Bernard JEAN-MARIE Pmt Group Meeting 1 PMT Testing o Pulse parameters at low gain o Study of Gain measurement reproducibility o Gain prediction accuracy o Measurement accuracy on linearity and stability o Criteria to select ECAL low gain pmts

Bernard JEAN-MARIE Pmt Group Meeting 2 R Pulse parameters at low gain (1) oPulse parameters measured from gain to oThe read boxes materialize a gain range of 15 (from G= to ) as expected for ECAL. This range corresponds for the LA3791 to V≈ 650 and 1000 volts oThe transit time spread about 5ns is acceptable. oAs expected, increase of rise time, width and fall time. oDue to the clipping, a possible systematic effect induced by the shape variation should be checked. o

Bernard JEAN-MARIE Pmt Group Meeting 3 R Pulse parameters at low gain (2)

Bernard JEAN-MARIE Pmt Group Meeting 4 Study of Gain measurement reproducibility (1) oInadvertently (!) the gain of the reference pmt has been measured 102 times over a 10 days period. oHV = 1000 volts, gain around oAlthough the voltage show a dependence with temperature, the gain stay stable. oIn fact V increases with temperature, but the gain decreases with temperature. Both effects cancel themselves. oThe distribution has a reasonable Gaussian shape with a sigma of 2.4%. oThis is a good estimate of the reproducibility of the gain measurement.

Bernard JEAN-MARIE Pmt Group Meeting 5 Study of Gain measurement reproducibility (2)

Bernard JEAN-MARIE Pmt Group Meeting 6 Gain prediction accuracy (1) oIn general, after measuring a box of 50 pmts, 2 pmts (AA1761 and AA1764) are measured. oAA1761 was choosen as it was linear an stable oAA1764 was choosen as it was non linear and stable oThe aim was to study the evolution of the measurement on a long period to detect possible evolution of the bench. oConclusions:  On Linearity: There is definitely some evolution in time AA1761 is very linear even at and possibly at lower gain AA1764 is non linear There is a definite correlation between the two pmts. This demonstrate that the linearity variation is a collective process affecting all the measurements at a given time.  On Stability The stability measurement is much more stable. Except for the points at which have a larger spread (almost erratic!).

Bernard JEAN-MARIE Pmt Group Meeting 7 Gain prediction accuracy (2)

Bernard JEAN-MARIE Pmt Group Meeting 8 Gain prediction accuracy (2)

Bernard JEAN-MARIE Pmt Group Meeting 9 Gain prediction accuracy (1) oHamamatsu Datasheets provide voltages for gain and oOne assumes a gain variation G = G° x V alpha oFrom those two voltage values, the two parameters G° and Alpha can be computed. oThe LAL bench measures G° LAL and Alpha LAL and the voltage V LAL for gain and oThe relation between G0 /GO LAL and Alpha /Alpha LAL can be fitted (see plots) oFor a given voltage at a given gain, the corresponding Hamamatsu voltage can be calculated. oFor example at G= :  Log(V)=(LOG10(G° LAL )+Alpha LAL *LOG10(V LALat5104 )-LOG10(1,09*GO LAL * ,46))/(0,91* Alpha LAL +0,05)  And G Hamamatsu = G° hamamatsu x V alpha hamamatsu oThis is represented on the plots. The gain accuracy is 6.7% and 8.3% at gain and oThis sigma includes all the experimental errors

Bernard JEAN-MARIE Pmt Group Meeting 10 Gain prediction accuracy (2)

Bernard JEAN-MARIE Pmt Group Meeting 11 Gain prediction accuracy (2) oGain parameterized by: G = G°x V alpha

Bernard JEAN-MARIE Pmt Group Meeting 12 Gain prediction accuracy (2)

Bernard JEAN-MARIE Pmt Group Meeting 13 PMT Selection (1) oGeneral rules:  There is no correlation between pmt gain and voltage : Use for the inner pmts (at the lowest gain) pmts operated at the maximum voltage. The contrary for the outer (squeeze the transit time spread).  There is a correlation between G 0 and voltage for a given gain Use G 0 to select pmts operated at highest voltage.  Select linearity on gain 10 6 and and (if it has been measured). A pmt linear from 10 6 to will have the best chance to be linear at lower gain. The spread in linearity is certainly a good criteria oSelection:  Green luminous index   G°   Linearity spread 10 6 and 10 4   Stability 

Bernard JEAN-MARIE Pmt Group Meeting 14 PMT Selection (2)

Bernard JEAN-MARIE Pmt Group Meeting 15 PMT Selection (2)

Bernard JEAN-MARIE Pmt Group Meeting 16 PMT Selection (2) Inner ECAL