It is feasible to optimize the tapper, as well as the entry and exit faces to optimize the collimator for the complex linear or planar neutron emission fields and moderator material in order to produce a thermal neutron beam of either near parallel moving thermal neutrons or converging thermal neutrons.
Development of this technology would first establish the supply of bimetalic composites meeting dimensional and other quality specifications. Test collimators would be build and tests to verify computational design models. With the verified models of the linear and planar neutron source, an optimal thermal neutron beam, producing assembly can be produced. The discrepancy was accounted by the manufacturing technology. It is apparent that such a short length collimator technology is ideally suited to the neutron source topology of the present disclosure and can be improved by one skilled in the art to achieve a commercially viable component.
The collimator may also be utilized for the other embodiments disclosed herein. A fourth aspect of the present invention is the utilization for relatively high speed and high throughput rate industrial applications. In particular the food industry with is very diverse range of products has a need for detection of foreign objects and substances that may contaminate food products. The flow rate of food product units has a wide range. Most readers will imagine the rate of production of packaged food.
An embodiment which can cope with such flow rates is disclosed as a variation of the above described embodiment which are configured for scanning a stream of highly variable objects.
If the objects are highly uniform, as is the case for a food production line, the detection of anomalous elemental or isotopic ratios can be recognized at a lower threshold of acquired statistical data. The effective neutron dose is correspondingly reduced. The embodiment is also able to deal with bulk food material such as frozen vegetables for real time detection of contaminants such as non-biological minerals, chemicals, elements and biological origin parasites such as worms.
The vegetable units are already frozen by immersion in liquid nitrogen. The mass flow rate is approximately kg per hour. This corresponds to a vegetable unit flow rate of 30, to , per hour. The size and traverse time may vary depending on the type and size range of the vegetables. If present, the contaminants or foreign bodies are distributed inside the frozen vegetable units. Detection must be fast enough to actuate a rejection mechanism for removal of the suspect vegetable unit.
The high speed will require scanning and recognition of approximately 8 - 80 vegetable units per second! The utilization of the present invention in a linear longitudinal traverse configuration embodiment, as described above, is one option for the lower flow rate. Another embodiment described below can cope with the higher rate. A fifth aspect of the present invention is an embodiment where objects to be scanned are passed through a cylindrical linear radially outward moving neutron field in a spiral locus. Such a traverse maximizes the specific exposure time to the neutron field while keeping the object conveyance system as mechanically simple as possible.
Objects that may be interrogated can be items such as frozen or non frozen vegetables, food items in general including solid or liquid forms, small high production rate manufactured items, postal letters and bulk material, in an appropriate conveyance system. In general the row of gamma detectors and associated gamma collimation and shielding is also wrapped around the cylindrical topology to view sections of the conveyancing track. The optimal design of such a system for a particular application will have many design parameters to consider. Those that are enabled by the present disclosure are associated with the linear or planar topology of the neutron source.
A point source would simply not be able to accommodate sufficient wrapped locus of conveyance means for the object to be scanned.
The exposure or dose would have to be achieved through a very substantial increase on the specific neutron output of the point source. Similarly the conventional prior art utilization of a linear topology source of neutrons only teaches embodiments where the traverse locus is substantially at right angles to the linear source and not wrapped about it with a similarly wrapped array of sensors and data multiplexed connections.
For a better understanding of the present invention and to show how it may be carried into effect, reference shall now be made by way of example to the accompanying drawings, in which:. FIGURE 1 shows a schematic of prior art utilization of neutrons in a typical bulk material analysis application where the material is moving through the neutron field on a conveyor belt with either point sources of radionuclide or an ideal but until recently not available line source neutron generator;. FIGURE 2 shows a the utilization of one or more long line source neutron generators in a shielded tunnel configuration with high continuous throughput in a neutron interrogation system for airport level 1 or 2 security screening or a package screening system;.
