1. 1 Downstream scraping and detector sizes Rikard Sandström University of Geneva MICE collaboration meeting 2007-02-24 CERN

2. 2 Introduction Study A –Full phase space beam approach. –Radial positions measured at cryostat end thick iron shield surfaces TOF2 thin iron shield surfaces calorimeter layer 0 surfaces calorimeter center and end. Study B –Matched beam approach. 140 MeV/c, 200 MeV/c –Radial positions measured at same z as in Study A.

3. 3 Setup, study A Geometry: –MICE stage6, with updated positions and iron shields. Iron shields not physically present in simulation, but using Virtual detectors at their surfaces. –Now with cryostats physically present. –Empty absorbers. Field: –Holger’s empty channel, beta 42 cm, 200 MeV/c field. http://mice.iit.edu/software/bfield/holger/FieldMaps24-01- 07/CoilconfigWangNMRironshield200MeVbeta42emptychannel.g4mice http://mice.iit.edu/software/bfield/holger/FieldMaps24-01- 07/CoilconfigWangNMRironshield200MeVbeta42emptychannel.g4mice –RF field OFF Beam: –The same “full phase space beam” as was used before.

4. 4 There are no good events going through the cryostat!

5. 5

6. 6

7. 7

8. 8 Outside calorimeter (air)

9. 9 Again… The large radius events are all low momentum, Hence, setting a minimum → pz fixing maximum rho !

10. 10 Setup, study B Geometry: –MICE stage6, with updated positions and iron shields. Iron shields not physically present in simulation, but using Virtual detectors at their surfaces. –Now with cryostats physically present. –4.2 mm diffuser for 140 MeV/c, 7.6 mm diffuser for 200 MeV/c. –Empty absorbers. Field: –Holger’s empty channel, beta 42 cm, 140 MeV/c and 200 MeV/c fields respectively. http://mice.iit.edu/software/bfield/holger/FieldMaps24-01- 07/CoilconfigWangNMRironshield140MeVbeta42emptychannel.g4mice http://mice.iit.edu/software/bfield/holger/FieldMaps24-01- 07/CoilconfigWangNMRironshield140MeVbeta42emptychannel.g4mice –RF field OFF. Beam: –Matched 140 MeV/c beam.

11. 11 Matched 200 MeV/c, thick shield

12. 12 Matched 200 MeV/c, TOF2

13. 13 Matched 200 MeV/c, thin shield

14. 14 Matched 200 MeV/c, EMCal0 Outside calorimeter (air)

15. 15 This beam uses the same field map as the full phase space beam, hence the same dependency on momentum

16. 16 Matched 140 MeV/c, thick shield

17. 17 Matched 140 MeV/c, TOF2

18. 18 Matched 140 MeV/c, thin shield

19. 19 Matched 140 MeV/c, EMCal0 Few muons make it through the preshower layer.

20. 20 Same tendency as before, but shifted w.r.t. p z due to different field map.

21. 21 Emittance Typically it is the high amplitude particles which are missing the detectors. –High bias on emittance measurement. However, MICE will measure change of emittance! –If no change of emittance between upstream and downstream, losing events does not affect the change of emittance measurement. This simulation contains no RF field, and empty absorbers, so bias on change of emittance as a function of TOF2 radius not meaningful here. –Instead, quoting bias on emittance measurement.

22. 22 Emittance Using no field approximation at TOF2 exit to calculate emittances: –ε = sqrt(  x 2  px 2 -  xpx 2 )/m p z [MeV/c]εxεx εyεy 1406.5966.618 2006.9236.955 p z [MeV/c]R [cm]dε x / ε x dε y / ε y 14042-0.70 ppm-0.80 ppm 20030-0.63 ppm-0.80 ppm Requiring dε/ ε < 1 ppm, gives minimum radiuses Typically 1 ppm is at radius where 0.1 ppm is lost.

23. 23 Conclusions The cryostat is no longer an issue. Setting TOF2 radius to –25 cm, start losing events pz<225 MeV/c –30 cm, start losing events pz<169 MeV/c –35 cm, start losing events pz<129 MeV/c According to no field approximation, minimum radius of TOF2 should be 42 cm to achieve dε/ ε < 1 ppm. –30 cm for 200 MeV/c settings. –Usually 0.1 ppm loss radially is barely acceptable.