Pulsed Radiation Source Research Articles

Numerical Simulation for Pulsed Radiation Source Generated by Electron Beam Irradiation Using Intense Pulsed Power Generator

Numerical Simulation for Pulsed Radiation Source Generated by Electron Beam Irradiation Using Intense Pulsed Power Generator

Experimental evaluation of accuracy in determining the direction to a pulsed source of gamma-radiation by a spherical absorber with CdTe detectors in a system of nuclear situation monitoring

The necessity and possibility of creating a dosimetric channel for determining the direction to the source of penetrating gamma-radiation in the nuclear situation monitoring system have been substantiated. The experimental assessment of a reduced error of the device for determining the direction to pulsed sources of radiation using a spherical absorber and CdTe detectors was carried out. These detectors can be used effectively only if there is appropriate electronic equipment, constructed in accordance with their characteristics and spectral-temporal characteristics of highly intense pulsed radiation. The direction to high-intensity pulsed radiation of linear accelerator Varian Clinac 600C (USA) by telluride-cadmium detectors was determined in the pulsed mode. This allowed conducting an experiment to determine the dependence of the coefficient of proportionality of recording pulses from each detector on the angle of direction to the source of pulsed radiation of the linear accelerator. A reduced error was assessed by comparing the received experimental data with a theoretical dependence based on a physical and mathematical model. It was recommended to divide the entire range of angles from 0° to 360° into five sub-ranges, in which three or two proportionality coefficients are responsible for determining the angle in space on gamma sources. The maximum reduced error does not exceed 10 % and the maximum angle error is not more than 8.4°. The most accurate determining of the angle to a radiation source can be carried out in the presence of a theoretically calculated and experimental database of proportionality coefficients for all angles in space and energy of radiation sources

Pulsed Continuous Spectrum Radiation Source With a Quartz-Sapphire Envelope

The results of experimental studies of electrical and radiative properties of xenon flash lamps with a double quartz-sapphire envelope are presented. Comparative studies of xenon lamps with quartz and quartz-sapphire envelopes were carried out. The possibility of a significant increase in brightness temperature of the xenon plasma and radiation efficiency in germicidal range (200-300 nm) is shown. The achieved values of the brightness temperature of 10 kK and the radiation efficiency of 8.2 % in the germicidal range demonstrate the prospects of using the presented source of pulsed broadband radiation for disinfection of various objects.

Electrical and spectral energy measurement techniques of pulsed continuous spectrum radiation sources

The techniques of total spectral energy and electrical measurements of high-current pulsed arc discharge are presented and substantiated. On the example of a flash lamp, three working circuits were reviewed and the following values were obtained: time dependences for circuit electrical parameters, values of the energy deposition into plasma, and radiative efficiencies for different spectral ranges.

Joint TDOA and FDOA Estimation for Interleaved Pulse Trains From Multiple Pulse Radiation Sources

In this article, we address the problem of estimating with high precision the time difference of arrival (TDOA) and frequency difference of arrival (FDOA) for interleaved pulse trains radiated from multiple sources. The pulse signal parameters of multiple sources are indistinguishable and as a result conventional de-interleaving techniques fail to separate the pulses emitted from each source. By noting that cross-correlating pulses from the same source at their true TDOA and FDOA produces consistent phases, a high-precision joint TDOA-FDOA estimator is proposed. Within the developed technique, a histogram-based clustering procedure is introduced to obtain initial TDOA and FDOA estimates. Then, an expectation maximization (EM)-based method is utilized to refine their estimates, where the unknown source labels of pulse signals are hidden variables and they are estimated together with TDOA and FDOA iteratively. Simulation results reveal the superior performance of the proposed algorithm compared to existing techniques, at the cost of moderate computational complexity increment.

Development and Characteristics of Pulsed Radiation Source Generated by Electron Beam Irradiation using Intense Pulsed Power Generator

Development and Characteristics of Pulsed Radiation Source Generated by Electron Beam Irradiation using Intense Pulsed Power Generator

The pulsed X-ray radiation source based on a semiconductor opening switch with the focal point diameter of 0.5 mm and its application.

This investigation is devoted to developing a pulsed X-ray radiation source. The high-voltage pulse generator is based on an inductive energy storage unit and a semiconductor opening switch, and the latter ensures a high pulse repetition rate. A high-voltage pulse generator has the following parameters: the pulse voltage amplitude up to 120 kV, the pulse current up to 180 A, the current pulse duration at 50% of the peak height of about 20 ns, and the pulse repetition rate up to 5 kHz. The source works consistently when the pulse repetition rate is increased. We developed the designs of an anode and an explosive emission cathode for the pulsed X-ray tube with the focal point of 0.5 mm, used in the experiments. The setup which makes it possible to investigate demountable models of pulsed X-ray tubes is described in this paper. We believe there are advantages of using an X-ray source with the flare duration of about 20 ns and the pulse repetition rate up to 5 kHz over continuously working X-ray sources. The source is unique for some problems, such as studying high-speed processes. The experiments have shown that a pulsed X-ray source works consistently together with a digital detector, and the generation of X-ray flares is easily synchronized with the detector and the rotation system. In the article, we discuss the issues of reducing image blurring for computerized tomography purposes, caused by fast rotation of the source and the detector relative to the object of investigation and reducing the radiation exposure of the investigated object. We also set further objectives of the investigation and present perspectives and limitations of this source.

