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SANS POLARIZED BEAM

EXPERIMENT SETUP

OPEN NSF COMMUNICATION

A program written in Igor Pro is used for monitoring and controlling the power supplies and a python bridge is used to communicate over the network between the NICE instrument control program and the Igor program.

  • On the 3He computer:
    • These steps can only be performed by a member of the 3He team
    • Open the Igor program
    • Open the python communication bridge
  • In the NICE program:
    • Select the menu option Window > Device Configuration
    • Install 'he3FrontPolarization' or 'he3BackPolarization' or both
      • NOTE: he3FrontPolarization is not usually applicable to SANS
    • Type a command in console to check communication
      • e.g. 'read he3BackPolarization' --> returns cell state (UP/DOWN)
      • e.g. IFTalk HeInterface “He3AnaEnabled()” in the console --> Returns “1 = 3He analyzer Enabled?” if the 3He interface is communicating
        • JRK Note: I don't think we can send IFTalk commands directly to the device anymore, but I will need to check.
      • If communication is not working, ask Spin Filter Team to check the 3He computer

REGISTER SPIN FILTERS

NICE maintains a list of known cells and related spin filter parameters. By registering a cell through NICE, cell information will be saved in the data file that can be used during the data reduction process.

  • In the NICE console:
    • type 'move registerHe3cell <cellName> <deviceName>'
      • e.g. 'move registerHe3cell Burgundy he3BackPolarization'

SETUP CELL IN/OUT POSITIONS

  • Manually place the Spin Filter Solenoid on the cradle
    • NG7 SANS:  the Spin Filter installs inside Sample Chamber
      • Set the lab jack to the correct height for a shielded solenoid
      • Manually install the solenoid cradle onto lab jack
      • Manually place the shielded solenoid onto the cradle
      • In NICE, define the cell IN and OUT positions
        • 'move backPolarizationGroup.inPosition <value>' and 'move backPolarizationGroup.inPosition <value>'
    • VSANS: Spin Filter installs onto 3He Platform

PERFORMING AN EXPERIMENT

SPIN FILTER MEASUREMENTS

The following steps are necessary transmission measurements (TM) for accurate data reduction: cell in, cell out, and beam block or background (only 1 per configuration). These measurements should be taken at the beginning of each experiment to determine the spin filter starting polarization as a group as well as 2-3 cell in/cell out TMs during each experimental cell lifetime. A final measurement group should be taken before changing spin filters or ending an experiment.

SPIN FILTER TRANSMISSION MEASUREMENTS

  • Set # of attenuators (must be the same for all grouped measurements)
  • Count cell in beam (minimum 2000 counts for statistics, typically 180 sec)
  • Count cell out of beam (minimum 2000 counts for statistics, typically 180 sec)
  • Count beam block or background (typically same count time as above)
    • NOTE: Background measurement should be taken for each configuration

 

Created April 10, 2020, Updated July 28, 2020