2 The Interaction of Radiation with Matter
35
Δ [eV]
f [Δ]
2 GeV protons
1 μm Si
100
80
60
40
20
0
0
50
100
150
200
250
300
Fig. 2.12 Straggling in 1 μm of Si (n = 4) for particles with βγ = 2.1, compared to the
Landau function (dashed line). The Bethe mean energy loss is = 400 eV. Measured straggling
functions of this type are given in Ref. [85]
Δ [keV]
f [Δ] [1/kev]
<Δ>
Δ p
w
0.6
0.4
0.2
0.0
1
2
3
4
5
Fig. 2.13 Straggling function f (() for particles with βγ = 3.6 traversing 1.2 cm of Ar gas
(n = 36) calculated using the convolution method (solid line) compared to the Landau
distribution (dashed line). Parameters describing f (() are the most probable energy loss p , i.e.
the position of the maximum of the straggling function, at 1371 eV, and the full width at half
maximum (FWHM) w = 1463 eV. The Bethe mean energy loss is = 3044 eV. The peak of
the Landau function is at 1530 eV