Physics and Engineering of Radiation Detection
196 Chapter 3. Gas Filled Detectors Note that, in order to determine the dead time using this method, one does not require the k ...
3.6. Geiger-Mueller Counters 197 However since at lower voltages the avalanche multiplication can not be achieved unless the pre ...
198 Chapter 3. Gas Filled Detectors A good example of an external quenching circuit is the one that rapidly drops the anode volt ...
3.7. Sources of Error in Gaseous Detectors 199 Hereαis called the recombination coefficient andSrepresents the source of charges ...
200 Chapter 3. Gas Filled Detectors coefficient for helium at 0.5atmis approximately 1. 7 × 10 −^7 cm^3 s−^1. Solution: Assuming ...
3.7. Sources of Error in Gaseous Detectors 201 collision frequencyνe.Intermsofτeandνethe probability of capture in a single coll ...
202 Chapter 3. Gas Filled Detectors smaller than the energy of the original electron. e+(XY..V Z) → (XY..V Z)−∗ (XY..V Z)−∗ → (X ...
3.7. Sources of Error in Gaseous Detectors 203 + Incident Radiation x Anode Cathode δx d Figure 3.7.1: Schematic showing the dri ...
204 Chapter 3. Gas Filled Detectors HereV 0 is the applied electric potential andE+is the electric field intensity due to the sh ...
3.7. Sources of Error in Gaseous Detectors 205 E_+ (volts) 0 5 10 15 20 25 30 E (volts) 50 100 150 200 250 Figure 3.7.2: Depende ...
206 Chapter 3. Gas Filled Detectors e is the electronic charge, Eγ is the photon energy, W is the energy needed to create an ele ...
3.8. Detector Efficiency 207 which the electric lines of force are passing through. Hence the electric field intensity due to a ...
208 Chapter 3. Gas Filled Detectors ηp. The electrons and ions thus produced drift toward opposite electrodes under the influenc ...
3.8. Detector Efficiency 209 pulse counting systems we essentially mean that the system does not miss any real pulse and does no ...
210 Chapter 3. Gas Filled Detectors whereNinis the number of incident photons andσ^2 mrepresents the standard devi- ation of mea ...
3.8. Detector Efficiency 211 efficiency of the detector. Solution: The quantum efficiency of the detector can be calculated from ...
212 Chapter 3. Gas Filled Detectors Example: A GM detector having a quantum efficiency of 0.34 and dead time of 50μs is used in ...
3.8. Detector Efficiency 213 The signal-to-noise ratio will then be given by SNRin = Sin √ Sin = √ Sin. (3.8.12) Example: A dete ...
214 Chapter 3. Gas Filled Detectors Example: If the detector of the previous example has a readout noise of 200 photons and a qu ...
3.8. Detector Efficiency 215 Problems 1.Compute the total and primary charge pairs created percmin a mixture of 90% argon and 10 ...
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