Operation Of Radiation Sources Research Articles

Numerical modeling and performance enhancement of micro combustor powered thermophotovoltaic systems using high contrast gratings

• Steady-state 3D modeling is done for parallel plate micro combustor TPV system. • Incorporated SiC porous foam enhanced power density by an order of magnitude. • HCGs are used to tailor emitted spectral radiation increased power density by 50%. • Reflector confine power to one side of micro combustor which doubled power density. Thermophotovoltaic (TPV) systems offer an efficient way to directly convert thermal energy into electricity using the radiation emitted from a high temperature source. Compared to the conventional photovoltaic (PV) systems, TPVs have additional elements such as filters to tailor and shape the radiated energy impinging on the PV cell to improve the conversion efficiency. High contrast grating (HCG) structures are integrated within the combustor walls which act as a selective filter. The filter plays a major role by suppressing the sub-band gap radiation and reflecting it back to the combustion source. Typically, amorphous silicon (a-Si) periodic gratings with quartz as a substrate material are optimized for gallium antimonide (GaSb) PV cells. In this work, we have carried out detailed Multiphysics simulations to study the performance of GaSb, Si and InGaAsSb PV cells when operating in a micro combustor emitting non uniform radiation source operating in a temperature range of 500–2000 K. Results show that the proposed TPV system can have a power density of 250 mW/cm 2 using GaSb PV cell. Further, significantly more photons can be converted to useful power with a higher cut-off wavelength PV cell such as InGaAsSb. Therefore, the power density can be as high as 410 mW/cm 2 . This study shows that the TPV systems employing low bandgap PV cells can have > 20 times higher power density compared to conventional silicon PV cells.

Sources of Ionizing Radiation Used in Modern and Advanced NBC Reconnaissance Devices (Lecture)

The lecture is intended to prepare students studying under an additional professional advanced training program for military specialists in radiation safety for all branches of the Armed Forces of the Russian Federation, as well as to train officials responsible for organizing and ensuring radiation safety in military units and organizations of the Ministry of Defense of the Russian Federation. The lecture addresses three educational questions: 1. Accounting and control of radiation sources in the system of state accounting and control of radioactive substances and radioactive waste. 2. General requirements for the operation of radiation sources. 3. Operation of sealed radionuclide sources as part of the technical means of the RCB for intelligence and control.

ОСОБЕННОСТИ ОБЕСПЕЧЕНИЯ РАДИАЦИОННОЙ БЕЗОПАСНОСТИ В ФГБУ ФНКЦРИО ФМБА РОССИИ

Purpose of the work is to justify the safety in the operation of radiation sources in the center of nuclear medicine. The paper reflects the advanced methods of nuclear medicine using radionuclides, used at the site of the Features of Ensuring Radiation Safety in the FSCCRO of FMBA of Russia, for the purpose of diagnosing and treating malignant neoplasms. At the same time, a necessary condition is to ensure the radiation safety of medical personnel, as well as compliance with the requirements and standards governing the safe operation of radiation hazardous facilities. The paper presents an analysis of individual effective doses of medical personnel of group A of the nuclear medicine center for the period 2020-2022, as well as the risks of stochastic effects during exposure to an average individual dose for personnel of group A. Results: Conclusion: a feature of the Features of Ensuring Radiation Safety in the FSCCRO of FMBA of Russia is a large concentration of radiation-hazardous objects on one site, which implies the fulfillment and observance of radiation safety requirements. The analysis of individual exposure doses for group A personnel indicates that the established control and permissible levels are not exceeded. At the same time, measures are proposed to optimize (reduce) the radiation load on medical personnel working with sources of ionizing radiation. The unique experience gained by the Center can be replicated when carrying out work to ensure radiation safety standards for newly built and existing medical institutions in Russia in order to provide high-tech medical care in the field of nuclear medicine.

