THE DAQ COMPONENTS

WFD Frontend

The WFD frontends are operated in interrupt mode. The interrupt is generated by an RPC call from the CAEN frontend, and following the interrupt the WFD frontend then starts the readout and processing of WFD data.

The readout and processing is managed by the function read_wfd_event(). The routine first merges the two phase WFD data into single phase WFD data and then searches for pulses and parametrizes these pulses. It writes two phase pulse-shape data into the data bank "WF0T", single phase pulse-shape data into the data bank "RE0T" and pulse parameter data into the data bank "FE0T".

The storage of two phase raw WFD banks, single phase raw WFD banks and fitted WFD banks is controlled from Settings/Banks sub-directory in the WFD ODB entry. The switches "Raw Segment Bank", "Raw Event Bank" and "Fitted Event Bank" turn on/off the recording of these three banks respectively. The parameter "Sampling Rate" is the pre-scale factor for storing raw events (a value of 1 would record all raw pulses, a value of 10 would record 10% of raw pulses). In addition a raw WFD event is stored if >1 pulse is identified in one contiguous island of the raw WFD data.

The identification and parameterization of pulses is performed by the function defFit(). The routine steps through the raw event ADC values and searches for continuous regions of above threshold ADC values. For each region it stores the peak's height, time area, width as defined by


where the summation runs from (peak channel - left window) to (peak channel + right window) and the pedestal value is the first non-zero ADC value in either sample one (y1) or sample two (y2). There are three adjustable parameters, the threshold used in identifying the peaks, and the left window and the right window that are used to calculate the peak area, etc. The parameters are accessible in the "Settings/Software" sub-directory of the WFD ODB entry. The parameters are individually adjustable for each channel of each WFD. Finally the defFit() routine also reports the number of pulses per island which permits the storage of the raw data for such pile-up events.

In addition the WFD ODB entry contains a sub-directory accessible in the "Settings/WF0T" that contains the various parameters associated with WFD hardware. These parameters include the sum threshold, individual threshold, offset, stretch, etc.

The WFD frontends are run either from the programs page on the Midas web interface or from the frontend processor by typing ./fewfd -h be01 -e mulan from the sub-directory /home/mulan/muLan/WFD.