Ionizing Radiation

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Ionizing Radiation
Radioactive Atom
Alpha Particle Neutron Particle Beta Particle
Gamma Ray (X Ray)
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Ne Helium Halogen Dry air
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0.68V
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RI V RC dV/dt V RI(1e-t/RC) RCt VRI(1-1/e)
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Vo 0.68V
time
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V 100 10
Mk eI, IV
104 105 106 107 M
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d dn dp
vme 107 cm/s, d o.1 cm Time d/v 3x10-9 10-7s
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• ?????? Z ???? ?????? (eV)
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• Si 14 1.12
  3.61
• Ge 32 0.74
  2.98

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42
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• ?????? Z ???? ?????? (eV)
  ??????/??? ????? /(eV)
• Si 14 1.12
  3.61
• Ge 32 0.74
  2.98
• CdTe 48 -52 1.47
  4.43
• Hgl 280 -53 2.13
  6.5
• GaAs 31-33 1.43 5.2

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• (keV FWHM) vs. ??? ??????/ ??????? ??????
• ?????? (keV) 5.9 1.22
  1.332
• Proportional Counter 1.2 ----
  ----
• X-ray NaI(Tl) 3.0 12.0
  ----
• 3 x 3 NaI(Tl) ---- 12.0
  60
• Si(Li) 0.16
  ---- ----
• Planar Ge 0.18 0.5
  ----
• Coaxial Ge ---- 0.8
  1.8

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Fundamental law of radioactive decay
AActivity?N
A (t) ½ Ao, at tT1/2
Here T1/2 is the half-life, the time it takes for
half the nuclei to decay - i.e. for A to decrease
to A/2.
? - Units time-1 (s-1, d-1, m-1, y-1)
Here ? is called the average lifetime.
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Half-Life
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Radioactive Decay
14C 14N
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Carbon and Uranium dating
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