Describe both the sensitivity and selectivity of a gas filled detector in each of the three operating voltage regions (ionization, proportional, and GM
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I have an ionization detector that is filled with a gas that undergoes ionization with an average of 100 eV of input energy. A positive voltage is applied to a wire running down the center of the cylindrical detector, while the outer cylinder wall is held at a negative voltage; I can control both of those voltages. a) I find that when I measure a Cs-137 source and then a Co-60 source at one voltage, I find that measured currents are proportional to my detected energy, with a measured energy resolution of 1.2% for Cs-137. What mode am I operating my ionization detector in: under-voltage, ionization, proportional, or Geiger? b) I then adjust my voltage and find a set current is produced by both Cs-137 and Co-60 sources. What mode am I operating my detector in now? Did I turn my voltage up or down?
Supreeta N.
Explain the difference between ionization chamber detector, proportional detector, and Geiger-Muller detector! Make it in table form!
Penny R.
A Geiger tube is a radiation detector that essentially consists of a closed, hollow metal cylinder (the cathode) of inner radius $r_{a}$ and a coaxial cylindrical wire (the anode) of radius $r_{b}$ (Fig. P25.61). The charge per unit length on the anode is $\lambda,$ while the charge per unit length on the cathode is $-\lambda .$ A gas fills the space between the electrodes. When a high-energy elementary particle passes through this space, it can ionize an atom of the gas. The strong electric field makes the resulting ion and electron accelerate in opposite directions. They strike other molecules of the gas to ionize them, producing an avalanche of electrical discharge. The pulse of electric current between the wire and the cylinder is counted by an external circuit. (a) Show that the magnitude of the potential difference between the wire and the cylinder is $$ \Delta V=2 k_{e} \lambda \ln \left(\frac{r_{a}}{r_{b}}\right) $$ (b) Show that the magnitude of the electric field in the space between cathode and anode is given by $$ E=\frac{\Delta V}{\ln \left(r_{a} / r_{b}\right)}\left(\frac{1}{r}\right) $$ where $r$ is the distance from the axis of the anode to the point where the field is to be calculated.
Timothy J.
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