Capillary Samples

Where possible, samples should be loaded in capillaries for data collection. This section describes how this can be done.

1. What size capillaries should I use?
It is normally recommended that users use 0.3 mm low X-ray absorption glass capillaries; the angular resolution is optimised by using as small a diameter as possible. Capillary sizes >0.5 mm are not recommended.

2. How much sample do I need?
For ease of experiment set-up, the length of sample needed in the capillary is usually 15-20 mm (or more), above the brass stub holding the capillary. However, if only a small amount of sample is available it is possible to work with as little as 3-5 mm of sample, if care is taken when positioning the sample.  The location of the beam on the sample using the two sample mounting options available is shown in Figure 1.  NOTE: samples prepared for use in conjunction with the cryostream and hot-air blowers must be long.

To seal the capillary break the funnel, and any excess capillary, off and seal it close to the sample, i.e. not more than 10 mm away. 

Figure 1. Photographs showing the distance between the goniometer head to the edge of the X-ray beam for short samples (left) and for long samples (right).

3. What type of capillaries should I use?
Most experiments will use 'special glass' capillaries, but high temperature experiments will require 'quartz' capillaries (these can be used up to 1370 K).

4. Where can I purchase suitable capillaries?
Capillaries can be purchased from Hampton Research or Charles Supper
http://hamptonresearch.com/menus.aspx?id=3&sid=110
http://www.charles-supper.com/en/page/category.cfm?idCategory=13

5. How do I pack sample in capillaries?
Hints for loading capillaries are as follows:

• The sample should be finely and uniformly ground
• Load only the smallest amount (<1 mm deep) of material into the capillary funnel at any one time - otherwise the sample becomes stuck pretty early on in the capillary.
• Vibration is the key to moving the sample down and a good light source behind the capillary is needed to see whether the sample has moved down the capillary and/or is coating the sides of the capillary.
• Vibration can be achieved by running a small, fine file across the capillary (while holding the capillary lightly between your fingers); or by 'dropping'/tapping the capillary on a hard surface, e.g. use a narrow tube of at least 15 cm length which the whole capillary will slide through and drop the capillary into the top and let it land on a bench top (this is a repetitive process); or by standing the capillary upright in a beaker or similar container, and placing this in a sonicator; or finally, if you have a vibrating hand held tool you can hold it to the capillary and get the sample to shuffle down.

If it has not been possible to load sample in a capillary, it may be appropriate in certain situations, to adhere the sample to the outer wall of the capillary using Vaseline.

Furnace Samples

Hints on the preparation of samples for furnace experiments are provided by Anton Paar and are available here.  Additional information regarding the reactivity of samples with platinum is available here; this information should be read carefully, well in advance of the proposed experiment. 

High-throughput Samples

As with capillary mounted samples, sample preparation for mounting on the high-throughput stage should be done in advance of arriving at the synchrotron, unless exceptional circumstances apply.  Samples should be prepared according to the following notes:

1. Machine multi-well sample cassette; instructions for the plate's manufacture are available here.
   • Cassettes may be 0.5, 0.8, or 1.2 mm thick, however, thicker samples must be used with caution due to the absorption issues that may arise.
2. Adhere kapton or mylar to one side of cassette, taking care to avoid impinging on a 5 mm border around the edge of the cassette.  Polymer film (kapton or mylar) should not exceed 25 micron thickness.
   • It is difficult to obtain commercial films thinner than 25 microns with adhesive backing.  Thinner films are available (without adhesive) and can be fixed to the cassette using a thin coating of spray adhesive.
   • Films that are 6 - 12 microns thick have demonstrated both robustness and acceptable levels X-ray absorption. 
   • Films can be purchased locally from http://www.sietronics.com.au/xrffilm.html and spray adhesive is available at office suppliers.
3. Place samples in wells. This can be achieved using a very small funnel or a disposable plastic pipette tip. Take care not to press the powders into the wells using spatulas or other flat instruments as unwanted crystallite orientation may result.  Powders will need to be finely ground so that the particle size is no more than 10 microns in diameter.
   • Eppendorf pipette tips are suitable for loading samples into wells.
4. Adhere kapton or mylar to the other side of the sample cassette, taking care to avoid impinging on a 5 mm border around the edge of the cassette.
   • Minimise cross contamination of sample wells by sealing single or groups of completed wells as you go. 

Figure 2. Photographs of the stages of filling the high-throughput sample casette.