-- BarbaraStoraci - 12 Mar 2009

Outer Tracker Scanning System in Situ

The performance of the detector modules is monitored at various stages of the commissioning and operation of the detector. Before and after irradiations reference measurements are performed with a scanning system of two 74 MBq 90Sr sources transported by a step motor.

Scanning System in Situ

Main Elements:

• Scanning Frame

• 2 90Sr sources of 74MBq, moved by a step motor

• Current-meter and Safety Garage

Schematic of the scanning source:

How to run the scan

For the Sr scans you need the portable computer OTSCAN01W.

The executable files can be found in: C:\Documents and Settings\Administrator\My Documents\CVI-programs. The file we need to start the scan of one module is clrscan.exe. We test the front layer and the back layer (the source is shining through the front layer). One layer is tested at a time.

As the front end boards do not measure current (but drift times), a custom made Ampere meter box is connected replacing temporarily the front end of the module to be tested. As this is a very delicate operation, only a limited number of people are allowed to do it.

Give source height : 4 for front layer, 4.5 for the back layer. Give module name: production/ serial number of the module. Both sides are A and B but there' s no rule which one is A and which B. Give high voltage:1600

Then click on "Accept to continue".

The system will prepare.

Check if all the settings are alright. If yes, click on "Accept to continue" in the second window. Then, click on "Start scan" in the new pop-up window. Even if the settings are not right, start the run, and change the settings manually from the CAEN menu. i.e. for high voltage setting push F 1 and the nominal voltage value.

The logbook is kept on a plus node in /calib/ot/Scanning tool/logbooks. All the scan logs are kept in one text file: logbook-scanning.txt.

You can choose to monitor the current in a given wire, or altogether (type 65, then Enter in "Wire choice" field).

Analysis

The analysis is typically carried out comparing the current behavior after and before an irradiation step. The ratio plot produced by this comparison is normalised using the average value obtained inside a region where the source is not present. A zone around the source, “source region”, is selected to study in details the effect of the irradiation. Two quantities are proposed to estimate the ageing effects: the average of the two absolute minima in the source region and the “region factor” quatified summing the deviation from 1 of all the cells inside the source region and dividing by the number of cells considered. If there are no gain changes in the irradiated area these two quantities must be 1 and 0 respectively.

How To Run it

• Connect to the plus node with "ot_oper" user

• Run the script: SrScan.sh [-t -n -f -m -s] #module
  • -t list of irradiation hours (useful only if you enable "trend_plot" function in the option file)
  • -n installation setup ('cern' for first monolayer, 'cern2' for second monolayer)
  • -m detector part scanned ('L_half' for the lower part of the monolayer, 'U_half' for the upper part of the monolayer, 'all' for the entire detector)
  • -f force to set new input file for the analysis
  • -s run single scan analysis

• Output save in: /scratch/everyone/ot_oper/SrScan/# module/output/plots