A RICH detector for CLAS12 CLAS12 European Workshop February 25-28, 2009- Genova, Italy Evaristo...
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Transcript of A RICH detector for CLAS12 CLAS12 European Workshop February 25-28, 2009- Genova, Italy Evaristo...
A RICH detector for CLAS12
CLAS12 European WorkshopFebruary 25-28, 2009- Genova, Italy
Evaristo Cisbani INFN Rome and ISSPatrizia Rossi
INFN- Laboratori Nazionali di Frascati
Hall BCentral Detector
Forward Detector
Hadron PID in CLAS12 BaselineGeV/c 1 2 3 4 5 6 7 8 9 10
/KTOF
LTCC
HTCC
/pTOF
LTCC
HTCC
K/pTOF
LTCC
• /K PID rely on LTCC performance in 3-5 GeV/c
• No K/p PID in 5-8 GeV/c
Ratio K/ ~ 0.1-0.15 If we assume a 10% inefficiency for Cerenkov rejection factor /k ~1:1
RICH detector
RICH detector
θC
€
cosθC =1
nβ⇒ cos−1 m2 + p2
np
⎛
⎝ ⎜ ⎜
⎞
⎠ ⎟ ⎟
r
L
2θ
θ(deg)
r(cm)= Ltanθ
38.4 79
K 36.4 73
p 30.3 58
P = 2 GeV/c L= 1m n=1.28 (liquid freon)
Good separation /K/p
Which RICH?
• Liquid Radiator (Freon)
–May cover up to 5 GeV/c–Relatively inexpensive (proximity focusing RICH)
•Aerogel + Gas Radiators
–May cover up to 10 GeV/c–Very expensive(cost Aerogel RICH ~ 5x Proximity Focusing RICH)
Location of the RICH
Replace part of LTCC:
- No impact on baseline design
- Nobody will probably complain
- Large space available (and to be covered!)
Replace HTCC:- Impact on baseline design
- Impact on tracking recontruction
Simulation done for LTCC
LTCC sector
~ 6.2 m2
entrance window
1 m depth
• A proximity Focusing RICH (~1 m2 surface) is working in Hall A and being used in the Transversity experiment
• Same RICH type used by ALICE experiment ( ~10 m2
surface)
Hall A Proximity RICH
Proximity Focusing RICH
The Proximity Focusing RICH consists of 3 basic components:
Cherenkov Liquid Radiator
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
Gap (gas filled space)
Photon Detector
Hall A Proximity RICH
• The Freon vessel (radiator) is the most fragile component of the detector• The Freon pressure is partially compensated by the glued spacers• Quarz planarity and parallelism 0.1 mm
Evaporation facility
• CsI is evaporated on the pad panel in the evaporation chamber: 120h x 110r cm2 (vacuum 10-7 mbar)• The evaporation facility - cost ~ 0.5 M$ has been built by the INFN Rome group (now at Stony Brook University)
Hall A RICH: QE measurements (July ‘08)
25
25
~ 25% Quantum Efficiency has been measured
K/ rejection ~ 1/1000
F. Garibaldi et al. NIM A502 (2003)
Hall A RICH in Hypernuclear Exp. (2003-2005)
• 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
Monte Carlo studies: purpose
Old GEANT3/Fortran/PAW based MonteCarlo framework the same used the for the development of the Hall A Proximity RICH but with different geometry and size!
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)
Limitation on photon production (~3000) old memory constraint. This becomes relevant for radiator thickness > 2.5-3.0 cmMain output parameter:k= mean error on Cherenkov angle
reconstruction of k and
Monte Carlo studies: framework
θCθCK
K-= (K+ )/2
Working Point
Assume:• Two radiators (only 1 simulated); one per sector• Detector span up to 2 sectors (detect photons from both radiators)• Radiator Polar acceptance: 5° ÷30° fix radiator size ~ 4 m2
• Max gap length = 80 cm
Not to scaleUnit: mm and degree
•Particles uniformely distributed in the phase space
•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 there are not detected)
•Geometry is rotated respect to the previous drawing … but represent basically the same idea
Monte Carlo Result: Example
x/y are not to scale
Points: MonteCarlo, Curves: analytical functions~ 1 mr difference C5F12 mandatory!
Geometry from the previous example
Radiator Type
C5F12 C6F14θCθC
n
Simulation with realistic phase space
To detemine the best photon detector size, ,K,p have been generated at the LTCC-RICH entrance window according with a realistic phase space distribution of reconstructed momenta and angles.
(GeV/c)
K- Separation
Radiator= 2 cm
Radiator= 1.5 cm
Radiator= 3 cm
• Radiator Thickness = 1.5, 2, 2.5, 3, 3.5 cm• Gap length = 80 cm• Pad/Pixel size = 0.75 cm
Angle reconstruction error vs:
100k events
K- Separation• Radiator Thickness = 2 cm• Gap length = 60, 80 cm• Pad/Pixel size = 0.75 cm
Gap Length= 60 cm
Gap Length= 80 cm
Separation at 5 GeV/c: 3 = 1/100 / 75% efficiency 1/10 / 95% efficiency
Angle reconstruction error vs:
100k events
Radiation thickness
Thickness (cm) X0 (%)
Entrance window
Al 0.05 0.5
Rohacell51 5 2
Al 0.05 0.5
Radiator
Neoceram 0.4 3
C5F12 2 10
Quartz 0.5 4
Gap
CH4 80 0.001
Photon Detector
Pad NEMAG10 0.08 0.4
GEM chamber 1 0.6
Total radiation thickness of the proposed RICH: ~20% X0
HBD @ Phenix
Replace MWPC with GEM Chamber faster, higher gain, stability at high rate
Photon Detector
Hall A RICH Factor Class12 RICH
Readout 95 4 380 (15%)
MWPC: Pads Planes 20 10 200 (8%)
MWPC: Parts (Macor Insulator) 15 10 150 (6%)
Freon (C6F14) 20 40 800 (33%)
Quartz+Neoceram 30 20 600 (24%)
Mechanical Structure 30 10 300 (12%)
Evaporation Fac. 500 1 500 (exist)
Freon Recirculation System 20 (?) 1.5 30 (?)
Total 210+520 2420+530
Class12/Hall ARadiator: 36-48 (min.-max. volume), 24 (surface)Detector: 13 (surface), 4 (chs)
GEM ~ 1.2 x MWPC k$(estimation from Lire, CHF, $ and Euro)
Costs - Very Preliminary!!
Monte Carlo simulations have been started to study the feasibility to replace 2 sectors of LTTC with a proximity focusing RICH detector
From very preliminary results it seems that: The best choice is to use Freon C5F12 but it must be cooled! (it evaporate at 29 C at STP !!)At present stage the Cherenkov angle resolution is not impressive
a careful analysis and design is required to improve both the performance and the detector size
orientation of radiator pad size…
work is in progress
Conclusions and outlook