Pulse Of Ionizing Radiation Research Articles

Neutron dose assessment in laser-generated ultra-short pulsed fields.

ELI Beamlines is one of the pillars of the Extreme Light Infrastructure European Research Infrastructure Consortium (ELI ERIC), the European project aiming at building the next generation of high power lasers for fundamental research and industrial applications. Several high-power lasers are hosted by the ELI Beamlines facility. Even at a power lower than the nominal one, when interacting with a target, the laser can generate mixed ionizing radiation fields of unique nature. One of the major laser systems, High-repetition-rate advanced petawatt laser system (HAPLS) was already used in commissioning experiments. Detecting the neutrons generated during these experiments has been a challenging task, since certain difficulties were faced. First, the experimental conditions were frequently altered during the commissioning phase (such as laser beam parameters, experimental geometry or target type). Next, the extremely short duration of the ionizing radiation pulse generated by the laser (~10-14s) complicated the correct interpretation of the data provided by the detectors designed and calibrated in standard fields. Here, one commissioning experiment is described, together with the means of addressing the problem of the detection of the ionizing radiation and the lessons learned in this endeavour.

On the potential biological impact of radiation-induced acoustic emissions during ultra-high dose rate electron radiotherapy: a preliminary study

Ionizing radiation pulses delivered at ultra-high dose rates in emerging FLASH radiotherapy can result in high-intensity low-frequency thermoacoustic emissions that may have a biological impact. This study aims at providing insights into the thermoacoustic emissions expected during FLASH radiotherapy and their likelihood of inducing acoustic cavitation. The characteristics of acoustic waves induced by the energy deposition of a pulsed electron beam similar to previous pre-clinical FLASH radiotherapy studies and their propagation in murine head-like phantoms are investigated in-silico. The results show that the generated pressures are sufficient to produce acoustic cavitation due to resonance in the irradiated object. It suggests that thermoacoustics may, in some irradiation scenarios, contribute to the widely misunderstood FLASH effect or cause adverse effects if not taken into account at the treatment planning stage.

Воздействия гамма-излучения на слоистую структуру кремний – ниобат лития.

In this work, it is shown that when an ionizing radiation pulse acts on surfactant-type devices in which a silicon single crystal is deposited with a gap on a piezoelectric substrate made of lithium niobate, the output signal is distorted. It was found that, depending on the type of conductivity of the material deposited on the lithium niobate, a different character of recovery of the device parameters was observed. The effect of ionizing radiation on air-gap devices operating as a memory correlator showed that the previously recorded signals were erased at a dose rate of ≥ 106 rad. To explain these dependencies, a model is used based on the fact that photo carriers excited by ionizing radiation in the depleted layer are captured by traps at the silicon-air interface for devices with an air gap and at the silicon-silicon oxide interface for monolithic structures The presented model, which takes into account traps not at the interface, explains most of the effects that cause a change in the output high frequency (RF) signal.

Mechanisms of Initiation of Unstable Latchup Effects in CMOS ICs

The results of research on nonstationary latchup effects (LEs) under the influence of heavy charged particles and ionizing radiation pulses, which are spontaneously counteracted depending on the operating conditions, are presented. This behavior is caused by the effects of the rail span collapse inside the complementary metal-oxide-system (CMOS) of very large scale integrated (VLSI) circuits. The experimental studies are carried out on both the ion accelerator and the laser facilities.

