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The ADC produces small variations in the channel width.
The effective width of each channel has been determined by adding up
all available ground calibration data (up to 1990 March 17 about
events) into a single spectrum 
and subtracting
a smooth spline function.
The correction table contains for each raw channel the lower 
and upper 
bin edges, where 
is the bin width.
The ADC non-linearity correction of the pulse height results then from
equation F.5
and is plotted in
Fig. F.2.
To avoid discretization effects random numbers r are used
to distribute an event amplitude within the bin.
Apparently, on average a pulse height event 
is transformed
into an event with 
, e.g., 
and 
.
It seems unclear whether this feature is intentional.
Also there is known a photon excess at lower energies
[Hasinger and
Snowden1992]
which could have been produced by an offset of 3-5 eV
(one channel is approximately 10eV).
Figure F.2: Correction tables for ADC non-linearities
(cf. Eq. (F.5)).
Upper panel: the effective bin width in channels of each ADC\
pulse height bin ( 
). It has been obtained by subtraction
of a smooth spline function from an accumulated spectrum
( 
events) of all available ground calibration data:
width = 1+ residual[data-model].
Lower panel: difference of upper edge of ADC bin and smooth
spline function.
The information was taken from file p$manpar:adc_bins.dat.
Parameters:
] ADC pulse height channel of event
(integer in [1,256])
SASS source code: package PSPC, bubble CT, subroutine CADC
SASS files:
