Performing VT experiments on 500MHz DMX spectrometer.

The case of lower than ambient temperature

* Fill up the Dewar with liquid nitrogen outside of NMR laboratory. Do not bring any
   magnetic Dewars into the NMR area. Follow the safety rules with handling of liquid
   nitrogen.
* Using gloves and eye protection insert carefully and slowly the heater into the Dewar.
   Make sure that O-ring is in proper place. Insertion should be slow enough that no spray
   of liquid nitrogen occurres outside of the Dewar. Install the clamp that connects the
   heater to Dewar.
* Hook up the VT nitrogen hose to the glass Dewar in the probe. The glass Dewar is very
   fragile, please be extremely cautious while working with it.
* Use the proper spinner turbine for VT experiments. Actually, the gray fiber glass spinners
   are design for such experiments.
* While in xwinnmr software type ‘EDTE ’ command and the EDTE main window appears.
* Make sure that target sample temperature is set to room temperature.
* Using EDTE menu set maximum heater power to 15. It is rather rare that higher value
   will be needed. Click “Apply ” and “OK”.
* Make sure that your target temperature does not exceed the limit of the probe
   specifications. Exceeding the probe’s limit temperature will damage the probe. The
   Magnet might also be damaged.
* Set the temperature 5 degrees lower than ambiet. Set the cooling current to ~35. It is
   rather rare that higher current will be needed
* Turn “ON” cooling by pushing the LN2 “ON/OFF” button on the console. Push the
   heater button ‘ON’ placed on VT controller. Another heater button “ON/OFF ” that is in
   the EDTE menu is not designed to work.
* Wait until sample temperature is close to target and decrease it another 5 degrees.
* To get to the final required temperature, proceed in the steps of no more than 5-8 degree
   to avoid thermal and current shock of hardware.
* When the required temperature is achieved wait certain period of time before you start to
   perform NMR experiment to equalize the temperature across the sample. A 20 –30
   minute period of time is usually needed. However, you may like to find out your own
   waiting time for temperature equalization. Do not move Dewar or touch the hose
   connecting it with probe. The hose is cold and stiff and applying force might break the
   probe’s glass Dewar.
* After experiment is finished, decrease the cooling current to 10 and increase the
   temperature in the 5 degree intervals until the room temperature is achieved. Never
   introduce the thermal shock to the system by changing the temperature with too large
   intervals.
*Turn off the heater by pushing heater button “ OFF” on VT controller.
* Turn off the cooling by pushing LN2 button “ ON/OFF”.
* Very carefully unhook the hose from probe (first remove the small clamp before you
   touch the hose) and remove the heater from Dewar. Remember that heater is very cold
   and safety precautions for handling of liquid nitrogen need to be observed.
* Exit the EDTE menu.
* To warm up probe’s electronic and shims to the ambient conditions an additional
    time between 30-120 minutes is needed. This depend on how long experiment
   took place and what was the final temperature. Mark your VT experiment in
   logbook so a next user will be aware about previous conditions. Consider those
   limitation while signing up so the sign up policy will be obeyed.
*To find out more details, please refer to the Bruker manual that is available in NMR
   laboratory.

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