Test for the CLAS12 RICH detector L. Barion, M. Contalbrigo, L. Pappalardo (INFN Ferrara) V. Lucherini, M. Mirazita, P. Rossi (INFN Frascati) M. Turisini (INFN Sanita’) Aldo Orlandi, Angelo Viticchie’ (INFN Frascati) for the preparation of the test set-ups CLAS Collaboration meeting, October 12-15, 2011 Marco Mirazita

Goals of the tests 1.Test MAPMT as single photon detectors  H8500C (normal glass) and H8500C-03 (UV glass) vs R Validate Monte Carlo simulations with a small scale RICH prototype - Laboratory set-up using laser blue light - Hadron (pion) beam test of RICH prototype

MAPMT characterization as single photon detectors 1) Single photon response - distance between peak and pedestal - peak width - threshold cut 2) Few photon response - distance between peaks - width of the peaks 3) Behaviour with HV - lowest HV for a given 1pe efficiency (80%? 90%?) 4) Uniformity of the PMT response - comparison between border and central pixels 5) Cross talk between pixels 6) Comparison between PMTs LASER BEAM LASER BEAM

Laser tests

Test laser setup LASER PC trigger IN trigger OUT fiber collimator filters MAPTM anode OUT 0 63 QDC gate black box Laser intensity can be adjusted via the remote control and using neutral density filters The fiber head can be remotely moved in (x,y) to scan the PMT surface Conventional electronics for data acquisition (CAEN V792) DAQ rate fixed at 100 Hz

short flat cables laser controller motor controller electronics

fiber head + collimator + filters MAPMT – H8500C

anode connections dynode output ground connections

Noise measurement HV=-1125V on but PMT covered by its cap QDC 0 QDC 15 PMT H8500C

Analysis of ADC spectra Poisson weights for 0,1,2,... p.e. pedestal  = average number of p.e. N = max number of p.e. photoelectron peaks Several shapes tried, gaussians provide better results in terms of convergence of the fits and uniformity of the parameters

ADC spectrum HV = 1000 V pixel 25 (border) pixel 36 (centre) Fits with up to 5 p.e. peaks

PMT response normalization constantaverage number of p.e. 1. p.e gain (QDC channels) fraction of 1 p.e. loss PMT H8500C HV = 1000 V

Results for 10 MAPMTs HV = 1000 V points: mean of 64 pins error bar: RMS of the 64 pins gain from data sheets (a.u.)

ADC spectrum vs HV HV = 1000 V HV = 1040 V HV = 1075 V pixel 25 (border) pixel 36 (center) better pedestal/signal separation easier threshold setting

HV scan Up to a factor 2 increase in the gain More than 85% detection efficiency for HV>1040 V Recommended working range HV= V

Measurement in magnetic field Compensating sextupolar magnet No field at the center Up  50 gauss going toward the border Perpendicular to the electron motion in the MAPMT HV=1040 V larger field smaller field

Magnetic field test Less than 15% gain loss Small decrease in detection efficiency No major degrading in the MAPMT response HV = 1040 V B=0 B>0 B=0 B>0

Cross-talk analysis Compare the pixel response when - it is directly illuminated by the laser - adjacent pixels are illuminated Threshold: 3  above pedestal

Cross-talk contamination N = events above threshold i = up,down,left,right = 2.1% = 2.0% = 2.1% = 2.6% For a given pixel:

Hadron beam test CERN, july 7-20, 2011

T9

The T9 hadron beam Magnet polarity set for negative particles 400 ms 40 s Time structure of the beam: 3 short pulses every 40 s duty cycle ~3% Transverse dimensions: few cm at the entrance window of the hall focused after ~7.5m (close to our setup) Hadron intensity particles per pulse N(  ) ~ 60 N(K)

The Experimental Hall Beam CLAS12 RICH GSI Glasgow

The Setup Beam Backward Scintillator 2x3 cm2 Two Forward Scintillators ~1x1 cm2 coinc. aerogel PMT Trigger of the DAQ: T beam *SC back *SC forwH *SC forwV Two Reference Scintillators ~2x3 cm2 black box 60 cm

The RICH prototype

The PMT array 10 H85008 R8900 H8500-C H8500-C-03 H8500-C H8500-C-03 H8500-C H8500-C-03 H8500-C H8500-C-03 H8500-C H8500-C-03

The acquisition electronics Maroc2 front end electronics 1 control board with 2 back planes up to 8 front end cards per back plane 64 channels per card, 4096 total channels preamplifier, adjustable from 1/8 to 4 ADC, about 80fC per channel control board back planes MAROC front end cards Visual C++ program to read the electronics (windows) Event transfer to disk in single or multi event mode

Preliminary test of the DAQ 2 reference scintillators for counting normalization trigger rate measured with a scaler event rate measured with DAQ system DAQ eff. = event rate / trigger rate 1. scan of trigger rate by moving the box in or out of the beam 2. take into account ~3% beam duty cycle black: single event buffering red: multi-event buffering DAQ efficiency DAQ rate before (empty symbols) and after (full symbols) duty-cycle correction DAQ rate DAQ rate in one spill ~200Hz