Method for Determining the Grüneisen Parameter of Pyroelectrics

c  , where  is the volume thermal expansion parameter, cp is the specific heat capacity, and с0 is the volumetric speed of sound. The Gruneisen parameter is an important parameter entering into the equation of state of a condensed matter; therefore, its determination, both theoretical and experimental, is of sufficient interest. As an example, we consider a method suggested in [2] where the characteristics of a stress wave arising in the sample of the examined material as a result of fast heating by a laser radiation pulse were measured. The material was transparent for radiation. The soughtafter parameter was determined from these measurements and the energy absorbed in the material. In the present work, a method for determining the Gruneisen parameter of pyroelectrics is suggested from the characteristics of the electric response of a material sample exposed to a gamma rays or neutron pulse. The problem of the response was solved in [3, 4]. Below we briefly describe some results of these works with application to the problem being solved. We consider a plane capacitor in which a polarized pyroelectric serves as a dielectric. The capacitance of the capacitor is C0, the area of its plates is S, and the distance between the plates is L. The polarization vector P is perpendicular to the plates connected through the active resistance R. The capacitor is mechanically free. We choose the coordinate system so that the х axis coincides with the direction of the polarization vector, and the origin of coordinates is placed at the capacitor center of gravity. The capacitor is irradiated by an ionizing radiation pulse whose duration tn is much smaller than the thermal time constant of the capacitor, that is, heating of the pyroelectric material is adiabatic. The temperature is uniformly distributed in the material. The electric response of the pyroelectric to uniform heating is the sum of the primary and secondary pyroelectric effects [5]. The first of them determines the polarization change provided that the shape and volume of the pyroelectric sample remain constant upon heating; the second determines the polarization change attendant to free deformation of the sample.

The method of time-resolved magnetic field effect in recombination fluorescence with magnetic field switching

A technique for studying the spin evolution of radical ion pairs is proposed, which is based on switching off the magnetic field with a certain time delay after the ionizing radiation pulse giving rise to the pairs. The spin evolution of radical pairs upon field switching is described by a quasiclassical model. The modeling of magnetic field effect curves, measured for n-decane solutions of deuterated and protonated paraterphenyl, provides fair agreement between theory and experiment.

Predicting the Failure Threshold of Dose Rate for ICs Exposed to Pulsed Ionizing Radiation of Arbitrary Pulse Shape

A computer simulation is conducted of IC response to one or more ionizing radiation pulses of arbitrary shape and width. The failure threshold of dose rate is examined as a function of pulse width. A method for estimating the failure threshold is devised and validated. It depends on experimental evaluation of the failure threshold for a very short and a very long radiation pulse. The theoretical results are confirmed by experimental data on the failure threshold of dose rate subject to pulse shape and width.

Modeling of High-Dose-Rate Pulsed Radiation Effects in the Parasitic MOS Structures of CMOS LSI Circuits

A theoretical analysis and a numerical simulation are reported of physical processes in the field oxide of CMOS circuits exposed to an ionizing-radiation pulse of high dose rate. Account is taken of (i) the field of radiation-generated charge carriers, (ii) the random distribution of the local field due to randomly scattered charges in the oxide, and (iii) geminate and bimolecular recombination. For weak and medium static applied fields, the dispersive transport of free holes is analyzed by the fractional Fokker–Planck equation, and a Monte Carlo simulation is conducted with regard to the oxide-charge field and the field dependence of hop times. The response of SOI oxide containing electron traps is considered. A method is proposed for the physical simulation of field-oxide radiation response at high dose rates. It consists in replacing pulsed irradiation at room temperature with steady-state irradiation at a low temperature.

Semi-permanent effects induced by an ionizing pulse in a MOS structure: experimental and theoretical study

The authors present an experimental and theoretical study of semi-permanent effects induced by an ionizing radiation pulse in an MOS transistor. Threshold voltage variation with time is studied for different applied gate bias voltages. The results presented indicate that the modeling of the time dependence response of an MOS transistor under an ionizing pulse of high dose add dose rate did not follow the pair separation fraction of the literature (see J. M. Benedetto and H. E. Boesch, Jr. 1986). The hypothesis of a generated photocurrent in bulk oxide as the origin of the field collapse and a new phenomenon for separating the generated pairs could explain the apparent independence of the initial shift from the gate voltage. >

Ionizing Radiation Response of GaAs JFETs and DCFL Circuits

Transient responses and logic upset threshold dose rates of planar, all-ion implanted GaAs E-JFETs and DCFL (= direct-coupled field-effect transistor logic) integrated circuits to ionizing radiation pulses of 20 ns duration from a LINAC are reported. It is experimentally verified that the logic upset dose rate of enhancement mode GaAs JFET integrated circuits is inversely proportional to the square of their channel length. For L = 1 ?m a theoretical value of ?UPSET = 1.175 × 1011 rad (GaAs)/s is predicted and medium scale integrated circuits have confirmed this value with experimental results in the range of 5 × 1010 to 1 × 1011 rad (GaAs)/s. A theoretical relation for logic upset dose rate and a correlation of experimental results with theory is presented. Long term conductance transients are not inherent to E-JFET inverters with resistive and depletion mode JFET load, but are present in source-follower circuits. A model for this circuit behavior will be presented.

