|Our TDC cards can be run in the following modes:
Mode A): 4 channel high resolution
Mode B): 4 channel normal resolution
Mode C): 1 channel fourfold fast multihit
Typical examples for the application of the different modes are:
Mode A) and B): If you have a set of angle selective detectors you might just detect one single reaction product per detector and you want to run as many detectors as possible with as high a resolution as possible. That's what the 4 channel mode is for.
Mode C): Photoionisation experiments with a 4pi detection angle where all the reaction products hit the detector within a nanosecond timescale. In this case a multihit capability of 0ns time difference between two adjacent events would be best. Therefore our TDC cards provide the 1 channel mode with, to our knowledge, the shortest multihit dead time available at the moment.
The running modes are selectable via software.
*Virtually dead time free operation
The maximum average count rate is 470.000 events/sec in the 4 channel mode and 150.000 events/sec in the 1 channel mode including the position information readout. Within these limits of permanent operation, our TDC cards run virtually dead time free. In practice this means that up to the average count rates specified above, the TDC card's (dead time) / (measuring time) ratio is ca. 0.8 per cent in the high resolution mode and ca. 0.4 per cent in the normal resolution mode. Please note that these specifications are due to the readout limitations of the TDC card interface and do not affect the multihit capability of 5ns described above. Within the limits of the multihit capabilities the maximum burst count rate is better than 120 MHz for the 4 channel mode and 200 MHz for the 1 channel mode.
Coincidence and multicard coincidence measurements
Our TDC cards are equipped with a 32bit parallel data input which can be used to mark every measured event with a time stamp, which is externally provided. Thus you don't have to set hardware gates and time windows any more to perform coincidence experiments. You just store every event together with its time stamp on the hard disk and select your coincident events later on by defining your restrictions using the software. This technique has the unique advantage that you can not only get coincident readouts from one card very easily but you can also combine as many cards as you like to build an extended multicard coincidence experiment. A typical example for the combination of cards is the coincident usage of two position sensitive detectors, one for electrons and and one for ions. Due to the fact, that all cards are provided with the same time stamp, you don't have to worry about exploding costs and technical difficulties any more by adding one or more detector(s) to your coincidence experiment. Any new card will automatically be ready for coincident usage with your existing setup.
Of course our TDC cards are also equipped with an inhibit input to set time windows in the "classical" way and to avoid data caused by unwanted measurements.