THE EGS5 CODE SYSTEM

Table 2.1: Symbols used in EGS5 and PEGS5.
Math FORTRAN Program Definition
1. π PI P 3.1415926536
2. c C P speed of light
= 2.997925 ×10 10 cm/sec
3. m e RME P electron rest mass
= 9.1091 ×10 −28 g
4. ¯h HBAR P Planck’s constant/2π
= 1.05450 ×10 −27 erg-sec
5. e CGS ECGS P electronic charge (CGS units)
= 4.80298 × 10 −10 esu
6. e MKS EMKS P electronic charge (MKS units)
= 1.60210 × 10 −19 Coul
7. N a AN P Avogadro’s number
= 6.02252 × 10 23 mole −1
8. (1 Rad)[ ◦ ] RADDEG P radian expressed in degrees
= 180/π
9. α FSC P fine structure constant
= e 2 CGS /(¯hc)
10. (1 MeV)[erg] ERGMEV P one MeV expressed in ergs
= e MKS × 10 13
11. r 0 RO P classical electron radius
= e 2 CGS /(m ec 2 )
12. m RM PE electron rest energy in MeV
= m e c 2 /ERGMEV
13. 2m RMT2 PE 2m
14. m 2 RMSQ PE m 2
15. ‘22.9’ A22P9 P constant in Nagel’s formula for
χ c in degrees. Taken from
Molière’s paper in which χ c was
expressed in grads. So to get χ c
in degrees, should really use 22.9
×360/400. Defined as A22P9 =
RADDEG √ 4πN a
× e 2 CGS /ERGMEV = 22.6960
16. ‘6680’ A6680 P constant in Bethe’s formula for
Molière’s b
= 4πN a (¯h/m e c) 2 (0.885) 2
/(1.167 × 1.13) = 6702.33
17. k, k 1 P photon energy in ergs
18. ˘k, ˘k1 P photon energy in MeV
19. E, E 1 P electron total energy in ergs
20. Ĕ, Ĕ 1 P electron total energy in MeV
21. T P electron kinetic energy in ergs
22. ˘T P electron kinetic energy in MeV
23. t P distance in centimeters
24. ˘t P distance in radiation lengths
= t/X 0
25. σ P cross section in cm 2 /(atom or
molecule)
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