1. Initiative in the Target Sector J. R. J. Bennett roger.bennett@rl.ac.uk CCLRC, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon, OX11 0QX, UK

2. Targets ISS Baseline Design Summary R&D Required

3. ParameterValueReason Beam Power4 MWBy definition Proton energy~10 GeVBased on calculated muon yield Beam repetition rate ~50 HzBased on Jet target (≤~50 Hz)/driver design Micro-pulse width~2 nsBased on muon yield (front end/phase rotation) Number of micro- pulses per macro- pulse ~4 (16  s spacing) Based on proton driver/front end design/size of storage ring Macro-pulse length~50  sBased on Jet target Target – Mercury Jet Based on advanced R&D/best choice Free Mercury Jet Target

4. The Proton Pulse macro-pulse micro-pulse Proton beam “macro-pulses” and “micro-pulses”.

5. Parameters of the RAL NF-Target Proton Beam pulsed10-50 Hz pulse length1-2  s 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/cm 3 (50 Hz) 2 cm 20 cm beam

6. ParameterValueReason Beam Power4 MWBy definition Proton energy~10 GeVBased on calculated muon yield Beam repetition rate~ 50 Hzdriver design/reduced thermal shock Micro-pulse width~1 nsBased on muon yield (front end/phase rotation) Number of micro- pulses per macro-pulse 3 (~60  s spacing) Based on proton driver/front end design size of storage ring Macro-pulse length120  s(beryllium window dissipation)/reduced thermal shock Target – Solid Tungsten Not chosen Shock studies incomplete Solid target

7. Some Comments 1. Pion production measurements needed urgently – HARP!!! Effects choice of energy and target material. 2. Front End Inefficient – look for better solution – ß-beams are elegant!!

8. My R&D Suggetions 1.Free Mercury Jet - After MERIT – may indicate further R&D needed. ???? 2.Improve/widen/increase experience with mercury jet and handling/safety. Consider low temperature eutectics as alternatives to Hg. 3.Contained flowing liquid metal targets?

9. 4.Shock studies in solids – tantalum, tungsten and carbon –for targets (and at high temperatures) and windows. 5.In-beam tests required. 6.Investigate low thermal expansion metals? 7.Produce a viable rotating/moving solid target design. 8.Radiation Damage in solids –high temperatures - annealing. 9.Produce a viable beam dump design for solid and free jet targets. 10.Design a target station and beam dump for Jet target and Solid target. Including remote handling, maintenance and replacement. 11. Safety aspects.

10. The RAL Thermal Shock Programme 1. Simulate shock by passing a pulsed current through a wire. 2. Measure the radial (and longitudinal) motion of the wire to evaluate the constitutive equations (with 3.). 3. Use a commercial package, LS-DYNA to model the behaviour. 4. Life time/fatigue test. 5.In-beam tests. 6. Investigate the possibility of widely spaced micro- bunches of proton beam to reduce the shock impact.