Evaluation of the performance of an ionization chamber cylindrical (PTW) by the ELEKTA linear accelerator: Case of pulsed radiation

The performance evaluation of cavity cylindrical ionization chamber dosimeters is the basis for the evolution of radiotherapy treatment processes. Studies focused on the statistical and physical performances of the ionization chamber dosimeter used in the radiotherapy department at the hospital oncology CHU-Fez-Morocco. This allowed having a qualitative and quantitative critical view, which is based on previous studies and works. The diagnostic of the dispersion results was calculated between measurements that were taken by the same dosimeter under different test conditions. These tests were then rechecked against two different operators. The general purpose of our study is to optimize measurement and treatment processes, with the desired level of quality according to international standards and protocols. The evaluation of this dosimeter is made by a source of pulsed radiation. This evaluation is carried out using an ELEKTA linear accelerator, using photon beams (6, 10 and 18 Mev). Experimental Results confirmed that the response of the cylindrical ionization chamber depends on several parameters, which influence the performance of the device/machine. The study reveals a total dosimeter uncertainty of the order 3.25 %, which is in the international standards. Even, this can cause an effect on the performance of the ionization chamber detector.

A Plasma Focus device as ultra-high dose rate pulsed radiation source. Part II: X-ray pulses characterization

A PF device has been setup, studied and evaluated as a fast pulsed self-collimated electron beam source for X-ray generation for radiotherapy applications. The worth of this source stands on the extremely short generation time (50 ns as reference delivery time) and on its intensity, being able to produce X-ray pulses able to transfer a dose in the order of 1 Gy each. The electron-X-ray conversion process for several metal targets is here analyzed using Monte Carlo simulations based on measured electron spectra discussed in Part I; some results have been benchmarked with experimental data. The perspectives of the development of a medical source based on this technology are finally evaluated.

A Plasma Focus device as ultra-high dose rate pulsed radiation source. Part I: Primary electron beam characterization

A Plasma Focus is a device able to generate in the pinch phase several kinds of radiation fields. One of them are the backward emitted electron's beams that can be used as source for X-ray pulses generation through the interaction with a suitable target. The worth of this source stands on two elements: first, being connected to the lifetime of the pinch phase, the electron current lasts a few tens of nanoseconds, we can say 50 ns as reference; second, the electron bunches carry a charge of the order of 0.1 mC. These two aspects grant the generation of X-ray pulses of extremely short duration, while the quite strong charge bunches allow a potential dose transfer by the X-rays in the order of 1 Gy per pulse. These characteristics have made this source of interest with respect to possible medical applications, in particular for radiotherapy of superficial tumors, given also that the extremely high dose rate could be of help in winning radio-resistance of specific cancer cells as in the case of melanoma.In this first part of the work, after a brief outline of the PF working principles, the experimental techniques used for the detection and the analysis of the characteristics of the primary electron source have been described. The results showing their correlation with the capacitor's bank energy and the possible scaling laws that could drive the setup of specific X-ray generation devices for radiotherapy treatments have been thoroughly discussed.

Efficiency of a laser radiation source with coherent pulse combining

The principle of operation of systems that allow the construction of laser sources of pulsed radiation, in which a multifold increase in the peak output power of the radiation is achieved without increasing the energy of the power sources, is described, and the corresponding block diagrams are presented. The efficiency of devices with coherent synchronous combining using a single-frequency helium–neon laser emitting at 632.8 nm and an erbium laser emitting at 1550 nm in their composition is analyzed. Graphs showing the efficiency of systems with helium–neon and erbium lasers versus the number of fiber-optic delay lines are plotted. It is shown that the highest efficiency in the devices considered here can be achieved using radiation at a wavelength of 1550 nm.

Increasing the peak power of a pulsed laser source using optical delay lines

We consider the implementation of a patented source of pulsed laser radiation, which allows economical use of power owing to the original structure of a parallel set of optical delay lines and the addition of the amplitudes of the pulses of the input laser radiation. The results of a computer experiment for different numbers of switching channels with the determination of the predicted output peak power of the laser source are presented. To assess the radiation source, the concept of system efficiency is introduced as the ratio of the output peak power to the number of channels of delay lines. The results of the calculations are presented in the form of efficiency graphs for different numbers of channels, considering losses in the optical fiber lines of the optical delay. The proposed source of pulsed laser radiation can potentially be used in optical communication lines, laser data systems, and medical devices.

