Patent Application
20140328510
This invention includes a method to determine the positions in a crystal of the tip and etch figure of a fission semi-track, comprised of: producing a series of transmitted light images; detecting the tip and etch figure of a fission semi-track; determining the positions and their statistical uncertainties of the tip and etch figure of a fission semi-track in the crystal. The method also is comprised of: accepting or rejecting as real a fission semi-track based on the statistical uncertainties of the positions of the tip and etch figure of a fission semi-track; accepting or rejecting as real a fission semi-track based on the judgment of a human being; capturing a reflected light image of the crystal surface and determining the size of one or more etch figures on the crystal surface. The prior art requires greater human labor and provides less information compared to this invention, being comprised of and limited to manually detecting each fission semi-track.
This invention includes a computer software program containing instructions to the tip and etch figure of a fission semi-track, comprised of: loading a series of transmitted light images; detecting the tip and etch figure of a fission semi-track; determining the positions and their statistical uncertainties of the tip and etch figure of a fission semi-track in the crystal; writing transmitted light images to a database; loading transmitted light images from a database. The computer software program also contains instructions comprised of: assessing the viability, using a scoring equation, of a tip of a fission semi-track; modifying the fission semi-track tip scoring equation based on the contents of a fission semi-track database; presenting to a human being for viewing by the human being a transmitted light image of the tip of a fission semi-track; calculating the statistical probability that a fission semi-track is a real fission semi-track. The prior art does not comprise the capabilities of the computer software disclosed here.
This invention includes a computer database of fission semi-tracks comprised of: allowing a fission semi-track to be inserted; allowing a fission semi-track to be removed; representing each fission semi-track in the database by one or more transmitted light images formed by the transmission of light through a crystal. The computer database also is comprised of: assigning to each inserted fission semi-track a statistical probability that the fission semi-track is a real fission semi-track; restricting the insertion of all fission semi-tracks to a human being; restricting the removal of a fission semi-track to the same human being to which insertion of fission semi-tracks is restricted. The computer database also is comprised of: restricting the insertion of all fission semi-tracks to a any member of a group of human beings; restricting the removal of a fission semi-track to any member of the same group of human beings to which insertion of fission semi-tracks is restricted. The prior art does not comprise such a database as is disclosed here.
This invention includes a method of determining the statistical probability that a fission semi-track is a real fission semi-track, comprised of: producing a series of transmitted light images; detecting the tip and etch figure of the fission semi-track; detecting the two sides of the fission semi-track; assessing the viability, using a scoring equation, of the fission semi-track tip; assessing the viability, using a scoring equation, of each fission semi-track side. The method is also comprised of: assessing the viability of the fission semi-track tip and each fission semi-track side based on the judgment of human being; assessing the viability of the fission semi-track tip and each fission semi-track side based on the collective judgment of group of human beings. The prior art allows only two, discrete values for the statistical probability that a fission semi-track is a real fission semi-track: 0 and 1. The method disclosed here allows for any value between 0 and 1, inclusive.
A latent fission track is a single, approximately linear, randomly oriented zone of molecular damage in a host solid resulting from the fission of a single, fissile atomic nucleus. latent fission tracks have cross-sectional diameters on the order of 10 s of Angstroms and lengths on the order of 1-20 micrometers and they are individually invisible using optical microscopy. Fissile atomic nuclei that form latent fission tracks include 235U, 252Ca, and 238U. Latent fission tracks may be created within a solid under carefully controlled laboratory conditions by the thermal-neutron-induced fission of 235U nuclei contained within the solid. In certain natural solids, such as the mineral apatite or volcanic glass, latent fission tracks form and accumulate by the spontaneous fission of 238U nuclei within the solid, some having formed shortly after the mineral crystallized or glass solidified, some having formed very recently, and some having formed during the intervening time span. Fissile 252Cf nuclei placed in proximity to a solid surface may be used to create latent fission tracks on that surface that may be used during specialized laboratory and industrial processes.
