60 research outputs found
Energy device for monitoring 4-10 MeV industrial electron accelerators
The electron beam energy is one of the critical parameters of electron accelerators since it can affect the dose distribution inside the body or in products to be irradiated with a beam of energetic electrons. A device has been developed for monitoring small variations in the electron beam energy that is easy-to-use during an irradiation run. It involves measurement of currents (or charges) collected by two identical aluminium plates, except for their thickness, and electrically insulated from each other, located in the beam. The ratio of these two currents (or collected charges) is quite sensitive to the beam energy; optimization of sensitivity is obtained by selecting the appropriate thickness of the front plate depending on the beam energy. In the present paper, we have investigated the feasibility of using this energy device at energies, from 4 to 10 MeV
Global optical/infrared - X-ray correlations in X-ray binaries: quantifying disc and jet contributions
The optical/near-infrared (OIR) region of the spectra of low-mass X-ray
binaries appears to lie at the intersection of a variety of different emission
processes. In this paper we present quasi-simultaneous OIR - X-ray observations
of 33 XBs in an attempt to estimate the contributions of various emission
processes in these sources, as a function of X-ray state and luminosity. A
global correlation is found between OIR and X-ray luminosity for low-mass black
hole candidate XBs (BHXBs) in the hard X-ray state, of the form L_OIR is
proportional to Lx^0.6. This correlation holds over 8 orders of magnitude in Lx
and includes data from BHXBs in quiescence and at large distances (LMC and
M31). A similar correlation is found in low-mass neutron star XBs (NSXBs) in
the hard state. For BHXBs in the soft state, all the near-infrared (NIR) and
some of the optical emission is suppressed below the correlation, a behaviour
indicative of the jet switching off/on in transition to/from the soft state. We
compare these relations to theoretical models of a number of emission
processes. We find that X-ray reprocessing in the disc and emission from the
jets both predict a slope close to 0.6 for BHXBs, and both contribute to the
OIR in BHXBs in the hard state, the jets producing ~90 percent of the NIR
emission at high luminosities. X-ray reprocessing dominates the OIR in NSXBs in
the hard state, with possible contributions from the jets (only at high
luminosity) and the viscously heated disc. We also show that the optically
thick jet spectrum of BHXBs extends to near the K-band. (abridged)Comment: Accepted for publication in MNRAS; 19 pages, 7 figure
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