E - 94 -107
RICH detector status report
- Why
- How
- Were we are
E-94-107 - High Resolution 1p shell Hypernuclear Spectroscopy F. Garibaldi, S. Frullani, J. LeRose, P. Markowitz, T. Saito
QuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.
forward angle&very good very good PIDPIDare needed to be able to get reasonable counting rates and unambiguous kaon identification in order to clean up the huge background
Kaon Identification through Aerogels:
AERO1 n=1.015
AERO2 n=1.055
p
k
KAONS = AERO1•AERO2
p k
All events
Hypernuclei -> smaller scattering angle -> higher background --> something else is needed
Contamination of pion and proton on the K signal with different PID systems, for the counting rates of two levels (10-2 Hz and 10-4 Hz)
Process Rates
signal (e,e’K) 10-4 – 10-2
accidentals
(e,e’)(e,pi)(e,e’)(e,p)(e,e’)(e,k)
1001000.1
RICH
0
without RICH with RICH
Cos =1/n / = tg N = p.e. per ring
/sqrt(N)
- n fixed by the momentum(2GeV/c)
C6 F14, transparent down to 160 nm
- compact (~ 50 cm)
- relatively thin (18% X0)
- 310 x 1820 mm2
- quarz window 5 mm
15 mm300 nm
€
Many parameters affect the detector performances (# p.e.)
- quartz transparency in the v.w. region of interest (160 - 220 nm)
- freon purity to not absorb the emitted Cherenkov light
- freon purity circuit + continuously monitoring
- CsI photocathode
- evaporation + on line QE absolute measurement
- QE is strongly affected by oxygen and moisture
- Careful handling of photocathodes after evaporation
- Continuous monitoring of gas “purity”
CERN tests
11/01 !! 7 GeV/C p beam
Argon CH4 (25/75)
2photocathodes
Romeand CERN
Equal performances
N = ~ 12N = ~ 12Can be be
extrapolated
to ~ 1414 with CH4
Evaporation system
110 cm
120 cm
Photocathode
UV source box
PMT Collection chamber
Rotating mirror (CaF2)
Movement system
10-6 mbar vacuum, 2 nm/s CsI deposition at T = 60 ºC (CERN experts indications). Vacuum - heating conditions start 15 –24 h before evaporation. A post -evaporation heat treatment is done for 12 hours.
Crucible bars
Evaporation layout
§ PhotoCathode– crucibles plane distance: 42 cm§ 4 μ m Ni– 1μ m Au support§ :0.8 ,crucible quantity g weight each one
~320 ( corresponding to nm thickness expected )and measured
.Pos X .Pos Y#1:Source 2.5 53.15#2:Source 61.5 53.15#3:Source 61.5 -12.85 [ ]:y cm 66#4:Source 2.5 -12.85
. [ ]:Ep min nm 286 [ ]:x cm 59. [ ]:Ep max nm 387
.:diff 26.1%
0,0
1Source 2Source
3Source4Source
Crucibles positions
1 3 57
911
13S1
S5
S90
50
100
150
200
250
300
350
400
350-400
300-350
250-300
200-250
150-200
100-150
50-100
0-50
Thickness (nm)
Expected thickness
64,40
3PD
Reference QE
0
0.05
0.1
0.15
0.2
0.25
150 160 170 180 190 200 210 220
Wavelength (nm)
QE (%)
CERN
Jlab
Jlab Cosmic tests June 03
Extrapolating to =0 and taking into account the geometric inefficiency and false triggers (cosmics): > ~ 12 p.e. (as at CERN)
2200 V
G~ 2.5 x 105
A0=26
Probably underestimated (protons below threshold, random coincidences etc.)
The detector has been tested succesfully at CERN Novembre 2000 (12 p.e.(14-15 with CH4)) 2 photocathode evaporated respectively at CERN and ROME
---> same result !(the best CERN had obtained with the same gas mixture)
After trasportation, mechanical problems(a. w. to photocatode distance)
lower gain --> lower # p.e.(Difficult to measure, difficult to fix) fixed July 2002 right gain back, but-wait for freon-Radiator accident-Fixed, but still some leak ->quench
--> lower gain (lower #p.e.)
Neverthless increasing HV (2100 to 2200V) gain back p.e 10-12 (very difficult to estimate with cosmic, conservative)
Fixing freon leakage ==> 12-14 p.e.(look at possible moisture contamination!)
detector ready end ofJuly-spare radiator-spare f.e. electronics-3 spare radiators to be evaporated by end of July
Slow control status to be checked (kaon meeting should be good (Jlab task)
DAQ integration (see Bodo)
Software - C++ code written by Guido being tested with CERN data for comparison with CERN (report next kaon mee.- improving the tracking (minimizing the angle error) using FPP?
Detector ready to be installed when needed - decision driven by Hall A installation schedule
(eventual “last” evaporation not to be anticipated)
- only test missing: hight rate behaviour on Jlab beam
- the CERN experience (the only one available) says that we should not have problem but no tests are possible with a continuous beam) (type of problem: charging up of photocathode (CsI))
- F.Piuz (Pilos proceedings): 24 hours with 6.4X10-10 Coulomb/mm2/s
- in our case (Hall A, our experiment at 250 KHz we have 2 x 10-13 coulomb/mm2/s
Conclusions