Thermal spike analysis of low energy ion tracks

The theoretical track diameter of low energy ions in organic materials is usually estimated through the model of dose deposition by delta rays, with results remarkably lower than the experimental values obtained via a replica method and electron microscopy. The track detector used here is Makrofol-E and the ions studied have specific energies between 1.4 and 100 keV/n. To evaluate the problem from another point of view, thermal effects for track formation, a modified version of the “liquid drop model” for insulators was applied. The electronic as well as nuclear energy deposition by an individual ion are considered and the thermal spike evolution is studied. The model allows for the formation of ion tracks in a range of energies previously considered as “forbidden”. There still exists a discrepancy between the experimental data and the track diameters predicted by the model, and although this difference is smaller than the obtained with previous calculations, it suggests the necessity of further adjustments.     

Four decades of nuclear tracks research in India

The science of solid state nuclear track detectors (SSNTDs)—“Trackology”—developed by R.L. Fleischer, P.B. Price and R.M. Walker in the early 1960s of the last century is an interesting and potentially useful concept with something to offer to almost all branches of science and technology. In fact nuclear tracks find applications wherever solid state damage occurs. Apart from the direct applications of far reaching consequences in nuclear physics, other areas as diverse as bio-medical sciences, cosmic rays and space physics, environmental research, geological sciences, material science, microanalysis, mine safety, nuclear technology, uranium prospecting, etc. have been greatly influenced by SSNTDs.

In this presentation, we attempt to provide an overview of the growth of nuclear tracks research in India over the last four decades and the contributions of various groups from Universities, Institutes, Nuclear Track Society of India and the Department of Atomic Energy in nurturing nuclear track research in the country. Finally, a summary of the significant contributions made by Indian scientists is also presented in this paper along with the overall impact it has made at the national and international level in many areas of basic and applied sciences such as cosmic rays and space physics, fusion–fission and particle evaporation, heavy ion ranges and energy-loss measurements, country-wide indoor radon–thoron survey, geochronology, environmental sciences, track-etch membranes and ion tracks technology, material science, physics and chemistry of fission, etc.     

离子束次级辐射对春麦的诱变效应

利用中能重离子束辐照生物靶材料时产生的中子、γ射线和次级碎片等次级辐射对春麦种子进行辐照 ,然后通过田间试验和实验室的分析测定 ,得到了 M1代植株的变化 . (1 )在生物学性状中 ,穗粒数、小穗数、千粒重、穗粒重、小穗密度和有效分蘖数变异率较大 ;(2 )除 SOD活性外 ,POD活性、CAT活性、MDA含量和蛋白质含量的变异率也较大 ;(3 )休眠种子和萌发种子辐照M1代在生物学性状的变化上存在很大的差异 ;(4)两个春麦材料的辐射敏感性差异明显 .由此表明 ,兰州重离子加速器辐照终端在进行生物学实验时产生的次级辐射是可能利用的诱变源. Secondary radiation such as neutrons, high energy light particees, γ rays is produced when ion beams with medium energy irradiate biological materials. Spring wheat was placed in radiobiological experiment area(irradiation terminal L2) to expose to the secondary radiation. The variation of M1 generation of the wheat seeds was obtained through test in the fields and measuremeat in laboratery: (1) There were very high variation rates in grain number, number of small...     

Track measurements of fast particle streams in pulsed discharge explosive plasma

This paper reports results of track registration for fast particles from the hot spot sparked inside a metal target. CR-39 track detectors placed in the ion pinhole camera, a magnetic analyzer, and Thomson-type mass-spectrometer in order were used to obtain images of the hot spot and to determine spectra of the fast particles. Using track detectors in the pinhole camera, we have obtained specific split images. The “average etch rate ratio versus track length” locus for track sample groups is depicted by means of squared diameters asymptotic method. Our analysis shows the majority of tracks belong to hydrogen nuclei. The track loci for the detectors from the pinhole or analyzers turn out to be split into two parallel streaks that have been interpreted as a proton–deuteron doublet. Data obtained using the Thomson analyzer clearly demonstrate the equal numbers of protons and deuterons for some parallel parabola sections.     