Sunlight simulation in investigating characteristics of small-size sunlight concentrators and multijunction solar cells

Presented are technical solutions on constructing optical systems for experimental simulating the sunlight parameters. Designs of two types of solar simulators are proposed. In the first one, the spectrum and the radiation angular divergence are simulated on the basis of a continuous light source, what corresponds to the principle “necessity and sufficiency” of simulated parameters of the light flux in investigating optical and power characteristics of small-size sunlight concentrators (Fresnel lenses). In the second type simulator, based on a pulsed radiation source, the emphasis has been placed on high-quality simulation of irradiance and spectrum for satisfying requirements in recording current-voltage characteristics of multijunction solar cells and in determining their efficiency.

The UV-C radiation mechanism to form HO2• radicals from water

The formation of chemically active particles in distilled water via continuous and pulsed light radiation was investigated. The source of the continuous radiation was a DKB-9 UV mercury low pressure lamp (λ = 253.7 nm). Upon UV lamp irradiation of water, hydrogen peroxide was formed in a yield of (1 ± 0.2) 10−7 mol (L s)−1. The pulsed radiation source was the plasma of a spark electric discharge in air with a continuous radiation spectrum and a weak maximum at λ = 220 nm. The radiation affected the water through quartz glass. In this case, nitrous and nitric acids formed in the water, but no accumulation of hydrogen peroxide was detected. The formation of the active products can be explained by the interaction of exited water molecules that formed due to the radiation. The energy threshold for the formation of hydrogen peroxide corresponds to a radiation wavelength of less than 1220 nm. To directly identify HO2• radicals, we studied redox reactions in solutions containing Fe2+, Fe3+ and I− ions at pH values from 0.8 to 8.1. The quantum yield of HO2• radicals in an acidic medium under the action of the mercury lamp radiation was 0.015 ± 0.005.

In vitro irradiation of colorectal cancer cells by pulsed radiation emitted from a hundred joules plasma focus device and its comparison with continuous irradiation

In the last years, pulsed reduced low dose radiation has been proposed as an alternative for treatment of recurrent cancer. Nonetheless, distinction between the effects of low dose pulsed and continuous radiation is barely known at cellular level. In order to study the effects of low dose pulsed radiation at cellular level, in vitro experiments are important to further advance the basic understanding in this area. In the present work we demonstrate the usefulness of a low-energy plasma focus device PF-400J as a potential source of low-dose pulsed radiation for in vitro cancer cell experiments. Colorectal cancer cell line, DLD-1, were irradiated by pulsed x-rays. Fifty pulses of x-rays provide ∼0.12 Gy dosis, which were measured using thermoluminescence detectors (TLD-100 dosimeters). Irradiation-induced DNA damage was assessed at different time points after irradiation. A statistically significant double strand break (DSB) DNA damage was observed at 30 minutes after irradiation. A comparison of DSB induced by continuous source in the same type cancer cells and pulsed irradiation is made at 30 minutes post-irradiation. In the case of pulsed irradiation, DSB per unit dose found higher. Our findings suggest that low-energy plasma focus devices could have potential application as pulsed radiation source in the area of in vitro cancer cell experiments.

Resonant parametric interference effect in spontaneous bremsstrahlung of an electron in the field of a nucleus and two pulsed laser waves

Resonant spontaneous bremsstrahlung of an electron scattered by a nucleus in the field of two moderately strong pulsed laser waves is studied theoretically. The process is studied in detail within the interference kinematic region. This region is determined by scattering of particles in the same plane at predetermined angles, at that stimulated absorption and emission of photons of external pulsed waves by an electron occurs in correlated manner. The correspondence between the emission angle and the final-electron energy is established in the kinematic region where the resonant parametric interference effect is manifested. The resonant differential cross section of ENSB process with simultaneous registration of both emission angles of the spontaneous photon and the scattered electron, can exceed by 4-5 orders of magnitude the corresponding cross section in the absence of an external field. It was shown for nonrelativistic electrons that the resonant cross section of ENSB in the field of two pulsed laser waves within the interference region in two order of magnitude may exceed corresponding cross section in the Bunkin-Fedorov kinematic region. The obtained results may be experimentally verified, for example, by scientific facilities at sources of pulsed laser radiation (SLAC, FAIR, XFEL, ELI).