Rapid Annealing Response of the Hardened 1802 Bulk CMOS Microprocessor

Rapid annealing test results show that the hardened RCA/Sandia 1802 Bulk CMOS Microprocessor will function immediately after application of intense ionizing radiation pulses. This result was established in LINAC tests using a comprehensive test procedure which exercised the μP in logarithmic time intervals from 10 μs to 1000 s. It was found that no loss of functionality occurs for doses up to about 280 KRads. At 790 KRads, the device initially loses functionality but anneals in 600 ms. At 1.6 MRads, the device loses functionality for 4 s, and at 2.4 MRads, the device loses functionality for at least 1000 s. A sample size of five devices was used. The 1802 μP was tested using hardware and software especially designed for this purpose. The microprocessor was exercised using software routines of exponentially increasing length starting at 10 μs after the pulse. A measure of μP functionality was therefore provided at logarithmically increasing sample times, After 2 seconds was reached, the routines repeated every two seconds up to 1000 seconds when the test ended. The hardware and software are described in detail.

Transient Response of GaAs IC's to Ionizing Radiation

Transient responses of GaAs E-JFET planar integrated circuits caused by a 25 ns wide ionizing radiation pulse from a LINAC were measured. Present technology circuits with 2.5 ?m channel length devices have a measured logic upset level of about 1 × 1010 rad(GaAs)/s and a survival dose rate of approximately 1 × 1011 rad(GaAs)/s. A theoretical analysis for logic upset dose rate and a correlation of experimental results with theory is presented. For E-JFET devices with a channel length of 1 ?m, a logic upset dose rate of 1 × 1011 rad(GaAs)/s is predicted.

Long-Term Radiation Transients in GaAs FETs

A long-term transient response mechanism has been discovered in certain GaAs FETs and FET logic circuits exposed to low level (~ 100 rad) ionizing radiation pulses. Recovery times ranging from 1 to 70 seconds have been measured following room temperature exposures. Charge trapping within the semiinsulating GaAs substrate appears to be a mechanism responsible for the observed behavior. Experiments conducted between 0° and 200°C have identified an acceptor level characterized by an activation energy in the 0.7 to 0.8 eV range.

Rapid Anneal of Radiation-Induced Silicon-Sapphire Interface Charge Trapping

The rapid ahneal phenomenon of the radiation induced charge trapping at the silicon sapphire interface was experimentally investigated using a junction FET structure from 10 ?sec through 1 second after an ionizing radiation pulse for various fabrication parameters and bias conditions. The fabrication parameters investigated include type of starting sapphire (Czochralski, ribbon, and gradient furnace), sapphire polish, pre-epitaxial anneal environment (air and hydrogen), and epitaxial growth method (uniform and burst). The back channel rapid anneal effect was also characterized as a function of bias applied to the device during the radiation pulse as well as the bias applied during the anneal time. The results show that the rapid anneal time constant is essentially independent of the bias applied during the radiation pulse as well as during the anneal time, although the initial and final values of leakage current are functions of drain bias. The experimental results also show that the rapid anneal time constant is essentially independent of the type of starting sapphire, but is a function of the pre-epitaxial sapphire anneal environment and epitaxial growth method.

