One of the biggest changes is that flexibility has been added in which isotopes have been measured – previous versions required 206, 207, 208, 232, and 238 (with an option for 204). This meant that users (particularly those with Nu multicollectors) that had not measured all of these isotopes needed a modified version of the DRS. The DRS is now able to run with any combination of masses, with the only restriction being that 206Pb and 238U must be included.
Another change has been to improve the DRS’ ability to identify the names of the different masses measured, regardless of their input channel name. Again, this increased flexibility will hopefully mean that fewer users need to modify the DRS to get it to work with data from their machine (that said, because of complex collector arrays and the complications of .nrf files, users of Nu multi-collectors will probably still need to use a “shortcut” file).
Next, I took up the kind offer by Joe Petrus that 207Pb/206Pb ages be moved from the VizualAge add-on to the main UPb DRS. In addition to building in the age calculation I have also modified it so that it uses a lookup table instead of an iterative calculation. I was concerned that the iterative calculation was theoretically capable of producing spurious ages, whereas the lookup table should be immune to this problem. For those interested, the lookup table spans ages from 1 Ma to 4600 Ma, in increments of 0.1%. The age for a given 7/6 ratio is then read from the table using linear interpolation between these increments (which means the actual accuracy of the lookup table readouts will be much much better than 0.1%). The decay constants used in generating the lookup table are 9.8485E-10 (235U) and 1.55125E-10 (238U).
In addition to those big things, there were also some minor changes/fixes:
—A minor bug in the down-hole fitting window that meant that manually adjusting the fit parameters sometimes failed has been fixed.
—The 238/235 ratio used in calculations is now a Global Variable that can be viewed and edited via the Edit Settings window (for now it’s still the old accepted value of 137.88).
—The Global Variable that allowed setting the number of histogram bins has been removed to avoid clutter in the Edit Settings window (if anyone feels that it was useful I’d be happy to reinstate it, but I got the impression it wasn’t being used).
And as always, any questions or discussions are welcomed on the Iolite forum…