The current web calculator allows one to obtain the residual spectral fluence or residual energy for protons and ions traversing a shielding material by exploiting the "SRIM Module.exe" (with an upper energy limit of 5 GeV/amu) included in SRIM 2013 code (SRIM Tutorials) - whose maximum available energy is 10 GeV/amu -, i.e., the used electronic stopping power tables are those provided by "SRIM Module.exe" code with a low energy limit of 1 eV.
The following link give access to the Web Applications for the calculation of the residual spectral fluence or residual energy for protons and ions traversing an absorber:
How to use this Calculator for particle spectral fluences or mono-energetic particles traversing an absorber
For an incoming particle spectral fluence or mono-energetic particles, this tool allows one to calculate the residual spectral fluence or residual energy after traversing a shielding material.
The input parameters and options for the tool are described below. When the input form has been completed, pressing the "CALCULATE" button will start the calculation and open the "Results" page (allow for pop-up in your browser settings). The result page will be also linked at the bottom of the calculator page.
- Input type
- Incident particle
- Target material
- Traversed path
- Number of steps
- Particle spectral fluence.
In the web Calculator, using the selector at the top of th calculator panel, the user can select the calculation of the residual spectral fluence or the residual energy for incoming protons or ions.
Spectral fluence is the default option:
User has to change selection for mono-energetic particles:
In the web Calculator, using the pull down menu, the user can select the species of incident particles, i.e., protons or any other elemental ions.
Except for proton and alpha particle masses, the user can also modify the mass (in amu) of the incident particle (e.g., for all isotopes one can refer to this page): the default mass is that of the most abundant isotope (MAI). Further information are available at the following webpage.
In the section "Target Selection" it is possible to specify an User Defined target material or a predefined Compound material. User can also select the target as gas, this is allowed only for single element and natural gas target (H, He, N, O, F, Ne, Cl, Ar, Kr, Xe, Rn).
The stopping power in target gases is usually higher than that in an equivalent solid target. The Gas/ Solid correction disappears for higher velocity ions with energies above 2 MeV/amu. But at lower velocities the effect can be quite large - almost a 2 times change in stopping bacause of the Phase effect near the Bohr velocity, 25 keV/amu.
in the User Defined section individual elements can be selected as well as the composition of the target material choosing the number of elements in the compound. The required parameters for each element are:
- Atomic number (Z)/Chemical symbol
- Stoichiometric index or element fraction
Electronic Stopping Power for User Defined Compounds
Electronic Stopping Power for User Defined Compounds can be determined by means of Bragg's rule, i.e., the overall Electronic Stopping Power in units of MeV cm2/g (i.e., the mass electronic stopping power) is obtained as a weighted sum in which each material contributes proportionally to the fraction of its atomic weight. For instance, in case of a GaAs medium ones obtains (e.g., Eq. (2.20) at page 15 in [ICRUM (1993)]):
where and AGa [AAs] are the Electronic Stopping Power (in units of MeV cm2/g) and the atomic weight of Gallium [Arsenic], respectively.
As discussed in SRIM. (see help of "The Stopping and Range in Compounds" in SRIM-2013), the Compound Correction is usually zero for compounds containing heavy atoms, Al(Z>=13) or greater. All experiments with compounds such as Al2O3, SiO2, Fe2O3, Fe3O4, SiC, Si3N4, ZnO, and many more, show less than 2% deviation from Bragg's rule which estimates the stopping by the sum of the stopping in the elemental constituents. That is, the stopping in Al2O3 is the same as the sum of the stopping in 2 Al + 3 O target atoms. For these compounds there is no need for a Compound Correction. This correction should be accounted for in compounds containing mostly H, C, N, O and F for ion stopping below 2 MeV per atomic mass unit and is negligible above 5 MeV per atomic mass unit. In the current calculator, no correction is applied for target atoms lighter than Al. Further details are available at SRIM Compound, and SRIM Compound Theory.
In the Compoud section it is possible to select a predefined compound including the SRIM compound corrections in the stopping power calculation.
For instance, in the following plot, it is shown the percentage difference of the stopping power of H2O (selected as User Defined material) and Water_Liquid (selected as a Compound) as a function of the incoming proton energy in MeV:
This input define the traversed path by a particle fluence. The traversed path is expressed in [g cm-2] ad is given by:
(absorber thickness in cm) x (absorber density in g cm-3) .
The lower limit of traversed path is equivalent to about 5 μm of Si (1.16x10-3 [g cm-2]), e.g., 0.96 cm in Dry Air at sea level with density equal to 1.20484x10-3 g/cm3 (as implemented in SRIM from ICRU-37 table 5.5).
Number of Steps
In the web Calculator, using the pull down menu, the user can select the number of steps of the calculation - i.e., the traversed path is divided by the number of the steps.
The results of each steps is used as input for the following one to obtain the final result for the total traversed path.
In each step, the minimum traversed path is equivalent to about 5 μm of Si (1.16x10-3 [g cm-2]), e.g., 0.96 cm in Dry Air at sea level with density equal to 1.20484x10-3 g/cm3 (as implemented in SRIM from ICRU-37 table 5.5). The number of steps will be accordingly modified to keep each step above the minimum.
Particle Spectral Fluence
This section define the points of the spectral fluence as a function of energy.
The input format is one point per line (Energy - Flux , separated by a space or tab); it is also possible to copy and paste values. The minimum value of the particle spectral fluence is 1 keV.
This section define the list of energy of the incoming protons or ions.
The input format is one energy per line; it is also possible to copy and paste values. The minimum value of the particle energy is 1 keV.
The result page contains the graph of the input spectral fluence and the spectral fluence after traversing the absorber. The table provides the values of the spectral fluence (above 1 keV) and the residual spectral fluence (above 1 keV) after traversing the absorber. In addition, the incoming and residual spectral fluences are provided. In case of mono-energetic particles a table with the incoming energy and residual energy is provided.
Residual energies were obtained disregarding multiple scattering effect, i.e., directions of flight of emerging particles were unchaged with respect to those of impinging directions.