Rafael Ballabriga Suñé Xavier Xirgu Aleixandre Towards the automation of the test of photomultiplier tubes in Barcelona Rafael Ballabriga Suñé Xavier Xirgu Aleixandre

Introduction Measures performed Instruments and Automation Summary Future Plans Open Questions Punts a tractar: Laboratory equipment: Ensenyar amb fotografies el setup que tenim al laboratori de la UB (2xPMTs, ADCs de càrrega, Oscil.loscopi, Taules mòvils i el seu control, Caixa negre i polsador de llum) Measures results: Quines mesures hem realitzat amb el setup. Current Status: Que estem preparats a realitzar, Estat del VME, Problema amb la font de llum. Future plans Dates de l’evolució del projecte. Summary

Measures Performed

Measures performed Absolute Gain Linearity Scintillation Pulses Analysis Crosstalk

Gain Measurement Two Methods have been tested Fitting the spectrum of large number of photoelectrons chosen 2 measures: spectrum/pedestal Easy to compute: Two methods have been chosen : Fitting the spectrum of a large number of photoelectrons Fitting the spectrum of few phe Mathematical simplicity of 1st method 2 ped sig phe σ ) μ ( N - = 19 10 602 . 1 ) ( - ´ = phe ped sig N R G m

Gain Measurement (Setup)

Gain Measurement (Results)

Linearity measurement Double pulse method has been used. Deviation from linearity expressed as: 100 (%) h H D - ´ = Ample de banda de l’oscil.loscopi!!!! Comentar el problema actual!!!

Linearity Measurement (setup)

Linearity Measurement (results)

Linearity as a function of High Voltage Linearity is a parameter dependent on the High Voltage The aim of this measure is to study this dependence Relative linearity has been found: A small high frequency noise has been observed when the LED driver is pulsed (~400μV peak)

Linearity as a function of High Voltage

Linearity as a function of High Voltage

Scintillator Pulse Analysis Objective: To study the performance of the system Scintillator-Fiber-PMT A 12x12 pad has been used with 101 cmts WLS fiber Aiming at: Mean number of photoelectrons/MIP Percentage of signal within 25 ns windows Podem tenir altres centellejadors per testejar??? Mascares???? Nomes tenim 1!!!!!

Scintillator Pulse Analysis (Setup I)

Finding the fiber’s optimal position (setup)

Scintillator Pulse Analysis (results) Histogram of the number of photoelectrons per signal Time response waveform

Scintillator Pulse Analysis (results) Mean time waveform in lineal axis (time vs voltage) Mean time waveform in logarithmical axis (time vs voltage) Slope=-0.8768E-1 Statistics=9568signals

Scintillator Pulse Analysis (results)

Scintillator Pulse Analysis (results)

Crosstalk Measurement A measure of the system Scintillator-Fiber-PMT A system to position automatically the fibers in the cathode has been designed The mask used in this test places diagonally the fibers in the fired pixel

Crosstalk Crosstalk results of two studied channels. 2 diagonal WLS fibers are placed in close contact with each channel. 2.51 100 3.35 2.01 2.09 29 28 36 27 20 35 19 37 21 2.35 100 2.60 2.43 2.26 45 44 52 43 36 51 35 53 37

Crosstalk 2.02 100 2.84 1.62 2.43 21 20 28 19 12 27 11 29 13 4.24 4.08 7.18 5.8 In the upper figure the fibers are placed in close contact with the cathode. In the bottom the fibers are placed 0.5 mm from the pixel.

Instruments & automation

Instruments and automation 2x64 channels PMT H7546 2x1 channel PMT XP2262 Light source (mimics scintillator pulses) 4 channel High Voltage Source 2x32 channel charge ADC (CAEN V792) PC with VME-MXI-2 interface (with LabVIEW software) 3 axis-motion stage ( X-Z motorized, Y manual) Oscilloscope TDS 380 Timers, discriminators, logic units Xp2262 used as a trigger PMT in test with cosmic rays. Amplada de banda oscilloscope The last ones are in a NIM standard Funcionament de la font de llum

Some pictures of the setup

Some pictures of the setup

Some pictures of the setup

Some pictures of the setup The LED pulser

Summary

Summary The setup in Barcelona has been shown It is still under construction aiming at a fully automated system Some measures have been made in order to test the performance of the PMT and calibrate the system

Future plans

Future plans Deadline: October 2003 Reduction of the noise of the LED pulse (1 month) in parallel with signals analysis Which tests are to be performed on each PMT? Absolute Gain of each channel Tests to be performed on some PMTs? Linearity Scintillator pulse analysis (Crosstalk) Deadline: means a massive test has to be designed and ready by October 2003 Fully Automated Criteria to decide which channels of which PMTs must be tested microVolt noise Can we get a complete set of pads in order toe reproduce the system in our Lab?

Open questions

Open questions Define the tests to be performed on each tube & criteria to decide which cannels Base study status Aging problem Performance under magnetic field? Possibility to test in the lab a complete set of Scintillators-fibres-PMT I have been abroad (Aging problem)