Barrel Calorimeter Shift

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The Barrel Calorimeter

The barrel calorimeter (BCAL) is a lead-scintillating fiber matrix readout with 3840 S12045 Hamamatsu multi-pixel photon counters (MPPCs). The MPPC light sensors operate a bias voltage less than 76 V. Liquid coolant is circulated through the readout assemblies to set and maintain the temperature of the sensors at their operating temperature between 5 and 25 degrees C.

Routine operation

During routine operation the user will need to monitor the environmental conditions, which may affect BCAL performance, as well as turn the system on and off. The following instructions are for non-experts during routine operation. Operations beyond what is specified here shall only be performed by the system expert or under his/her direction. If the expert directs an operation outside the ones described here, a specific note must be entered into the log book.

Control and monitoring of the system is accomplished using the Hall D graphical user interfaces (GUI) to EPICS [1] [2]. A description of how to bring up the GUI screens can be found in Section Slow Controls. We briefly describe the use of these interfaces:

Checking the environment

Fig. 1. Environmental sensors for the BCAL. The sensors measure quantities for the upstream and downstream ends independently. This includes the forty-eight temperature readings of each RTD on the cooling plates, which are in thermal contact with the back of the MPPC sensors, the nitrogen flow, and the four measurements of temperature, humidity and dew point of the gaseous atmosphere of the readout electronics.

The temperature and humidity measurements of the BCAL can be displayed using the GUI shown in Fig. 1 . The controls and monitoring of environmental conditions is accomplished separately for the upstream and downstream readouts of the BCAL, which are connected to individual chillers and nitrogen gas flow lines. The coolant in the chiller (water for initial operations and later water and 20% propylene glycol for operation at 5 degrees C) is circulated through input and output manifolds which feed two readout assemblies in series. The temperature of the chiller will be set prior to operation to maintain a relatively constant temperature for the light sensors. The coolant flows through the cooling plate in each readout assembly, which is in thermal contact with the multi-pixel photon counters (MPPCs), and their temperature is recorded using RTDs attached to the plate. The temperatures are displayed in the figure and should normally read within about 1 degree of each other. The space enclosed by the readout electronics is monitored using four temperature and humidity sensors, which determine the dew point, on both the upstream and downstream. These measurements are displayed on the GUI to monitor the humidity level of the environment of the electronics. The space enclosed by the readout assembly is purged with dry nitrogen to avoid condensation, and the nitrogen flow rate is also indicated on the GUI. During routine operation, this GUI is for information only.

Voltage control

Fig. 2. Graphical interface for setting the voltages on the BCAL. Indicated are the pulldown menus for retrieving saved voltages from a file and the menus for turning the voltages on and off.

The low voltage (LV) and bias voltages for the MPPC sensors can be set using the GUI show in Fig. 2. The voltages for normal operation are recorded in files, which can be restored using the button in the top middle of the screen. The names of the files for the 2016 run are BCAL_BIAS_aProduction_spring2016.snap and BCAL_LV_aNominal_Settings.snap. The default files are located at the top of the pulldown list. The LV and bias settings must be restored separately. Once the voltages have been restored to the memory of the voltage supplies, the user may turn the voltages on by using the "All U Bias" and "All U LV" left buttons in the middle of the BCAL sketch. The voltages for the downstream side are controlled using the buttons on the right. The voltage read back and the current draw of each channel are histogramed and plotted at the bottom of the GUI. When all voltages are on at their set values, the display turns green. Changes to the voltage settings are only allowed by an expert, or under his/her guidance.

Interlocks

The voltages and the chiller are interlocked using the temperature and dew point measurements described in Checking the environment. If the temperature exceeds the preset value in the GUI, or the dew point comes within a predetermined window of the measured temperature, or the chiller goes off, the interlock will be set and it will disable the voltage supply crates and turn off the chiller. Should the interlock system trip, an expert should be called to reset the condition. Changes to the interlock settings are only allowed by an expert, or under his/her guidance.

Expert personnel

The individuals responsible for checking that the BCAL is ready to take data and setting its operating parameters are shown in following table. Problems with normal operation of the BCAL 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.

Table: Expert personnel for the BCAL system
Name Extension Date of qualification
Elton Smith 269-7625 May 20, 2014