Coulomb explosion and thermal spikes

A fast ion can electronically excite a solid producing a track of damage, a process initially used to detect energetic particles but now used to alter materials. From the seminal paper by Fleischer et al. [Phys. Rev. 156, 353 (1967)] to the present, "Coulomb explosion" and thermal spike models have been often treated as competing models for describing ion track effects. Here molecular dynamics simulations of electronic sputtering, a surface manifestation of track formation, show that in the absence of significant quenching Coulomb explosion in fact produces a spike at high excitation density, but the standard spike models are incorrect.     

Single track effects, Biostack and risk assessment

The scientific career of Prof. Bucker has spanned a very exciting period in the fledgling science of Space Radiation Biology. The capability for placing biological objects in space was developed, and the methods for properly packaging, retrieving and analyzing them were worked out. Meaningful results on the effects of radiation were obtained for the first time. In fact, many of the successful techniques and methodologies for handling biological samples were developed in Prof. Bucker's laboratories, as attested by the extensive Biostack program. He was the first to suggest and successfully carry out experiments in space directly aimed at measuring effects of single tracks of high-energy heavy galactic cosmic rays by specifically identifying whether or not the object had been hit by a heavy particle track. Because the "hit" frequencies of heavy galactic cosmic rays to cell nuclei in the bodies of space travelers will be low, it is expected that any effects to humans on the cellular level will be dominated by single-track cell traversals. This includes the most important generally recognized late effect of space radiation exposure: radiation-induced cancer. This paper addresses the single-track nature of the space radiation environment, and points out the importance of single "hits" in the evaluation of radiation risk for long-term missions occurring outside the earth's magnetic field. A short review is made of biological objects found to show increased effects when "hit" by a single heavy charged-particle in space. A brief discussion is given of the most provocative results from the bacterial spore Bacillus subtilis: experimental evidence that tracks can affect biological systems at much larger distances from the trajectory than previously suspected, and that the resultant inactivation cross section in space calculated for this system is very large. When taken at face value, the implication of these results, when compared to those from experiments performed at ground-based accelerators with beams at low energies in the same LET range, is that high-energy particles can exert their influence a surprising distance from their trajectory and the inactivation cross sections are some 20 times larger than expected. Clearly, beams from high-energy heavy-ion accelerators should be used to confirm these results. For those end points that can also be caused by low-LET beams such as high-energy protons, it is important to measure their action cross sections as well. The ratio of the cross sections for a high-LET beam to that of a low-LET beam is an interesting experimental ratio and, we suggest, of more intrinsic interest than the RBE (Relative Biological Effectiveness). It is a measure of the "biological" importance of one particle type relative to another particle type. This ratio will be introduced and given the name RPPE (Relative Per Particle Effectiveness). Values of RPPE have appeared in the literature and will be discussed. A rather well-known value of this quantity (13,520) has been suggested for the RPPE of high-energy iron ions to high-energy protons. This value was suggested by Letaw et al. Nature 330, 709-710 (1987)] we will call it the Letaw limit. It will be discussed in terms of the importance of the heavy-ion component vs light-ion component of the galactic cosmic rays. It is also pointed out, however, that there may be unique effects from single tracks of heavy ions that do not occur from light-ion tracks. For such effects, the concepts of both RBE and RPPE lose their meaning.     

