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Since the minibunches are separated by a few hundred ns, the total time during which a hit in the detector is possible is in the order of 1us. The signals from the detector during a hit are a about 0.5us, which means that it is not sufficient to do a HOLD on the signals a fixed time after a bunch crossing - this has been the case until 1994. Furthermore it is not only desirable to measure the pulse height, but also to correlate the pulse to a specific minibunch.

The electronics is based on a sample and hold circuit, the HOLD is issued a fixed time after the BCO. No modifications is done on the present electronics. Instead is a peakfinding system added. Minor modifications is done on the transmission of signals between FASTBUS and the MUX card crates.

A gate is opened for each minibunch at the time when we expect a peak. A peak finder will then try to find a peak within this gate. If a peak is found a HOLD is sent to the electronics.

The VSAT trigger will not look at the minibunchstructure, but consider the whole train as a single bunch. The on/offline software has to use the minibunch number stored for each VSAT module to find out the "true" trigger type.

The main part of the electronics is implemented on a FASTBUS card, that contain FlashADCs and a CPU which will monitor the performance of the peakfinding system.

Ulf Mjoernmark
Fri Apr 21 14:33:36 METDST 1995