ArArCALC saves all age calculation data files in separate directories according to project name (see also: File Organization). This guarantees an automated and well-structured file organization. However, these project names are logged together with all irradiation parameters in the ArArCALC.log file (see also: Using the ArArCALC.log File). This log file can be accessed and updated through a set of easy-to-use dialogboxes. To activate the Changing Irradiations and Projects dialogbox, select the Options # Irradiation and Projects menu item.

The Changing Irradiations and Projects dialogbox lets you choose what via the option buttons Irradiations and Projects in the lower left Change panel. After making a selection, you can use the Add, Edit and Delete buttons to update either the list of project names or irradiations. To add a new list item, you first need to fill in the name of a new irradiation or project in the textbox in the upper right corner, followed by clicking the Add button. To edit or delete an existing irradiation or project, you first click on its name in the list box, followed by clicking either the Edit or Delete button.

If you want to save your edits, please hit the Save button first, because the Close button will close the Changing Irradiations and Projects dialogbox without saving. If you want to ignore or undo any of your changes, hit the Close button without hitting the Save button first.

When adding or editing irradiation definitions, ArArCALC will show you the Change Irradiation dialogbox to allow you to define the irradiation parameters, including up to 999 irradiation segments or cycli (see further below).

information
In this tab you can find summary info and notes for a particular irradiation. In here only the Notes can be edited and it is highly recommended that you provide a short description of the irradiation in this field. This description may include which reactor was used, whether the samples were shielded or not, the purpose of the irradiation, the related project(s) and what time zone was used in the definition of the Irradiation Cycli or Segments (see below). The Date and Total Duration of the irradiation are automatically calculated from the Irradiation Cycli data, where the Date represents the first segment listed in the irradiation list and the Total Duration the summed durations as listed in the first column.

Interference Correction
In this tab you should define the Interference Correction factors and their uncertainties. These constants differ per reactor and whether the samples were shielded or not.

Irradiation segments
In the final tab you can define the Duration, Date, End Time and MW (reactor power) of all Irradiation Cycli or Segments. It is highly recommended that you use either GMT or your Local Time Zone, as long as you consistently apply it throughout ArArCALC. For example, you should make certain that you apply the same Time Zone when you define your irradiations and when you supply dates and times in the Sample Parameters (see also: Sample Parameters). Use the spin button to increase or decrease the Number of Irradiation Segments. Click on a line in the list box to adjust your settings, which will appear for editing in the text boxes at the bottom of this dialogbox. To speed up data entry you can also check the Auto Fill option.

The program ArArCALC does not contain any constant in its computer code. Every constant, parameter and setting can be set by the user. This is done to give you 100% control over what you calculate in ArArCALC. Below follows a list of adjustable settings in the Preferences dialogbox.

Calculation Preferences

Isochron Settings
These options let you influence the precision of the YORK2 Isochron calculations (see reference: York, 1969). The Convergence determines how small the difference in slope of the isochron should be for two consecutive iterations to result in a successful least-squared fit. The Convergence is here expressed as a percentage of the slope itself (see also: Isochron Calculations). The number of Iterations determines after how many iterations the isochron calculation should be terminated, in case the calculation is not converging. If you set the Convergence to a higher precision (a lower percentage), you also should adjust the number of Iterations accordingly (to a higher number). Clicking the option button Weighted YORK-2 forces ArArCALC to calculate a least-squared linear fit with correlated errors that is weighted by the inverse of the variance (see reference: York, 1969). You can overrule this setting when performing isochron calculations by selecting Normal Isochron # Weighted YORK-2 or Normal Isochron # Unweighted YORK-2 in the menu bar. You can do the same for the Inverse Isochron independently.

Data Reduction Settings
The data reduction settings determine the precision when you apply the Exponential Fit to your mass spectrometry data. The Convergence is expressed as a percentage of the curvature coefficient that is iteratively derived in this least-squared fit (see also: Line Fitting).

Error Propagation
By checking Irradiation Constants in the Error Propagation box, the errors on the irradiation correction factors will be propagated in the reported analytical error (see also: Analytical, Internal and External Errors). You can set these errors in the Change Irradiation dialogbox (see also: Managing Irradiations and Projects). If the Multiply Errors by Sqr(MSWD) is checked, then the errors on the ages and some isotope ratios (e.g. ⁴⁰Ar/³⁶Ar and ⁴⁰Ar/³⁹Ar) will be multiplied by the sqr(MSWD) in case the MSWD becomes larger than 1 (see also: Analytical, Internal and External Errors). Both options are activated by default in ArArCALC.

Ar40, Ar39, Ar38, Ar37 and Ar36
You can chance the option buttons to the right of the Preferences dialogbox in order to set your Default Calculation Type for the raw data reductions (see also: Line Fitting). You can do this independently for each isotope by choosing from four calculation types: exponentional (Exp), parabolic or second order polynomial (Par), linear (Lin) and averaging (Ave). You can always overrule these default settings in ArArCALC when performing the actual line fits.

Other Calculation Settings
With these checkboxes you can determine which Additional Corrections to apply (or not apply) during the age calculations (see also: Other Calculation Settings). However, it is always recommended that you apply the corrections for ³⁷Ar and ³⁹Ar Decay following sample irradiation, for ³⁶Ar Ingrowth in chlorine-rich samples, and for Procedure Blanks. However, for samples younger than 1 Ma it is recommended that you uncheck the Force Negative Intensities to be Zero ... option. This will allow for more accurate age calculations, because negative ages (or error bars) are statistically expected and valid for these kind of samples. ArArCALC will generate a warning when you select a non-default setting.

