February 7, 2008 A.Drozhdin

1. February 7, 2008 A.Drozhdin 1, 2 3

2. February 7, 2008 A.Drozhdin Tevatron Run-II beam collimation system.

3. February 7, 2008 A.Drozhdin Primary D49, secondary EO3 collimators and bent crystal location at the Tevatron EO straight section.

4. February 7, 2008 A.Drozhdin EO O-shape bent crystal configuration used in the calculations. Amorphous layer (1 μm thick) is presented as a separate part of the crystal, and is located upstream of the crystal. Crystal is aligned at 0.006 mrad parallel to the envelope of the beam.

5. February 7, 2008 A.Drozhdin Initial particles distribution at the crystal entrance (left). As the crystal is positioned at x=-3.749 mm from the beam pipe center, the particle population at the crystal starts from this coordinate for any particle amplitude independently on momentum. Particles with different momentum have different closed orbit and different amplitude but almost the same X coordinate in the crystal. Angular coordinate X' is different for these particles because of closed orbit and amplitude is different (right).

6. February 7, 2008 A.Drozhdin strip crystal channeled Coll. edge Particle number lost in collimator E03 and F172 (top and middle) with all primary and secondary collimators in a working positions, D49 is retracted by 2mm. Particle distribu-tions in a vicinity of horizontal internal edge of collimator EO3 (bottom). The collimator edge of EO3 is at X=-4.216 mm and collimator F172 is at X=-5.183 mm. The probability of these particle scattering out of the collimator jaws is big. The beam loss in the accelerator and back-ground in the detectors should be proportional to this probability. Crystal bending angle is 0.15 mrad, length is 3mm.

7. Beam position and distribution February 7, 2008 A.Drozhdin crystal Coll. E03 Extracted and circula-ting beam position in the Tevatron at first turn after interaction with channeling crystal. All collimators are retracted from accelerator apertu-re. Transverse plane is shown at EO3 and other locations. Crystal ben-ding angle is 0.15 mrad, length is 3mm. Crystal is aligned with respect to envelope of the beam. It is assumed that particle interaction rate with crystal is 3e+07 per sec. and circulating beam is 1e+13 X 47700=4.44e17 per sec. This means that crystal collimation rate is ten order of magni-tude less compared to circulating beam. strip crystal Flying wire

8. Beam position and distribution February 7, 2008 A.Drozhdin Bend, S=3226.3m Bend, S=3523.8m Coll. F172 strip crystal Extracted and circulating beam position in the Tevatron at first turn after interac-tion with channeling crystal. All collimators are retracted from accelerator aperture. Crystal bending angle is 0.15 mrad, length is 3mm. A49 hor. separator S=5209.5m All channeled particles are lost at this separator

9. Beam position and distribution February 7, 2008 A.Drozhdin Extracted and circulating beam position in the Tevatron at first turn after interac-tion with channeling crystal. All collimators are retracted from accelerator aperture.Crystal bending angle is 0.15 mrad, length is 3mm. A49 ver. separator BO lostp strip crystal C49 ver. separator C49 hor. separator Coll. EO3 Flying wire DO phtl

10. February 7, 2008 A.Drozhdin channeled Coll. edge Particle number lost in collimator E03 (top) with all primary and secon-dary collimators in a working positi-ons, D49 is retrac-ted by 2 mm. Particle distribu-tions in a vicinity of horizontal internal edge of collimator EO3 (bottom). Crystal bending angle is 0.44 mrad, length is 5mm. O-shape crystal

11. Beam position and distribution crystal O-shape crystal Coll. EO3 Extracted and circulating beam position in the Tevatron at first turn after interaction with channeling crystal. All collimators are retracted from accelerator aperture. Transverse plane is shown at EO3 and other locations. Crystal bending angle is 0.44 mrad, length is 5mm. Crystal is aligned with respect to envelope of the beam. Flying wire

12. Beam position and distribution Bend, S=3226.3m Bend, S=3226.3m Most of channeled particles are lost at these magnets aperture Coll. F172 O-shape crystal S=5209.5m Extracted and circulating beam position in the Tevatron at first turn after interaction with channeling crystal. All collimators are retracted from accelerator aperture.Crystal bending angle is 0.44 mrad, length is 5mm. Crystal is aligned with respect to envelope of the beam. A49 hor. separator

13. Beam position and distribution A49 ver. separator BO lospt O-shape crystal C49 ver. separator C49 hor. separator Flying wire Coll. EO3 Extracted and circulating beam position in the Tevatron at first turn after interaction with channeling crystal. All collimators are retracted from accelerator aperture.Crystal bending angle is 0.44 mrad, length is 5mm. Crystal is aligned with respect to envelope of the beam. DO phtl

14. February 7, 2008 A.Drozhdin Coll. edge Peaks at +/-0.048mrad O-shape crystal Particle number lost at crystal collimation in collimator E03 and F172 with all secondary collimators in a working positions. The beam loss in the accelerator and background in the detectors should be proportional to the number of particle scattered out of collimators E03 and F172 or passed through the edge of these collimators. Crystal bending angle is 0.44 mrad, length is 5mm. channeled

15. 0 mrad, 73% 0.032mrad, 11% Particle distribution at the crystal exit at first turn, calculated using CATCH, for different angle of incoming particles. Ten thousand particles was taken at the crystal entrance. All initial particles have the same coordinates and momentum. It was found an additional ``parasitic'' channeling at six incoming angles. This occurs at angles of +/-32, +/- 48 and +/- 64 μrad with respect to the crystal axes. The critical angle (thickness of channe-led beam) is 2 μrad for incoming angle of 48μrad, and 1μrad for incoming angle of 32 and 64μrad. The critical angle for zero incoming angle is equal to 0.064mrad, 11% 0.048mrad,48% 9μrad. A percentage of extracted through channeling and multiple Coulomb scattered particles are shown on figures. This happens because of large step-size (DZ=2μm) at particle trajectory calculation in the crystal, and causes a problem at calculations of collimation efficiency for broad range of crystal misalignment. These peaks disappear at DZ<0.7 μm.

16. February 7, 2008 A.Drozhdin Total lost at E03 and F172 Passed through 0.1 mm layer Channeled Loss at B0 Particle number lost at crystal collimation in collimator E03 and F172 with all secondary collimators in a working positions. The beam loss in the accelerator and background in the detectors should be proportional to the number of particle scattered out of collimators E03 and F172 or passed through the edge of these collimators. Crystal bending angle is 0.44 mrad, length is 5mm.

17. February 7, 2008 A.Drozhdin Schematic view of loss monitor T:LE033 position with respect to collimator E03 used in simulation of LE033 reading at crystal collimation.