Calibration for the KEK Beamtest in June 94

Author: Riko Wichmann
This page was created August 18, 1995, last modified December 1, 1995

Characterization of the Runs

The calibration was performed for threshold scans using the whole range of injected charges
(0.5 fC - 4 fC). The run label was choosen to be 343 corresponding to the run number with the smallest calibration charge.
A calibration for the chips on board 3 connected to n-side (chip 12 and 13) could not be obtained since the s-curves for these chips seems to be inverted, even though the order of the threshold voltages is okay. The efficiency was determined by oring two timeslices (2 and 3).
Here we present some results for board 0.

General Results

Threshold curves of channels, which could not be fitted by a s-curve show "-1" for the response curve parameters m_i and for the noise. This means normally, that the channel was always on over the scanned threshold range.
Bonded channels can be separated from non-bonded by
1. larger value of m_3 for bonded channels
2. larger noise for bonded channels
For chip 0, strips were "ganged" in different ways. Strips ganged in the same way were separated by a cut on the channel number from other gang patterns and by a cut on the noise from non-bonded LBIC channels.
For the p-side noise, we extracted the following values:
1. 2 strips ganged (chip 2) : 0.2 fC
2. all channels bonded (chip 3): 0.17 fC
3. non bonded channels (chip 2): 0.1 fC
For the n-side noise, we extracted the following values:
1. 4 or 3 strips ganged (chip 0): 0.28 fC
2. 2 strips ganged (chip 0) : 0.24 fC
3. no ganged strips, floating neighbors (chip 0) : 0.17 fC
4. all channels bonded (chip 1): 0.2 fC
5. non bonded channels : 0.12 fC
The noise for the p-side is slightly less than the one for the n-side, which agrees with the results we found before.
We found a uniform value for the 3 fit parameters m_i for each chip.
For the highest calibration charge, the s-curve for bonded channels on the n-side couldn't be fitted in a lot of cases.

Average Calibration Parameters

The following table gives the average of the response curve parameters over channels 10 to 54 (to exclude effects of the edges) which were bonded to the chip. The separation of bonded and non-bonded channels was performed by a cut on the noise (bonding map).

run   chip#  |    m_1  |    m_2  |   m_3  |  Remarks
----------------------------------------------------------------------------------------
343:    0    |  31.48  |  160.1  |  563.9 | averaged over channel 10 - 54
             |  29.25  |  161.6  |  528.9 | 4 strips ganged
             |  30.22  |  156.9  |  554.4 | 3 strips ganged
             |  32.5   |  162.6  |  567.2 | 2 strips ganged
             |  33.2   |  161.1  |  572.5 | alternating bonded/non-bonded LBIC channels 
        1    |  32.82  |  169.5  |  582.8 | all channels bonded
        2    |  27.76  |  160.9  |  736.2 | 2 strips ganged
        3    |  22.12  |  164.1  |  708.9 | all channels bonded

Some Plots displaying the Results

Here are some postscript plots illustrating the above stated results:

the fit parameter m_i as a function of channel for chip 0, chip 1, chip 2, chip 3
the noise for one channel as a function of injected charge and the noise at appr. 1 fC injected charge as a function of channel for chip 0, chip 1, chip 2, chip 3

Conclusion

The threshold scans were performed using 100 events per threshold. New measurements of the noise as a function of event number show, that the noise does not depend on the number of events - neither for the "old" CDP (1.2 micron process) nor for the "new" CDP (0.8 micron process). Data will be available in a short while in this page.
As before ( calibration for February 95 ) a uniform calibration by averaging the parameter of the response curve could be obtained.
The reason, why the s-curves for the highest calibration charge couldn't be fitted, might be due to the steepness of the s-curve so that there were just 2 or 3 data points on the downward slope. Taking a smaller step size for the threshold voltage at high calibration charges might enable the fitting program to calculate the s-curve parameter.

Complete Calibration Data

The complete calibration data for all 15 chips can be downloaded as gzip'ed tar-files from my directory /pub/wichmann/kek_jun94 on the scipp ftp server (use anonymous ftp if not using the above link).

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