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 performance

5. Design (cont) C 4 F 10 chosen for its high index-of-refraction 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? What modifications are necessary? Finite element analysis by Ravi Anumagalla

6. Model 4: No top and Bottom faces, includes a C Channel on one face Max Stress : 263 ksi Max Deflection : 1.59 inches Boundary Conditions: Pressure on all faces (14.7 psi), Fixed at the bottom and top surface,

7. Model 4: Plot shows surfaces where stresses are in the range of 0-23 ksi

9. Design (cont) Can the present box be re-used? What modifications are necessary? Finite element analysis by Ravi Anumagalla – Weight goes from 750lbs to ~2200lbs. – Higher risk factor Another idea: window-less titanium cylinder with interior supports (concept 1) Cylindrical chamber w/ windows (concept 2)

10. Modified box concept (1)

11. 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%).

12. 0.36%

13. Conclusion Pressurized Cerenkov design continuing. 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).

14. R ich /K separation for p > 2.5 GeV/c Radiator C6F14 n=1.29 Ch ~ 5mr Radiator C5F12 n=1.24 Ch ~ 5mr 4 separation at ~ 2.5 GeV/c4 separation at ~ 3.0 GeV/c Mauro Iodice – R ICH2004 - Playa del Carmen, Mexico - Nov.30 Dec. 5, 2004

15. R ich /K separation with C5F12 (n=1.24) radiator (14 cm proximity gap) >20 separation at ~ 2 GeV/c ~ 4 separation at 3.0 GeV/c Mauro Iodice – R ICH2004 - Playa del Carmen, Mexico - Nov.30 Dec. 5, 2004 M onte C arlo Simulations