HI-13串列加速器生物用新终端7Li离子束流监测诊断研究

7Li离子属于高LET辐射,是辐射生物学基础研究中常用的重离子射线之一,它是硼中子俘获治疗癌症中起关键作用的离子,在辐射诱变育种等领域也有较好的应用前景。实验在北京HI-13串列加速器R20支线生物用新终端上进行,对43 MeV 7Li离子束斑大小、均匀性和监测注量的准确性进行测量和评估,结果表明:均匀性好于90%的最大束斑面积为5.0cm×5.0cm;4.2×104 ～1.5×105 particles/cm2/s注量率范围内,两种不同探测器测得的注量率变化呈线性关系,闪烁体探测器监测的注量与CR39探测器测得的绝对注量的误差小于10%。这些束流特性能够满足辐射生物学实验要求,有利于进一步开展与硼中子俘获治疗癌症或辐射诱变育种中7Li离子的辐射生物学相关研究。7Li ion with high linear energy transfer (LET) radiation has been used in radiobiological research, takes main effect in Boron Neutron Capture Therapy and is applied in radiation mutagenic breeding. This experiment was carried on the new terminal established for radiobiological application, located at the end of R20 branch beam line of HI-13 tandem accelerator. The beam qualities of 7Li ions of 43MeV generated by HI-13 tandem accelerator, including spot size and uniformity and particle fluence accuracy were measured using different detection methods. The results showed that beam uniformity was over 90% at 5cm×5cm area, the flux of S1 and M3 had a good linear relationship as particle flux ranged from 4.2×104 particles/cm2/s to 1.5×105 particles/cm2/s, and particle fluence accuracy was better than 90%. All the results showed that the beam qualities of 7Li ions finely met the basic requirements for radiation biological experiment. It provides important method to study biological effects for fundamental research and tumor therapy or radiation mutagenic breeding application associated with 7Li ions.     

A search for superheavy nuclei tracks in extraterrestrial olivine crystals

A study is made for the search of superheavy nuclei in Marjalahti, Eagle Station and in other pallasite olivines. The olivine crystals are calibrated for heavy ion track lengths by using heavy ion beams from cyclotrons. The calibration for ultra heavy ions which are presently not available with sufficient energy to produce volume tracks in olivine crystals, is based on Katz and Kobetich model of track formation. The length spectrum of volume tracks, revealed by puncturing them with focussed Nd-glass laser beam, is measured and the abundances of different nuclei groups are calculated. Partial annealing has been used at 430°C for 32 hr which eliminates the interfering tracks due to nuclei of atomic numberS ≤ 50. During the scanning 4 cm³ olivine crystals, about 360 long tracks of uranium group as well as two very long tracks have been found. If these tracks belong to superheavy nuclei, the relative abundance of super heavies is found to be 6 × 10⁻¹¹ in galactic cosmic rays.     

High energy heavy ion tracks in bubble detectors

Bubble detectors which are commonly used as neutron detectors have been demonstrated through this study to be good detectors for registration of high energy heavy ion tracks. Large size bubble detectors made in China Institute of Atomic Energy were irradiated to heavy ions Ar and C up to 650 MeV/u and 400 MeV/u, respectively. Very clear features of stringy tracks of high energy heavy ions and their fragmentations are manifested and distinguishable. A single track created by a specific high energy heavy ion is composed of a line of bubbles, which is visible by naked eyes and retained for months wihhout reduction in size. The creation of heavy ion tracks in bubble detectors is governed by a threshold whose essence is approximately a critical value of energy loss rate (dE/dX)_c similar to that of etch track detectors. Ranges of heavy ions in bubble detectors are apparent and predictable by existing formulas. Identification of high energy heavy ions and the applications to heavy ion physics, cosmic rays, exotic particles and cancer therapy monitoring are obviously promising. The experimental and theoretical aspects of high energy heavy ion tracks in bubble detectors as well as the expectable applications are presented and discussed.     

Analysis of MIR-18 results for physical and biological dosimetry: radiation shielding effectiveness in LEO.

We compare models of radiation transport and biological response to physical and biological dosimetry results from astronauts on the Mir space station. Transport models are shown to be in good agreement with physical measurements and indicate that the ratio of equivalent dose from the Galactic Cosmic Rays (GCR) to protons is about 3/2:1 and that this ratio will increase for exposures to internal organs. Two biological response models are used to compare to the Mir biodosimetry for chromosome aberration in lymphocyte cells; a track-structure model and the linear-quadratic model with linear energy transfer (LET) dependent weighting coefficients. These models are fit to in vitro data for aberration formation in human lymphocytes by photons and charged particles. Both models are found to be in reasonable agreement with data for aberrations in lymphocytes of Mir crew members: however there are differences between the use of LET dependent weighting factors and track structure models for assigning radiation quality factors. The major difference in the models is the increased effectiveness predicted by the track model for low charge and energy ions with LET near 10 keV/micrometers. The results of our calculations indicate that aluminum shielding, although providing important mitigation of the effects of trapped radiation, provides no protective effect from the galactic cosmic rays (GCR) in low-earth orbit (LEO) using either equivalent dose or the number of chromosome aberrations as a measure until about 100 g/cm 2 of material is used.     

