Multichannel Analyzer MCA4 / Questions and Answers

Is the MCA4 or the MCA4-2 an alternative to the functionality of the MPA-3/2P 2 parameter MPA-3 system?  This is for acquisition and display of analog (0-5V) X and Y position data from a position-sensitive detector.

The multiparameter version of the MCA4 works in a rather simple way. The software evaluates the 8 ns timestamps of the PHA data. The size of the coincidence window can be set in the software in units of 8 ns. Any ADC event can open the coincidence window and if another ADC event comes within the coincidence time interval, a dualparameter map is incremented at the respective position.

The MPA-3 does the coincidence handling by a hardware logic, the coincidence time window is set in that logic. A "bit-shuffle-ram" enables to define "dependent groups" of coincidence data, so it is possible to select recording only events when all ADC's in a special group have valid data within the coincidence time. The MCA4 has no such groups. It is different as just single ADC data with time stamps are in the list file and not combined coincidence data that can be filtered before recording.

The maximum count rate is better at the MCA4, here a count rate of about 1 million events per sec can be used in each of the 4 ADCs. The MPA-3 has a maximum rate of about 350 kHz per ADC in coincidence mode.

An advantage of the MPA-3 is that you can connect a 7072T and do coincidences of TDC data. This is useful for many position-sensitive detectors. If the detector of your customer uses a time difference for the position information, the customer must use a 7072T with MPA-3-2 and cannot use a MCA4-MPA2. He could then think about using a MCS6A if the 100 psec resolution is good enough. Of course he could also connect two TAC's to a MCA4-MPA2. Time differences can be presently histogrammed directly only with a resolution of 8 nsec.

The options are only a matter of  the enabled features in a licence key. All features can be easy upgraded by sending a new licence key with email to the customer. What can be done is PHA and SVA with up to 4 analog inputs, each can be gated by a gate signal input.

The 8 ports of the digital I/O port can be used for tag bits that are sampled with a rate of 2.5 µsec. The MPA-3 can in principle use unused higher bits of ADC ports as tag bits. (The MPA4T has tag bits with a time resolution of 6.4 nsec, but these are in combination with the fast TDC inputs and are not available at the MPA4.)

For the multiparameter function the 8 ns RTC option for each multiparameter input is required and the dualparameter feature for two or 4 channels must be enabled in the software via the licence key.

With the MCS option it can be used for multiscaling with one Start and two Stop inputs, either using an internal defined dwelltime in steps of 10 ns or an external clock input.

It is now possible to record 400 MHz with a dwelltime of 30 ns for one channel and 50 ns for 2 channels, the dwelltime range can be set in units of 10 ns from the minimum time up to 781 h.

See the comparison chart.

Multiparameter Multichannel Analyzers, Multichannel Analyzers, MCA4