700 MeV normalized to 4 MW fixed power pi+ 0.5<p<0.7 GeV More pi+ from carbon at low energy, gets ~ equal at about 4 GeV pi- yield similar at low energy (better with Hg at higher energies)‏ pi- 0.5<p<0.7 GeV

Graphite vs Mercury energy deposition: GEANT4 GEANT4 (hadronic “QGSP physics list”)‏ Mean energy deposition vs Ek(p)‏ Power deposited = 4 MW * <Edep> / Ek(p)‏ Power deposited in target: Hg: ~ 1 - 0.6 MW for Hg C : ~ 0.8 - 0.1 MW considerably lower for Carbon

Conclusions (Longhin) Getting experience with the SPL-Fréjus neutrino fluxes and physics reach. Software tools are ready / working and being updated. [...] Graphite target option simulated. Looks appealing. W.r.t. Hg: much lower energy deposition (but dissipation more difficult...)‏ lower K contamination (~-30/40% for E = 2-5 GeV)‏ much lower neutron flux (~ -15 X)‏ higher or equal pion yield (depending on E) comparable neutrino fluxes despite collection system was not yet optimized for longer target technically less challenging (see T2K He cooled target)‏

A few parameters for graphite targets: Comparisons between T2K and SPL-SB Beam energy GeV Beam power kW Power deposited in target Beam sigma (cm) Days to fluence of 10^21 p/cm2 T2K Phase 1 design 30 750 22 0.424 84 days T2K 5 year Roadmap 1660 49 T2K ‘Ultimate’(?) 30-50 4000 117 SPL-SB 5 50 (200/4) 0.5 15 days

T2K Secondary Beam Line TS BD DV Kamioka Target station (TS) Primary beam line Fast extraction 50 GeV PS ring Kamioka Target station (TS) •Target & horns in helium vessel •Helium vessel and iron shields cooled by water ‘280 m’ neutrino detector Decay Volume (DV) •94m long helium vessel cooled by water •6m thick concrete shield TS Hadron Absorber (Beam Dump) •graphite core in helium vessel DV BD

4 MW Beam Dump / Hadron Absorber Graphite Blocks Beam Displacement (max) = 8.5 mm at 4 MW Could possibly use similar design for SPL-SB 18

T2K Target & horn system Inner concrete shields Inner iron shields Support structure = Helium vessel 3rd horn 2nd horn Baffle Target and 1st horn Beam window

Assembled Beam Window Installed on Oct. 23rd 2008.

Baffle Installation Beam collimator in front of the 1st horn Installation succeeded on Jan. 10th.

Specification of T2K Phase 1 Target Design Graphite rod, 900 mm (2 interaction lengths) long, 26 mm (c.2σ) diameter c.20 kW (3%) of 750 kW Beam Power dissipated in target as heat Helium cooled (i)to avoid shock waves from liquid coolants e.g. water and (ii)to allow higher operating temperature Target rod completely encased in titanium to prevent oxidation of the graphite Helium cools both upstream and downstream titanium window first before cooling the target due to Ti-6Al-4V material temperature limits Pressure drop in the system should be kept to a minimum due to high flow rate required (max. 0.8 bar available for target at required flow rate of 32 g/s (30% safety margin)) Target to be uniformly cooled (but kept above 400°C to reduce radiation damage) It should be possible to remotely change the target in the first horn Start-up date: 1st April 2009

Target Design: Helium cooling path Inlet manifold Outlet manifold Graphite to titanium diffusion bond Flow turns 180° at downstream window Upstream Window Graphite-to-graphite bond

Graphite-Graphite bonding Graphite transfer to Aluminium Diffusion Bond + Graphite-Graphite bonding test IG43 Graphite diffusion bonded into Ti-6Al-4V titanium, Special Techniques Group at UKAEA Culham Graphite-Graphite bonding Graphite transfer to Aluminium Aluminium intermediate layer, bonding temperature 550ºC Soft aluminium layer reduces residual thermal stresses in the graphite

Prototype Target Integration with 1st Magnetic Horn – August 2008

T2K Target replacement: remote handling system

Steady state target temperature 30 GeV, 0.4735Hz, 750 kW beam Radiation damaged graphite assumed (thermal conductivity 20 [W/m.K] at 1000K- approx 4 times lower than new graphite) Maximum temperature = 736˚C

(Neutron) Irradiation effects on Graphite Expected radiation damage of the target The approximation formula used by NuMI target group : 0.25dpa/year MARS simulation: 0.15~0.20 dpa/year Dimension change : shrinkage by ~5mm in length in 5 years at maximum. ~75μm in radius Degradation of thermal conductivity … decreased by 97% @ 200 C 70~80% @400C Magnitude of the damage strongly depends on the irradiation temperature. – It is better to keep the temperature of target around 400 ~ 800 C 400 600 800 1000 Irradiation Temperature(C) 1 2 3 (dpa) 400oC 800oC Thermal conductivity (After/Before) Toyo-Tanso Co Ltd. IG-43 JAERI report (1991) 2dpa -0.5% 1dpa Dimension change Toyo-Tanso Co Ltd. IG-11

Graphite damage by 200 MeV proton irradiation at room temperature (Simos) Threshold ~ 10^21 p/cm2

Progression of target technology with Beam Power: Is there a missing technology? Increasing power SOLIDS LIQUIDS Fluidised powder Contained liquids Monolithic Segmented Moving Open jets Fluidised powder could have some of the advantages of both solids and liquids

Fluidised powder as a new target technology: The new rig is ready for take off! Work by Chris Densham, Peter Loveridge & Ottone Caretta (RAL), Tom Davies (Exeter University) and Richard Woods (Gericke LTD) Presented by Ottone Caretta EUROnu-IDS meeting 2009 CERN March 2009

A flowing powder target for a Superbeam or Neutrino Factory? Helium Tungsten powder hopper Helium beam Beam window

Powder jet targets: some potential difficulties Erosion of material surfaces, e.g. nozzles, valves Activated dust on circuit walls (no worse than e.g. liquid mercury?) Activation of carrier gas circuit Achieving sufficient + uniform material density – typically 50% material packing fraction for a powdered material No point in arguing – need to do experiments!

The powder loop

Ready, steeeady... Risk Assessment, H&S GO! Pneumatics Instrumentation Electrics Control & DAQ High Speed camera GO!

The new powder test rig installed at RAL & working!!!

The control interface (Caretta)

New powder test rig at RAL – first results from last week

Summary:Targets for a Neutrino Superbeam Yield ~ target production & capture efficiency × reliability Target efficiency much simulated/optimised, however system reliability is empirical Graphite targets achievable for deposited powers up to ≈ 30 kW for multi-GeV proton beams Limits of solid target technology not yet demonstrated Important to distinguish between beam power and power deposited in target as heat - only 5% beam power deposited in 2λ graphite target for 5 GeV beam Open liquid metal jet is baseline for a future neutrino factory or muon collider, but probably not possible for a Superbeam New ideas may be required for Superbeam targets e.g. different materials (Be?), flowing powders

Extract from work programme outlined at December workshop

EUROnu WP2 Target initial study path foreseen: - Progression matched to increasing beam powers & radiation damage 1 Investigate limits of static solid graphite targets: Need to optimise beam / target /horn parameters for both physics and engineering performance (larger diameter beam will reduce radiation damage and increase target lifetime) Experience from T2K (start-up date next month!) Synergy with target studies for T2K roadmap to 1.66 MW Investigate static, helium cooled pebble-bed target Limits of graphite Metal pebble bed e.g. Be Flowing powder target studies – also relevant for NF Beam window study in parallel to above Integration of target with horn system and target station