Physics and Engineering of Radiation Detection

156 Chapter 3. Gas Filled Detectors Figure 3.2.1: Variation of drift velocity of electrons in methane, ethane, and ethylene (14) ...

3.2. Diffusion and Drift of Charges in Gases 157 Figure 3.2.2: Variation of drift velocity of electrons in a mixture of argon, p ...

158 Chapter 3. Gas Filled Detectors Figure 3.2.3: Variation of drift velocity of electrons in a mixture of xenon and C 2 H 6 wit ...

3.2. Diffusion and Drift of Charges in Gases 159 Figure 3.2.4: Variation of drift velocity of electrons in mixtures of (krypton ...

160 Chapter 3. Gas Filled Detectors the capture mean free path can be written as μc = fNmησ (3.2.16) λc = 1 fNmησ . (3.2.17) Now ...

3.3. Regions of Operation of Gas Filled Detectors 161 whereNAis the Avogadro’s number,ρis the weight density, andAis the atomic ...

162 Chapter 3. Gas Filled Detectors E 1 E 2 E 2 E 1 Geiger− Pulse Height Bias Voltage > region limited proportionality Muelle ...

3.3. Regions of Operation of Gas Filled Detectors 163 of charges occurs in such a way that the output pulse remains proportional ...

164 Chapter 3. Gas Filled Detectors The above equation is true only for a uniform electric field. In an non-uniform field, the T ...

3.3. Regions of Operation of Gas Filled Detectors 165 of electrons and ions (see, for example (37)). The electrons move much fas ...

166 Chapter 3. Gas Filled Detectors 3.3.D RegionofLimitedProportionality As we increase the bias voltage, more and more charges ...

3.3. Regions of Operation of Gas Filled Detectors 167 To understand the breakdown quantitatively, let us write the equation for ...

168 Chapter 3. Gas Filled Detectors calledPaschen minimum, which is the voltage below which the breakdown is not possible. An ex ...

3.4. Ionization Chambers 169 where u ≡ Pd, and v ≡ A ln (1 + 1/γ) The minimum in theVbreak−u(that is,Vbreak−Pd) curve can be obt ...

170 Chapter 3. Gas Filled Detectors 3.4.A CurrentVoltageCharacteristics................. Fig.3.4.1 shows the current-voltage cha ...

3.4. Ionization Chambers 171 E E +V −V +V −V +V −V anode cathode (a) −V +V anode cathode (b) Figure 3.4.2: (a) Parallel plate io ...

172 Chapter 3. Gas Filled Detectors vn vp V 0 Veff C R − + t t x − + Incident Radiation d Figure 3.4.3: Simple parallel plate io ...

3.4. Ionization Chambers 173 In the short circuit condition, this total energy should be equal to the total of kinetic and poten ...

174 Chapter 3. Gas Filled Detectors Vp tn tp Veff Vn N 0 e/C t Figure 3.4.4: Pulse shape of an ideal parallel plate ion chamber. ...

3.4. Ionization Chambers 175 the electron collection efficiency over the parallel plate geometry. Fig.3.4.6 shows a typical cyli ...