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Last modified 07/02/2003 16:30

It has been shown that the addition of 0.5m length collimators at the A48 location provides two benefits to CDF:

1. Protection against high beam losses as a result of an A0 abort kicker prefire.

2. Reduction of beam halo background originating from elastic beam-gas scattering that can bypass the current collimation system.

Protecting the CDF silicon tracking systems is especially important given the higher than expected rate of prefires over the past few months.  (Redesigning the abort kicker system to solve the prefire problem is a separate, longer-term project.)  The current need to reduce halo-related background is debatable, but the Run II goal for proton intensity is still 50% above typical intensities at present.  Strictly speaking, a single collimator rising vertically from the bottom of the beam pipe is sufficient for reducing high losses from an abort kicker prefire.  Maximum benefit for beam halo background reduction requires collimator steel on all 4 sides.

The current proposal calls for installing two 0.5m long collimators (similar to the existing L-shaped secondary collimators) in the A48 warm section upstream of the CDF Roman Pots.  Option 1 (shown below) has been ruled out because there is not enough space for 2 collimators in the space vacated by the A spool.  Option 2 requires 2 new cryogenic bypasses, removal of the A spool, removal of the Q1 magnet, replacing the P spool with the H spool, and moving the Roman Pot beampipe downstream ~50" toward the superconducting dipole magnets.  Modifications of Option 1 are being considered as well. The so-called "minibar" scheme is also under investigation to reduce the number of fake missing E_T events in CDF possibly caused by secondary muons arising from proton showers in the collimator.

• "Tevatron Abort Kicker Prefire Simulations" (Church and Drozhdin)  (pdf)

• "Beam Loss and Backgrounds in the CDF and D0 Detectors due to Nuclear Elastic Beam-Gas Scattering" (Drozhdin et al) (document server entry)

• "MARS Simulation of Beam Loss and New Collimator Impact on the CDF and D0 Subdetectors" (Nicolas et al) (pdf)

• Presentations at the A48 Collimator Project Review (June 3, 2003) (doc server entry)

• Impact of the A48 Collimator on the Tevatron Dipoles (pdf)

Photos

• New Cryo Bypass (as of May 1, 2003) - waiting for survey of beam tube ends

Security, Privacy, Legal

Last modified 07/02/2003 16:30