1.3.1 Comparison Data Collection
We have therefore embarked on a comparison study, reported herein, with the
intention of benchmarking these facilities relative to each other. This also provides
a mechanism to describe the experimental procedure and make available template
CIFs for a general data collection carried out on either facility by the NCS. Full
procedural descriptions, along with data collection and refinement parameters and
statistics, are provided as Electronic Supplementary Material to this article.
A suitable sample was selected, i.e. very stable and with suitable diffracting
power to give workable results on both systems. Using a very accurate diode and
taking into account the size of the beam and attenuation factors, it was measured and
calculated that the flux density at the sample is over three orders of magnitude greater
at the synchrotron source. Very similar data collection strategies were designed for
both facilities in order to ensure a rigorous comparison with similar coverage. In
order to obtain comparable data, the home laboratory collection was run at the
equivalent of 100 s per degree, while the synchrotron collection was performed at
2 s per degree and using 10% of the incident beam. While the home laboratory
experiments are clearly considerably slower, it can be seen that there is more
observed data collected and the resulting agreement factors are better. One might
now begin to conclude that for single crystals that are at the limit of hypothetical
diffracting power, a very powerful home source will provide equally good results as
a synchrotron. However, there will be samples where the hypothetical diffraction
limit is not achievable in-house and the superior flux of the synchrotron will produce
a better model. There will of course also be situations where the considerably more
rapid data collection capability of the synchrotron will be of benefit. However one
also has to be cautious as the dose received by the sample will often be very similar
(less flux over a long time against more flux in a short period) in both facilities and
therefore the best/correct strategy and facility must be selected in the case of samples
that are prone to serious radiation damage.
1.4 Conclusion: Learning from Large Facilities
Large, national facilities drive innovation and act as a beacon for instrument and
process development. These facilities indicate the future for conventional, smallerscale facilities and act as an indicator of the direction in which the field is going in for
the medium term. The example of the instrumentation and capabilities in the home
laboratory of the NCS illustrates how the synchrotron-driven approaches can be
translated to the everyday facility while demonstrating exactly what is possible and
that the difference between local and national facilities needn’t be so large.
There is a clear impact arising from the development of faster, more accurate
technology and the increasingly automated methods that have been derived to make
the most efficient and effect use of these instrument advances. Not only do these
92
S. J. Coles et al.
We have therefore embarked on a comparison study, reported herein, with the
intention of benchmarking these facilities relative to each other. This also provides
a mechanism to describe the experimental procedure and make available template
CIFs for a general data collection carried out on either facility by the NCS. Full
procedural descriptions, along with data collection and refinement parameters and
statistics, are provided as Electronic Supplementary Material to this article.
A suitable sample was selected, i.e. very stable and with suitable diffracting
power to give workable results on both systems. Using a very accurate diode and
taking into account the size of the beam and attenuation factors, it was measured and
calculated that the flux density at the sample is over three orders of magnitude greater
at the synchrotron source. Very similar data collection strategies were designed for
both facilities in order to ensure a rigorous comparison with similar coverage. In
order to obtain comparable data, the home laboratory collection was run at the
equivalent of 100 s per degree, while the synchrotron collection was performed at
2 s per degree and using 10% of the incident beam. While the home laboratory
experiments are clearly considerably slower, it can be seen that there is more
observed data collected and the resulting agreement factors are better. One might
now begin to conclude that for single crystals that are at the limit of hypothetical
diffracting power, a very powerful home source will provide equally good results as
a synchrotron. However, there will be samples where the hypothetical diffraction
limit is not achievable in-house and the superior flux of the synchrotron will produce
a better model. There will of course also be situations where the considerably more
rapid data collection capability of the synchrotron will be of benefit. However one
also has to be cautious as the dose received by the sample will often be very similar
(less flux over a long time against more flux in a short period) in both facilities and
therefore the best/correct strategy and facility must be selected in the case of samples
that are prone to serious radiation damage.
1.4 Conclusion: Learning from Large Facilities
Large, national facilities drive innovation and act as a beacon for instrument and
process development. These facilities indicate the future for conventional, smallerscale facilities and act as an indicator of the direction in which the field is going in for
the medium term. The example of the instrumentation and capabilities in the home
laboratory of the NCS illustrates how the synchrotron-driven approaches can be
translated to the everyday facility while demonstrating exactly what is possible and
that the difference between local and national facilities needn’t be so large.
There is a clear impact arising from the development of faster, more accurate
technology and the increasingly automated methods that have been derived to make
the most efficient and effect use of these instrument advances. Not only do these
92
S. J. Coles et al.