DEPARTMENT OF NUCLEAR PHYSICS - NUCLEAR ENGINEERING - MEDICAL PHYSICS

Researchers show how creating interference patterns with four laser beamlets improves the efficiency of energy transfer when accelerating electron and ion beams. This method can be used to enhance biological and astrophysical research.

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Technology to measure the flow of subatomic particles known as antineutrinos from nuclear reactors could allow continuous remote monitoring designed to detect fueling changes that might indicate the diversion of nuclear materials. The monitoring could be done from outside the reactor vessel, and the technology may be sensitive enough to detect substitution of a single fuel assembly.

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Abstract:

A permanent electric dipole moment (EDM) of a particle or system is a separation of charge along its angular momentum axis and is a direct signal of $T$ violation and, assuming $CPT$ symmetry, $CP$ violation. For over 60 years EDMs have been studied, first as a signal of a parity-symmetry violation and then as a signal of $CP$ violation that would clarify its role in nature and in theory. Contemporary motivations include the role that $CP$ violation plays in explaining the cosmological matter-antimatter asymmetry and the search for new physics. Experiments on a variety of systems have become ever-more sensitive, but provide only upper limits on EDMs, and theory at several scales is crucial to interpret these limits. Nuclear theory provides connections from standard-model and beyond-standard-model physics to the observable EDMs, and atomic and molecular theory reveal how $CP$ violation is manifest in these systems. EDM results in hadronic systems require that the standard-model QCD parameter of $\overline{\theta }$ must be exceptionally small, which could be explained by the existence of axions, also a candidate dark-matter particle. Theoretical results on electroweak baryogenesis show that new physics is needed to explain the dominance of matter in the Universe. Experimental and theoretical efforts continue to expand with new ideas and new questions, and this review provides a broad overview of theoretical motivations and interpretations as well as details about experimental techniques, experiments, and prospects. The intent is to provide specifics and context as this exciting field moves forward.

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The depth-dose curve depends on the inhomogeneity of the material irradiated by electron beam

Abstract:

Electron linear accelerator with average energy 9.92 ± 0.48 MeV, UELR-10-15S2, was set up and operated at the Research and Development Center for Radiation Technology, Vietnam Atomic Energy Institute, for irradiating foods and medical devices directly without X-ray converter. Inside the homogenous products, the depth-dose curve depends on electron beam energy and product density, and moreover, it also depends on the inhomogeneity of the irradiated material. In this article, the depth-dose distribution is calculated by MCNP simulation code and measured by a film dosimeter inside the inhomogeneous products. The results show that the maximum deviation of the depth-dose curve between inhomogeneous and homogeneous products with the same density is about 20%. So the area density limit for irradiating double sided on the electron beam (9.92 ± 0.48 MeV) is in the range from 6.1 to 9.7 g/cm² instead of 8.5 g/cm² in general.

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