To start a high voltage control session, start the hv_controlinterface from a personal computer that is designed to recognize ports on the serial terminal server or which has a physical serial line run to the Lecroy 1440s. For the MIPP experiment, access to the high voltage mainframes can be established through e907daq.fnal.gov. The hv_controlcontrol program can be run via any standard terminal, including xterms and telnet/ssh sessions. For non-standard terminals make sure the $TERM environment variable is set to accurately reflect your terminal type. When started, if the interface is not correctly drawn, reset your $TERM type and restart the program.
Upon start up the control interface will bring up an access verification screen to allow you to set your detector group ID. The soft ware is designed to ONLY allow write access to channels that belong to your detector group. This prevents other groups from accidentally reprogramming your detectors, or placing your detectors at inappropriate values.
When the access screen is displayed choose the group that most accurately corresponds to the detector that you wish to modify. After choosing a group you will be prompted for the password that corresponds to that group. If an incorrect password is entered the program will terminate to prevent access.
After access verification is established the hv_controlautomatically will attempt to open a serial line to the HV1440 located in MIPP Relay Rack 051.1. By default the port will be openned at 9600 baud with 8 bit, no parity, 1 stop bit. These settings will match the default power on settings that the HV1445 controler cards are set to. In the event the control code is unable to open the port with the default settings, a status window will be displayed.
After the port is successfully opened, the control interface will initialize the 1440 mainframe, selecting the appropriate mainframe identifier1.2 and then query the unit to determine its current high voltage state. The 1440 mainframes have two state flags that are denoted as HV ON/OFF and HV ENABLED/DISABLED. The HV ENABLED state is set from the front pannel of the 1440 mainframe and corresponds to the saftey enable button. While this button is toggled to the disable state, a hardware voltage inhibit is placed on the entire mainframe. The HV ON/OFF flag represents the current voltage state of the high voltage cards in the mainframe. If the state is set to OFF, no high voltage is present on the output of the high voltage cards regardless of the demand setting of each high voltage channel. If the state is set to ON, each and every channel in the mainframe is brought up to a voltage to match that of the value set in the channel's demand register. Channels whose demand register is set to 0 are considered off even though small amounts of voltage from adjacent channels may leak over on to the given channel.
The current power state of the selected 1440 mainframe is displayed in the lower right hand corner of the control interface. Under standard opperating conditions it should read ``HV ON/ENABLED''. If there is an error in determining the power state of the mainframe this status indicator will read ``HV Error''. Correct the problem or reinitialize the mainframe using the ``Reset Mainframe'' option from the Advanced menu.
It is important to realized there is no true single channel OFF state available on the 1440 mainframes. When you toggle the 1440 power state flag to OFF you are turning off ALL 256 possible channels on the mainframe. This will affect all detectors who recieve power from the current 1440. For safety reasons we do not place restrictions on the ablity of a user to turn off all the high voltages on the mainframe in an emergency.
In the event of an emergency, use the ``!'' option to quickly power off all channels on the 1440 mainframes.