CERN Program Library Long Writeup W5013 - CERNLIB ...

Geant 3.16 GEANT User’s Guide PHYS337
Origin : N.Van Eijndhoven Submitted: 26.07.93
Revision : Revised: 16.12.93
Documentation :
1 Subroutines
Birks’ saturation law
CALL GBIRK
(EDEP)
EDEP
(REAL) and on output the energy equivalent to the calorimeter response in the current step.
Organic scintillators are usually calibrated with particles whose energy is near the minimum ionisation
(γβ ≈ 4). However, the energy response of such scintillators for large local energy deposit is attenuated.
GBIRK returns the energy detected by the scintillator in the current step.
2 Method
The phenomenological description of the response attenuation of organic scintillators
Birks’ law:
∆E
R =
1+C 1 δ + C 2 δ 2 δ = 1 dE
ρ dx
The values quoted in [74] for the parameters C 1 ,C 2 are:
[73] is known as
MeV g −1 cm 2 (1)
C 1 =0.013 g MeV −1 cm −2 and C 2 =9.6 × 10 −6 g 2 MeV −2 cm −4
These values have been measured for various scintillators. If the charge of the particle is greater than one, a
better description can be obtained by correcting C 1 :
C 1 ′ = 7.2
12.6 C 1 ≈ 0.5714C 1 (2)
The values of the parameters of Birks’ formula (if defined) are in the ZEBRA bank next to the material bank:
JTM = LQ(JMATE-NTMED) pointer to the current tracking medium bank;
JTMN = LQ(JTM) pointer to the next bank to the current material one, where the specific tracking
medium parameters are stored;
MODEL = Q(JTMN+27) flag controlling the correction (2) for multiply charged particles:
C1 = Q(JTMN+28)
C2 = Q(JTMN+29)
≠1 correction is not applied;
=1 correction is applied;
first parameter of the Birks’ formula;
second parameter of the Birks’ formula.
These parameters are set via the GSTPAR routine, with names BIRK1, BIRK2 and BIRK3, respectively. For
instance, to define the standard Birks’ parameters for tracking medium ITM with correction for multiply
charged particles, one would have to insert the following piece of code, after the definition of tracking
media but before the call to GPHYSI
CALL GSTPAR(ITM,’BIRK1’,1.)
CALL GSTPAR(ITM,’BIRK2’,0.013)
CALL GSTPAR(ITM,’BIRK3’,9.6E-6)
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