FIGURE 3 shows cathode grid cell of WO in two forms which in normal operation with the anode can maintain a planar zone of neutron emission;. FIGURE 4 shows a short and a longer cathode embodiment neutron generator with examples of neutron shielding, moderation and collimation;. FIGURE 5 shows an embodiment of a generalized industrial application of a long line source neutron generator utilized for the screening of a standard product on a production line such as found in the food industry;.
FIGURE 6 shows examples of segmented cathode and associated shielding and collimation to achieve generation and escape of neutrons at specific locations along a long line or planar source;. FIGURE 7 shows a schematic of a linear geometry neutron source utilized to screen a high throughput rate of postal letters whereby the letters are conveyed through the neutron field for a maximum amount of time in order to accumulate an elemental abundance signature for each letter by multiplexing of the many gamma sensor data streams in synchronization with the transit of each letter;.
Several linear neutron source units which may have continuous or segmented electrode neutron emission zones are connected together by a vacuum manifold which allows the free movement of the reactant gas. FIG 9 shows the utilization of the linear neutron generator in a mobile application on a railway carriage. The objective is to detect hidden explosives that are planted under the rail tracks and concealed by the stones. The maximum speed of the track may be approximately kilometer per hour.
However the combined shipping container plus neutron source and gamma detector array may be in motion on a vehicle such as a crane spreader or a container moving "straddler" vehicle. The present invention makes use of the length characteristic or more generally the three dimensional topology of neutron generators which are able to provide this feature to teach utilization in example embodiments which have not been disclosed in prior art. The applicable neutron generators have a non-point-like zone of neutron emission.
With point-like neutrons sources such as radionuclides or the well known neutron generators that have been available prior to emission field characteristics similar to line sources have been achieved by the use of multiple point sources as shown in FIG. IA where a conveyor belt 1 or similar mechanism carrying bulk material 2 is irradiated at a defined location by a flux of neutrons for an elemental analysis technique.
The requirement for a line source has been implicit since the introduction by manufacturers of online mineral analysis systems with an array of point sources. The utilization of such a line source 3 is illustrated in FIG. The disadvantage of radionuclide sources 4 is illustrated in FIG.
This is illustrated by the diminished intensity 5 representation.
ID indicates the continued nominal performance of a plasma-gas target type of neutron generator as disclosed in WO and incorporated by reference herein. The air transport security authorities have developed performance specifications. A crucial requirement is 8 seconds per bag for the scanning and data evaluation process. All checked baggages must be subjected to level 1 and 2 screening. At present the reliability of Level 1 and 2 screening is dependant on the human operators who must recognize anomalies presented to them bag after bag after bag.
Suspect objects are diverted to a so called level 3 examination where penetrating radiation interrogation systems typically utilizing X-rays are used to construct a three dimensional map in a displayable form for a human operator to interpret. The present tunnel neutron interrogation system does not have to generate images of luggage interiors for recognition of anomalies.
The neutron interrogation can directly detect anomalies of element abundances which are indicators of the present of substances such as explosives. This has been described in numerous prior art and technical publications. The present disclosure is not concerned with a particular combination of sensors and signal processing means but rather the options that can be exploited with a hitherto unavailable neutron source topology.
With the length of a neutron generator of the type described by WO at least being limited only by the power supply performance required it is plausible to construct a single line source with a length of approximately 5 metre. It is also feasible to have a tunnel facility of length 10 metre with only one neutron generator reaction chamber assembly. This can be achieved by segmenting the cathode so that active segments of, for example, 0. The' non- active segments draw no power and hence the same power requirement for a contiguous 5 metre electrode can be associated with the afore mentioned segmented 10 metre neutron generator 11 illustrated in FIG.
In FIG. The illustration neglects radiation protection at the ends of the tunnel for clarity. In a practical implementation there will be bends at each end of the tunnel in order to prevent a straight line path from any radiation source within the tunnel system to the outside. A mechanical conveyor 13 in Fig. There is a spacing of approximately 0. These parameters are specified by air transport security regulations. The duration of interrogation of a particular item of luggage within the example tunnel system is therefore 20 seconds.
