Name of the exercise

Scintillator DAQ system

Responsible for the exercise

Jorgen Petersen

Description of the exercise

This exercise is a continuation of exercise # 3. First, standalone programs are executed to give an understanding of the QDC and TDC VMEbus modules. A full DAQ system is then run on a multi-processor configuration, with the readout application on the VMEbus processor and the run control, GUI and infrastructure on a desktop Linux PC. Event rates and dumps are examined. An event monitoring program produces histograms of the QDC and TDC channel data which allow to compute the charges of the input signals to the QDC and the speed of the cosmic muons.

What will the students learn

  • about QDC and TDC VMEbus modules
  • DAQ system
    • run control. GUI, infrastructure
    • event format
    • event monitoring, measuring charges (QDC) and time of flight (TDC)


This exercise may take more than 2 hours

List of material

The material of exercise # 3 plus a VMEbus crate with DAQ modules as shown in DAQSchool_VMECrate.pdf. Desktop PC(s) for run control etc. and a server PC.

Relevant information

Instruction sheet

  • as an introduction, have a look at the attached sheets, ScintillatorDaqSchool.pdf,DAQSchool_VMECrate.pdf, TDC_v1290.pdf, QDC_V792.pdf, corbo.pdf,DAQ_infraStructure.pdf
  • verify that the detector is working i.e the scaler counts for scintillator 0, scintillator 1 and the coincidence are counting such that the TDC and QDC receive signals( note for the tutor: if the coincidences are not counting, remove the CORBO busy from the trigger coincidence by pushing the button).
  • open a window on PC pcdaqschool1 (or pcdaqschool2) and login as user daqSchool on the VMEbus processor tdb-sbc-01(or tdb-sbc-02): ssh daqSchool@tdb-sbc-01(or tdb-sbc-02), pw=abcd
  • source ./setup to define the environment
  • run the program v1290scope which is a low-level test and debug program for the CAEN V1290 TDC
  1. cd DAQ/DataFlow/rcd_v1290/i686-slc4-gcc34-opt
  2. ./v1290scope Use defaults for the command parameters.
  3. dump the registers (option 2). Are data ready? ( bit DREADY in the status register). What are the values of the match window width and the window offset? see TDC_v1290.pdf
  4. configure the TDC (option 3)
  5. read an event (option 5). The event has a format as shown in the CAEN manual pages: Output Buffer Register. How many words are read? (Check in the global trailer).What are the values of the TDC measurements (in ns). Do they make sense? see TDC_v1290.pdf. Exit from the program (type0).

