Test pulse calibration Marina Artuso summarizing the work

+ Test pulse calibration Marina Artuso summarizing the work of R. Badman, A. Borgia, P. Collins, X. Llopart, R. Plackett. J. Wang Marina Artuso VELO Upgrade Meeting

+ 2 The goal n Determine an absolute gain calibration (average over the ASIC and per pixel) in order to: n Determine TOT to charge calibration and produce Landaus which give an absolute measure of the collected charge for parametric studies (sensitivity to HV, thresholds…) n Determine the minimum detectable charge at any given threshold (input to simulation) n Verify influence of proper charge weighting on resolution and more realistic comparison with simulation Marina Artuso VELO Upgrade Meeting

+ 3 The problems & caveats n We had several of them: n Timing of the test pulse with respect to the shutter n Identify the proper pattern to avoid cross talk (spacing 16 seems to be ok) n Absolute value of the test pulse n Reliability of the threshold scan n Best data so far taken by Xavi, will be the basis of the discussion today, much more on the failed attempts on a future presentation n Note: these results are a subset of the studies undertaken at CERN and SU, more systematic studies to come Marina Artuso VELO Upgrade Meeting

+ 4 The test pulse offset Measured from difference between anin_n 02 and anin_no 4 & compare with tpulse value from daq program Obtained 35. 3 m. V Test_in has Ct=7. 5 f. F (qt=46. 875 e-/m. V) Marina Artuso VELO Upgrade Meeting

+ The non-linear response 5 Separation depends upon offset and 2*thl Edge of response to negative tp for thl = 420 Marina Artuso VELO Upgrade Meeting

+ 6 Fitting for the surrogate function n Use (see http: //aladdin. utef. cvut. cz/ofat/Methods/Time. Pix. Calibration/inde x. htm) Marina Artuso VELO Upgrade Meeting

+ D 04 -W 0015 Data from Xavi Gain Curves for THL = 400 Data taken by Xavi, 10 testpulses per setting, readout sum of 10 To. Ts. Thus efficiency curve can not be produced. Each point is an average over all pixels. Error bar represents the spread. Marina Artuso VELO Upgrade Meeting 7

Fit Parameter Distributions for + THL=400 8 D 04 -W 0015 Data from Xavi To. T 0 (count) Gain (count/m. V) C Parameter (count m. V) Marina Artuso VELO Upgrade Meeting T Parameter (m. V)

+ 9 Threshold Determined from Calibration Number of Pixels THL = 400 Threshold ( x 46. 875 e ) Marina Artuso VELO Upgrade Meeting D 04 -W 0015 Data from Xavi n Threshold determined from gain curve (intersect with TOT=0). The value is slightly lower than the true value due to noise. n The mean threshold is 33. 74 x 46. 875 = 1582 e n Assuming THLeq=460 from noise center method, THL=400 corresponds to ~1500 e, consistent with the calibration. n Threshold spread is ~ 36 e.

+ 10 Summary of the fit results at 3 different thresholds THL gain tot 0 c 420 0. 21± 0. 008 21± 2. 2 123. 4± 43. 4 41. 8± 1. 7 980 400 0. 21± 0. 007 30. 6± 1. 8 134. 8± 41. 9 30. 2± 1. 5 1580 380 0. 19± 0. 007 47. 3± 1. 8 187. 1± 44. 7 16. 6± 1. 0 2090 Marina Artuso VELO Upgrade Meeting t Thr (e-)

+ Alternative threshold determination 11 D 04 -W 0015 Data from Alessandra n Threshold can be determined from center of efficiency curve (n-of-nonzero TOT wrt tp). n Threshold can also be calculated from To. T vs testpulse charge curve. (first nonzero TOT). From this method the threshold is measured to be (33. 74 x 46. 875=1581 e), which is 32 e lower than what is obtained from efficiency curve mode. Threshold(efficiency) [m. V] Marina Artuso VELO Upgrade Meeting Threshold(gain) [m. V] Difference (gain - efficiency) [m. V]

+ 12 Mean Threshold determined from efficiency curve thl=400 (Xavi) Pixels Responding 70000 60000 Number of pixels 50000 40000 30000 20000 10000 0 0 500 1000 1500 2000 [e-] Marina Artuso VELO Upgrade Meeting 2500 3000 3500

+ 13 Conclusions n We have inverse surrogate functions for all the pixels of the DUT studied in test beams 2009 & 2010 n We have a reasonable determination of the minimum detectable charge at various thresholds, note that a threshold of about 750 e- tb 2009 data are dominated by noise n This information is now available for relevant analyses Marina Artuso VELO Upgrade Meeting