1. 1 Question to the 50GeV group 3GeV からの 54π と 81π 、 6.1π の関係 fast extraction 部の acceptance (81π?) Comments on neutrino beamline optics?

2. 2 Optics of Primary Proton Beam line A. K. Ichikawa(KEK), 12 th Nov. 2003, nuTAC@KEK

3. 3 Overview Preparation section Normal conducting Arc Section R=105m Super conducting Final Focusing Section Normal conducting  Single turn fast extraction  8 bunches/~5  s  3.3x10 14 proton/pulse  3.94 (3.64) sec cycle (depend on abort scenario)   =6  mm.mr,  p/p=0.31% @50GeV   =7.5  mm.mr,  p/p=0.36% @30GeV  Total bending = 84.5 o

4. 4 Beam loss No way to know absolute beam loss Assumed by HAND Assure hands on maintenance (1W/m) Shielding design based on the assumption Same order as KEK-PS beam line  ~10 2 relative suppression!!  Challenging Fast ext.(kicker, septum) 1.125kW (0.15%) Preparation section (ctrl’ed loss by collimator) 0.75kW (0.1%) 50GeV ring 0.5W/m Final Focusing section 0.25kW (0.05%)

5. 5 3.3m 1.1m 1.4m Arc section optics (fitting result) Admittance : 205  mm.mr for horizontal, 294  mm.mr for vertical

6. 6 Preparation section –Overview- Make matching with the Arc. Consists of normal conducting magnets. Almost no freedom on the Length and angle Total Length : 52.3m → Tight spacing 3.84 degrees bending Scrape beam halo to protect super conducting magnet in the Arc

7. 7 Preparation Section –optics- beam Arc sectionPrep. section Well Matched w/ Arc Monitor horizontal vertical collimator ~1cm

8. 8 Concept of our ‘collimator’ Scrape very peripheral halo only. Preparation and Focusing sections accept 60  mm.mr beam. Arc section accept >200  mm.mr beam., while extracted beam is expected to have 6~10  mm.mr emittance. Put where we can put Preparation section consists of many normal-conducting magnets. The magnets themselves works as collimators for the arc section. Iron block collimators will be added to empty places to support the halo scraping. This is very much different from sophisticated scrapers for accelerators. Not movable, probably no cooling

9. 9 Preparation section Acceptance : 60  mm.mr (c.f. Acc. design = 6  mm.mr)

10. 10 Collimators Radiation shield at the exit of the preparation section Radiation Dose at conventional magnet in preparation section Simulation study for preparation section collimators Preparation section

11. 11 Focusing Section Beam should fit to target (30mm  ) whatever the emittance is. Focus 6~24  beam Accept 60  beam. Vertical steering magnet Change off-axis angle w/ this.

12. 12 Focus 6  mm.mr beam Arc section Monitor horizontal vertical 15mm

13. 13 Focus 24  mm.mr beam 15mm

14. 14 Momentum dispersion at target 2.4mm @  p/p=0.4% Cannot be zero due to limitation of beam line length. Zero is preferable but this is acceptable.

15. 15 Supplement

16. 16 Arc section – fitting results- Admittance : 165  mm.mr for horizontal, 262  mm.mr for vertical

17. 17 Boundary Condition for the design  about 80 o bending  R~105 m  Beam size in the arc should be as small as possible to prevent quenching  Beam halo should be cut at Preparation section Super conducting magnet Collimator B x = Q*y/r B y = D + Q*x/r Two candidates for the arc section design (Separate Function) FODO x10 (20 D’s & 20 Q’s) Combined function FODO x14 (28 magnets) Q D Q D

18. 18 Combined Function –Merit & Demerit?-  Merit Reduce # of components can increase # of (Q-)magnets. Smaller beam size space btw magnets monitor can be installed cost reduction  Demerit No example in the world Tunnability is restricted need corrector? After discussion on 6 th March 2003 with experts, we adopt combined function scheme !

19. 19 Treatment of Combined function w/ SAD Quadrupole magnet displaced by  x. Fitting condition for the cell (a)Periodic (b) 90 o phase advance (c) Align orbit and magnet at this point f or each of two magnets (d) Bend by 5.76 o Fitting parameters,  x (by hand), Q grad, angle of magnet

20. 20 Simulation Study (w/ GEANT3 & Geant4) Magnet geometry and field are set via data file. applicable to different beamlines. Magnet w/ Iron poles are stationed. Particles are tracked. Particle interact w/ magnet accoring to hadron production model. Secondary hadrons and electro magnetic showers can be traced. In the simulation, combined function section works as expected from optics calculation!

21. 21 Final Focus Arc Preparation section Simulation Setup with Geant4 proton hit [number] energy deposit [MeV] x x’ These input parameters were fixed, and relative variation of beam loss were estimated. Input beam parameter for ‘halo’ TWISS : same as those from 50 GeV design  =0~200  mm.mr (uniformly distribute in the phase space)  p/p =2%

22. 22 Simulated beam loss at each components proton hit [number] energy deposit [MeV] Total beam loss in Preparation section is assumed 750W (0.1%) by hand. Arc FF Total beam loss  750W 3.7W On this assumption, energy deposited in each components were normalized. Preparation section Total loss deposited in components  508W

23. 23 Radiation dose at the magnets in Preparation Section