Nuclear tracks in solids: registration physics and the compound spike

Observations of GeV heavy ion and MeV cluster-ion tracks in crystalline solids give us new insight into registration physics. Thermal and ion explosion spikes no longer compete; a ‘compound spike’ accounts for both. Ion explosion dominates for surface tracks (electronic sputtering). And there can also be transient plasma stopping in the bulk. For clusters there are ‘vicinage effects’—both electronic and nuclear—which can influence track dimensions and structure. Displacement cascades in large energetic clusters may lead to projectile “fission” and coherent flow into sub-tracks. The absence of tracks in certain targets, and their size/structure in others, leads to a model of projectile assisted prompt anneal (PAPA) in 10⁻¹¹s, either partial or complete, often by swift epitaxy, on elemental lattices (e.g. silicon) or on compound sublattices (e.g. fluorite). Phase transformations are important, but simple target amorphization is rare—the exception, not the rule. For many targets the thermal spike (macroscopic) fails, since ‘point’ defects (atomistic) characteristic of the target, their motion, and the electronic band structure, determine latent track detail. Circumstances in which the Bragg Rule of Additivity fails completely are revealed, and the kinetic threshold for constructive phase transitions in tracks described. This same track physics applies generally also to geothermometry—the opposite time extremum (10⁺¹¹s)—where annealing is due to defect assisted delayed anneal (DADA). Differences between etching rates of induced and spontaneous fission tracks can be explained. The geothermobarometric “Wendt/Vidal effect” (2002)—combined pressure, temperature and stress (with time) influences on fission track annealing (in e.g. apatite)—is briefly discussed.     

Science and technology with nuclear tracks in solids

Fission track dating has greatly expanded its usefulness to geology over the last 40 years. It is central to thermochronology—the use of shortened fission tracks to decipher the thermal history, movement, and provenance of rocks. When combined with other indicators, such as zircon color and (U–Th)/He, a range of temperatures from C to C can be studied. Combining fission track analysis with cosmogenic nuclide decay rates, one can study landscape development and denudation of passive margins. Technological applications have expanded from biological filters, radon mapping, and dosimetry to the use of ion track microtechnology in microlithography, micromachining by ion track etching, microscopic field emission tips, magnetic nanowires as magnetoresistive sensors, microfluidic devices, physiology of ion channels in single cells, and so on. In nuclear and particle physics, relatively insensitive glass detectors have been almost single-handedly responsible for our knowledge of cluster radioactivity, and plastic track detectors together with automated measuring systems have been used at the Bevalac, Brookhaven, CERN, and GSI, mainly to study fragmentation of high-energy heavy nuclei. Almost everything we know about the ultraheavy cosmic rays has been learned using Lexan on the Long Duration Exposure Facility and BP-1 phosphate glass on the Mir Station. New topics include development of calorimetric aerogels capable of measuring kinetic energies of hypervelocity interstellar and interplanetary dust grains in space and research on identification of strains of Bacillus spores by measurements of their size and swelling rates when humidified.     

Gamma ray photon-induced modifications in Triafol-TN and Triafol-BN polymeric track detectors

Photon induced modifications in Triafol-TN and Triafol-BN polymers have been studied in the dose range of 10¹–10⁶ Gy at room temperature using a ⁶⁰Co source. To monitor the chemical and structural changes induced by gamma rays, UV, IR, and ESR studies were carried out. Thermal studies were also conducted for understanding the effects of gamma irradiations on these polymers. Variation of track etching characteristics and activation energy for bulk etching have been studied at different gamma rays doses. The experimental results are presented and discussed.     

Nuclear tracks: present and future perspectives

Current research work related to the development of nuclear tracks comprising: (i) fundamental principles (nuclear track physics and chemistry, as well as development of track detectors and the relevant hard- and software), (ii) development of nuclear instruments and methods (etch track radiometers for ions, neutrons and cosmic rays, radon monitoring devices, radiography and fission track dating) is briefly outlined. The paper concentrates on a literature survey of applications of nuclear tracks in (iii) physical sciences (high-energy physics, nuclear physics and earth sciences), (iv) biomedical sciences (radiation protection, environment, cancer therapy), and (v) technological sciences (materials, nano-technology and nuclear technology).

