Diamond Detectors for Ionizing Radiation - HEPHY

CHAPTER 6. CHARACTERIZATION 30
Figure 6.3: Schematics of the grounded base trigger amplier.
order to cut o low frequency (1=f) noise, a miniature transformer was utilized in the
prototype tests discussed in [33]. In our setup we used a simple RC combination of low
and high pass, providing similar signal processing.
The risetime of the amplier is specied to be < 600 ps, while the noise is stated to
be ENC 1000 e + 60 e pF ,1 . Compared to the integrating charge-sensitive amplier
discussed above, basically accuracy is sacriced for speed.
6.1.3 Readout Electronics
The front-end electronic is very sensitive against any kind of electric inuence. Therefore,
a central ground point is essential, together with the shielding of the complete setup.
In the Vienna characterization station, the front-end has been packed into a coppershielded
box, which is kept closed during measurement. This is also necessary as the
detectors and the VA2 chip are sensitive to light. Fig. 6.4 shows a photograph of the box.
During measurements, the lid is closed and the collimator with the source mounted onto
it. Fig. 6.5 shows the detailed schematics of the Vienna characterization station. The
diamond detector is AC coupled to the VA2 to allow dierent potentials. As the VA2 chip
output stage obviously is not very powerful, a repeater card (designed by A. Rudge and
the Ohio State University) is foreseen, which buers both incoming and outgoing VA2
signals.
For calibration purposes, a well dened step pulse is attenuated and sent to the VA2
input over a small capacitance, injecting a charge of
Q = CV : (6.3)
There are two separated voltage dividers in the attenuator, because inevitable stray ca-