Initiative in the Target Sector J. R. J. Bennett CCLRC, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon, OX11 0QX, UK

Targets ISS Baseline Design Summary R&D Required

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

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

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

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

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!!

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?

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.

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.