Presently about 350 papers per year are being published in this field. Increased activity is noted in ion track technology (track-made membranes, modern nano-tech methodology including biological and biological-like samples, nano-electrode bio-electrochemistry, bio-magnetic assays and probes). New applications of nuclear tracks in fundamental (possibility of the detection of neutron quantum states in a gravitational field, nucleus–nucleus interactions, search for new chemical super-heavy elements) and applied science (precise measurements of the behaviour of radiation in human tissue in connection with of long term space missions and treatment of cancer) are surveyed, and possible research in the next decades is presented and examined in this review paper.     

基于蒙特卡洛和器件仿真的单粒子翻转计算方法

文章提出了一种基于蒙特卡洛和器件仿真的存储器单粒子翻转截面获取方法,可以准确计算存储器单粒子效应,并定位单粒子翻转的灵敏区域.基于该方法,计算了国产静态存储器和现场可编程门阵列(FPGA)存储区的单粒子效应的截面数据,仿真结果和重离子单粒子效应试验结果符合较好.仿真计算揭示了器件单粒子翻转敏感程度与器件n,p截止管区域面积相关的物理机理,并获得了不同线性能量转移(LET)值下单粒子翻转灵敏区域分布.采用蒙特卡洛方法计算了具有相同LET、不同能量的离子径迹分布,结果显示高能离子的电离径迹半径远大于低能离子,而低能离子径迹中心的能量密度却要高约两到三个数量级.随着器件特征尺寸的减小,这种差别的影响将会越来越明显,阈值LET和饱和截面将不能完全描述器件单粒子效应结果.     

Tsallis entropy approach to radiotherapy treatments

The biological effect of one single radiation dose on a living tissue has been described by several radiobiological models. However, the fractionated radiotherapy requires to account for a new magnitude: time. In this paper we explore the biological consequences posed by the mathematical prolongation of a previous model to fractionated treatment. Nonextensive composition rules are introduced to obtain the survival fraction and equivalent physical dose in terms of a time dependent factor describing the tissue trend towards recovering its radioresistance (a kind of repair coefficient). Interesting (known and new) behaviors are described regarding the effectiveness of the treatment which is shown to be fundamentally bound to this factor. The continuous limit, applicable to brachytherapy, is also analyzed in the framework of nonextensive calculus. Here a coefficient that rules the time behavior also arises. All the results are discussed in terms of the clinical evidence and their major implications are highlighted.     

Compilation of low-energy gamma rays

A compilation of selected nuclear gamma rays has been prepared in order to identify the most attractive candidate nuclei for a gamma-ray laser. The compilation consists of two parts: (1) a listing of selected gamma rays emanating from an isomeric state and (2) a listing of selected gamma rays following the decay of an energy level close to the isomeric state. The compilation is based on the latest “Nuclear Data Sheets” (Ref. 1) for each A-chain available on 1 January 1987.     

About some physical mechanisms of statistics of radiation-induced effects formation and non-linear cell response in low dose area

A new cascade-stochastic approach to solve the direct and inverse problems of radiation-induced effect statistics in track biodetectors is presented in this paper. The analysis of the experimental data has made it possible to establish a non-linear nature of the “dose–effect” dependence in low dose area. For the first time, a new determination of the relative biological efficiency and quality coefficient of ionizing radiation in area of low doses are proposed.     

High precision localization methods for HZE-particles

For experimental investigations in the field of microdosimetry of heavy ions a high precision localization method for biological objects relative to the path of the penetrating ion is mandatory. New methods are described for corn seeds of Arabidopsis thaliana and spores of Bacillus subtilis. In the latter case the actual penetration point of the particle in the spore layer is determined by an individual microetching technique with an accuracy of about 0.2 μm. This is done after removing the spores from the hit area by “break-through” etching. With the help of reference spores the impact parameter is determined for correlating the biological effects with the physical event. Besides the aspect of water during the track development is described.