Latent fission tracks derived from the fission of 235U or 238U nuclei are randomly oriented within their host solid and exhibit a number per unit volume that correlates with the number per unit volume of parent fissile nuclei within the host solid, all other environmental factors, such as temperatures experienced by the latent fission tracks and the chemical state of the host solid, being equal. In a natural solid containing fissile 238U nuclei, latent fission tracks form throughout time due to the predictable nuclear fission of the 238U nuclei. When a natural solid is maintained at sufficiently low temperatures, new latent fission tracks accumulate and previously formed latent fission tracks experience slow, spontaneous conversion back to undamaged solid but they remain as latent fission tracks. Therefore, at sufficiently low temperatures, the number of latent fission tracks per unit volume in a natural solid correlates with both the 238U nuclei per unit volume and the duration of time over which latent fission tracks have accumulated. Knowledge of the number of latent fission tracks per unit volume and the number of 238U nuclei per unit volume in a natural solid provides the analyst a basis for age dating of the natural solid and a basis for deciphering aspects of Earth's history
The number per unit volume of latent fission tracks derived from the thermal-neutron-induced fission of 235U nuclei correlates with both the number of 235U nuclei per unit volume in the host solid and the integrated flux of thermal neutrons to which the solid was exposed. latent fission tracks derived from induced fission of 235U nuclei may be used to create and study latent fission tracks under carefully controlled laboratory conditions, and they are commonly thought to be indistinguishable upon formation from their 238U-derived counterparts due to the close similarities between the 235U and 238U nuclear fission processes.
A latent fission track must be rendered visible to enable study by a human being (herein, analyst) of its characteristics. A commonly applied process is to dissolve the latent fission track in a chemical mixture and then enlarge the resultant void space to a size visible using an optical microscope. This process is commonly referred to as etching. To accomplish etching, the solid containing latent fission tracks is polished to expose an interior plane of the solid. Some of the randomly oriented latent fission tracks may intersect this exposed interior plane. The exposed interior plane is then placed in contact with an appropriate chemical mixture. The chemical mixture dissolves any latent fission track that intersects the exposed interior plane at a greater rate than it does the surrounding undamaged solid. Following initial, relatively rapid dissolution of the latent fission track, further exposure of the undamaged solid to the chemical mixture gives rise to enlargement of the void in the undamaged solid where the latent fission track had been. Contact between the exposed interior plane of the solid and the chemical mixture is terminated when the void where the latent fission track had been is large enough to be viewed using an optical microscope.
The void space where a latent fission track had intersected the polished and etched plane of the solid penetrates into the volume of the preserved solid and is commonly referred to as a fission semi-track because part of the latent fission track had been polished away during the process of exposing the interior plane. In some instances, a fission semi-track intersects another latent fission track that is wholly confined in the preserved solid, permitting the chemical mixture to reach and preferentially dissolve the wholly confined latent fission track and enlarge its resultant void space sufficiently for optical viewing by the analyst. Such a fission semi-track that provides a pathway for the chemical mixture to reach and dissolve a wholly confined latent fission track is commonly referred to as an etchant pathway. Any wholly confined latent fission track that is reached by the chemical mixture via an etchant pathway, is preferentially dissolved and its resultant void space enlarged sufficiently for optical viewing by the analyst, and exhibits visible tips at each end of its longest axis, is commonly referred to as a confined fission track (herein, also confined fission track). The definition of etchant pathway is broadened to include any continuous combination of fission semi-tracks, confined fission tracks, cracks, disruptions or defects in the solid molecular structure, or human-induced fission semi-tracks or other zones of damage to the solid molecular structure that connect the polished and etched plane of the solid to the wholly confined latent fission track.
Fission semi-tracks and confined fission tracks may be viewed by the analyst using an optical microscope. An optical microscope transmits light through and/or reflects light off of a solid surface containing fission semi-tracks and/or confined fission tracks and modifies the light pathways so that the micrometer-sized fission semi-tracks and confined fission tracks are made visible to and distinguishable by (henceforth, visible to) the analyst. Once visible to the analyst, either directly through the optical apparatus of the microscope or indirectly using a charge coupled device affixed to the optical microscope that permits display of the visible features on a computer display screen, features of the fission semi-tracks and/or confined fission tracks of interest to the analyst are measured and documented.
The number of 235U-derived or 238U-derived fission semi-tracks per unit area of a polished and etched plane of a solid correlates with the number of latent fission tracks per unit volume of that same solid that existed before that solid was polished and etched. The number of 252Cf-derived fission semi-tracks per unit area of a treated solid surface correlates with the integrated flux of 252Cf-derived fission-fragment nuclei incident upon the surface.
