A Pressurized Gas Cerenkov Detector for PID in Hall A

1
A Pressurized Gas Cerenkov Detector for PID in
Hall A
Robert J. Feuerbach Jefferson Lab Design and
prospective fabrication in collaboration
withArgonne National Laboratory, Rutgers
University, and Jefferson Lab
2
Overview

• Design Goals
• Separate ? and K for momenta above 2.3GeV/c.
• Continue to differentiate e/?
• Features
• Operates at pressures up to 10 psig, using C4F10
  or CO2 as the radiator.
• Expect average of 10 p.e. for a 2.3GeV/c pion
  with C4F10

Experiments Pentaquark (E05-009), Transversi
ty SSA (E03-004) (backup), Flavor Asymmetry
in SIDIS (PR04-114 cond. app.)
3
Performance Criteria
Transversity
Pentaquark
4
Design (cont)

• C4F10 chosen for its high index-of-refraction
• Availability might be an issue
• Try to re-use as much of the current detector as
  possible to control costs and unknowns
• Re-use optics from present cerenkov.
• Can the present box be re-used? NO
• Finite element analysis by Ravi Anumagalla
• Weight goes from 750lbs to 2200lbs.
• Higher risk factor

5
Design (cont)

• Another idea window-less titanium cylinder
  with interior supports (concept 1)
• Cylindrical chamber w/ windows (concept 2)

6
Modified box concept (1)
7
Modified design (2)

• Reuse mirrors/optics/PMTs
• Windows (.3 to 1mm thick Ti or Al)
• Windows MIGHT be swapped out tomatch the needs
  of an experiment.
• (Pressurized vs. fewer delta-electrons)

Window Knock-on electrons(10-3)
37um Tedlar 0.60
250um Al 0.83
380um Ti 1.19
1mm Ti 2.19
8
Common features

• PMT sealed against interior for servicing while
  the chamber is pressurized.
• Simple stationary gas system since it will be
  filled from the Hall B gas system.
• Size is compatible with current short cerenkov.
• Low-number of knock-on electrons for 0.4mm Ti
  window (lt2) for Kaons in C4F10, and lt0.15 for
  pions in CO2.

9
Design performance
10
0.36
11
Conclusion

• Pressurized Cerenkov design can proceed, but on
  hold at the moment.
• Should provide excellent pi/K separation for
  momenta greater than 2.3 GeV/c. Rejection factor
  of 370 for a threshold of 3p.e.'s.
• Modified design (2) is estimated at 49k
  (including contingency) 5 wks design and
  engineering.