The cathode pads are read-out by AFTER ASIC. One chip has 72 active channels and 4 reference channels for pedestal subtraction. Each channel consists of charge-sensitive preamplifier, pole-zero cancellation of preamplifier decay time, RC2 shaper and 512-cell SCA to store waveform. Amplifier gain, pole-zero time constant and shaping time are programmable. Detailed information is in the manual, but the most relevant slow control settings are summarized in the following tables.

The full range of the AFTER chip and the ADC is ±1V, the gain setting determines what charge that corresponds to, leading to a gain value.

Gain setting Charge range (fC) Gain (mV/fC)
0 120 8.333
1 240 4.167
2 360 2.778
3 600 1.667

The peaking time is defined as the time the pulse takes to go from 5% to 100% pulse height. This peaking time translates to other relevant times as shown in the next table.

Illustration of various time characteristics of the filtered AFTER signal
Peaking time (5%-100%) Fall time (100%-5%) FWHM Rise time (50%-100%) Fall time (100%-50%)
116.7 202.5 158.4 67.59 90.82
200 438.2 311.6 121.3 190.3
505 1194 843 329.2 513.7
993 2351 1689 656.1 1033
1912 4283 3213 1268 1945

Phenomenologically the pulse shape can be described by the function

${\displaystyle f(t)=\left({\frac {t}{k\tau }}\right)^{k}\exp \left(k-{\frac {t}{\tau }}\right)}$

Extracting the above mentioned rise and fall times from this formula for different values for the parameter k yields a relatively good match for ${\displaystyle k=4}$. The resulting numerical relationship between peaking time ${\displaystyle t_{r}}$ and ${\displaystyle \tau }$ from this is ${\displaystyle t_{r}=3.1365\tau }$

The following tables contains the 5%-100% rise times for the different AFTER settings together with the corresponding value for ${\displaystyle \tau }$.

Time setting Peaking time (ns) ${\displaystyle \tau }$ (ns)
0 116 37.0
1 200 63.8
2 412 131.4
3 505 161.0
4 610 194.5
5 695 221.6
6 912 290.8
7 993 316.6
8 1054 336.0
9 1134 361.5
10 1343 428.2
11 1421 453.1
12 1546 492.9
13 1626 518.4
14 1834 584.7
15 1912 609.6