Input data

The function calc_CobbleDoseRate() requires a user defined input (as a data.frame), which contains information on the cut rock slices, mineral used (quartz or feldspar) radionuclide information, grain size and water content. An example data set is available. To see the example data set, simply load the luminescence package, import and view the example data set:

library(Luminescence)
data("ExampleData.CobbleData", envir = environment())
View(ExampleData.CobbleData)

The example data set then shows a table with headers and all required columns. Headers for these columns to be used with your own data are also provided under the Help option of the function calc_CobbleDoseRate() in RStudio.

Calculations

The function calc_CobbleDoseRate() performs a set of calculation which includes:

• Dose rate conversions: Therefore, the function requires the user to define the set of dose rate conversion factors which should be used. The user can choose between conversion factors by Adamiec and Aitken (1998), Guérin et al. (2011), Liritzis et al. (2013) or Cresswell et al. (2018). For these calculations the function calc_CobbleDoseRate() links to the function `convert_Concentration2DoseRate´.
• Dose rate correction for grain size: A grain size correction is necessary for the calculations. Here the function uses the correction factors by Guérin et al. (2012). The function automatically uses these grain size correction factors. Please remember that the grain size correction factors differ for quartz and feldspar. Thus, it is important that you provide the correct mineral in your data import table. The ExampleData.CobbleData is for feldspars (see “FS” input in column 5 of the ExampleData.CobbleData set).
• Scaling of gamma dose rate for cobble diameter: Riedesel and Autzen (2020) showed that the gamma dose rate by the cobble itself is dependent on the size of the cobble. The function calc_CobbleDoseRate() assumes that the cobble is spherical and applies the relationship between gamma dose rate attenuation factor and diameter of the cobble presented by Riedesel and Autzen (2020).
• Calculation of dose rate profiles: The dose rate profiles into the cobble are calculated for the cobble itself and the dose rate contribution from the adjacent sediment following the dose rate attenuation coefficients presented by Riedesel and Autzen (2020). Let’s now use the example data set with the latest available dose rate conversion factors by Cresswell et al. (2018) for the calculations and run the function:

results <-
  calc_CobbleDoseRate(input = ExampleData.CobbleData, conversion = "Cresswelletal2018")

results$DataIndividual

Results

Results of the calculations achieved using the function calc_CobbleDoseRate() are provided as RLum Results. The RLum Results contain tables, which include (1) the input data, (2) the beta and gamma dose rates for each cobble slices delivered by the cobble itself or the adjacent sediment and (3) the total beta and total gamma dose rates delivered by the cobble and the sediment added for each rock slice of the cobble. To view the respective RLum Results table type results$input, results$DataIndividual or results$DataComponent in the R console:

And now?

These results can be used to calculated total dose rates, for example by using the function use_DRAC() which also available in the R package Luminescence. Here you are able to insert your user defined beta and gamma dose rates.
Should you be interested in your alpha dose rate, you can either use the function use_DRAC() or the function convert_Concentration2DoseRate(). If your cobble is located in a complex stratigraphy, where multiple sedimentary layers might influence your gamma dose rate the R function scale_GammaDose() might be useful for you.