Calculator Inputs
The selected material loads default density and effective mass number values. You can still edit both fields for custom engineering cases.
Plotly Graph
The graph compares residual alpha energy across the selected medium and reference air.
Example Data Table
| Energy (MeV) | Air Range at STP | Aluminum Range | Lead Range |
|---|---|---|---|
| 4.0 | 2.5440 cm | 15.6904 µm | 10.3528 µm |
| 5.0 | 3.5553 cm | 21.9280 µm | 14.4685 µm |
| 6.0 | 4.6736 cm | 28.8251 µm | 19.0193 µm |
| 7.0 | 5.8894 cm | 36.3238 µm | 23.9671 µm |
These sample values help validate trend behavior before entering your own case inputs.
Formula Used
This calculator starts with an empirical alpha range relation in air at standard conditions:
Rair,STP = 0.318 × E1.5
Here, R is the range in centimeters and E is the alpha energy in MeV.
Ambient gas conditions adjust the air result with an ideal-gas correction:
Rair,ambient = Rair,STP × (T / 288.15) × (101.325 / P)
The selected medium uses a Bragg-Kleeman style scaling estimate:
Rmaterial = Rair,STP × (ρair / ρmaterial) × √(Amaterial / Aair)
An engineering safety margin then increases the final design thickness:
Rdesign = Rmaterial × (1 + Margin / 100)
This gives a fast engineering estimate. Detailed shielding work should use measured stopping-power tables or dedicated transport software.
How to Use This Calculator
- Enter the alpha particle energy in MeV.
- Select the target material from the dropdown list.
- Review or edit density and effective mass number values.
- Set the ambient temperature and pressure for air correction.
- Choose a safety margin for design thickness.
- Press Calculate Range to display results.
- Review the graph, summary cards, and example table.
- Export your calculation using the CSV or PDF buttons.
Frequently Asked Questions
1) What does this calculator estimate?
It estimates how far an alpha particle can travel in air or a selected engineering material. It also shows a design range with margin and a residual-energy graph.
2) Why is the range so short in dense solids?
Alpha particles are heavy and doubly charged. They lose energy quickly through ionization. Dense solids contain more stopping electrons per unit path, so the penetration distance drops sharply.
3) Is the result exact for every material?
No. This page gives a practical engineering estimate. Exact design work should use measured stopping-power tables, calibrated experiments, or specialized transport models for the specific material and energy.
4) Why are temperature and pressure included?
Gas density changes with ambient conditions. Lower pressure or higher temperature reduces density, allowing a longer path in air. The calculator adjusts the reference air result with a simple gas-scaling correction.
5) What is the effective mass number field?
It is a scaling parameter used in the material-conversion step. Default values are provided, but you can edit them when using a custom engineering approximation or matching your project standard.
6) Why does the graph show residual energy?
The residual-energy graph helps you visualize how the alpha particle slows as it travels. It is useful for quick comparisons between air and the chosen medium during screening studies.
7) Which input energy range works best?
The empirical relation is commonly used for typical alpha energies, especially in the low-MeV range encountered in many engineering and radiation problems. Results outside that region should be treated more cautiously.
8) When should I add a safety margin?
Add a margin when you need a conservative design thickness, when material properties vary, or when operating conditions are uncertain. It is a practical step during preliminary engineering screening.