Major deveopments in the design of the AGFM were made by Flanders who
changed to a different coil configuration [10], employing an alternating field with
a gradient perpendicular to the field vector. This is shown in Figure 2.1, and
allowed the use of a non-resonant extension, similar to that used earlier by
Reeves [4]. This was especially advantageous, as it allowed the resonant element
28and piezoelectric biomorph to remain at room temperature, while the temperature
of the sample was varied in the range 77 to 900 K. This largely negated the need
for a nulling coil (impractical at 900 K), or excessive frequency tracking during
experiments, as the resonant properties were found to be nearly stable when
using a long extension (100 – 150 mm), that had been suitably heat-shielded.
Quartz fibres and capillary tubes were used as extensions, with diameters suited
to the sample mass and sensitivity required, in the range 70 µm to 300 µm. The
biomorphs used were the only resonant element present, and were of the order of
20 mm long and 0.6 mm thick.
Major deveopments in the design of the AGFM were made by Flanders who changed to a different coil configuration [10], employing an alternating field with a gradient perpendicular to the field vector. This is shown in Figure 2.1, and allowed the use of a non-resonant extension, similar to that used earlier by Reeves [4]. This was especially advantageous, as it allowed the resonant element 28and piezoelectric biomorph to remain at room temperature, while the temperature of the sample was varied in the range 77 to 900 K. This largely negated the need for a nulling coil (impractical at 900 K), or excessive frequency tracking during experiments, as the resonant properties were found to be nearly stable when using a long extension (100 – 150 mm), that had been suitably heat-shielded. Quartz fibres and capillary tubes were used as extensions, with diameters suited to the sample mass and sensitivity required, in the range 70 µm to 300 µm. Thebiomorphs used were the only resonant element present, and were of the order of 20 mm long and 0.6 mm thick.
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