Rule-guided identification of cosmic-ray patterns in PLASTEX

Summary Some techniques devised in the computer science fields of pattern recognition and expert systems are being applied to the interpretation of EAS responses in the PLASTEX experiment. An attempt is made to codity in a set of rules the expertise of trained researchers who are able to recognize and classify different hit patterns even in the presence of noisy background, and in spite of imperfections in the detector response. The patterns expected to be useful include, but are not limited to, track patterns. The software described here, as a progress report, automatically finds patterns corresponding to isolated tracks, and patterns composed of tracks that connect with each other in a layer of dense material. Tracks are reconstructed iteratively, using both geometrical and internal consistency arguments. Multihits, geometrical inefficiency, mechanical imperfection and track bending are taken into account. Data preprocessing is applied to multihits according to a theoretical model of the particle-detector interaction, and the presence of tracks in dead detector areas is inferred by probabilistic arguments. Finally, particle scattering is allowed for using a variable-size tolerance cone during the track reconstruction procedure. Examples are given of application of the method to recognition of nearly straight tracks, such as those expected to be made by high-energy muons, and of more complicated patterns made of connected straight tracks. Paper presented at the V Cosmic Physics National Conference, S. Miniato, November 27–30, 1990.     

The Mott Problem in One Dimension

In the α decay of a nucleus, the tracks left in the medium by the α particle are linear, even though its initial wave function is spherically symmetric. Understanding this quantum phenomenon has been called “the Mott problem”, ever since Mott’s fundamental paper on the subject (Mott in Proc. R. Soc. London Ser. A 126:79 1929). Here we study a one dimensional version of the Mott problem. The particle emitted in the decay is represented as a superposition of waves, one traveling to the left, the other to the right. The atoms with which the particle interacts are modeled as two level systems. The wave equation obeyed by the particle is taken to be the massless Dirac equation. For a certain space-time structure for the particle-atom interaction, it is possible to derive an explicit space-time solution for the entire system, for an arbitrary number of atoms. In the one dimensional solution, the coherent superposition of right and left-moving wave packets leaves behind tracks of excited atoms. The Mott problem on the nature of the tracks left behind is addressed using the reduced density matrix, defined by taking the trace over all particle degrees of freedom. It is found that the reduced density matrix is the incoherent sum of two terms, one involving excited atoms only on the right; the other involving excited atoms only on the left, implying that tracks will show excited atoms on one side or the other. In one dimension, tracks which involve excited atoms exclusively on one side or the other are the analog of straight tracks in three dimensions.     

Informational contenet of the high order diffraction pattern

The information content of the diffraction pattern in the region of very high orders is considered. It is shown that high order diffraction pattern represents a superresolution width indicator of the particle track in nuclear emulsion. A principally new experimental setup designed for width measurements of the wires and particle tracks is described. The first experiments performed for tungsten wire as an object are presented. It is shown that the relative error of the measurement made by this new technique is as small as 0.03% for tungsten wire of the diameter ≅26 μm. The article is published in the original.     

Formation of particle tracks

Abstract

The formation of particle tracks, and such phenomena as the detection of charged particles, and the damage produced by charged particles, are intimately related to the spatial distribution of ionization energy deposited by δ-rays. Changes in the spectrum of δ-rays with the velocity of the primary particle, imply that linear measures of the interaction of the primary particle with the medium, such as specific energy loss, or primary ionization, are unsatisfactory measures of effects produced in the medium, for they contain no knowledge of the spatial deposition of the lost energy.     

A new method for detection of alpha particles in 1 mm thick polycarbonate detectors using 50 Hz – HV ECE method

Recent studies in our laboratory have proved that electrochemical etching (ECE) of polycarbonate track detectors (PCTD) under 50 Hz – high voltage (HV) field conditions has potentials for time-integrated heavy charged particle detection and dosimetry applications. The rationale in the study is the ECE process of alpha particle tracks in 1 mm thick PCTDs by a 50 Hz – HV generator at optimized ECE conditions. Tracks of 3.2 MeV alpha particles from a collimated beam of an ²⁴¹Am source degraded in air and background tracks were registered. The effects of HV and ECE duration on alpha track registration efficiency and track diameters were studied for 3 sets of 50 Hz – 4, 5 and 6 kV field conditions in a PEW solution (potassium hydroxide, ethanol and water) at 26 °C. The optimized ECE conditions obtained at this stage of development for 1 mm thick PCTDs are 50 Hz – 4 kV in PEW solution at 26 °C for 10 h. Alpha track registration efficiency at 3.2 MeV is about 30% with 37 ± 6 μm mean track diameter. The mean background track density at the above stated optimized conditions is about 571 ± 16 tracks.cm⁻² with a mean diameter of 65 ± 5 μm. All tracks are observable by the unaided eyes. The mean background track diameter is near two times larger than that of alpha particle tracks at the optimum conditions applied; they are easily distinguished against each other. This high background track density while at this stage of development seems a drawback for low dose and low fluence particle applications, it has minimal effects on high fluence ion detection applications. The simple 50 Hz – HV generator used proved to be convenient for efficient alpha track amplifications. Studies are underway for improvement of the method in particular for reducing background track density.     

