Search results for " NEUTRON"

A TEST of the NATURE of the FE K LINE in the NEUTRON STAR LOW-MASS X-RAY BINARY SERPENS X-1

2015

Broad Fe K emission lines have been widely observed in the X-ray spectra of black hole systems, and in neutron star systems as well. The intrinsically narrow Fe K fluorescent line is generally believed to be part of the reflection spectrum originating in an illuminated accretion disk, and broadened by strong relativistic effects. However, the nature of the lines in neutron star LMXBs has been under debate. We therefore obtained the longest, high-resolution X-ray spectrum of a neutron star LMXB to date with a 300 ks Chandra HETGS observation of Serpens X-1. The observation was taken under the "continuous clocking" mode and thus free of photon pile-up effects. We carry out a systematic analys…

Caratterizzazione del campo misto neutroni-gamma nella colonna termica del reattore TRIGA di Pavia tramite attivazione neutronica e rivelatori ad ala…

2014

Determinazione della componente fotonica all’interno della colonna termica del reattore TRIGA mediante letture ESR di dosimetri di alanina

2014

Nuovi composti fenolici per la dosimetria a risonanza di spin elettronico (ESR) in campo misto neutroni-gamma

2014

Characterization of the terminal column of TRIGA Mark II reactor of Mainz through of alanine pellets.

2017

We have studied the ESR response of alanine pellets with and without gadolinium exposed to the thermal column of the TRIGA Mark II research reactor at the University of Mainz (Germany). The choice of Gd as additive nucleus is due to its very high capture cross section to thermal neutrons and to the possibility for secondary particles produced after interaction with thermal neutrons of releasing their energy in the neighborhood of the reaction site. In particular, it was found that low concentration (5% by weight) of Gd brings about a neutron sensitivity enhancement of more than 10 times without heavily reducing tissue equivalence. Monte Carlo (MC) simulations of both response of alanine and…

I fenoli come nuovi materiali per la dosimetria EPR in campo misto neutroni-gamma

2014

Timing and Spectral properties of Low Mass X-ray Binary Systems hosting Neutron Stars

Orbital Evolution of an Accreting Millisecond Pulsar: Witnessing the Banquet of a Hidden Black Widow?

2007

We have performed a timing analysis of all the four X-ray outbursts from the accreting millisecond pulsar SAX J1808.4-3658 observed so far by the PCA on board RXTE. For each of the outbursts we derived the best-fit value of the time of ascending node passage. We find that these times follow a parabolic trend, which gives an orbital period derivative $\dot P_{\rm orb} = (3.40 \pm 0.18) \times 10^{-12}$ s/s, and a refined estimate of the orbital period, $P_{\rm orb} = 7249.156499 \pm 1.8 \times 10^{-5}$ s (reference epoch $T_0 = 50914.8099$ MJD). This derivative is positive, suggesting a degenerate or fully convective companion star, but is more than one order of magnitude higher than what is…

Caratterizzazione dosimetrica della facility a neutroni termici del reattore TRIGA di Pavia: studio della dose da fotoni mediante rivelatori ESR

2014

Neutron and gamma-ray radiation fields characterisation in an 241Am-Be irradiator in view of its use as reserach tool

2019

Introduction A neutron irradiation facility based on four 241Am–Be sources, activity of 1.11·1011 Bq each (yield ~7.0 ·106 n s-1), consisting in four source-channels and an irradiation channel placed in a tank filled with light water both as moderator and biological shielding, was realized at DEIM Department. The aim of this work is to evaluate neutron and gamma fluxes in several points inside the irradiation channel, in view of its use as a testing tool in various research activities. For this goal, an experimental measurement campaign was started also to validate Monte Carlo (MCNP5 code) simulation results. Methods Experimental measurements of neutron radiation fields (fast and thermal) w…