Venting

These instructions assume that initially, the roughing manifold (RM), the growth chamber (GC) and the load chamber (LC) are all under UHV. The all metal valve between the RM and LC is open, and the all metal valve between the GC and RM is closed. If the RM is at atmosphere, pump it down first by roughing it out with the scroll and slowly opening it to the load chamber to be pumped down by the turbo.

1. Turn on the Bravo GC N2 gas (~15 psi). Make sure the Viton seal is closed on the roughing manifold and open the green quarter turn valve to purge the line.

   1. insert picture here

2. Check that gallium is at the correct power (2.5%), and that the heated viewport filament, RGA, and beam flux gauge are off.

   1. RGA: page 31 of manual: Warning: Do not operate the RGA if the pressure in the chamber is greater than 10^-4 Torr.

3. Close the GC cryo gate valves (this protects the cryos when the GC is at atmosphere and prevents them from dumping gas into the chamber).

4. Open the all metal valve between the GC and RM (under the table). Keep an eye on the pressures as you do so. The RM is now open to both the GC and LC, and they are all under UHV.

5. Turn off the ion gauge filament on the GC before turning off the turbo.

   1. "Reactions of gas molecules with the hot filament can seriously affect the composition of the gas, and the reliability of the pressure measurements." - from the ion gauge manual, pg 17

   2. "Some of the processes triggered by these reactions include: (1) active pumping of selected gas components, (2) outgassing of impurities into the vacuum environment, (3) thinning of the filament, and (4) poisoning of the filament surface (change in work function and emissivity) - from the ion gauge manual, pg 36.

6. Turn off the turbo pump, and close the all metal valve between the LC and RM. Wait for the turbo to fully spin down.

7. Turn off the scroll pump.

8. Slowly open the Viton seal to bring the GC and RM up to atmosphere with N2 gas. Don't rely on the pirani gauge past about 400 torr as it gets unreliable around these pressures. You should instead watch the pressure gauge on the RM and tap it periodically because it gets stuck. Close the quarter turn valve when the RM pressure is at atmosphere (0 on the gauge). Make sure not to pressurize the chamber!

Pumping down Initially, the roughing manifold (RM) and growth chamber (GC) are at atmosphere, and the all metal valve between them is open. The load chamber (LC) is at atmosphere, and the all metal valve between the LC and the RM is closed.

1. Close the RM Viton seal.

2. Open the all metal valve between LC and RM, turn on the scroll pump and wait for the pressure to bottom out (~low mtorr).

3. Turn on the turbo pump.

4. Wait for the GC to pump down.

5. Turn on the ion gauge.

6. Close the all metal valve between GC and RM.

7. Open the cryo gate valves.

8. Turn the pressure interlock back on!