Track of a fiber fuse: a Rayleigh instability in optical waveguides

The phenomenon colloquially known as a fiber fuse occurs when an optical fiber carrying high power is damaged or in some way abused. Beginning at the damage site a brilliant, highly visible plasmalike disturbance propagates back toward the optical source at speeds ranging from 0.3 to approximately 3 m/s, leaving in its wake a trail of bubbles and voids. We suggest that the bubble tracks in fused fibers are the result of a classic Rayleigh instability that is due to capillary effects in the molten silica that surrounds the vaporized fiber core. We report measurements of the bubble distribution and the collapse time that are consistent with this contention.     

α SPECTROMETER USING CELLULOSE ACETATE NUCLEAR TRACK DETECTOR MADE IN CHINA

By using the method of etching tracks from the reverse side of a plastic SSNTD, the cellulose acetate SSNTD made in China can be used for α spectrometer. The energy resolution for α particles of 5.31—8.78MeV is in the region of 66—90keV. A formula to obtain the α particle ranges in cellulose acetate SSNTD is given. The α particle ranges in it have been measured and compared with the calculated ranges.     

Negative binomials and multiplicity distributions in 250 GeV/cK + and π+ interactions on Al and Au nuclei

The negative binomial distribution (NBD) is fitted to all charged and to negative particle multiplicity distributions in restricted rapidity intervals, both in the forward and backward c.m. hemispheres of positive meson interactions on Al and Au nuclei. For negative particle multiplicity distributions, the NBD parameters are also determined as a function ofn _g, the number of grey tracks, corresponding to varying number of intranuclear collisions. The data are interpreted in terms of the clan picture of Giovannini and Van Hove and compared to the MCMHA and Fritiof models. Both models reproduce quite well the global multiplicity distributions, but not when sub-samples are considered with fixed number of grey tracks. Regularities are better visible on the parton than on the particle level.     

Alpha particle track coloration in CR-39: Improved observability

A comparative study of the observability of alpha particle tracks in CR-39 was performed with an optical microscope before and after coloration. The implantation of ink helped in observing the damage zones. At first glance through the microscope, the coloration makes the tracks stand out right away. This coloration is helpful, from the start, in the morphological study of the tracks (size, area, orientation, shape, perimeter). This operation is advantageous in distinguishing the alpha particle tracks from stains or scratches. Thus, the routine counting of the tracks is more easily performed. Consequently, this procedure allowed us: to decrease significantly the standard deviation of the approximate total of the parameters given from the image analysis system (Olympus CUE2); to envision the possibility of reasonably decreasing the etching time in order to limit the loss of information caused by the destruction of the CR-39 during chemical etching and to use a weaker enlarging lens in order to cover a larger field of observation for the counting operations.     

基于Matlab编程对最速降线问题的研究

利用Matlab编程对"最速降线"问题进行研究,得出了质点在重力场中沿起点、终点相同的不同轨道曲线运动的一些结论,通过关系曲线非常直观地表示出质点沿不同轨道运动的关系.     

Measurement of charged-particle multiplicities in gluon and quark jets in pp collisions at square root of s = 1.8 TeV

We report the first largely model independent measurement of charged particle multiplicities in quark and gluon jets, Nq and Ng, produced at the Fermilab Tevatron in pp collisions with a center-of-mass energy of 1.8 TeV and recorded by the Collider Detector at Fermilab. The measurements are made for jets with average energies of 41 and 53 GeV by counting charged particle tracks in cones with opening angles of theta(c) = 0.28, 0.36, and 0.47 rad around the jet axis. The corresponding jet hardness Q = Ejet theta c varies in the range from 12 to 25 GeV. At Q = 19.2 GeV, the ratio of multiplicities r = Ng/Nq is found to be 1.64+/-0.17, where statistical and systematic uncertainties are added in quadrature. The results are in agreement with resummed perturbative QCD calculations.     

用扫描隧道显微镜研究肿瘤细胞膜表面的纳米结构

用扫描隧道显微镜技术研究肿瘤细胞膜的超分子结构以及外加纵向电磁场对其超分子结构的作用.结果表明,在扫描隧道显微镜照片中,肿瘤细胞膜表面纳米结构的图象由环形波纹构成.在外加纵向电磁场的作用下,肿瘤细胞膜的表面环形波纹结构消失,出现了一些损伤的痕迹.这可能是在电磁场作用下肿瘤细胞膜表面带电离子的运动受洛仑兹力以及感应电流的综合影响所致.     

