1. RICH detector for CLAS12
… continue to explore feasibility of proximity focusing RICH in LTCC sector(s)
INFN-Rome and ISS
CLAS12-RICH
Working Group Meeting ?
08 October 2008
08 Oct 2008
Clas12-RICH

2. Reminder The proximity focusing RICH consist of 3 basic components:
Cherenkov Liquid Radiator
Gap (gas filled space)
Photon Detector
The Radiator must be in a container (vessel) with UV transparent window (QUARTZ window)
The Photon Detector must detect and localize the photon that hits on a given surface: we assume a “pads like” detector
08 Oct 2008
Clas12-RICH

3. MonteCarlo Studies purpose
Estimate the optimal radiator thickness
Larger the thickness, higher the number of photons, higher the uncertainties on photon emission
Larger the thickness more challenging is the vessel technology (and more expensive the system)
Estimate the optimal Gap length
Larger the gap, better the ‘focusing’, but larger must be the detection plane
08 Oct 2008
Clas12-RICH

4. MonteCarlo
Old GEANT3/Fortran/PAW based MonteCarlo framework used for the development of the Hall A Proximity RICH
Different Geometry and Size!
Limitation on photon production (due to old memory constraint), becomes relevant for radiator thickness > cm
Charged particles phase space at the LTCC-RICH entrance window assumed uniformly distributed with +/- 10 degree divergence
Use arcs as radiator and detector geometries (see next)
Main output parameter:
skp=mean error on Cherenkov angle reconstruction of k and p
08 Oct 2008
Clas12-RICH

5. Working Point Assume: Two radiators (only 1 simulated); one per sector
Detector span up to 2 sectors (detect photons from both radiators)
Polar acceptance: from 5 to 30 degree  fix radiator size ~ 6.4 m2
Max gap length ~ 80 cm
08 Oct 2008
Clas12-RICH

6. MonteCarlo Result, Example
Black dots are charged particle positions at RICH entrance (the envelope is the radiator)
Contour lines are positions at the detector level of all photons generated in the radiator
The large arc is the detector surface (photons out of the are not detected)
Geometry is rotated respect to the previous drawing … but represent basically the same idea.
x/y are not to scale
(“k Acc.Efficiency = …” is meaningless here)
08 Oct 2008
Clas12-RICH

7. Radiator Type ?  C5F12 Left C5F12, Right: C6F14
(points are MonteCarlo,
curves are analytical functions)
Left C5F12, Right: C6F14
(Geometry from the previous example)
~ 1 mr difference  C5F12 mandatory!
08 Oct 2008
Clas12-RICH

8. Radiator Thickness / Proximity GAP
Angle reconstruction error
versus
Radiator Thickness,
Gap length
Pad/Pixel size
Optimal combination:
Freon Thickness ~ 3 cm
GAP Length ~ 80 cm
PAD size < 1 cm
C5F12
single sector radiator
2sector photon detector (26 m2)
Note: MC statistics is poor
08 Oct 2008
Clas12-RICH

9. Photon Detector Size
The drawings inside the plot represent different detector sizes simulated
Black dots: represent the black arc
At different external radius
Red triangle: corresponds to the red single sector
Blue square: corresponds to the blue single sector with optimal external radius
Green Triangle: Optimal sector (± 45 degree) and external radius
08 Oct 2008
Clas12-RICH

10. Photon Detector Size / Single Sector Detectors
2.04 mr
Single Sector Detector
+/- 30 degree, r2=417 cm
1.76 mr
Detector Optimal Extension
+/- 45 degree, r2=417cm
08 Oct 2008
Clas12-RICH

11. K-p Separation
08 Oct 2008
Clas12-RICH

12. Considerations
The Freon C5F12 must be cooled, it evaporate at 29 C at STP !!
Detector is huge!
The photon detector size must probably be between m2 (for 2 sectors)
Unfortunately the Cherenkov angle resolution is not impressive; probably there is margin of improvements (both in performance and reduction of size), a careful analysis and design is required!
08 Oct 2008
Clas12-RICH