Summer Student 2003Ferro Livia1

Summer Student 2003Ferro Livia2 Contents Experimental setup Thermal behaviour and cooling performance of the TOB structures  Variation of pedestal vs time  Temperature vs time Ongoing  Correlation between variation of pedestal and temperature To do  Complete thermal characterization  Investigations on clustering algorithm  Signal to noise performance Conclusions

Summer Student 2003Ferro Livia3 Experimental setup Double Sided rod (12 modules 48 APVs) CCUM 5 Rod equipped with external thermistors (16) support of hybrids opto-hybrids frame cooling pipe ambient (in/outside box) Internal probes also read out Some thermistors are better insulated by a special tape

Summer Student 2003Ferro Livia4 Experimental setup Run taken on 15/05/2003 Data analysis with ROOT: the first time it is used to study thermal behaviour of the rod Measurements philosophy: Always acquire map of external T Cooling at ambient temperature Start run when in thermal equilibrium (study transient) Stop run when new equilibrium reached (study new conditions)

Summer Student 2003Ferro Livia5 Pedestal Channel dependent but time independent offset Should be constant in time The pedestal of channel i is defined as the average of ADC counts over a sample of events: P i = ev

Summer Student 2003Ferro Livia6 Variation of pedestal The pedestal as a function of time in our case is defined as the mean ADC on 128 strips One optohybrid per two APVs Example: module #9 Δped (ADC counts) Time (s) Same optohybrid Start at ~2 minutes after the LV ON

Summer Student 2003Ferro Livia7 Thermal measurements Temperature measured with 16 external probes  Optohybrids (4)  Supports of the hybrids (5)  Air outside the cage  Cooling pipe  Air inside the cage  Carbon fiber  Air over the DCU of module 9  Top cover of the rod Temp (C) Time (s) Special insulating tape LV onStart runStop runLV off Thermal difference in equilibrium conditions between one optohybrid (the hottest) and the cooling pipe: ΔT = (9.26 ± 0.05) °C

Summer Student 2003Ferro Livia8 Fit of temperature vs time Fit of variation of pedestal vs time Variation of pedestal in function of temperature What kind of relation? Pedestals and temperature

Summer Student 2003Ferro Livia9 Fit procedure Temperature T(t) = A + B exp(-t/τ) Error on T: 0.2 C (thermistor resolution = 1C + 10 measurements for each point) τ tells us the time after which pedestal has established Variation of pedestal Δped = Ped n – Ped 0 Δped(t) = A’ + B’ exp(-t/τ’) Error on Δped: 0.3 ADC counts (from previous evaluation of the noise) underestimation because of bin-by-bin correlation and CMN not considered (average per event)

Summer Student 2003Ferro Livia10 Module #11 – special insulating tape Time (s) Temp (C) Time (s) Δped (ADC counts) Δped (ADC counts) APV#41 APV#43 (τ = ± 11.3)s τ = (282.1 ± 1.1)s τ = (301.3 ± 2.1)s A well behaved module  2 /ndf ~ 6

Summer Student 2003Ferro Livia11 Linearity Δped (ADC counts) Δped (ADC counts) Temp (C) APV#41APV#43 Good linear correlation Angular coefficients:ω ~ 4 counts/degree ω ~ 2 counts/degree Error to be calculated

Summer Student 2003Ferro Livia12 Linearity Module #7 Time (s) Temp (C) Time (s) Δped (ADC counts) Δped (ADC counts) APV#25 APV#27 Oscillations: not an isolated case! τ = (166.9 ± 11.2)s τ = (374.8 ± 1.7)s A bad behaved module

Summer Student 2003Ferro Livia13 Oscillations Time (s) Δped (ADC counts) Example: module #12 – APV#47 Maybe, during the run, there were some variations of the probe position To understand

Summer Student 2003Ferro Livia14 Conclusions so far… τ values: optohybrid connected to module #11: (225.0 ± 11.3) s pedestals: (282.2 ± 1.1) s (301.3 ± 2.1) s Thermal difference between the hottest optohybrid and the cooling pipe: ΔT = (9.26 ± 0.05) C Maximum angular coefficient ~ 4 counts/degree Good linear relation between the variation of pedestal and the temperature To understand: strange oscillations Are the measurements the same at –20 °C? To do: complete the analysis (embedded probes…) calculate Silicon temperature cluster finding + …