However the item never stops moving. This is very beneficial for extending the operational lifetime of the mechanical conveyor equipment. The duration of exposure to neutrons, assuming that there is a total length of neutron emission field of 5 m, will be 10 seconds. Compare this to a single neutron interrogation station where the object being scanned may only receive perhaps 6 seconds of neutron flux and gamma spectroscopic data acquisition or even less per "voxol" of scanned volume. If "voxol" scanning is performed the effective neutron exposure time may be only approximately 1 second.
The time dilation effect of the long neutron source is to increase the exposure time by a factor of 5 to 10 times, depending on the assumptions made about the scanning technique or techniques that may be utilized in such a long tunnel system. Such a time dilation is a significant mitigation factor for neutron generator performance and cost.
The conveyor 13 is omitted for clarity as are many fine detail features. An array of gamma detectors plus neutron detectors and perhaps x-ray detectors is positioned to achieve an optimum view of the scanned items while mitigating the sensors' damage by the neutron flux. The sensors 16 do not have to be positioned in a line as illustrated. Also omitted for clarity are the details of neutron moderation and collimation and sensor collimation and shielding.
These aspect is illustrated in subsequent figures. The sensors are available from various manufacturers who also provide comprehensive modular electronics and support equipment. It is possible for anyone skilled in the art to design a data processing architecture that will process raw sensor data into digital data packets which are sent to a centralized data processing computer The multiple sensor data is multiplexed or commutated by the data processing system so that relevant data and processed statistical results are accumulated for each item moving through the tunnel.
The accumulated statistics for 10 seconds of interrogation may then, or during the accumulation, be assessed automatically for anomalous patterns. In the case of an anomaly a signal 18 is sent to a divertor device which is positioned at some point near the tunnel exit and the suspect item is intercepted for level 3 inspection.
Illustrates a linear neutron interrogation tunnel system where the entire system is laid out in a straight line. It is also feasible to construct such a system in various folded and curved topologies that may save floor space. Vertical directions of transit where the conveyor has bucket or tray holders for the item to be scanned can be envisaged.
One or more line or plane source or curvilinear topology neutron sources can be utilized. A short cathode as shown in FIG. The cell structure is mounted on a stem 23 which is attached to a high voltage feed through as described in WO The extent of the neutron emission zone is determined be the inner wall anode structure. Therefore the neutron emitting zone can be briefly described as a central disk with a diameter somewhat greater than the mean diameter of the cathode cage with the thickness of said cage and a superimposed disk with an outside diameter matching the anode inner wall diameter.
The larger diameter disk will have a neutron intensity distribution that is somewhat gaussian plus regions of greater intensity corresponding the radial star beams through each grid hole pair. This aggregated zone of neutron emission can be described as planar when viewed along the axis of the support spindle.
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In this case the typical long cathode grid cage electrode topology of WO is distorted to achieve the cage structure shown. Again there are opposing hole pairs The end disks of FIG. It is apparent that the cathode and anode topology is still similar to that disclosed in WO so that the operation of a steady glow discharge plasma-gas target is still feasible under similar conditions.
The planar neutron emission zone has its central plane coincident with the long axis in FIG. It is apparent that shapes other than rectangular can be formed and the vanes mounted so as to define the hole pairs. If a circular planar neutron source is required the frame can be made circular. FIG 4 A illustrates a source topology which may be approximately circular and planar as viewed along the axis of motion of the collimated neutrons. The electrode will be generally of the form shown in FIG. FIG 4B also illustrates a source topology which may be approximately circular or rectanular and planar as viewed along the axis of motion of the collimated neutrons.
The electrode will be either a long version of the form generally shown in FIG. Although a cursory glance at FIG. The illustrated systems deliver a collimated beam of thermal or slow neutrons which may be used for certain types of radiography or medical therapy such as Boron Neutron Capture Therapy or neutron activation tomography.
A beam of thermal neutrons 42 is formed by a collimator 43 of the Soller type or as disclosed by Franks GB which teaches a Soller type collimator for point sources or preferably the rolled bimetallic micro-Soller type as disclosed by B. The transmission foil may be ten of microns thick while the absorbing layer is as thin as practicable to minimize cross-sectional blockage.
