1. Target material and thickness considerations Alain Blondel, with thanks to Dean Adams and Dan Kaplan Priority for rebuild is to have a target mechanism that works. The design that is proposed, with a hollow cylinder in Ti, is consistent in principle at least with fitting a target tip of shape and material optimized for the purpose.

2. Simulations performed by Dean Adams, of the beam phase space at the location of the target. ORBIT simulation showing beam distributions at MICE target at 8 ms. Rms(x ’ ) +- 4 mrad Rms (y ’ ) +-6 mrad cut at x=0 (or y=0): Rms +- 1.5mrad energy spread +- 2.7 MeV.

3. The following 3 pictures show the longitudinal bucket with all 4 of our new cavities working as designed. The bucket height goes from 12 to 15 MeV from 8 to 10 ms. To maintain a well trapped bunch with enough room to raise the extraction kickers then the beam energy spread cannot exceed ~ +- 5 MeV.

4. Bucket Acceptance = 5.54051 eV s dEmax= 8.82298 MeV Head = -77.5000 deg Tail = 179.400 deg, bucket length = 256.900 deg

5. Bucket Acceptance = 4.58743 eV s dEmax= 12.2937 MeV Head = -112.400 deg Tail = 180.000 deg bucket length = 292.400 deg

6. Bucket Acceptance = 6.61365 eV s dEmax= 15.0250 MeV Head = -180.100 deg Tail = 180.100 deg bucket length = 360.200 deg

7. Two extreme philosophies: 1.Make MS and dE/dx small enough that a large fraction of particles hitting the target remain in the beam envelope 2.Assume that particles are lost anyway when they hit the beam and maximize the number of nucl. interactions Under philosophy 1, low Z target is very advantageous. A Berylium target of 3mm thickness will generate a MS rms of 1mrad and keep 70% of particles. (hits the target ~3 times before being kicked out) 0.3 mm thickness will keep 95% of particles. This factor is a straight gain for a given beam loss. If we insist on having only a given fraction of X0 in the beam, (this can be done with any material), we gain a factor 7 wrt Ti for Be, 4 for Carbon. TARGET MATERIAL

8. Target material and shape considerations:

9. Philosophy 2 (assume that particles are lost anyway when they hit the beam and maximize the number of interactions…) leads to maximizing the interactions per gram. Here, the low Z materials are only slightly better. need 75 g/cm^2 of Be (40cm at d=1.85 g/cm^3) 86 g/cm^2 of C (41cm at d=2.1 g/cm^3) 125 g/cm^2 of Ti (27cm at d=4.5 g/cm^3) to obtain one interaction of a proton. Here the gain is less obvious. Other considerations (resistance to heat, ease of implementation, etc…) maybe overbearing.

10. Target material and shape considerations:

11. Beam area = B=4x4 cm^2 Target area=T= 0.5 x0.1 cm^2 T/B~300 Turns=1500/ms Could be some gain in hitting more than once? This is where the target is now

12. From P. Smith’s thesis: Is this saturating? This is where we were hitting a limit.

13. There are some unknowns at this point in particular how deep do we dip the target in the beam really. We seem to intersect 2 10 9 protons when running at 50 mV. Does that mean we are intersecting 10 10 protons at 250mV? (the actual linearity of the beam-loss-monitors vs particle production has not been demonstrated precisely -- should be placed on the run list!) Total is 2 10 13 protons circulating in ISIS, we are presently hitting a very small fraction of the beam at each turn. We want to intersect 1.5 10 12 which is ~10% of the beam! The energy deposited by 1.5 10 12 protons in 1cm of Ti is 1.6J.