Parametric interference effect in nonresonant pair photoproduction on a nucleus in the field of two pulsed light waves

Nonresonant electron-positron pair photoproduction on a nucleus in the field of two pulsed light waves is studied theoretically. The process is considered in detail within the interference kinematic region, when stimulated absorption and emission of photons of external pulsed waves by an electron and a positron occurs in a correlated manner. Within this region, a correspondence between the emission angle and energy of the produced particles appears. The distribution of the obtained differential cross section over the pair kinetic energy is characterized by presence of oscillations, within the interference region. Each of the maxima corresponds to the definite partial process with emission and absorption of an equal number of photons of both waves. It was shown that the differential cross section within the interference region for certain values of the pair energy may exceed the cross section in other scattering kinematics in two orders of the magnitude. Obtained results may be experimentally verified, for example, by scientific facilities at sources of pulsed laser radiation (SLAC, FAIR, ELI, XCELS).

Evaluation of Major Factors Affecting Spatial Resolution of Gamma-Rays Camera

Gamma-rays camera is mainly used in image diagnostics of intense pulse radiation sources. The spatial resolution of the camera was measured on a 60Co gamma-rays source with edge method. The spatial resolution MTF (modulation transfer function) at the 10% intensity was about 2 lp/mm and the maximal single-noise ratio (SNR) of the camera was found to be about 5:1. In addition, the spatial resolution of the camera was measured with pulse X-rays with 0.3 MeV in average energy and exclusion of effects of secondary electrons from consideration. Accordingly, the spatial resolution MTF at the 10% intensity was about 5lp/mm, verifying effects of secondary electrons induced by 1.25MeV gamma-rays in the scintillator upon the spatial resolution. Based on our analysis, dispersion sizes of secondary electrons in the scintillator are about 0.4 mm∼0.6 mm. Comparatively, as indicated by detailed analysis of spatial resolutions of the MCP image intensifier and CCD devices, both have little effect on the camera's spatial resolution and could be well neglected.

Optimazation of broadband third-harmonic UV generation in highly nonlinear photonic crystal fiber

The generation of pulse radiation with different frequency based on nonlinear optical frequency conversion technology is an effective method to produce lasers with the wavelength in the visible light or ultraviolet (UV) light range. In recent years, the developments of photonic crystal fiber (PCF) technology and ultra-short pulse technology have brought new solutions to the problems that the system needs great maintenance work, has low frequency conversion rate and much difficulty in popularizing, which the traditional frequency conversion system based on nonlinear crystal is confronting. Research on UV pulse radiation has been consistently attracting much attention of many academics. Particularly, narrowband and broadband UV pulse radiation sources are complementary, each having its own characteristics and scope of applications. The generation of narrowband UV pulse radiation of high sensitivity and high resolution through third harmonic generation (THG) in PCF has already been reported. However, the frequency conversion rate of narrowband UV pulse radiation is relatively low and the tunable ability of the spectrum is limited. These imperfections can be exactly completed by broadband UV pulse radiation. Broadband UV pulse radiation based on THG in PCF can be realized efficiently in PCF. This means that the conversion of UV light increases substantially, and simultaneously, the narrowband UV radiation of any wavelength in a certain range can be acquired more easily and the tunable ability of narrowband UV pulse radiation can be enhanced further. In this paper, the femtosecond pulse with a central wavelength of 1035 nm at a pulse repetition rate of 50 MHz is coupled into a highly nonlinear photonic crystal fiber with an appropriate length. The Raman self-frequency shift soliton produced from the ultra-short input pulse acts as a pump resource of third harmonic, transmitting through fundamental mode in PCF. Phase-matching between the fundamental mode and the high order modes is achieved and the third harmonic transmitted by specific high order modes (such as HE13) at deep UV wavelength is acquired effectively. Besides, the very high order UV mode (HOUVM) transmitting third harmonic with shorter wavelength is stimulated when intentionally inputting the ultra-short pulse into the PCF in the direction of a certain angle deviating from the axis of fiber core. Broadband deep UV (320-360 nm) pulse radiation with a UV light conversion rate of 3.6% can be acquired effectively in nonlinear PCF by stimulating a number of adjacent HOUVMs and achieving phase matching between the modes. Good agreement between theoretical results and experimental results is achieved.

Modeling Single-Event Transient Propagation in a SiGe BiCMOS Direct-Conversion Receiver

The propagation of single-event transient (SET) signals in a silicon–germanium direct-conversion receiver carrying modulated data is explored. A theoretical analysis of transient propagation, verified by simulation, is presented. A new methodology to characterize and quantify the impact of SETs in communication systems carrying modulated data is proposed. The proposed methodology uses a pulsed radiation source to induce distortions in the signal constellation. The error vector magnitude due to SETs can then be calculated to quantify errors. Two different modulation schemes were simulated: QPSK and 16-QAM. The distortions in the constellation diagram agree with the presented circuit theory. Furthermore, the proposed methodology was applied to evaluate the improvements in the SET response due to a known radiation-hardening-by-design (RHBD) technique, where the common-base device of the low-noise amplifier was operated in inverse mode. The proposed methodology can be a valid technique to determine the most sensitive parts of a system carrying modulated data.