Central Drift Chamber Shift

The Central Drift Chamber

The Central Drift Chamber (CDC) is a straw tube chamber. It has 28 layers(rings) of straws each 150cm long. It is operated with an Argon CO2 gas mixture of 50% each by mol. The nominal high voltage (HV) is +2110V and the pre-amplifier cards require low voltage (LV) drawing 0.47A of current. The gas supply is monitored and controlled by the Gas System GUI while the HV and LV are monitored and controlled by the HV GUI.

HV GUI

Fig. 1. CDC HV, LV GUI panel.

The HV GUI controls and monitors the HV and LV of the CDC. In figure 1 you see an example of the GUI with one channel off. There are three representations of the CDC status in terms of individual HV channels (left) in groups of sectors (middle) and in groups of rings(right). The color code is as follows; if the channels is off it is red as well as the sector it belongs to. The buttons in the three CDC representations have menus to select different functions like turning on or off all channels belonging to this sector or actually displaying the full list of all the channels with all the different parameters that can be set or changed. There are two graphs for the HV and two graphs for the LV to show the voltage setting for each channel as well as the current it draws. This is a very useful visual indicator to check whether any channel is deviating from its operating parameters. The voltages and currents for the HV and LV should be compared to a reference plot to do this test.

The shift worker will use the GUI to turn on and off all HV and LV as well as monitor its proper settings. If any channel out of spec can not be reset by turning on/off its HV and/or LV the detector expert on call has to be contacted.

Detector Expert On Call

The individuals responsible for the operation of the CDC are shown in the following table.

Table: Expert personnel for the FDC system

Name	Extension	Date of qualification
CDC EXPERT ON CALL	XXX-XXX	June 4, 2014	Benedikt Zihlmann	269-5310	June 4, 2014