The intersection between a fission semi-track and the polished and etched plane of the solid yields a well-defined geometrical shape commonly referred to as an etch figure. Etch figures exhibit characteristics, such as maximum length and width, that depend on the duration of exposure of the polished and etched plane of the solid to the chemical mixture used for etching, the temperature of the chemical mixture during etching, the composition of the chemical mixture, and the orientation of the fission semi-track relative to the polished and etched plane of the solid. Etch figures also exhibit characteristics, such as maximum length, maximum width, and symmetry or asymmetry, that depend on the nature of the polished and etched plane itself, including the chemical composition of the solid, the physical properties of the solid, and, for anisotropic solids such as anisotropic crystals, the crystal lattice plane represented by the polished and etched plane of the solid.
The ideal fission semi-track represents the etched void space left by the dissolution of a latent fission track that had intersected the polished and etched plane of the solid. The ideal fission semi-track is randomly oriented like its latent fission track precursor, and exhibits a range of possible end-to-end lengths, from very short, for the case where most of the latent fission track had been polished away, to long, for the case where a small fraction of the latent fission track had been polished away. In plan view, the ideal fission semi-track projects a complete and closed geometrical figure to the analyst when viewed using an optical microscope comprised of visible traces of the void space left by the dissolution of the latent fission track. One end of the ideal fission semi-track is composed on an etch figure and the other end is composed of the dissolved latent fission track tip trace. Between the two ends of the ideal fission semi-track are sub-parallel dissolved latent fission track side traces that connect the two ends and converge at the dissolved latent fission track tip trace.
A real fission semi-track may be comprised of a complete and closed geometrical figure visible to the analyst, having as a direct analog an ideal fission semi-track. A real fission semi-track may also have any portion of its etch figure, dissolved latent fission track tip trace, and/or dissolved latent fission track side traces rendered invisible to the analyst. Henceforth, fission semi-track refers to real fission semi-track. Part or all of the etch figure end may be rendered invisible to the analyst by overlapping, adjacent etch figures, cracks, other etched features, or other imperfections on the polished and etched plane of the solid. Latent fission track tip and side traces may be rendered partially or wholly invisible to the analyst by any combination of intersecting fission semi-tracks, confined fission tracks, cracks, disruptions or defects in the solid molecular structure, or human-induced fission semi-tracks or other zones of damage to the solid molecular structure that connect the polished and etched plane of the solid to the dissolved latent fission track traces.
When seeking to find a fission semi-track, the analyst seeks an etch figure or a part or parts thereof, an opposing dissolved latent fission track tip trace or a part or parts thereof, and/or intervening, sub-parallel dissolved latent fission track side traces or parts thereof. The analyst then attempts to envision, based on the accumulated memory of the analyst, the equivalent ideal fission semi-track for this combination of visible etch figure or a part or parts thereof, an opposing dissolved latent fission track tip trace or a part or parts thereof, and/or intervening, sub-parallel dissolved latent fission track side traces or parts thereof. If the analyst is able to positively envision an equivalent ideal fission semi-track for this combination of visible etch figure or a part or parts thereof, an opposing dissolved latent fission track tip trace or a part or parts thereof, and/or intervening, sub-parallel dissolved latent fission track side traces or parts thereof, the analyst accepts the combination of visible etch figure or a part or parts thereof, an opposing dissolved latent fission track tip trace or a part or parts thereof, and/or intervening, sub-parallel dissolved latent fission track side traces or parts thereof as a fission semi-track and adds this new fission semi-track to the accumulated memory of the analyst. The greater the fraction visible of properly positioned and oriented etch figure or a part or parts thereof, an opposing dissolved latent fission track tip trace or a part or parts thereof, and/or intervening, sub-parallel dissolved latent fission track side traces or parts thereof, the greater is the confidence of the analyst that this combination of visible etch figure or a part or parts thereof, an opposing dissolved latent fission track tip trace or a part or parts thereof, and/or intervening, sub-parallel dissolved latent fission track side traces or parts thereof is a fission semi-track. The analyst is never fully certain that these visible etch figure or a part or parts thereof, an opposing dissolved latent fission track tip trace or a part or parts thereof, and/or intervening, sub-parallel dissolved latent fission track side traces or parts thereof are, in fact, a fission semi-track and the current art does not include a means of quantifying the degree of certainty.
