Difference between revisions of "Central Drift Chamber Shift"

Revision as of 07:38, 18 June 2014

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.

Routine Operation

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.

The gas system controls for the CDC are common with the FDC. See either the oepration of the FDC section, or the section on the Gas System.

Interlocks

The low voltage that powers the preamplifiers is interlocked with the air blower cooling the preamplifiers.

Expert Personnel

The individuals responsible for checking that the CDC is ready to take data and setting its operating parameters are shown in following table. Problems with normal operation of the CDC should be referred to those individuals and any changes to their settings must be approved by them. Additional experts may be trained by the system owner and their name and date added to this table.