PHY6040 | Particle Detectors | Dr C N Booth |
where | is the mean energy loss in passing through thickness Δx, |
, | |
m_{e} is the mass of the electron, | |
Z and A are the atomic number and mass of the medium being traversed, | |
z is the charge (in units of electronic charge) of the projectile particle, | |
β and γ are the usual relativistic parameters, | |
ρ is the density of the medium, | |
I_{0} is its mean ionisation energy, | |
ε is the shell correction and | |
δ is the density effect. |
(For an alternative formulation and description, with different notation, see the BriefBook.)
The energy loss therefore only depends on the incoming particle's velocity, and not directly on its mass, as is shown in the figure below.
The energy loss therefore shows four regions: