Crystallography Central Facility

Updated Oct-16-2007
by Chunhua Hu

Lab Tour

1. First things to be done here: find a suitable crystal (shape, size) and mount them on a sample holder (Nylon loop, glass fiber). Sometimes a small 'operation' is needed for some 'ill' crystals!

2. Diffaction experiments are performed by a modern Bruker SMART Apex CCD diffractometer.    A Monocap collimator enhances X-ray intensity (say 2-3 times).     An Oxford Cryosystems 700 cooler freezes crystals to reduce atomic movements and vibrations. (100K default)     A PIII 844MHz computer with 256M RAM is running Windows 2000 Professional to control the Apex. (No internet connected!) The data may be transferred by USB stick or writable CD or 3.5" floppies.

3. Power supplies and a 60 liter ES-60 dewar are located in the rear side of the Apex. A full Dewar of liquid N2 can last up to 4 days without refilling. A floating device (click here to see its design diagram) was made to help know the appropriate time to refill LN2.

4. There are three dry air units:   @above: AirCel®, refrigerated compressed air dryer (Model VF-50), produces clean, dry compressed air.   @above left: The compressed air from AirCel passes through a Wilkerson manual dryer (Model X03) in order to remove water vapor. The very dry air is transferred to make a seal for Neslab's coolant bath.   @ left: The dry air from AD51 dry air Unit is used to make a dry air shield to avoid icing when the crystal is cooled down to a very low temperature. It works very fine in the lab. No icing was observed at 100K up to now. Its feature of 'silent operation' could not be proven in the lab because of other very noisy stuffs, eg. air conditioner.

5. Neslab The Neslab chiller (Model RTE-140) has a running teperature of 0°C, which works together with a Peltier cooler in the Apex CCD detector to maintain the CCD temperature between -41 to -43°C    Coolant mixture: (Total 7200 ml)    Distilled water (from grocery store): 3480 ml (48%)    Lab-grade ethylene glycol: 3000 ml (42%) (anti-bacteria)    Optishield (Original): 720 ml (10%) (anti-corrosion)

6. Haskris (Model R175) Haskris water chiller supplies a water flow with a rate of at least one gallon a minute and of a pressure of 70-80 psi and at a temperature of about 68°F to cool the X-ray tube. Its 60L tank was filled with 55L distilled water and 5L Lab-grade ethylene glycol.   Rear side view of Haskris water chiller

7. A tranditional Siemens P4 four circle diffractometer (the grandmother of Apex) was moved to sit with Apex, which is thought useful for comparison, teaching and perhaps some special purposes. It is not operational yet.