detection of γ-rays from nuclear decay: 0.1 < eγ < 20...
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Detection of γ-rays from nuclear decay:
0.1 < Eγ < 20 MeV
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γ-ray interaction
γσ EZpp ln2≈
ionization occurs in limited regions of the absorber
Ge
µ
ppCph σσσµ ++=
Linear attenuation coefficient (probability per unit path)
γ
γσEE
ZC
ln≈
54
5.3
−=
≈
n
EZ n
phγ
σ
I/I0
t
e-µt
= hν
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= c/ν=hc/E
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Eγ = hν
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Derivation of Compton Scatterig Formula
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Detector response We detect recoil electrons
and NOT photons !
)(256.02
/21
22
2
cmEifMeVcm
cmEE
EEE
ee
eCEgap
>>=≈
+=−=
γ
γ
γγ
Egap
Important characteristics: § energy resolution: δEγ/Eγ = FWHM/Eγ
§ peak-to-total: P/T = Areapeak/Areatotal
Egap
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Study of Detector response
Accurate study of detector response
is done with MonteCarlo GEANT simulations
133Ba in-beam spectrum
after unfolding
Backscattering peak: θ=π ⇒ (Εγ)min ~mec2/2 =256 keV important for θ≥ 1100
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