Operation

The following operational sequences will allow the filling of the reference cell with the three gases:

• Fill with N$_2$
  • Step 1: Vent to 16 psia.
  • Step 2: Evacuate until vacuum reaches 1 mtorr.
  • Step 3: Hold the N$_2$ button down while checking the high-pressure gauge, until the desired pressure is established.
  • Repeat steps 2,and 3 three times.
• Fill with $^4$He
  • Step 1: Vent to 16 psia.
  • Step 2: Evacuate until vacuum reaches $< 10$ mtorr.
  • Step 4: Hold the $^4$He button down while checking the high-pressure gauge, until the desired pressure is established.
  • Repeat steps 2, and 3 three times.
• Fill with $^3$He
  • Step 1: Vent to 16 psia.
  • Step 2: Evacuate until vacuum reaches $< 1$ mtorr.
  • Step 4: Hold the $^3$He button down while checking the high-pressure gauge, until the desired pressure is established.

The pressure at the location of the gas manifold is measured by a baratron gauge. The baratron pressure is read into the data stream and is also output to a remote sensing unit located in the counting house.