Home › Calculators › Stopping Power & LET

Stopping Power & LET Calculator

Look up proton and electron stopping powers in silicon using NIST PSTAR and ESTAR data. Shows electronic (ionizing), nuclear (displacement), and total stopping power components with LET conversions. Related: Fluence to Dose (electronic S/ρ → TID) | Displacement Damage (nuclear S/ρ → NIEL)

Lookup Parameters

Note: This tool covers protons and electrons using NIST stopping power data. Neutrons are uncharged and do not have a defined stopping power or LET. Heavy ion LET requires SRIM/TRIM calculations, which are not included here.

How It Works

Stopping power describes the average energy loss per unit path length of a charged particle traversing a material. The mass stopping power S/ρ (MeV·cm²/g) is the stopping power divided by the material density, making it material-density-independent.

Electronic vs. nuclear stopping:

  • Electronic (collision) stopping — energy lost to atomic electrons via Coulomb interactions. This is the ionizing component responsible for total ionizing dose (TID) in electronics. Dominates at all but the lowest proton energies.
  • Nuclear stopping — energy transferred to atomic nuclei via Coulomb elastic scattering. This is the non-ionizing component responsible for displacement damage (lattice defects, NIEL). Significant for protons below ~10 keV; negligible above ~100 keV.
  • Total stopping = electronic + nuclear. This determines the particle range (CSDA range) and overall energy deposition rate.

Linear Energy Transfer (LET):

LET is numerically equal to the stopping power but expressed in units convenient for single-event effects (SEE) analysis. The standard SEE unit is MeV·cm²/mg. The conversion from mass stopping power is:

LET [MeV·cm²/mg] = S/ρ [MeV·cm²/g] × 10−3
LET [keV/µm] = S/ρ × ρSi × 0.1 = S/ρ × 0.233

where ρSi = 2.33 g/cm³. The LET values shown here use the total stopping power (electronic + nuclear).

Proton LET and SEE:

Proton direct-ionization LET is very low (< 0.6 MeV·cm²/mg across all energies), well below most SEE thresholds. Proton-induced SEE in space and accelerator environments is overwhelmingly caused by nuclear reaction secondaries — high-LET recoil nuclei and fragments produced when the proton undergoes a nuclear interaction in the device. These secondaries are not captured by the stopping power data shown here; proton SEE cross-sections require either testing or Monte Carlo simulation (GEANT4, FLUKA, CRÈME).

References

  1. NIST PSTAR: Stopping-Power and Range Tables for Protons — electronic and nuclear stopping powers for silicon. National Institute of Standards and Technology.
  2. NIST ESTAR: Stopping-Power and Range Tables for Electrons — collision stopping powers for silicon. National Institute of Standards and Technology.
  3. ICRU Report 49, “Stopping Powers and Ranges for Protons and Alpha Particles,” International Commission on Radiation Units and Measurements, 1993.
  4. ICRU Report 37, “Stopping Powers for Electrons and Positrons,” International Commission on Radiation Units and Measurements, 1984.

Need Heavy Ion LET or SEE Analysis?

Heavy ion LET calculations require SRIM/TRIM or transport codes. We can help with SEE rate prediction, LET spectrum analysis, and proton SEE cross-section estimation.

Contact Us