1. WP2 (SuperBeam) Targets Status of Work Programme
Chris Densham

2. 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

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

4. 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)

5. 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

6. 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?

7. 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

8. 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

9. 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?

10. 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)

11. 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

12. 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-

13. 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

14. 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: ~ MW for Hg
C : ~ MW
considerably lower for Carbon

15. 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)‏

16. 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

17. 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

18. 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

20. 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

21. Assembled Beam Window
Installed on Oct. 23rd 2008.

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

23. 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

24. 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

25. 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

26. Prototype Target Integration with 1st Magnetic Horn – August 2008

27. T2K Target replacement: remote handling system

28. Steady state target temperature
30 GeV, Hz, 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

29. (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
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

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

31. 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

32. 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

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

34. 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!

35. The powder loop

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

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

38. The control interface (Caretta)

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

40. 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

41. Extract from work programme outlined at December workshop

42. 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