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Test pulse calibration Marina Test pulse calibration Marina

Test pulse calibration Marina - PowerPoint Presentation

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Test pulse calibration Marina - PPT Presentation

Artuso summarizing the work of R Badman A Borgia PCollins X Llopart R Plackett J Wang Marina Artuso VELO Upgrade Meeting The goal Determine an absolute gain calibration average over the ASIC and per pixel in order to ID: 812823

marina threshold upgrade artuso threshold marina artuso upgrade velo meeting thl data xavi test charge tot gain efficiency curve

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Slide1

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

Slide2

The goal

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

2

Marina Artuso VELO Upgrade Meeting

Slide3

The problems & caveats

We had several of them:Timing of the test pulse with respect to the shutterIdentify the proper pattern to avoid cross talk (spacing 16 seems to be ok)Absolute value of the test pulseReliability of the threshold scan 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

Note: these results are a subset of the studies undertaken at CERN and SU, more systematic studies to come

3

Marina Artuso VELO Upgrade Meeting

Slide4

The test pulse offset

Measured from difference between anin_n02 and anin_no4 & compare with

tpulse

value from

daq

program

Obtained 35.3 mV

Test_in

has Ct=7.5fF (qt=46.875

e

-

/mV)

4

Marina Artuso VELO Upgrade Meeting

Slide5

The non-linear response

Edge of response to negative

tp

for

thl

= 420

Separation depends upon offset and 2*

thl

5

Marina Artuso VELO Upgrade Meeting

Slide6

Fitting for the surrogate function

Use (see http://aladdin.utef.cvut.cz/ofat/Methods/TimePixCalibration/index.htm)

6

Marina Artuso VELO Upgrade Meeting

Slide7

Gain Curves for THL = 400

Marina Artuso VELO Upgrade Meeting

7

Data taken by

Xavi

, 10

testpulses

per setting, readout sum of 10

ToTs

. Thus efficiency curve can not be produced.

Each point is an average over all pixels. Error bar represents the spread.

D04-W0015

Data from

Xavi

Slide8

Fit Parameter Distributions for THL=400

Marina Artuso VELO Upgrade Meeting8

Gain (count/mV)

ToT

0

(count)

C Parameter (

count

mV

)

T Parameter (mV)

D04-W0015

Data from

Xavi

Slide9

Threshold Determined from Calibration

Threshold determined from gain curve (intersect with TOT=0). The value is slightly lower than the true value due to noise.The mean threshold is 33.74x46.875

= 1582

e

Assuming

THLeq

=460 from noise center method, THL=400 corresponds to ~1500 e, consistent with the calibration.

Threshold spread is ~ 36 e.

9

THL = 400

Threshold ( x46.875 e )

Number of Pixels

D04-W0015

Data from

Xavi

Marina Artuso VELO Upgrade Meeting

Slide10

Summary of the fit results at 3 different thresholds

THLgain

tot0

c

t

Thr

(

e

-)

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

10

Marina Artuso VELO Upgrade Meeting

Slide11

Alternative threshold determination

Threshold can be determined from center of efficiency curve (n-of-nonzero TOT wrt tp).

Threshold can also be calculated from

ToT

vs

testpulse

charge

curve

.

(first

non-zero TOT)

. From

this method the threshold is measured to be (33.74x46.875=1581 e), which is 32 e lower than what is obtained from efficiency curve mode.

Marina Artuso VELO Upgrade Meeting

11

Threshold(efficiency) [mV]

Threshold(gain) [mV]

Difference (gain - efficiency) [mV]

D04-W0015

Data from Alessandra

Slide12

Mean Threshold determined from efficiency curve

thl=400 (Xavi)

12

Marina Artuso VELO Upgrade Meeting

Slide13

Conclusions

We have inverse surrogate functions for all the pixels of the DUT studied in test beams 2009 & 2010We have a reasonable determination of the minimum detectable charge at various thresholds, note that a threshold of about 750 e- tb2009 data are dominated by noiseThis information is now available for relevant analyses

Marina Artuso VELO Upgrade Meeting

13