Understanding the thermometry of hot nuclei from the energy spectra of light charged particles
Résumé
In the Fermi energy domain, the temperature of hot nuclei can be determined using the energy spectra of evaporated light charged particles. But this method of measurement is not without difficulties both theoretical and experimental. The present study aims to disentangle the respective influences of different factors on the quality of this measurement: the physics, the detection (a $ 4\pi$ detector array such as INDRA) and the experimental procedure. This analysis demonstrates the possibility of determining from an energy spectrum, with an accuracy of about 10%, the true apparent temperature felt by a given type of particle emitted from a hot nucleus. This temperature allows to deduce the initial temperature using an appropriate method. However, three conditions are necessary: a perfect particle detector, important statistics and very weak secondary emissions. According to the GEMINI event generator, for hot intermediate mass nuclei, only deuterons and tritons could meet these conditions. In this case the determination may be better than 15%. With a realistic experimental device, insufficient angular resolution and topological distortions, caused by detection, can distort spectra to the point where it is very difficult to determine the apparent temperature correctly. Experimental reconstruction of the moving frame of the hot nucleus can also be responsible for this deterioration.