Principle

An alpha-spectrometer, consisting of a silicon surface barrier layer detector, a preamplifier, a pulse height analyser and a recording device for registration of the spectra is calibrated by means of an open alpha-emitter of known alpha-energy (²⁴¹Am). The energy spectrum of a radium source which is in equilibrium with its decay products, is recorded and evaluated. The alpha-energies found in this way are allocated to the corresponding nuclides of the radium decay series.

Tasks

1. The alpha-spectrum of the ²²⁶Ra is recorded, the settings of the pulse analyzer (amplification) and recorder (x and y input sensitivity) being selected so as to make best possible use of the recording width.
2. The calibration spectrum of the open ²⁴¹Am-emitter is recorded at the same settings.
3. The alpha-energies corresponding to the individual peaks of the alpha spectrum of the radium are calculated and, on the assumption of a constant energy loss in the source covering, the alpha-active nuclides of the radium decay series corresponding to the individual peaks are determined on the basis of the values in the literature.

Learning objectives

• Decay series
• Radioactive equilibrium
• Isotopic properties
• Decay energy
• Particle energy
• Potential well model of the atomic nucleus
• Tunnel effect
• Geiger-Nuttal law
• Semiconductor
• Barrier layer