  • run the program v792scope which is a low-level test and debug program for the CAEN V792 QDC
  1. cd DAQ/DataFlow/rcd_v792/i686-slc4-gcc34-opt
  2. ./v792scope
  3. VMEbus base address = 0
  4. dump the registers (option 2). Are data ready? Check also the LED on the module
  5. configure the QDC (option 3)
  6. read an event (option 4). How many words are read? Which channels have data and which are pedestal(empty) values?
  • we now run the full DAQ system
  1. open a window on pcdaqschool1 (or pcdaqschool2) and login as user daqSchool, pw = .....
  2. source ./setup to define the environment
  3. start the DAQ system: setup_daq -p part_Scintillator -d part_daqSchool(or -p part_Scintillator1 -d part_daqSchool1). This script will read the configuration database and start a number of processes on the server: run control, GUI and a number of infrastructure SW components as sketched in DAQ_infraStructure.pdf. This is a somewhat long procedure and should result in a GUI display as shown in DaqSchoolGUI1.pdf. The "wheels" in the infrastructure panel should be green! You may need help from the tutor here ...
  4. We now go through the run states in order to start a run. Click on BOOT and then INITIALIZE. The readout application is now loaded on the VME processor.
  5. click CONFIG and OK on "remember ..". This configures the VMEbus modules, the CORBO, QDC and TDC.
  6. If you don't see the DFPanel tab close to the top of the GUI, click LOAD Panels and load the first panel: DFPanel should now appear in the bar above the Run Control panel.
  7. click START.
  8. data taking should now start. Click on the DFPanel and the L1 button to display the event rate. Is it what you would expect after exercise # 3? Check also the LEDs on the VME modules (the event rate is computed by the Information Service(OS) which periodically sends a command to the Readout Application to obtain the rate which is then retrieved by the GUI).
  9. click on the ED button at the top to produce an Event Dump. Expand "part_Scintillator" and "ReadoutApplication"(the lower one). Click on" Scintillator". Click the black right arrow in the panel above to dump an event. The first nine words constitute an Event(ROD) header. The following words are the data from the QDC and the TDC. Do you recognise the data?
  • Event Monitoring This part demonstrates event monitoring. An event monitoring program obtains a sample of events from the readout application and analyses them, in this example by producing histograms of the values from the QDC channels as well as the time difference between the two TDC values. The histograms can then be viewed via the GUI. The code for the monitoring program can be found in /DAQ/DataFlow/ROSMonitor/src/ (the parts which are specific to the DAQ school are marked with ***)
  1. Open another window and login as user daqSchool on pcdaqschool1 (or pcdaqschool2), pw=....
  2. source ./setup to define the environment
  3. cd DAQ/DataFlow/ROSMonitor/i686-slc4-gcc34-opt
  4. run the monitoring task: ./emon_task -h explains the parameters
  5. ./emon_task -p part_Scintillator (or part_Scintillator1) -t ReadoutApplication -e 1000 -v2 ( 1000 events in debug mode)
  6. events are now being monitored with debug information. At the end the histograms are stored such that they can be viewed from the GUI.
  7. In the GUI click on the OH button (Online Histogram). Click on Histogram Repository, part_Scintillator, ScintMon. Double click on the histograms to view them.
  8. record the mean values of the QDC histograms and the mean value of the time difference histogram. The time histogram is not centrered around zero. Why?
  9. the pedestal values of the QDC channels are now measured. Remove the inputs to the QDC channels by unplugging the LEMO cables on the PM bases (the cable that goes into the delay unit).
  10. run the monitoring program again as described in point
  11. display the histograms of the QDC channels. Record the pedestal values.
  12. using the formula shown in QDC_V792.pdf, compute the mean charges of the signals from the scintillators. Do they agree with the results obtained in exercise #3?
  • we now want to measure the time of flight of the muons between the two scintillators.
  1. increase the distance between the scintillators by about 30 cm. What is the event rate?
  2. run the monitoring program again with 200 events. Record the mean value of the time histogram viewed from the GUI.
  3. What is the difference wrt the value measured before? Compute the speed of the cosmic muons.



-- JorgenPetersen - 2009-08-25

Topic attachments
I Attachment History Action Size Date Who Comment
PDFpdf DAQSchool_VMECrate.pdf r1 manage 328.6 K 2009-11-11 - 11:44 JorgenPetersen  
PDFpdf DAQ_infrastructure.pdf r1 manage 9.0 K 2009-11-13 - 10:58 JorgenPetersen  
PDFpdf DaqSchoolGUI1.pdf r1 manage 140.8 K 2009-11-11 - 15:38 JorgenPetersen  
PDFpdf QDC_V792.pdf r1 manage 26.4 K 2009-11-11 - 11:37 JorgenPetersen  
PDFpdf ScintillatorDaqSchool.pdf r1 manage 70.6 K 2009-11-11 - 11:57 JorgenPetersen  
PDFpdf TDC_v1290.pdf r1 manage 10.2 K 2009-11-12 - 15:28 JorgenPetersen  
PDFpdf corbo.pdf r1 manage 4.4 K 2009-11-11 - 11:36 JorgenPetersen  
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Topic revision: r16 - 2010-01-18 - JorgenPetersen
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