| About ROSAT |
ROSAT Home Page | ROSAT Images |
|---|
The position of an event in the PSPC is determined from the amplitudes
of signals on the two mutually perpendicular cathode grids, K1 and K2
(Fig. 3.1).
The cathode grids are divided into 25 (for cathode K1) and 23
(for cathode K2) cathode strips.
Each strip consists of seven or eight individual cathode wires
linked together and connected to a charge-sensitive preamplifier.
Typically an event will induce a signal on 3 to 5 strips,
although this is not the case for events with pulse heights
corresponding to 
keV
(see Sect. 3.5.4).
The signals from each preamplifier processed and have their
signals digitized by means of pulse shapers, peak detectors,
and analog-to-digital converters (ADCs).
After verifying the validity of an event, the position is
calculated by a centre-of-gravity calculation and assigned
an 
position.
(A detailed description of the method of position determination
and its ground calibration measurements can be found in [Briel et al.1988].