February 7, 2008 A.Drozhdin

1, 2

3

Tevatron Run-II beam collimation system.

February 7, 2008 A.Drozhdin

Primary D49, secondary EO3 collimators and bent crystal location at the Tevatron EO straight section.

February 7, 2008 A.Drozhdin

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.

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).

February 7, 2008 A.Drozhdin

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.

February 7, 2008 A.Drozhdin

strip crystalchanneled

Coll. edge

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.

February 7, 2008 A.Drozhdin

strip crystal

crystal

Coll. E03

Flying wire

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.

strip crystal

Beam position and distribution

Bend, S=3226.3m

Coll. F172

Bend, S=3523.8m

S=5209.5m

A49 hor. separator

All channeled particles are lost at this separator

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.

strip crystal

Beam position and distribution

A49 ver. separator

BO lostp

C49 hor. separator

C49 ver. separator

DO phtl

Coll. EO3

Flying wire

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.

February 7, 2008 A.Drozhdin

O-shape crystal

channeledColl. edge

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.

O-shape crystal

Beam position and distribution

crystal

Coll. EO3

Flying wire

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.

O-shape crystal

Beam position and distribution

Bend, S=3226.3m

Bend, S=3226.3m

Coll. F172

S=5209.5m A49 hor. separator

Most of channeled particles are lost at these magnets aperture

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.

O-shape crystal

Beam position and distribution

A49 ver. separator

C49 hor. separator

BO lospt

C49 ver. separator

DO phtl

Flying wire Coll. EO3

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.

February 7, 2008 A.Drozhdin

O-shape crystalchanneled

Coll. edge

Peaks at +/-0.048mrad

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

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.

0 mrad, 73% 0.032mrad, 11%

0.048mrad,48% 0.064mrad, 11%

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.

February 7, 2008 A.Drozhdin

Total lost at E03 and F172

Loss at B0

Channeled Passed through 0.1 mm layer

Schematic view of loss monitor T:LE033 position with respect to collimator E03 used in simulation of LE033 reading at crystal collimation.

February 7, 2008 A.Drozhdin