A confined fission track preserves characteristics of its respective dissolved latent fission track including its position and orientation within the host solid, and its approximate length. Other features of a confined fission track may be useful to the analyst including its geometrical dimensions, its inclination angle to the observational optical axis, its depth below the polished and etched solid surface, and the number, size, characteristics, and positions of other preferentially dissolved features intersecting the confined fission track including, but not limited to, other fission semi-tracks and confined fission tracks.
For a confined fission track to provide information useful to the analyst, both of its tips must be visible to the analyst. It is known from natural solids containing 238U-derived latent fission tracks that a young latent fission track yields a confined fission track exhibiting a length from tip to tip that is usually greater than the length of a confined fission track derived from a latent fission track that formed millions of years ago, all other environmental factors being equal such as temperatures experienced since formation of the latent fission tracks, and resultant confined fission track crystallographic orientation. It is also known from laboratory experiments that a latent fission track that experienced relatively high temperatures yields a confined fission track exhibiting a length that is usually less than the length of confined fission track derived from a latent fission track that experienced relatively low temperatures, all other environmental factors being equal such as latent fission track ages and crystallographic orientations. This time and temperature dependence of the lengths of confined fission tracks provides the analyst a basis for deciphering aspects of Earth's history.
In plan view, the ideal confined fission track, if it existed, would project a complete and closed geometrical figure to the analyst when viewed using an optical microscope. This closed geometrical figure would be composed of two opposing tips, with each tip exhibiting a trace visible to the analyst that is concave inward toward the other, and with the tips connected to each other by two approximately parallel and continuous visible traces of the confined fission track sides.
The ideal confined fission track is never encountered in practice because only segments of, and never all of, the real confined fission track side traces are visible to the analyst. Henceforth, confined fission track refers to any real confined fission track. Therefore, the confined fission track projects visible tip traces and partially visible side traces to the analyst, forming an incomplete, open geometrical figure similar to that envisioned by the analyst for the ideal confined fission track but with parts of the side traces invisible. This is because a confined fission track is etched via an intersecting etchant pathway. At the intersection of the etchant pathway and the confined fission track, a segment of one or each of the confined fission track side traces must be dissolved rendering the dissolved portion or portions of the side traces invisible to the analyst. The confined fission track may also intersect other preferentially dissolves features, rendering additional parts of the side traces invisible to the analyst. Dissolution of any portion of the host solid that would otherwise reveal a visible portion of a confined fission track side trace causes a portion of the confined fission track side trace to be invisible to the analyst. A portion of the confined fission track side trace may be present but rendered invisible to the analyst if it is obscured by a more prominent feature in the host solid. A portion of the confined fission track side trace may be rendered invisible to the analyst if the pathways of the light in the optical microscope do not permit the trace to be resolved by the analyst.
When seeking to find a confined fission track, the analyst seeks two visible, opposing dissolved latent fission track tip traces. The analyst then looks for two approximately parallel dissolved latent fission track side traces, or visible portions thereof, between these opposing dissolved latent fission track tip traces. The analyst then attempts to envision, based on the accumulated memory of the analyst, the equivalent ideal confined fission track for this combination of visible latent fission track tip and side traces. If the analyst is able to positively envision an equivalent ideal confined fission track for this combination of visible latent fission track tip and side traces, the analyst accepts the combination of visible latent fission track tip and side traces as a confined fission track and adds this new confined fission track to the accumulated memory of the analyst. The greater the fraction visible of properly positioned and oriented dissolved latent fission track side traces between the opposing dissolved latent fission track tip traces, the greater is the confidence of the analyst that this combination of visible latent fission track tip and side traces is a confined fission track. The analyst is never fully certain that these visible latent fission track tip and side traces are, in fact, a confined fission track and the current art does not include a means of quantifying the degree of certainty.
