1. Proposal for a programme of Neutrino Factory research and development WP-3 The Target The Neutrino Factory Target Lead Author - J R J Bennett CCLRC, RAL

2. Schematic diagram of the target and collector area

3. Parameters Proton Beam pulsed10-50 Hz pulse length1-2 ms energy 2-30 GeV average power ~4 MW Target (not a stopping target) mean power dissipation1 MW energy dissipated/pulse20 kJ (50 Hz) energy density0.3 kJ/cm3 (50 Hz) 2 cm 20 cm beam

4. Target Developments – so far 1. Mercury Jets 2. Contained Flowing Mercury 3. Granulated Targets 4. Solid targets 5. Solid Rotating Ring

5. Proton beam Mercury jet Solenoid Effective target length ~20 cm Schematic diagram of the mercury jet target

6. To mercury pump & heat exchanger Protons Tube containing flowing mercury 20 T solenoid magnet Schematic diagram of the contained flowing mercury target

8. Solid bar target Need to dissipate the heat: a) water cooling difficult – “dilutes” target b) radiation cooling not possible c) need moving target – multiple targets

9. drive shaft protons spoke solenoid coils vacuum box target Rotating wheel target 1MW Target Dissipation (4 MW proton beam) tantalum or carbon radiation cooled temperature rise 100 K speed 5.5 m/s (50 Hz) diameter 11 m

10. Plan View of Rotating Band Target (Bruce King et al) shielding rollers Access port rollers protons to dump cooling solenoid channel 1 m water pipes x z

11. The RAL scheme Large rotating toroid cooled by Thermal Radiation This is very effective at high temperatures due to the T 4 relationship (Stefans law).

12. Schematic diagram of the radiation cooled rotating toroidal target rotating toroid proton beam solenoid magnet toroid at 2300 K radiates heat to water-cooled surroundings toroid magnetically levitated and driven by linear motors

14. Thermal Shock

15. Simple explanation of shock waves inertia prevents the target from expanding until: the temperature rises by ΔT and the target expands by Δd (axially) target Short pulse of protons Time t = 0 2d2d t > 0 v is the velocity of sound in the target material;  is the coefficient of linear expansion End velocity ΔdΔd

16. Shock, Pulse Length and Target Size If a target is heated uniformly and slowly – there is no shock! Or, when the pulse length t is long compared to the time  taken for the wave to travel across the target – no shock effect! So, if we make the target small compared to the pulse length there is no shock problem. If No problem! Assume t = 2 ms, V = 3.3x10 5 cm s -1, then d = 0.7 cm Also need sufficient pulsed energy input.

17. Table comparing some high power pulsed proton targets

18. Table comparing some high power pulsed electron targets

19. Proposed R&D 1.Calculate the energy deposition, radio-activity for the target, solenoid magnet and beam dump. Calculate the pion production (using results from HARP experiment) and calculate trajectories through the solenoid magnet. 2. Model the shock a) Measure properties of tantalum at 2300 K b) Model using hydrocodes developed for explosive applications at LANL, LLNL, AWE etc. c) Model using dynamic codes developed by ANSYS

20. Proposed R&D, continued 3. Radiation cooled rotating toroid a) Calculate levitation drive and stabilisation system b) Build a model of the levitation system 4. Individual bars a) Calculate mechanics of the system b) Model system 5. Continue electron beam tests on thin foils, improving the vacuum 6. In-beam test at ISOLDE - 10 6 pulses 7. In-beam tests at ISIS – 10 9 pulses

21. solenoid collection and cooling reservoir proton beam Levitated target bars are projected through the solenoid and guided to and from the holding reservoir where they are allowed to cool.