Overview
This page contains information for physics experimenters who wish to make use of the NSRL data acquisition system software.
The NSRL data acquisition system is a set of CAEN VME-based signal processing modules which are synced to the timing of the accelerator’s extraction.
The software provides a way to configure these modules, control the system, and start/stop runs. It also allows plots of run data to be viewed as it is being acquired or for offline analysis.
The content on this page is currently targeted towards users already familiar with conducting physics experiments at NSRL and contains mostly high level overviews rather than step-by-step operating instructions. An updated version of this page containing a complete user manual is currently under development.
Source Code
A public copy of the nsrlDataAcquisition DAQ software is available here as a gzipped tar file. The AAAREADME file contains compilation instructions for the source code.
VME Module Setup
- Provide an event trigger to the TDC module in the right-most slot of the VME crate. This trigger is daisy-chained to all other VME modules that need it. If you are using it as an ADC gate also, verify that the timing and width are correct.
- Ensure that a Spill signal (Booster-T0) is provided to Channel 15 of the VME Scaler V560. This should already be in place.
- Plug your signal cables into the appropriate modules, (ADCs, TDCs, Scalers, etc.)
Launching Software
- From a C shell terminal running on a controls network computer (likely ACNLING4) log in as nsrl.
- Enter nsrlDataAcquisition to launch the DAQ GUI.
- Enter the information about the beam species, energy, and other info, and click on “SAVE” to save the configuration file.
- Select the channels to which your signal cables are plugged on the GUI representation of the VME crate. This enables data collection from those channels.
- When you are ready to capture, click “START CAPTURE”.
- After the first readout, click “START DATA CONSOLE” then click “ANALYZE” to view data as it is acquired.
Offline Analysis
Data files are stored in /operations/app_store/nsrlDataAcquisition/data and given unique names made up out of the ion species, energy, date, and a cycle number that is incremented with every run. These files should not be modified. To work on the data, copy files to another working directory, such as /home/cfsb/nsrl/daq/data, and work with them there.
Theory of Operation
Signals for analysis must be brought to the VME Crate in the Physics Lab. There are modules in the VME crate for digitizing Photomultiplier signals (QDCs), Silicon detectors (Peak sensing ADCs), Timing (TDCs), and scalers for counting.
The system requires two signals to process events:
- Event Trigger
- Readout Trigger
Event Trigger
The “Event Trigger” causes the information to be digitized, i.e. it serves as the Common Start for the TDCs. It also serves as the Integration Gate width for the QDCs, and Peak search window for the peak sensing ADCs. It is not used by the Scaler modules. This pulse should be a discriminated phototube pulse, or output of a coincidence unit, or logic gate. It should be at least 20 nanoseconds long.
This same pulse (it can be shaped or stretched) serves as the Integration Gate for the QDC. Note: the falling edge of the QDC Gate must come at least 15 ns before the signal to be integrated. There are analog delay modules and delay lines in the rack to be used as delay lines for the signal inputs to the QDCs or ADCs to give them the correct timing relative to the Gates.
The event trigger must be plugged into the right-most VME module—a CAEN VME V775N TDC—in slot 20. The event trigger must be plugged into the LEMO-00 input labelled GATE/COMM. Note: there are two such inputs; either one will work. They are daisy-chained together. The second GATE/COMM connector is then available to use as an output for providing event triggers to all other VME modules used in the event.
Readout Trigger
The “Readout Trigger” is used to tell the computer when to read out the VME crate. In general, the system was designed with the NSRL Beam Spill Structure in mind, i.e. events come during the ~400 millisecond spill and then there is no event for ~3.8 seconds. To minimize readout deadtime, all events are store on-board the VME modules until there is a Readout Trigger.
The Readout Trigger is usually provided by the Booster-T0 which is regenerated in the Dosimetry control room with a V-102 module. It is a TTL level, and it needs a level shift for VME. Any simple NIM-level pulse can be used to trigger readout of the data buffer on the VME crate, should the B-T0 not be available for any reason, or should the user want readout at intervals other than once every spill. The readout trigger pulse must be plugged into Channel 15 of the VME Scaler module V560 (there are two of them, so use the Left-most module).
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