Fission semi-tracks and confined fission tracks are commonly studied and their characteristics documented by an experienced analyst for the purpose of deciphering aspects of Earth's history. The preferred embodiment of the invention pertains to fission semi-tracks and confined fission tracks in natural apatite crystals or crystal fragments but the current invention may be applied to other natural solids in a similar manner.
Natural apatite, a common mineral in many types of Earth rocks, often contains trace amounts of fissile 238U nuclei. Henceforth, an individual apatite crystal or apatite crystal fragment is referred to as a crystal. Crystals or crystal fragments that have been liberated from their host rock are immersed in a polymeric epoxy, the polymeric epoxy is permitted to harden, and the crystals are then cut and polished using polishing grit to expose individual interior planes of the crystals. This configuration of crystals mounted in hardened polymeric epoxy is commonly referred to as a crystal mount.
Referring to
In the preferred embodiment of the invention, the crystal mount and the visible features it contains are viewed by the analyst using a Nikon Optiphot2 optical microscope using either transmitted light, reflected light, or a combination of transmitted and reflected light at 1562.5× magnification. The analyst may directly view the crystal mount and the visible features it contains by looking through the microscope oculars or indirectly view the crystal mount and the visible features it contains by looking at a computer display screen containing a black and white or color visualization of the crystal mount and the visible features it contains made possible using a charge coupled device affixed to the microscope and interfaced with the computer. Other optical microscopes, magnifications, and charge coupled devices may be used by the analyst to directly or indirectly view the crystal mount and the visible features it contains. In the preferred embodiment of the invention, the analyst views the crystal mount and the visible features it contains on a computer display screen as prescribed and a static visualization on the computer display screen of the crystal mount and any visible elements it contains is commonly referred to as an image.
On the crystal mount, two visible and different points are separated by a fixed distance that can be expressed in a unit of length. On the image, these same two fixed points are separated by a fixed number of computer display screen pixels. In the preferred embodiment of the invention, the image for a given combination of optical microscope model, magnification, and charge coupled device is calibrated in both the horizontal (henceforth, X) and vertical (henceforth Y) directions yielding conversion factors in units of length/pixels. These conversion factors permit the distance between any two points on the image, separated by some number of computer display screen pixels, to be expressed in a unit of length. In the preferred embodiment of the invention, the unit of length is the micrometer but other units of length may be used.
In the preferred embodiment of the invention, the optical microscope is affixed with an apparatus that obtains a record of the relative height of the crystal mount within the optical pathways of the optical microscope. This apparatus is interfaced with the same computer to which the charge coupled device is interfaced. The relative crystal mount height within the optical pathways of the optical microscope is scaled such that any change in height of the crystal mount within the optical pathways of the optical microscope may be expressed in a unit of length. In the preferred embodiment of the invention, the unit of length is the micrometer but another unit of length may be used.
In the preferred embodiment of the invention, the height of the focal plane that intersects the optical pathways of the optical microscope is fixed at a fixed magnification. A change in height of the crystal mount within the optical pathways of the optical microscope represents an identical change in height of the crystal mount relative to the focal plane.
In the preferred embodiment of the invention, crystals 1-1 on the crystal mount are pre-viewed by the analyst and a subset of the crystals 1-5 containing fission semi-tracks 1-2 of interest to the analyst is specified and a second subset of crystals 1-6 containing confined fission tracks 1-3 of interest to the analyst is specified. The fission semi-track subset of crystals 1-5 and the confined fission track subsets of crystals 1-6 may be intermixed or they may be combined into a single subset of crystals.
Referring to
For each crystal specified by the analyst as containing fission semi-tracks 2-1 or confined fission tracks 2-2 of interest, the crystal mount is positioned so that the specified crystal is approximately centered within the image on the computer display screen. The crystal mount is then positioned so that the polished and etched plane of the host crystal containing the fission semi-track 2-1 or confined fission track 2-2 is at the height equal to the focal plane of the optical pathways of the optical microscope. In the preferred embodiment of the invention, this positioning of the crystal mount is done using reflected light. Transmitted light with or without reflected light may be used for this positioning. Transmitted light, if on, is turned off, reflected light is turned on, and lighting is adjusted as needed by the analyst. The crystal mount is moved so that the focal plane is 1.0 micrometers away from the polished and etched plane of the host crystal and outside of the preserved volume of the host crystal. The image is recorded for this grain mount position. The crystal mount is then moved, in a series of 0.5 micrometer steps, so that the focal plane of the optical pathways of the optical microscope is moved toward the interior of the preserved volume of the host crystal. At each step, the image is recorded for the grain mount position. This process is ended when the focal plan is positioned 20.0 micrometers away from the polished and etched plane of the host crystal and within the preserved volume of the host crystal. Another starting distance, other than 1.0 micrometers, of the focal plane away from the polished and etched plane of the host crystal, may be used. Other step-wise movements, other than a fixed 0.5 micrometers, may separate adjacent positions of the polished and etched plane of the host crystal. Another ending distance, other than 20.0 micrometers, of the focal plane away from the polished and etched plane of the host crystal, may be used.