Configuring the Input Filter

Defining your own Input Filter is most critical while using ArArCALC. Although it may look complicated, it gives you the flexibility to read-in different types of mass spectrometry data files. ArArCALC does not read-in binary files and expects that the measurements were saved in sequentional text files. Furthermore, the actual intensity measurements should be given per line, including the intensity (in volts, amps or counts) and the time (in hours, minutes or seconds) after inlet of the argon gas in the mass spectrometer. By clicking on the Settings button you can define the internal structure of both the header and data sections in a separate dialogbox (see explanation below). By checking the Choose Input Filter when ... checkbox, ArArCALC allows for the selection of an input filter every time you open a new data file. Otherwise the input filter selected in the list box shown below will be used by default.

General Settings
The File Structure is determined by the Number of Header Rows and the Number of Peak Measurements for each measurement cycle, and whether the text file is Space, Comma or Tab delimited. The Number of Peaks should be at least five to cover all five argon peaks between Ar36 and Ar40. In the Peak Cycle Structure the user defines which lines represent peak measurements for the argon isotopes and which lines represent baseline measurements. These lines can be assigned in random order as long as the Number of Peaks is not exceeded. If you provide two baseline measurements, ArArCALC calculates an average baseline (see Ar36 through Ar39 below). If you provide one baseline measurement, the baseline value will be subtracted as is (see Ar40 below). You can also fill in "0" when your data already have been baseline corrected (by your data acquisition software, for example). Two positions for the masses Ar41 and Ar35 have already been reserved for future importing and monitoring of this data.

Record Settings
In the Record Settings tab you can define which records in the peak lines represent the Peak Measurement, the Error on Peak Measurement and the Time Measurement. Here you can also define in which units the Time and Intensity Measurements are given and you can define settings such as the File Extension, the Maximum Number of Records and Header Lines, and how the Date and Time parameters and the Errors are represented in the data files. By default ArArCALC assumes absolute errors.

Header Structure
Your raw data files may contain more than 1 header line. In the Header Structure tab you can define on which header line (H#) and on which record position (R#) the Sample Name or J-Value was stored. This of course requires that these headers were originally saved in the data file. In the rather simple example below, only one parameter is stored, namely the Number of Cycli, which is stored in the first record of the first header line. Further below a more complicated example is shown and explained as well.

Example Input Filters

This is one of the most simple text files possible (see settings in the dialogboxes displayed above). Its space delimited and it has the minimum amount of headers. The Number of Headers should be set to 1 and consequently the Cycle # should be set to [1,1] as well. Since there is only one header line with only one parameter in it, all other possible header positions should be set to zeros (which is the default value). In this example, each measurement cycle produces 10 individual peak measurements (5 isotopic peaks and 5 baselines) and thus the Number of Peaks should be set at 10. The net peak of Ar40 is calculated based on peak 1 minus the average baseline calculated from peak 2 and peak 2, the net peak of Ar39 is calculated based on peak 3 minus the average baseline calculated from peak 2 and peak 4, etc. etc.

This is a more complicated text file that can be read-in by ArArCALC (see settings in the dialogboxes displayed below). Its comma delimited. It has 10 header lines as is set for the Number of Headers. Each measurement cycle produces 6 individual peak measurements (5 isotopic peaks and 1 baseline at mass 35.5), explaining why the Number of Peaks is only set to 6. The net peak of Ar40 is calculated based on peak 1 minus the average baseline calculated from peak 6 and peak 6 (which is the actual baseline value as measured on mass 35.5), the net peak of Ar39 is calculated based on peak 3 minus the average baseline calculated from peak 6 and peak 6, etc. etc.

The number of cycles can be found on the first record of the 9th header line in this text file and the Cycle # is thus set to [9,1]. The Sample Name, Material, Location and Analyst are all located on the first record of header lines 1 through 4. The Temperature for the measurement is located on header line 5, the J-value and Fractionation Correction Factors and their errors are located on header lines 6 and 7 at records 1 and 2, respectively. The Irradiation Name is located on the first record of header line 8. Finally, the Date and Time are located on header line 10 at records 1 and 2 as well. Since the One String for the Data and Time checkboxes have been selected (see above) only one option is available to you for the Date and Time. If you have them unchecked, you can point to individual values for the Day, Month, Year, Hours and Minutes in the header structure.

Constants

The Decay Constants and their percentual standard deviations can be set and changed in the Preferences dialogbox below. Here you can also define the data for Decay Activities and Other Physical Constants that are needed for the primary age calculations and recalibrations based on the formulations of Karner & Renne (1998), Renne et al. (1998) and Min et al. (2000). For more details read the Primary Age Recalibration Toolbox help page. The expected units are given in the brackets, unless the numbers are dimensionless.

Laboratory Preferences

The information you fill out in the Laboratory Identifiers panel will always be printed as headers and footers, next to the date, time and the ArArCALC version number, when you are making a printout from within ArArCALC. You can also set the File Location of the mass spectrometry data files on your hard disk to ensure that ArArCALC swiftly finds your data files. Finally, you may want to set a Password to protect your settings in the Preferences and Irradiation and Project dialogboxes. Setting passwords is, in particular, advised for the person who is managing the Master ArArCALC.log file, in order to circumvent accidental deletion of these important parameters (see also: Using the ArArCALC.log File).

The standard Age Calculation workbooks with the extension *.AGE cannot be opened in Microsoft Excel 2000-XP-2003 without running ArArCALC. These files are password protected to circumvent the possibility of (unexpected) changes made to the workbooks, leaving these files unreadable by ArArCALC itself. However, if you save your calculations via the File # Save as Editable Excel File (Ctrl+E) option, the password protection and the Microsoft Excel macros are removed. Now you can open these newly-saved files with the extension *.XLS in Microsoft Excel and change the format of their data tables and diagrams manually. A progress bar appears, showing you the status while saving these editable files.