Calculate the magnitude in volts of the signal produced in a Geiger-Muller counter following the interaction of an X-ray of energy 8 keV in the counter gas, stating the assumptions that you need to make (assume that the detector has a capacitance of 50 pF) and then comment on the size of the signals if a gamma-ray of 800 keV interacted in the counter instead.
[5 MARKS]
Calculate the current in nA that would be produced in a properly operating free-air ionization chamber with an active volume containing 2 g of air and exposed to a flux of radiation depositing a constant dose rate of 0.3 J/kg/h (0.3 Gy per hour) in the air.
[4 MARKS]
2.
Regarding semiconductor detectors:
co Why is it that silicon semiconductor detectors can be operated at room temperature but germanium semiconductor detectors must be cooled to much lower temperatures (typically 77K to 177K) in order to operate correctly?
[2 MARKS]
(ii) Sketch the band structure of the energy levels in a typical semiconductor on a diagram with energy in
the vertical direction, indicating the typical magnitude of the band gap and also the locations
of typical donor levels and acceptor levels.
[2 MARKS]
With reference to silicon semiconductor detectors,
@ Explain why the electric field in the region of a p-n
junction reaches a maximum exactly at the
position of the junction.
[2 MARKS]
(Jo Sketch a graph showing the magnitude of the electric field in the region of the junction as a function of distancector in which