In the preferred embodiment of the invention, the subset of crystals specified by the analyst for study of its fission semi-tracks is subjected to the prescribed processes of transmitted light image recording and reflected light image recording separately from the subset of crystals specified by the analyst for study of its confined fission tracks. Images are recorded for transmitted light followed by the recording of images for reflected light. It is possible to mix specified fission semi-track and confined fission track grains during image recording and it is possible to record images for transmitted light, then for reflected light, while at each specified crystal.
The transmitted light recorded images and reflected light recorded images for each of these crystal mount positions may contain one or more fission semi-track 2-1, one or more confined fission track 2-2, and any other feature of interest to the analyst including one or more of the following: etch figures, etched or un-etched fluid and/or mineral inclusions, etched cracks, etched disruptions or defects in the apatite crystal structure, and any part of an etchant pathway.
In the preferred embodiment of the invention, each pixel of the transmitted light recorded images and the reflected light recorded images is converted to its equivalent color on the gray scale with color ranging from black to white. The equivalent color is then converted to a number, black set equal to zero, white set equal to 255, and a color between black and white set equal to a value appropriate to the position of the color between black and white. Brightness refers to this gray scale number with a higher number having greater brightness. A visible feature in these images is defined by a brightness difference between adjacent pixels, a brightness gradient among pixels in a given direction, and/or a brightness curvature which is the rate of change of the brightness gradient among pixels in a given direction. The pixel information from the transmitted light and reflected light recorded images, including the original color, may be converted to different equivalent colors and/or different numerical values, and brightness may be defined in a different mathematical sense and other commonly used image processing concepts such as contrast may be used.
In the preferred embodiment of the invention, detecting and characterizing a particular visible feature requires limits to be set on the search area size over which a particular feature is sought for two dimensional features such as an etch
Each crystal possesses grain-wide characteristics that may be associated with all fission semi-tracks 2-1 and confined fission tracks 2-2 it may yield, including but not limited the equation of a line in X,Y,Z space that is parallel to the crystallographic c-axis of the crystal 2-4. It is common practice for the analyst to consider only crystals for which the crystallographic c-axis is parallel to or nearly parallel to the polished and etched crystal surface on the crystal mount. Etch
The major axes of the ellipses fitted to the etch
The etch figures found and used to determine the crystal Dpar 3-3 and Dper 3-5 values are used to search for and identify any potential fission semi-track 3-2 for the crystal. Referring to
It is possible that a fission semi-track 2-1 may not exhibit a well defined fission semi-track tip 2-5 because the fission semi-track tip 2-5 may be below the etch
The greater the number of fission semi-tracks 2-1 in the fission semi-track database, the greater is the accumulated experience available to the computer program from which the fission semi-track scoring algorithm may be developed and refined and to which new potential fission semi-tracks 2-1 may be compared. In the preferred embodiment of the invention, a fission semi-track scoring algorithm is available which seeks to estimate the relative likelihood that a combination of characterized etch
In the preferred embodiment of the invention, the fission semi-track scoring algorithm may present to the analyst an estimate of probability that a potential fission semi-track is a fission semi-track. This probability may include an assessment of the overall distribution of potential fission semi-track lengths and orientations relative to a theoretical prediction or a similar number of ideal fission semi-tracks with the purpose being to identify potential fission semi-tracks exhibiting characteristics such as a preferred orientation or preferred length that is highly unlikely for the theoretical ideal fission semi-tracks. The computer program containing the fission semi-track scoring algorithm presents to the analyst the ability to accept this estimate of probability or override this estimate with a value specified by the analyst.
