COLD VT  OPERATION ON THE VARIAN 400

ATB probe on the 400 can be used from  - 80 to  + 130  C

If you are going  above > 100  C          YOU MUST USE TANK NITROGEN

                        below < - 40  C

NEVER TURN OFF THE CONTROLLER WITHOUT FIRST DROPPING THE BUCKET

1.  Turn on the nitrogen tank at about 60 lbs  (blue line)

      Turn off the air – yellow lever                (off is perpendicular --  on is parallel)

      Turn on the nitrogen – red lever

2.  Type   “temp”  on the command line, to bring up window.

3.  Select a temperature, using the slide bar BELOW 25 C,  start with  15 C,  hit “reset VT”

      button, then turn the temperature control  “on”.

4.  Check to see that the VT  flow rate on the magnet leg is ~ 10, then wait about  5 minutes

      for the line and coil to flush thoroughly.

5.  Take out the black rubber stopper in the white styrofoam bucket and then pour liquid

      nitrogen from the a dewar in.

6.  Type “su” on the command line and wait for the beep.

7.  Watch the acqstat window.  It should say “status: VT regulation” on the top and the

      “setting: 15 C” on the bottom and the “actual temperature”.

      (the actual temperature can also be observed on the hardware box)

8.   If it goes down too far too fast, lower the VT flow rate on the magnet leg a little  but no

       lower than five.   As you go down in temperature you should raise the flow rate back to

       ~10. This flow rate controls the “coldness” you  are adding.

DO NOT TYPE ANYTHING ELSE.....WAIT FOR THE BEEP .... the beep means that it is stable, and it will say “setup complete” in the text window.

9.  Put in your sample in the normal way.   Lock and shim.

10. Always keep your eye on the lock level and the spinning in the acqstat   window as this is

       the first sign something is going wrong.  If the sample  freezes, the lock level will drop

       out.   If you have moisture in the lines, the  sample will not spin.

11.  You can now slowly lower the temperature and take spectra.  Lower the  temperature on

        the slide bar.  You should give the sample ~10 min to equilibrate at a different

        temperature, and you should re-shim.   At each  new temperature do “su” and wait for

       the beep before starting the spectra  (setup in GLIDE or ”ga” if you are running manually.

12.  When you are done,  raise the temperature control bar by increments of 20.   When you

        reach 15 C and it is equilibrated, lower the bucket from the coil.

13.  When the frost is gone from the coil, quickly turn off the nitrogen tank and  then the red

         nitrogen lever, put back on the air with the yellow lever, raise the temperature to 25 C. 

14.   Leave the temperature controller on for a minimum of ½ hour.   At the end  of this time

         you should wipe the styrofoam bucket dry and put the bucket   back up.  Leave the black

         stopper off for the rest of the day.

SHOULD YOU HAVE TO STOP IN THE MIDDLE .....DO NOT TURN OFF THE CONTROLLER,   DROP THE LIQUID NITROGEN BUCKET FIRST!!!   Then bring the controller up to 15.