1. A Pressurized Gas Cerenkov Detector for PID in Hall A Robert J. Feuerbach Jefferson Lab Design and prospective fabrication in collaboration with: Argonne 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 C 4 F 10 or CO 2 as the radiator. Expect average of 10 p.e. for a 2.3GeV/c pion with C 4 F 10 Experiments: Pentaquark (E05-009), Transversity SSA (E03-004) (backup), Flavor Asymmetry in SIDIS (PR04-114 cond. app.)

3. Performance Criteria Pentaquark Transversity

4. Design (cont) C 4 F 10 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 to match the needs of an experiment. (Pressurized vs. fewer delta-electrons) WindowKnock-on electrons (*10 -3 ) 37um Tedlar0.60 250um Al0.83 380um Ti1.19 1mm Ti2.19

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 (<2%) for Kaons in C 4 F 10, and <0.15% for pions in CO 2.

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.