LDMX Power Supply Control

The power supplies are controlled by a few python scripts.

MPOD Control

The ECal and Tracker LV and HV are connected to MPODs. This is a simple class and script to control MPOD modules through SNMP commands

Dependencies

Used and tested with net-snmp v5.9.4.

Need WIENER-CRATE-MIB.txt to specify how MPOD talks via SNMP. This file should be placed in the installation location of net-snmp in the install/share/snmp/mibs subdirectory along side the other configuration files.

Usage

Besides access to the executables installed by net-snmp, we avoid using any other Python libraries.

python mpod_control.py [--dry-run] {enable|disable|print} {config.json}

Two environment variables are checked

• MPOD_CRATE_IP defines the IP address of the MPOD Crate
• NET_SNMP_INSTALL defines where net-snmp is installed

HCal PS Control

The HCal power supplies are serially connected to the DAQ server over USB. The HV and LV power supplies are B&K Precision 1698.

Note

The LV line has an initial pulse of current that is relatively far above the normal operating current (~1A), so the power supply current limit should be set to 3A to allow this pulse through when the power is initially connected.

Usage

Use the USBmappingJSON.sh script to list out the different devices connected via USB.

./USBmappingJSON.sh

From this list, you can use the Serial column as the --serial argument and the VID:PID column as the --vid_pid argument. You can also create a JSON file in this directory named .hcal-power-supply-names.json to use as a cache for these values. They only depend on the power supply actually in use. The file used for the 2026 cosmics test stand looked like

{
  "hcal-hv": {
    "serial": "0000:00:14.0",
    "vid_pid": "067b:2303"
  },
  "hcal-lv": {
    "serial": "AL05K8T0",
    "vid_pid": "0403:6001"
  }
}

And then you --read the current settings.

sudo python hcal-ps-control.py --name hcal-hv --read

and turn on/off with the --output argument.

sudo python hcal-ps-control.py --name hcal-lv --output True

In order to avoid sudo you can ask your friendly neighborhood administrator to sudo chmod 666 the /dev/ttyUSBii file that is reported by the USB mapping to be connected the power supply.