In the preferred embodiment of the invention, the fission semi-track database is searchable. Search indices may be comprised of the identity of the analyst who decided to add the images of the fission semi-track 2-1 to the fission semi-track database, Z value of each image, the probability that the fission semi-track images are actually for a fission semi-track, the Dpar 2-8 and Dper 2-9 values of the associated etch
In the preferred embodiment of the invention, the fission semi-track database is specific to the identity of the analyst that made the decision to add each set of images of a fission semi-track 2-1 to the fission semi-track database. Each set of images of a fission semi-track 2-1 in the fission semi-track database is transferable to an analyst having a different identity on the condition that there is consensus between the two analysts that the images represent a fission semi-track.
In the preferred embodiment of the invention, new potential fission semi-tracks 2-1 may be scored against a fission semi-track database where two or more analysts agree by consensus that each set of fission semi-track images in the database represents a fission semi-track 2-1. A consensus group is composed of two or more analysts contributing to a fission semi-track database containing images of fission semi-tracks agreed to by consensus.
In the preferred embodiment of the invention, fission semi-tracks 2-1 may be sorted according to any of the available types of information including but not limited to analyst identity or consensus group, the probability a fission semi-track is actually a fission semi-track, and the overall score produced by the fission semi-track scoring algorithm. A subset of the fission semi-tracks meeting specified sorting criteria applied to the available types of information and/or specified scoring criteria may be selected for purposes of deciphering aspects of Earth's history.
In the preferred embodiment of the invention, a computer program is made available to the analyst to aid the analyst with the decision whether a potential fission semi-track is an actual fission semi-track. This program presents to the analyst images of the potential fission semi-track on a computer display screen and allows the recall of images from the fission semi-track database. Images of the potential fission semi-track may be presented on the computer display screen simultaneously with recalled images of a fission semi-track from the fission semi-track database or they may be displayed separately or at different times at the choosing of the analyst. Images of the potential fission semi-track and recalled fission semi-track from the fission semi-track database are presented to the analyst with crystallographic orientation normalized whereby the crystallographic c-axis directions for the associated images are aligned in the Y direction of the computer display screen. Images of the potential fission semi-track and recalled fission semi-track from the fission semi-track database are presented to the analyst with fission semi-track position normalized whereby the mid-points of the potential fission semi-track and recalled fission semi-track axes are placed at the center of the image displayed on the computer display screen. Images of the potential fission semi-track and recalled fission semi-track from the fission semi-track database are presented with X and Y direction length scales normalized whereby they present to the analyst the same X and Y direction length scales for the associated images. Other means of normalizing images of the potential fission semi-track and recalled fission semi-track from the fission semi-track database may be used. The computer program presents to the user the option of viewing a series of fission semi-track images from the fission semi-track database whereby the series is defined by specified sorting criteria applied to the available types of information and/or specified scoring criteria. The computer program presents to the analyst the option of parsing through the series of fission semi-track images from the fission semi-track database and the option to modify the specified sorting criteria applied to the available types of information and/or specified scoring criteria defining the series of fission semi-track images. This ability to compare images of a potential fission semi-track to images of recalled fission semi-tracks from the fission semi-track database provide a basis for an experienced analyst to train an inexperienced analyst.
In the preferred embodiment of the invention, available information for a fission semi-track includes various uncertainty values including but not limited to the probability that the fission semi-track is actually a fission semi-track and the uncertainties on fission semi-track length and fission semi-track axis offset angle from the crystallographic c-axis. Other uncertainties include grain-scale values such as the uncertainties of crystal Dpar and Dper values. These uncertainties may be passed on to any method of interpretation that utilizes the fission semi-track for purposes of deciphering aspects of Earth's history. Uncertainties may be passed to the method of interpretation using standard statistical protocols and/or they may be passed to the method of interpretation using numerical methods such as a Monte Carlo simulation. As the fission semi-track database becomes larger and the fission semi-track scoring algorithm is developed further and refined, the understanding of these uncertainties by the analyst will increase and the means of passing them to the method of interpretation will improve and the ultimate result is that the means of deciphering aspects of Earth's history that utilizes the fission semi-track will improve.