Sources of Ionizing Radiation Used in Modern and Advanced NBC Reconnaissance Devices (Lecture)

The lecture is intended to prepare students studying under an additional professional advanced training program for military specialists in radiation safety for all branches of the Armed Forces of the Russian Federation, as well as to train officials responsible for organizing and ensuring radiation safety in military units and organizations of the Ministry of Defense of the Russian Federation. The lecture addresses three educational questions: 1. Accounting and control of radiation sources in the system of state accounting and control of radioactive substances and radioactive waste. 2. General requirements for the operation of radiation sources. 3. Operation of sealed radionuclide sources as part of the technical means of the RCB for intelligence and control.

Determination of the test-samples electron density via dual energy computer tomography

In this work we determines electron density using data obtained via CT scanner with one radiation source operating in two modes: with 80 kV and 120 kV voltage. We perform tomography study of calibration phantom with predetermined electron densities. Single linear relationship between energy-subtracted Hounsfield unit and relative electron density is determined. Using determined relationship the relative electron densities of phantom calibration samples is calculated. The comparison of calculated and nominal values proves the possibility of the samples relative electron density determination using energy-subtracted Hounsfield unit with error less than 2%.

Design and Simulation of a Multi-Sheet Beam Terahertz Radiation Source Based on Carbon-Nanotube Cold Cathode.

Carbon nanotube (CNT) cold cathodes are proving to be compelling candidates for miniaturized terahertz (THz) vacuum electronic devices (VEDs) owning to their superior field-emission (FE) characteristics. Here, we report on the development of a multi-sheet beam CNT cold cathode electron optical system with concurrently high beam current and high current density. The microscopic FE characteristics of the CNT film emitter is captured through the development of an empirically derived macroscopic simulation model which is used to provide representative emission performance. Through parametrically optimized macroscale simulations, a five-sheet-beam triode electron gun has been designed, and has been shown to emit up to 95 mA at 3.2 kV. Through careful engineering of the electron gun geometric parameters, a low-voltage compact THz radiation source operating in high-order mode is investigated to improve output power and suppress mode competition. Particle in cell (PIC) simulations show the average output power is 33 W at 0.1 THz, and the beam–wave interaction efficiency is approximately 10%.

A Cold-Cathode Microwave and Terahertz Radiation Source: Experimental Realization @10’s GHz and Computational Design @THz

Due to their unique characteristics of instant responses and low-power consumption, vacuum electronic devices based on field emission cold-cathode have potentials for realizing compact and novel high frequency electromagnetic wave radiation sources. Herein, a cold-cathode radiation source operating in the frequency range from gigahertz to terahertz is developed, which is based on frequency multiplication by taking advantage of nonlinearity of field electron emission. The radiation source is realized by introducing a compact structure with two re-entrant cavity resonators. Based on such a structure, radiation sources of frequencies at 12.10 GHz and 0.1 THz were, respectively, designed and simulated numerically. Based on the simulation results, the 12.10-GHz radiation source using carbon nanotubes cold-cathode was fabricated and tested experimentally. The results showed that an electromagnetic wave output at 12.10 GHz with power of $98~\mu \text{W}$ can be achieved upon excitation by a 6.05 GHz input signal with power of 1.05 mW. Our study provides an approach for microwave and terahertz wave generation.

A windowless VUV excilamp

An open windowless excilamp capable of operating on argon (λ ∼ 126 nm), krypton (∼146 nm), and xenon (∼172 nm) dimers is described. The lamp has a total radiating surface area of 23 × 23 = 529 cm2. At a total power of ∼0.8 W radiated through this area, the average output power density at λ ∼ 126 nm is ∼1.6 mW/cm2 at a distance of 2 cm from the emitting surface. A pulsed discharge between insulator-coated anode and thin wire cathode ensures a high efficiency of the proposed radiation source operating in the vacuum ultraviolet spectral range.