Self-Consistent Atmospheric EMP Coupling in Three Dimensions

This article describes a three-dimensional, finite-difference solution and program for self-consistent treatment of Maxwell's equations in air in the presence of an ionizing radiation pulse. The solution is based on polar coordinates, and gives the surface current density on a conducting body. Ionizing radiation generates primary Compton electrons, which in turn create secondary electrons and electromagnetic fields. Our solution yields these fields, and then self-consistently tracks the Compton-electron trajectories in the fields. It also determines the air conductivity due to the secondary-electron and air-ion densities, and correspondingly modifies the electromagnetic-field propagation. Finally, it keeps account of the air-ion and secondary-electron density changes due to generation by primary electrons, avalanche, and recombination. Numerical results are presented for the current on a vertical conducting post 2m high and 15cm in diameter when exposed to a 1 MeV ? pulse of 2×1012 rads/sec peak amplitude and 40 nsec FWHM. These results are presented for the ancle of ? incidence 10° and 45° from horizontal. For comparison, we show the way omission of self-consistency and/or ?-shadowing modifies the current.

Radiation Hardness of a High Speed ECL Microcircuit

The results of gamma irradiation (both break-out transistors and complete microcircuits) lead us to conclude that circuits produced using this process are very tolerant to this type of hostile environment. This would indicate good surface passivation resulting in low surface leakage currents. The circuits are reasonably tolerant to neutron radiation. As expected, the transistor current gains are degraded. However, the circuits are still functional after exposure to 1 × 1015 n/cm2. The probable reasons for this tolerance are (1) the construction necessary to produce such high speed circuitry results in a very narrow base region with a small emitter-base depletion region and (2) Emitter Coupled Logic operates at higher currents (than TTL for example) and the gain is degraded less (relatively) at higher currents (and thus higher operating frequencies). The above conclusion regarding higher tolerance at higher frequency is true for ECL circuits in general and this differential configuration in particular. However, it is not valid for high-speed circuits in general. If transistors are switched at higher current levels for higher frequencies, they would probably be more tolerant to neutron radiation. Each high speed logic family will have to be evaluated on its own merits and for particular applications for use in radiation environments. Another result that would be desirable is the transient response of the complete microcircuit to ionizing radiation pulses.

The Effects of Pulsed Ionizing Radiation on the Operation of Surface Acoustic Wave Amplifiers and Convolvers

In a previous paper (IEEE Trans. Nucl. Sci.; NS-21: No. 6, 141 (1974)) we described the effects of transient ionizing radiation on passive surface acoustic wave (SAW) devices and also the permanent displacement damage resulting from high-energy nuclear radiation on the operation of a SAW monolithic amplifier. This paper will conclude the study of the effects of transient ionizing radiation on SAW devices by presenting the effects of a short-duration, high-intensity ionizing radiation pulse on the SAW amplifier, various SAW convolver structures and reflective-array pulse compression (RAC) filter device. By way of brief summary, the operation of the amplifier was found to be relatively unaffected by short-duration radiation pulses, whereas many of the convolver structures were affected by the radiation. A long-term change in phase as a result of radiation was found in the RAC device, and this change is postulated to result from a radiation-induced temperature change. (auth)

Effect of ionizing radiation on second breakdown

Constant current pulses, 5–100 μsec in duration, with amplitude sufficient to cause second breakdown in each pulse, were applied to p +-n-n + vertical junction silicon-on-sapphire diodes. The diodes were irradiated on every other pulse by a 20 nsec ionizing radiation pulse from a Nd-glass laser with approximately 4 × 10 3 rad. per pulse. In all cases where the density of carriers generated by the ionizing radiation was greater than the impurity doping density of the most lightly doped part of the test diode, the reverse-bias second breakdown delay time was increased as a result of irradiation. There was no evidence of heating due to laser radiation in any of the test devices up to the threshold of laser damage.

A Method for the Routine Measurement of Dielectric Photoconductivity

An instrumentation and data reduction technique for the routine analysis of dielectric photoconductivity data has been developed. This technique provides detailed conductivity versus time data during and shortly after an ionizing radiation pulse. Thus, it complements the timeintegral of conductivity technique, which can provide good long-term delayed conductivity data, and it offers some advantages over similar methods developed to measure conductivity. The unique features of this technique include the use of spline functions in the data reduction, the use of a sample designed to provide noise current cancellation, and circuit analysis that includes a mismatched transmission line.