The preamp chip threshold (Qthr) and noise for each channel have been measured
at three different Ud settings (Ud = 1000, 1200 and 1400 mV), using an attenuation
of 16 dB, and at four values of input capacitance Cdet (Cdet = 0, 56, 100 and 180 pF).
See here for details of the method used.
At Cdet = 0 pF and 100 pF, the data are available for boards
1-28, 39-57, 60-76 and 78-83, for a total of 70 in all. At Cdet =56 pF, for boards 1-38,
and at Cdet = 180 pF, for boards 1-90, excluding boards 58, 59 and 77.
Results for Cdet = 180 pF are presented in
Fig.1_180pF. Page 1 gives
the Qthr and noise distributions; pg. 2 - the Chi2 fit to the threshold curve for all three Ud
settings; pg. 14 - the means of the Qthr and noise values for each board
versus board number; pg. 15 - the residuals for the
Qthr and noise distributions, which are the differences between each channel's value and
the mean value for that chip.
Note that the average value of the noise obtained in this analysis is around 2.1 fC instead of
1.5 fC as found in the previous analysis of boards 1-28. This is because we now
fit the threshold curve to a more convenient Gaussian error function,
instead of a Fermi function. To address this issue properly, we need in future
tests to decrease the step size in the DAC code for the input signal from 20 to 5, and
eliminate the binning effect. Another feature is the use of the Chi2
in this analysis. One can see that the mean Chi2 is close to one only for
Ud = 1400 mV. At higher thresholds, the fit is not as good as for Ud = 1400 mV.
The gain and the discriminator offset (the difference between the nominal 1600 mV value and
the observed value)
are obtained from a fit to the Qthr values at all three Uthr (page 18 in
distributions can be seen on pg. 29, the mean values on pg. 32 and the residuals
on p. 31.
The means and widths of the distributions for all boards together, as well
as the widths of the channel residuals, are given in Table 1 below. A comparison with
the same table for the CMP16E chip (our previous submission,
shows significant improvement in Qthr and the Qthr residual distributions. Their
widths are 1.5 times less than for the CMP16E chip. This is likely due
to the AMI transition from a 1.2 micron to a 1.5 micron technology between the two
Results at Cdet = 0, 56 and 100 pF are shown in
Fig.1_100pF. All parameters
except the noise are independent of Cdet (see
Fig.1_Cdet where the mean values of the
parameters are presented).
There is an interesting feature in the data taken at Cdet = 0 pF.
Channel #16 in all boards
has systematically different values from the rest of the channels for Qthr, noise and
gain (see pages 16 and 33 in