Evolution of a Microstructure of Materials under Irradiation

The evolution of a microstructure of metals (or alloys) under irradiation resulting in swelling of the material is considered for the case with the formation of Frenkel pairs. A closed system of equations describing the evolution of the microstructure of the material exposed to irradiation is obtained, and relationships for the swelling rate are derived. It is shown that the swelling rate varies linearly with time for a stationary source of point defects (the number of Frenkel pairs per lattice site). An expression for the swelling rate is deduced for a radiation source operating in a more realistic pulsed mode.

Heating and Melting of Asphalt–Paraffin Plugs in Oil‐Well Equipment Using an Electromagnetic Radiation Source Operating in a Periodic Mode

This paper considers the elimination of asphalt–paraffin plugs in wellbore equipment using a high‐frequency radiation source which is energized and de‐energized periodically. The dynamics of melting of plugs is analyzed numerically. The time of removal of plugs is determined with variation in the off‐duty ratio of the operating cycle of the high‐frequency oscillator and the time of its continuous operation in a cycle.

SPring-8 Program.

SPring-8 is a third-generation synchrotron radiation source operating in the soft and hard X-ray region. It consists of an injector linac of 1 GeV, a booster synchrotron of 8 GeV and a storage ring with a natural emittance of 5.9 nm rad. The storage ring can accommodate 61 beamlines in total, and 26 of them are under construction. The project has been carried out jointly by JAERI and RIKEN and construction of the facility started in 1991. Commissioning of the injector linac was started in August 1996 and an 8 GeV electron beam was injected into the storage ring in March 1997. The first synchrotron radiation from a bending magnet was observed at the front end of the beamline on 25 March and radiation from an undulator was observed on 23 April. On-beam testing of seven beamlines, four of them from in-vacuum undulators and three from bending magnets, started in July. The maximum stored current is currently fixed at 20 mA and the lifetime at maximum current is longer than 20 h. The dedication is scheduled for October 1997.

A far-infrared grating free-electron laser

Design parameters for a compact radiation source operating in the infrared region of the spectrum are presented. The source is configured as a free-electron laser oscillator, utilizing an annular electron beam and a coaxial waveguide with a corrugated central conductor. A compact source that is tunable in the wavelength band 35–55 μm with output in the kilowatt range is shown to be feasible.

Safety in the operation of radiation sources and use of irradiated foods

The utilization of ionizing radiation for the preservation of foods represents an important advance in the field of food processing. Careful evaluation of the wholesomeness of irradiated foods has been made, and work is continuing; but, thus far, these foods have not been found io be toxic to experimental animals or man. In animal feeding experiments, with a broad spectrum of foods tested, longevity, reproduction, and lactation performance in general are the same as for animals maintained on diets of unirradiated food. Investigations conducted io the present time with mice and rats have not revealed any evidence as to radiation induced carcinogens. While some radiation damage to the macronutrients and micronutrients has been noted, the nutritive value for these foods is equivalent to, or in some cases better than, that for heat processed foods. Ionizing radiation has been shown to be quite effective in alteration of proteins, with the result that certain foods exhibit reduced allergenic properties. Of clinical significance, also, is the fact that low radiation doses of 14,000 rads effectively interrupt the reproductive cycle of the trichinae present in pork, and thereby eliminate the public health problem of trichinosis. Under present methods of processing, none of the irradiatedmore » foods has induced radioactivity. High energy radiation in the area of 24 Mev has been shown to produce transient and short lived radioactive isotopes. In the event that accelerated electrons with high energies are utilized in radiation treatment of food, the potential hazard of these radioactive isotopes, which are induced, will then be explored. An excellent safety program in the operation of radiation sources has been achieved. Radioactive contamination of food cans, by gamma - irradiation with mixed fission products in the canal water, has been eliminated. Health physics procedures guarantee the safety of the product as to both contamination and induced radioactivity. Careful monitoring of personnel and equipment at the radiation sourre has resulted in an excellent record for safety. (auth)« less