A sealed source is measured with a high-purity germanium detector inside an unlined…

PHYSICS · Subjective · Fermi University Physics · Nuclear Physics · Radiation interactions, detection and dosimetry · Radiation interactions, detection and dosimetry

The Nucleus Resolved, Ch From a pulse to a number: detectors, resolution and what a spectrum establishes

Problem

A sealed

^{22}\mathrm{Na}

source is measured with a high-purity germanium detector inside an unlined lead shield.

^{22}\mathrm{Na}

decays by positron emission to an excited state of

^{22}\mathrm{Ne}

that emits a

1274.5\,\mathrm{keV}

gamma ray; the positron annihilates to give two

511\,\mathrm{keV}

photons (the electron rest energy is

511\,\mathrm{keV}

). Besides the two full-energy peaks at

511\,\mathrm{keV}

and

1274.5\,\mathrm{keV}

, the recorded spectrum shows six weaker features at approximately

75\,\mathrm{keV}

171\,\mathrm{keV}

341\,\mathrm{keV}

764\,\mathrm{keV}

1062\,\mathrm{keV}

and

1786\,\mathrm{keV}

. For each of the six features, name it and state whether its energy and its presence are set mainly by the source, the detector or the shield.

Related theory

Nuclear Physics

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