A. Da Re

Improvement of calibration assessment for gold fast-neutron activation analysis using plasma focus devices

By exploiting the gamma detector-shielding configuration in a plasma focus (PF) device dedicated to fast-neutron activation analysis of gold, a reliable neutron counter may be established. The decay of 207Pbm induced by neutrons in the lead shielding surrounding the photon detector produces gamma photons of 569.7 and 1063.6?keV, which peaks are registered in the same spectrum containing the 279?keV peak of the photons following the 197Aum decay from fast-neutron activation. These decay peaks are found to be linearly correlated to the neutron flux and represent a stable and robust internal standard for monitoring the intrinsic variability in neutron flux production by PF devices. A comparison with the usual external neutron counter techniques shows a great improvement both for the calibration assessment and for the in-field measurements when this internal counter is considered.

Energy spectra measurements of X-ray emission from electron interaction in a dense plasma focus device

Electrons generated during a pinch implosion in a hollow anode Mather-like plasma focus device (PF) are considered as a possible X-ray source via the impinging of those particles on medium and high-Z targets. A usual PF device has been slightly modified to optimise the X-ray production and their measurements by means of a suitable and non-invasive spectrometer. This ensemble allows measurements of X-rays generated booth by electrons turning back to the anode and by target collision of the so-called relativistic electron beam. The spectrum of the emitted photons is evaluated by using a differential absorption based technique. The X-ray spectrometer consists of a stack of LiF dosimeters which act both as detectors and filters to give curves of attenuated intensities. Finally, the energy distribution is calculated from such attenuation curves using an iterative procedure based on spectral algebra formalism.

SANS measurements with polarised neutrons on FeAg magnetic granular samples: compositional and magnetic morphology

Abstract We have performed small angle neutron scattering measurements with polarised and non-polarised neutrons on FeAg magnetic systems prepared by plasma sputtering deposition with the co-sputtering method. We have prepared various samples with an iron content ranging from 10% to 30% and for iron concentration up to 20% they display a superparamagnetic behaviour. Particular attention has been dedicated to these systems, in order to investigate the evolution of granular phase morphology with iron content. The data collected with polarised neutrons can be interpreted in terms of the presence of nanosized particles surrounded by non-magnetic regions. Our data also indicate that samples “magnetic” morphology is greatly affected by iron percentage while the compositional shows negligible modifications.

Fe-Ag magnetic granular systems: a SANS study with polarised neutrons

Abstract We present small angle scattering measurements performed on Fe–Ag granular systems using polarised neutrons. Various samples with different iron concentration have been investigated and the analysis of the experimental data points out that samples morphology does not change remarkably with Fe content. Finally, the study of the polarised signal indicates the presence of Fe rich regions in the nanometer range of size having a negligible magnetisation.