Run conditions Most of the 2 weeks of data taking to deal with the electronics - timing between MAPMT signals and trigger - find stable conditions of low voltage supply - optimization of preamp gain No stable conditions were found with 12 MAPMT only 1 back plane was used 8 MAPMT H8500 (HV=1075 V) few preliminary data with R8900 (HV=970 V) preamp gain = 4 E beam (GeV) Aerogel (cm) cm N. of triggers t (cm)n k 102= k 103= k 103= k k

ADC distributions R8900 gain = 0.5 PRELIMINARY RUN

ADC distributions H8500 gain = 0.5 PRELIMINARY RUN

ADC distributions H8500 gain = 4 FINAL CONDITIONS

ADC distributions threshold to remove pedestal 2.5% of the pedestal height = 0.05 Fit of the distribution additional exponential background

Hit distributions aerogel n=1.05 aerogel n=1.03 1cm2cm 1cm 3cm integrated distributions of hits above threshold

Cerenkov ring calculation Minimization of: Free parameters are the center coordinates (X C,Y C ) and the radius R The problem can be solved analitically Procedure : 1.Calculate center and radius with all hits above threshold 2.If the distance of a hit from the ring is bigger than 2 pixels (12mm) it is removed and a new calculation is done 3.The iteration is stopped if no more hits have to be removed or if N hits <3

Some ring GOOD EVENT

Some ring BAD EVENT

Some ring blue: first iteration red: last iteration Background hit Cross-talk hit? Analysis of cross-talk hits: when 2 or more hits in adjacent pixels, keep only the one with highest QDC readout

Aerogel with n=1.05: ring reconstruction 1 cm 2 cm 3 cm red: good hits black: hits for the fitted ring (at least 3) blue: cross talk hits hits per event rescaled to full circle fraction of event with a ring Number of hits per event

Aerogel with n=1.05: radius mean sigma Expected radius for pions ~110mm  measured ~120mm  increasing with t Larger radius, better resolution for larger t  expected opposite 1 cm 2 cm 3 cm

Radius resolution estimation  n free parameter, everything else known from geometry Cerenkov angle resolution  beam  3 mm

H8500 – entrance window H8500-C (normal glass) H8500-C-03 (UV glass) With UV glass about 0.5 hits more ~+20% Smaller differences for increasing threshold Number of hits per ring t=2 cm

Fitted Radius: H8500 types Fitting rings with 4 PMT of the same type H8500C normal glass H8500C-03 UV glass =119.0±0.1 mm  =4.48±0.03 mm =118.4±0.1 mm  =4.48±0.02 mm t=2 cm

Runs with mirrors PRELIMINARY ANALYSIS 4 x R8900 MAPMT E = 1.5 GeV

Radius reconstruction no mirrors  =4.48±0.03 mm  =7.9±0.3 mm = 4.9 on half ring ~ 10 on full ring Xtalk ~ 3-4 hits No cross talk hit analysis PRELIMINARY ANALYSIS

Conclusions and outlook Laser tests of MAPMTs has been (are being) performed in Frascati measurements at 1000 V in agreement with data sheets, but too low HV for reliable single photon detection increasing HV (>~1040 V) sufficiently good single photon detection efficiency can be obtained no large effect from small magnetic field (preliminary) We had successful test at CERN we saw pion Cerenkov rings close to what we expected there things that need to be analyzed more in detail electronics is a crucial point  H8500 could be good single photon detectors

Next RICH prototype Larger gap lenght ~ 1 m About 20 MAPMT to accomodate in the prototype Radial geometry CLAS sector geometry

backup slides

Pedestal measurements: stability RMS (QDC channels) Run number QDC 0 QDC Very low noise, high stability over a week of measurements PMT H8500C

ADC fitting functions GAUSS SKEWED GAUSS peak distance

Radius resolution Larger thickness means: - larger uncertainty on the emission point  R/R = t/d  3  9 % -larger number of hits ~5.5 t=1 cm ~8.7t=3 cm  /  -30 % - more surfaces to cross ? - other effects? t=2 cm black: N  5 red: N<5 sigma(R) No effect on the radius means

Aerogel with n=1.05: ring center mean (X) mean (Y) XY coordinates of the center t=2 cm sigma (X) sigma (Y)

1 cm E=4 GeV Aerogel with n= cm E=4 GeV radius 3 cm E=10 GeV XY coordinates of the center 3 cm E=10 GeV Two rings for pions and kaons?

Aerogel with n=1.03 More BKG hits in lower PMTs Applying fiducial cuts E=4 GeVT=1 cm

H8500 – border/center PMT Number of hits per ring Number of pixels:N(center) = 40 N(border) = 24 R=1.7 Number of hits:R>2 t=2 cm