Month: September 2021

Scientists of Tomsk Polytechnic University jointly with colleagues from Spanish universities have offered a simple method how to enhance the responsivity of terahertz radiation detectors by 3.5 folds using a small Teflon cube.  The 1 mm cube must be put on the surface of the detector without changing the inner design of the detector.

Such detectors are applied, for instance, in a full-body scanner, spectrometer, in medical devices for diagnosing skin cancer, burn injuries, pathological changes in the blood.  The research findings are published in the Optics Letter academic journal (IF: 3,714; Q1).

Terahertz range lies between microwave and infrared ranges in the electromagnetic spectrum. Waves shorter than 1 mm refer to the terahertz range. Their feature lies in that they are capable to percolate various materials and at the same time, they do not lead to atomic ionization of matter alternatively to X-rays.

“Terahertz radiation detectors are, as a rule, rather compact devices.  Nowadays, researchers from different countries are interested in the enhancement of their responsivity and other parameters.  The higher responsivity, the weaker signals can be received and more precise measurements can be carried out,” Oleg Minin, Professor of the Division for Electronic Engineering of the TPU School of Non-Destructive Testing, one of the authors of the article, says.

“Most researchers are trying to solve this problem by changing the design of the detector and the materials it is made from. It is complicated and often very expensive. Meanwhile, our solution is plain to see.”

In their experiments, the scientists used a microparticle in the form of the Teflon cube, an available dielectric material through which electromagnetic waves of the terahertz range are capable to percolate.  The cube was put on the surface of the detector.

“There is a responsive site inside of the detector.  The site can be made from various materials but its typical scale is always less than the wavelength.  It is the area responsible for trapping electromagnetic waves and transferring them. Due to the form and material, our cube possesses a capability to focalize radiation well, falling on the responsive site of the detector, in the scale limited to or smaller than a diffraction-limited system. The experiments conducted jointly with the Spanish colleagues proved it: the particle focalized the radiation and the emitted radiation fell into the responsive area,” Oleg Minin explains.

According to the scientists, the developed method of detector responsivity enhancement without changing its design is applied to almost any detectors of various ranges.

During the experiments, the scientists fixed responsivity enhancement by 11 decibels, which is 3.5 folds higher than the standard parameters of the detector.

The researchers from the University of Salamanca (Spain), Polytechnic University of Valencia (Spain), Institute of High-Pressure Physics of the Polish Academy of Sciences (Poland) and Imperial College London (England) took part in the research. The research was conducted with the support of the TPU Competitiveness Enhancement Program.

Scientists of Tomsk Polytechnic University (TPU) are developing a unique nano-coating for radiation protection, capable of self-healing. It will help protect electronics and seriously increase the radiation resistance of various materials in the nuclear and space industries, the authors said. The research findings are published in the Metals academic journal.

New radiation-resistant materials, as experts explained, will not only improve many nuclear facilities but also will effectively protect electronics from radiation damage. Such protection is especially relevant for astronautics as cosmic radiation can disable electronics outside the Earth’s atmosphere very fast.

The main danger of radiation is exposure to charged particles and neutrons. The TPU scientists have experimentally confirmed that the multilayer composite nano-coating of zirconium and niobium can heal the defects caused by these factors.

“Radiation defects in materials are caused by vacancy defects, which are atoms knocked out of the crystal lattice, or additional atoms which stuck in it. Both types of damage can accumulate resulting in product failure. After long-term irradiation of our coating with a proton flux, the concentration of defects either remains unchanged or decreases due to the drain of defects to the boundaries of the layers, where they eliminate each other,” Roman Laptev, Associate Professor of the Division for Experimental Physics of the TPU School of Nuclear Science and Engineering, explained to the Sputnik international news agency.

Such properties of the coating offer significant opportunities for increasing the radiation resistance of various materials in the nuclear and space industries, the TPU researchers believe. The composite, obtained by magnetron sputtering, consists of five layers of each material with a thickness of about 100 nm.

“Transmission microscopy and X-ray structural analysis have shown that after irradiation, voltage arises in the structure due to the accumulation of protons. Calculations and experiments both revealed a displacement of zirconium atoms from the optimal position with the formation of areas of low electron density, near which inserted ions accumulate annihilating positrons during analysis,” Roman Laptev said.

For experimental analysis of the structure of defects before and after irradiation, a unique high sensitive method was used – spectroscopy of Doppler broadening of the annihilation line using fluxes of positrons with controlled energy, the TPU scientists noted.

The research was carried out within the No. 20-79-10343 project of the Russian Science Foundation in cooperation with experts from the Weinberg Research Center and the Dzhelepov Laboratory of Nuclear Problems of the Joint Institute for Nuclear Research. In the future, the research team intends to study new material at higher radiation doses