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Instructions for HI runs

  • The two upper plots show the average occupancy of the SSD: you have to compare the plots published by the agent to the one in the picture below. If you note white areas not corresponding to the ones in this picture, call the expert.
  • The bottom right plot shows the typical distribution of the SSD Data Size: if you don't see this broad distribution and if the Mean in the Statistics Box is smaller than 25kB, please contact the SSD oncall expert. In case this plot is ok, please follow the instruction below for further checks .
  • The bottom left plot shows the data size per DDL: if you see that data size per DDL is <1 call the expert.
  • Please, go on reading the description of the plots in the twiki: if you notice something strange in the online plot, don't hesitate to include it in the report, or to call the SSD expert to clarify it
  • Typical SSD QAshifter plots in Pb-Pb Physics Runs (normal trigger mix): SSD_DQM1_27112011.png
  • Typical in Pb-Pb Physics plots QAshifter runs SSD
  • Typical in Physics plots proton-proton QAshifter runs SSD>


SSD DQM Plots description:

In the following the plots produced by the SSDQAshifter agent and the checks that should be done by the DQM shifter.

Average occupancy per module for layer 5 and 6

The white holes correspond to the area of the detector (modules/half ladders) that are taken out of the acquisition. Any variation of the colour means differences of the noise level for each SSD module.

To be checked: Check the colours. The plots do not have to show red areas.

If red areas appear during PHYSICS runs: Save the histogram, attach it to the run in the logbook and inform the SSD on call expert.

If red areas appear during TECHNICAL runs: For technical runs due to several reasons several modules will become noisy. You don't have to do anything.

SSD data size per DDL

This histogram plots the average SSD data size per DDL. The SSD has 16 DDL which should approximately have similar amount of data. In case the common mode (CM) values are not sent this means that the SSD data size is ~2.2KB/DDL. In case the common mode (CM) values are sent this means that the SSD data size is ~7.5KB/DDL. There is no possibility to transfer this information (CM sending or not) to the shifter. The default behaviour is to send common mode once every 16 events. In any case the average value should be as uniform as possible; however, small variations are normal taking into account that all DDLs do not have the same number of active channels (e.g. channels switched off etc). A distinct peak is an indication of (many) noisy channels for this DDL. A 20% variation on average is normal.

To be checked: All the DDL should have always a similar amount of data (around 3.6 in pp, higher in PbPb). This is a reference plot for the proton data taking.


If for one DDL the data size increase of about 20% in PHYSICS runs: Save the histogram, attach it to the run in the logbook and inform the SSD on call expert.

SSD data size

This is the SSD data size distribution. The SSD firmware gives the possibility to send the CM values on every event, once every 8 events, once every 16 events (default) or never. In the latter case and in the case of the default ZS threshold (3sigma) the data size should be around 32KB. When sending the CM values, we add another 80 KB per event. This means that the default behavior would be to have two distinct peaks, the one centered around 32KB and the other around 115KB. The position of the two peaks can change for the data taking conditions. The two structures in physics runs are rather narrow. During technical runs they become much broader and exhibit large tails (under investigation).

To be checked: Check that the plot shows only two peaks and that they are not too much broad

If multiple peaks appear during PHYSICS runs: Save the histogram, attach it to the run in the logbook and inform the SSD on call expert.

If multiple peaks appear during TECHNICAL runs: This can happen in technical runs. You don't have to do anything.

Event size during the HI tests:

In the present configuration (4sigma zero suppression) the expected average event size for the SSD is ~95kB (dN/dy = 700).

Please note that the final configuration is under internal discussion. The decision will be taken by the project leader.


  • Open two terminals and connect to the DQM machine typing the command: sshdqm SSD01
  • Start 2 GUI (one for each terminal) typing amore -d SSD -m SSDUIQA -g configFileAMORE.txt in the first terminal and amoreGui in the second.
  • From the first shell you obtain the usual SSD expert interface. Press Init and then Start to see the plots.
  • From the second shell you can see a general DQM user interface. In the left part you have the list of the running agents. In you click on the agent name you can see all the plots published by the agents.
  • IMPORTANT: If the plots published by the agent SSD01 are not updated, ask to the DQM shifter to stop and restart the SSD01 agent. If you are at home, from time to time check that the summary image of the SSD01 agent is saved in the logbook. If not, call the DQM shifter and ask to stop and restart the agent.


  • 12th November 2011: modified layout for the shifter. Average occupancy plots taken from LowMult, Data Size taken from HighMult. See entry in the logbook by Francesca.
  • Typical SSD QAshifter plots in PbPb 2011 Physics Runs - usual trigger mix:

General Instruction for the DQM Shifter (CERN TWiki)



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