Getting off the track

The production of MeV/amu heavy-ion and MeV cluster-ion beams has allowed continuous damage tracks to be made in a wide variety of materials. Using simple phenomenological models of the track-formation process one can estimate in advance the morphology of the tracks that will result from a particular set of irradiation parameters, i.e., target material, ion type and energy. In this talk I shall discuss the use of these models and how they are applied in a specific example: the pinning of quantized magnetic-flux vortices in a high-temperature superconductor. For this application one must also employ models for the interaction of the vortex and the column of damage. On the basis of such simulations it is found that although damage tracks are extremely useful for increasing the flux pinning, and hence the critical current, it would be even better if one could control the track positions and radii over a wider range of values. A new development in nanotechnology will be discussed that may, indeed, allow this to be accomplished easily and inexpensively.     

Cluster analysis of HZE particle tracks as applied to space radiobiology problems

A cluster analysis is performed of ionizations in tracks produced by the most abundant nuclei in the charge and energy spectra of the galactic cosmic rays. The frequency distribution of clusters is estimated for cluster sizes comparable to the DNA molecule at different packaging levels. For this purpose, an improved K-meansbased algorithm is suggested. This technique allows processing particle tracks containing a large number of ionization events without setting the number of clusters as an input parameter. Using this method, the ionization distribution pattern is analyzed depending on the cluster size and particle’s linear energy transfer.     

An Immersed Boundary-Lattice Boltzmann Prediction for Particle Hydrodynamic Focusing in Annular Microchannels

We numerically study the dynamics of particle crystals in annular microchannels by the immersed-boundary(IB)lattice Boltzmann(LB) coupled model, analyze the fluid-particle interactions during the migration of particles,and reveal the underlying mechanism of a particle focusing on the presence of fluid flows. The results show that the Reynolds and Dean numbers are key factors influencing the hydrodynamics of particles. The particles migrate onto their equilibrium tracks by adjusting the Reynolds and Dean numbers. Elliptical tracks of particles during hydrodynamic focusing can be predicted by the IB-LB model. Both the small Dean number and the small particle can lead to a small size of the focusing track. This work would possibly facilitate the utilization of annular microchannel flows to obtain microfluidic flowing crystals for advanced applications in biomedicine and materials synthesis.     

Detection, dosimetry and microdosimetry using high energy C beams

Samples of polyallyldiglycolcarbonate (PADC) track etch detectors (TED) were exposed to high energy ¹²C nuclei at the particle beam of the Dubna synchrophasotron. The energy of ¹²C nuclei varied between 0.1 and 1.5 GeV per amu.

At the low studied energies the linear energy transfer (LET) of these nuclei is higher than the detector threshold value. Then, the primary particle tracks are directly etched in the detector surface. The detection efficiency approaches to 100% at perpendicular incidence. Their LET has been established by means of standard authomatized procedure recently developed. The LET values found here are in good agreement with theoretical ones.

At 1.5 GeV per amu (LET 8.4 KeV μm⁻¹) the secondary particle tracks were evaluated in all the exposed detectors. The energy deposited by these particles was compared to the energy deposited through primary ionization losses. It was found out that its contribution to the total dose is relatively lower than for protons of comparable energies. In some of these samples even the tracks of the primary nuclei were observed. It follows that the detection threshold of the developed LET spectrometer should be below 10 keV μm⁻¹.     

Fission fragment track etching modelling for the cellular localisation of Neptunium-237 nuclei in rat tissues

Heavy ion recording in dielectric isotropic detectors has a wide range of applications in uranium cartography or dating. In this study, solid state nuclear tracks detectors (SSNTDs) have been applied to localise neptunium-237, in vivo, by means of the neutron-induced fission cartography of neptunium-237 nuclei in organ sections. At the cellular level, a precise localisation can only be achieved with a good understanding of the etch pit evolution during the chemical etching process.

A tailor-made software for modelling the etching process has been developed to simulate the profile of an etched track produced by a neutron-induced fission fragment. This software is based on a model that considers the evolution of the track etching velocity along the damage trail in order to perfectly model the shape of the track.     

The observation of iron latent tracks in mica muscovite

Latent ion tracks in muscovite are not easily observed by T.E.M. because they fade in the electron beam. For this reason until now, observation of latent tracks by T.E.M. has only been reported for fission fragments in this mineral.

In this paper, observation of iron latent tracks in muscovite by T.E.M. is reported. The fading of tracks is explained by the formation of radiation defects induced by the electron beam. These defects produce a background in which the tracks vanish.     

The determination of the neutron component of cosmic radiation fields in spacecraft

Poly allyl diglycol carbonate (PADC or CR-39^®) etched track detectors may be used to estimate the neutron component of the cosmic radiation in spacecraft using simple techniques developed for neutron personal dosimetry. Electrochemically etched pits are identified and counted using fully automated read-out procedures. The neutron component of the radiation field at the location of the dosimeter will produce electrochemically etchable tracks, as will the proton and energetic heavy charged particle components, depending on particle type, energy and angle of incidence. The response to incident charged particles which produce tracks and are counted as if produced by a neutron, will lead to an over-estimate of the neutron component. A correction can be applied to take account of this, or an additional chemical etch carried out which allows discrimination. Recent results for exposures in low-Earth orbit are reported.