It is essential to specify all materials (for source, container, absorbing layers, detector elements, etc.) as accurately as possible. Angle offers a list of common materials for particular cases, but if none of them is adequate, you can specify the material manually or load it from a previously saved material file. To do this, choose the option “Specify material...” from the material drop-down list, i.e. pop-up menu. Any of these two options will open the material entry window. It is possible to define the material in three ways, each represented by buttons at the top of this window:
When specifying the material as a mixture of elements, you have to define the number of elements, element symbols and mass shares in percentages.
When entering the material as a compound, you have to enter the number of elements, element symbols and the number of atoms.
In Angle 5 you can enter the compound using the chemical formula – simply type it in the “Chemical formula” box and Angle will automatically break it down to symbols and atoms.
Formulae can be entered in condensed form. For example, Al2(SO4)3 can be entered in two ways: as Al2S3O12 or Al2(SO4)3.
Although Angle accepts both upper- and lower-case letters in formulae, you should pay attention to use the proper character case to avoid ambiguities. For example, “caco3” will be interpreted as CaCo3 (one atom of calcium and three atoms of cobalt). Proper way to enter calcium carbonate is CaCO3 (with uppercase letter “O”).
Angle automatically breaks down the chemical formula to symbols and atoms and displays them in the table below. You should always use this table to check if the formula was entered correctly.
The third way to define a custom material is as a mixture of compounds. First, you need to enter the number of compounds. Then, you have to define each compound, as well as its mass share in the material, with each compound in a separate tab.
Finally, regardless of the way in which you define a material, you have to enter the material density and give it a name.
After you enter all material parameters click on the “OK” button to complete the procedure. At this point you will be asked if you would like to save the material to disk, for further use.
Knowing material composition as well as possible contributes to the accuracy of the calculated results. However, bear in mind that in work with regards to gamma-attenuation, it is not necessary to know the exact material composition, particularly not for materials in trace quantities.
However, material density is crucial for the proper accounting for gamma attenuation, and should be known as accurately as possible; if not available otherwise, it is eventually a simple mass to volume ratio, both readily measurable.
One should be particularly vigilant when specifying the so called “generic” materials (e.g. rock, soil, sediment, ash, resin, plastic, glass, wood, concrete, etc.). Such generic names usually encompass a large number of materials with varying characteristics (including composition and density). Specifying the actual data, whenever possible, for the actual material is therefore highly advisable. Again, density has a substantial impact on the calculation result, so please check for the actual density of the material.
From the material entry dialog box, you can load any previously saved material by clicking on the “Load saved material” button and choosing a material file.
Semiconductor and scintillation detector gamma-efficiency calculations