Laser spot size cross-calibration.

At this time, HDIP version 1.4 is well under development. A few new features has been added in this new version, one of which enables automatic cross-calibration of references and samples of different measurement conditions. HDIP can now successfully take into account changes in repetition rate, spot size and shape in external calibration. Each reference set now has a "Surface removal rate", which is the surface area fired upon by the laser every second. This is the result of a simple calculation of the shape and spot sizes. When multiple reference nodes with a different surface removal rate are included into a single set (of calibration curves), the software will adjust the response of each reference node to match the surface removal rate of the set as a whole. The surface removal rate of the entire set is determined by the first reference node which is added by the set. When the surface removal rate of the set is different from the calibration target (the node/signal/image which you want calibrate), HDIP will apply a correction factor to account for this difference. The correction will always be applied, but has no effect on the result when the acquisition conditions within the experiment are kept the same for every scan. A warning will be displayed to the user when references with different spot size are included into a single set.

There are a few things to note on the surface removal rate correction: 1. The surface removal rate correction does not account for changes in ablation rate; when operating different spot sizes, shapes and repetition rates, significant bias can be introduced due to changes in the ablation rate. 2. Operating at different spot sizes may introduce additional bias as a result of changes in elemental fractionation. 3. Larger differences in spot size and repetition rate will result in increased bias.

These changes should have no effect on existing reference sets, so these can still be used as before. We look forward to releasing more information on version 1.4, as its release in Fall 2020 draws closer.