A RICH Detector for strangeness physics A RICH Detector for strangeness physics in Hall A at Jefferson Labin Hall A at Jefferson Lab
. Why
. How
. Main Characteristics/Expected performances.
. Tests. CERN. Cosmics. Beam
. Conclusions and outlook
IMAGING 2003 – Stockholm – 24th – 27th June 2003
F. Cusanno – Hall A RICH collaboration
-N Interaction-N Interaction
VN = V( r ) + V( r ) S.SN + V(r ) SN.lN + VT( r) S12
Very important for astrophysics (neutron star formation)
E-94-107 - F. Garibaldi, S. Frullani, J. LeRose, P. Markowitz, T. Saito
Process Rate
signal (e,e’K) 10-4 – 10-2
accidentals
(e,e’)(e,pi)(e,e’)(e,p)(e,e’)(e,k)
1001000.1
• RICH Project started Summer 98• Test CERN November 00
= msr
p/p = 5%
p/p =1 x 10-4
Cos =1/n / = tg With N p.e. per ring
/N
- n fixed by the momentum(2GeV/c) C6F14, transparent down to 160 nm
- compact (~ 50 cm)- 310 x 1820 mm2- relatively thin (18% X0)- quarz window 5 mm
15 mm300 nm
MCarlo
radiator
• NEOCERAM• Quartz cylinders, 5mm quartz window
50*
50*
50*
100*
100*
100*
VMEtransferttime (μ )s
.kHz180101202000 /48kHzADC
2.8kHz36010300800 /48kHzADC
3.3kHz30210192200 /24kHzADC
16
30
710
(Sum μ )s
2.9kHz102402000 /24kHzADC
6.4kHz1096200 /48kHzADC
1.4kHz10600800 /24kHzADC
Maximum,100%rate
dead time
Trigger andend overheadtime
(μ )s
Digitization(time μ )s
Clock/#frequency
of ADC
*100 / ,pad event is assumed 1μσ/dataword + 50 μs /event; at this low occupancy a block movementdoes not decrease the time (pedestal)
The network datatransfert will go in parallel mode via 100 Mbit FastEthernet
6.4
6.4KHz
Freon System
The fluid is degassed by bubbling high purity nitrogen through a bed of 2 micron pore, sintered stainless steel cylinders and then through the liquid to scavenge air in solution in the fluid. The sintered stainless cylinders maximize the contact area between the nitrogen and the radiator liquid. This significantly speeds the degassing of the radiator liquid. The nitrogen then passes through a cold condenser that removes the perfluorohexane from the air/nitrogen/perfluorhexane stream and returns the perfluorhexane to the tank. The fluid also passes over an alternating pair of molecular sieve filters before being pumped to the radiator.
Several methods are used to verify the quality of the radiator fluid. The effluent from the degassing tank passes through an oxygen and moisture sensor. An on-line transmission monitor measures the transmission of the liquid in the return flow from the radiator. Periodically the return flow is temporally diverted through an optical sample cell. The light from a mercury vapor light, filtered to select the appropriate wavelength (184 nanometers) is passed through a beam splitter. One light beam goes through the sample cell and its intensity measured with photodiode. The other light beam goes directly to another photodiode and is used as a reference. The ratio of outputs from the two photodiodes is an approximate measure of radiator liquid transmission at the selected wavelength.
Bandpassfilter
gas system
CERN tests Nov ‘00
CERN tests 11/00
7 GeV/C beam
Argon CH4 (25/75)
2 photocathodes (Rome and CERN)
Equal performances
N = ~ 12
Jlab Cosmic tests Aug 01 2100 V
On beam tests
March 02
2150 V 2250 V
G~ 5 x 104
G~ 1 x 105
MPWC Gain Comparison
STARPRESENT STATUSOLD STATUS
HV (V) ALICE OUR RICH
1900 2.8 2.6
2000 4.7 4.4
2100 6.8 6.3
MIP signal size (# of pads)
‘Good working’ range
Jlab Cosmic tests June 03
Scan in positioning: presently we are on the left side, 160 mm distance from boundary (and >0). Extrapolating to =0 in with the whole ring in the active area: ~ 10-11 p.e. (as at CERN)
2150 V
G~ 2.5 x 105
A0=26
ConclusionsConclusions• The present Hall A PID setup is not sufficient for unambiguous K identification needed for hypernuclear spectroscopy
• A Proximity focusing C6F14/CsI RICH detector has been built and tested
• Performances in the expectations - gain problem understood and fixed
CsI evaporation technique unders control
Detector ready to be installed for the Hypernuclear experiment
