EU FP6 Design Study Target Section Roger Bennett roger.bennett@rl.ac.uk

1. EU FP6 Design Study Target Section Roger Bennett roger.bennett@rl.ac.uk CCLRC, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 0QX, UK

2. target protons Typical Schematic Arrangement of a Neutrino Factory Target

3. Specification • Proton Beam • pulsed 10-50 Hz • pulse length 1-2 ms • energy 2-30 GeV • average power ~4 MW • Target • mean power dissipation 1 MW • energy dissipated/pulse 20 kJ (50 Hz) • energy density 0.3 kJ/cm3 (50 Hz)

4. Design Considerations Need to knowBeam current density profile and target geometry Power density distribution within the target Apply thermal calculations Cooling, Stresses including Pulsed Effects, Temperatures Radiation Effects Shielding, Activity, Remote Handling, Beam Dump, Radiation Damage, Maintenance, Target Changes, Disposal Magnet Magnetic field, sc magnet (heat and radiation), Forces, Induced Currents

5. Target Developments – so far • Mercury Jets • Contained Flowing Mercury • Granulated Targets • Solid targets • Solid Rotating Ring

6. 2 cm 20 cm Solid Target Heavy metal - Tantalum Beam hits the whole target Not a stopping target

7. Solid Targets Need to remove the heat - 1 MW BUT The PERCIEVED problem is:-

8. SHOCK

9. Shock, Pulse Length and Target Size • If we heat a target uniformly and slowly – there is no shock! • Or, • When the pulse length t is long compared to the time t 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. • Also need sufficient pulsed energy input.

10. Solid Metal Spheres in Flowing Coolant • P. Sievers, CERN • Small spheres (2 mm dia.) of heavy metal are cooled by the flowing water, liquid metal or helium gas coolant. • The small spheres can be shown not to suffer from shock stress (pulses longer than ~3 ms)and therefore be mechanically stable. • Can have several targets and recombine the pion beams.

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

13. The Mercury Jet • Proposed for the USA and by CERN • The jet breaks up when the beam hits it, but the beam has interacted with the jet before it has time to break up. So no problem. Tests show that the “next jet” is not prevented from appearing in time. Jet velocity ~30 m/s. • No power limit? • The jet hits the walls and they must take the heat and the effect of the mercury hitting the walls. Not thought to be a problem. • The mercury is condensed and recycled. It can also be distilled so removing some of the radioactive isotopes formed in the jet. • Easy to remove the “target” by draining out. • Interaction of the jet with the magnetic field of the solenoid is not a problem. • A mercury pool in the target chamber can serve as the beam dump.

14. Handling the mercury is hazardous. If the mercury escapes - severe hazard. Messy! • Need windows between the other parts of machine. • There has been considerable success with the developments of mercury jet targets. • Further tests at full flow (in the solenoid) and with full proton beam power is required. • The outlook is good.

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

16. Looks like we have a problem for large targets! (2 cm diameter, 20 cm long)

17. BUT! Have we seen shock wave damage in solid targets?

18. What do we know? There are a few pulsed (~1ms) high power density targets in existence: Pbar – FNAL NuMI SLAC (electrons)

19. Table comparing some high power density pulsed targets

20. Encouraged to further investigate shock in solid targets

21. Bruce King et al

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

23. Target Section Topics • Mercury jet. • 2. Contained liquid metal. • 3. Granular targets. • 4. Solid targets. • 5. Beam dump. • 6. Proton beam interactions. • 7. Target station design. • 8. Maintenance, remote handling. • 9. Safety.

24. Each Subsections has a Team Leader • Responsible for producing the outlines of an R&D programme • “Recruiting” appropriate persons

25. Mercury Jet • Form jet in magnetic field at correct flow • In-beam tests – US/E Collaboration – nToF beam line – LOI • Safety Issues • Helge Ravn, CERN • Jacques Lettry, CERN • Adrian Fabich, CERN • USA

26. 2. Contained flowing liquid metal targets Guenter Bauer, Juelich Helge Ravn, CERN Jacques Lettry, CERN Adrian Fabich, CERN

27. 3. Granular targets Peter Sievers, CERN Bruno Autin, CERN Andre Verdier, CERN Francois Meot, CERN

28. 4. Solid targets • Shock Studies • Levitation • Firing individual bars • In-beam tests at ISOLDE and ISIS • Chris Densham, RAL • J R J Bennett, RAL • Neil Bourne, RMCS • Alex Milne, RMCS • Dave Rodger, Bath • Paul Leonard, Bath

29. 5. Beam dump Guenter Bauer, Juelich

30. 6. Proton beam interactions • Pion optimisation • Calculations - Energy density distributions, activation etc. in target and surroundings. • Paul Soler, Glasgow • Chris Booth, Sheffield

31. 7. Target station design, integration of the whole system, including the collectors. Guenter Bauer, Juelich Helge Ravn, CERN Jacques Lettry, CERN Adrian Fabich, CERN Jean-Eric Campagne, LAL Simone Gilardoni, CERN Chris Densham, RAL J R J Bennett, RAL

32. 8. Maintenance, remote handling Guenter Bauer, Juelich

33. 9. Safety Marco Silari, CERN Guenter Bauer, Juelich