1. Beamline-to-MICE Matching Ulisse Bravar University of Oxford 2 August 2004 MICE performance with ideal Gaussian beam JUNE04 beam from ISIS beamline (Kevin Tilley) Software, beam momentum and coil currents manipulation Results, cooling of the actual ISIS beam

2. Cooling a Gaussian beam Beam in the middle of the upstream spectrometer:   = 6  mm rad = 200 MeV/c   = 33 cm Gaussian distributions:  x = 3.3 cm  px = 20 MeV/c Coils from Mice Note 49: about 15% cooling LH spectrometers z (m)   (  m rad)

3. ISIS beam Simulations of the MICE channel performed with ICOOL Beamline designed by Kevin Tilley with TURTLE Latest beam design: JUNE04 Pb diffuser is 8 mm thick Turtle-Icool interface planes: a)Middle of upstream spectrometer b)After Pb diffuser, prior to solenoid c)After Q9, prior to Pb and solenoid Work in progress: a)Interface Turtle-Icool midway between Q6-Q7 b)Simulate the entire beamline with Icool

4. Beamline layout MICE beamline (NOT TO SCALE !!!) Q7Q8Q9 Quadrupole triplet Drift Pb diffuser 0.8 cm Solenoid & Spectrometer LH Focus coil TURTLE – ICOOL INTERFACES

5. Beam design concept (1) MICE wants…… x/y x’/y’ 2. Particular input emittance 1. Matched beam …. at matching point (4T Spec Solenoid)

6. Beam design concept (2) Scheme to provide simultaneously:- This is the driving Design Concept in this design work: To use ‘Beamsize’ & ‘Scatterer thickness’ to provide both beam matching, & required emittance generation. 1. Focus Beam with x/y x’/y’ MICE ACCEPTANCE 2. & Matched after passing thru’ required scatterer [Above figure illustrates case match region immediately follows scatterer]

7. JUNE04 beam Beam is not cylindrically symmetric at Q9, far from Gaussian… Designed to achieve   = 33 cm and  = 0 in spectrometer solenoid Central momentum of ‘useful’ beam p = 236 MeV/c Design emittance  y ONLY = 6  mm rad This means: ( / mc)  y  y’ sqrt(1-r 2 ) = 6 mm rad

8. Beam at Q9 (1) p tot (GeV/c)p y (GeV/c)p x (GeV/c) x (m)y (m)

9. Beam at Q9 (2) Beam is everything but Gaussian Top: x – p z correlation Bottom: a) is not 0 b)p x is asymmetric x (m) p x (GeV/c) p z (GeV/c)

10. x – p z correlation Correlation after Q9 Disappears after Pb scatterer and inside spectrometer 265 MeV/c x (m) p z (GeV/c)

11. Cooling (1) Ideal Gaussian beam JUNE04 beam Designed assuming that the optics of the cooling channel were optimised for a central momentum of: = 200 MeV/c Interface Turtle – Icool: centre of upstream solenoid Transmission = 80% COOLING = ??? z (m)   (  m rad)

12. A few steps MICE channel designed for p central = 200 MeV/c Beam at Q9 designed to provide = 236 MeV/c, due to A 2 – p correlation Steps: Scale ALL coil currents in the MICE channel by 236/207 Include Pb diffuser in Icool Propagate Turtle beam from Q9 into centre of spectrometer Inside upstream spectrometer, select ONLY events with p tot within 5% of 236 MeV/c p tot CUT p tot (GeV/c)

13. B-field in Icool Fringe field from Q9 not included in Icool simulation B z from solenoid ‘almost’ zero at Q9 Pb scatterer inside fringe field from solenoid B z in solenoid >> 4 T Q9 Pb z (m) B z (T)

14. Icool vs. Turtle p tot in the centre of the upstream spectrometer: a) Icool b) Turtle Note: Turtle uses thin lens approximation for solenoid fringe field p tot (GeV/c)

15. Longitudinal momentum JUNE04 beam, all events JUNE04 beam with p tot cut z (m) (GeV/c)

16. Cooling (2) JUNE04 beam, all events JUNE04 beam with p tot cut z (m)   (  m rad)

17. Cooling (3) Ideal Gaussian beam  = 15.8% Transmission = 98.6% JUNE04 beam  = 11.1% Transmission = 72.8% 7,075   after Q9 5,412 total   in upstream spectrometer Of these, 1,543   pass the cut on p tot 1,124   left in downstream spectrometer z (m)   (  m rad)

18. Beta functions Gaussian beam, starting in upstream solenoid JUNE04 beam, all events JUNE04 beam with p tot cut z (m)   (m)

19. Conclusions MICE coils and JUNE04 beam need some more work We have an actual beam + cooling channel design that works !!! Beamline: a)Reduce central momentum to = 207 MeV/c b)Have central momentum in the centre of the p tot distribution, not in the tail c)More interface planes Turtle-Icool Keep an eye on event rate: 1,124  + / 7,075  + = 15.9% !!!