A second high voltage stand-off assembly may be employed if the mass of the electrode assembly is deems excessive. The reactant gas is stored and released to maintain the necessary pressure by a getter pump A labyrinth structure 46 accommodates coolant input and outlet as well as cables. The high voltage power supply 47 may be attached close the the reactor chamber to provide a compact neutron beam emission unit as may be utilised for medical and some industrial applications where movement while actually operating may be a characteristic.
The products are typically food products. The objective is to use neutron interrogation techniques to identify anomalies from the normal elemental abundance ratio of the food product. An anomaly is likely to indicate the presence of a contaminating substance or object or a plurality thereof within the food product unit. The level of sensitivity needed to be achieved is much less than the parts per billion 10 9 level that may be achieved in a laboratory.
One specification is the permissible level of contaminant which may be parts per million 10 6 or greater. The level of sensitivity and reliability of the statistical data will depend in part on the accumulated neutron dose and gamma measurement time. The greater the number of neutron hits, so the the amount of gamma quanta that may be captured by the sensor array. It is therefore apparent that a scanning system will have to combine neutron source specific intensity per unit length with overall effective length and transit time of the object being interrogated along the length of the neutron emission field.
The linear topology reduces the neutron intensity requirement to a level that is practically achievable and less demanding of the radiation shielding.
A higher specific neutron intensity in the same configuration will increase the elemental ratio sensitivity. An embodiment of this teaching is illustrated by a liner source 50 in FIG. The number of such conveyor units may be selected with consideration of the size of the food product units and sub-system equipment accommodation. The neutron moderation, detectors and other features are omitted in order to show how the objects to be interrogated are guided through the neutron field surrounding the linear topology neutron source in order to increase the time and accumulated neutron radiation dose while avoiding a constriction of the flow of food product on the production line.
The utilisation of more than one conveyor effectively lengthens the available transit time by slowing the transit speed while simultaneously maintained the total throughput rate. Materials handling and conveyor system mechanical design skills are available to one skilled in the art for the implementation of a divider and recombination function at the front and back end of the neutron interrogator system. A suspect package or food unit diversion mechanism may also be similarly implemented. WO produces a neutron emission zone along the axis which is perpendicular to the page.
The neutron generator vessel and heat exchanger structure. Collimation of the neutrons will be implemented by means of the shielding materials 56 where apertures 57 will be provided to collimate the emitted neutrons into a beam passing through the transit track 58 of the objects being scanned. The neutron beams may be conical or fan-like so as to optimize the collection of gamma quanta from the target scanning zone while avoiding stray gamma quanta from adjacent scanning zones.
The gamma sensors may be implemented with NaI or with HpGe technology or any other deemed appropriate. A typical installation will avoid a direct impingement of neutrons on the detector. Therefore the detector will be positioned to view the object to be scanned but offset from the bean beam as shown in this example.
The longitudinal positioning of scanning zones and sensors will be determined by equipment accommodation considerations and the characteristics of the achievable gamma and neutron collimation features. Spacing of the scanning zones along a given conveyor guide or track may be influenced by isolation of one scanning zone from another to avoid gamma quanta reaching the adjacent scanning zone detector and thus causing false information.
Similar considerations of interference and accommodation may also determine the relative spacing of scanning zones on adjacent conveyor tracks. Co-planar or staggered arrangements may be implemented. There will be a data processing architecture utilizing equipment that is readily available from some commercial nuclear instrument manufacturers that will enable one skilled in the art to implement a sensor data multiplexing system that will accumulate the data flowing from the appropriate sensor as each product unit passes through the respective scanning zone. Even before all scanning zone data have been received for a particular product unit, running pattern recognition software will have had sufficient time to determine if the elemental and isotopic abundance ratios are normal or anomalous.
It is also feasible to incorporate sensors other than gamma quanta energy sensors. In particular neutron sensors 62 will be utilized to measure the neutron flux attenuation that would be caused by contaminants such as plastic micro particles or larger plastic objects. The high hydrogen content of plastics will scatter neutrons and thus reduce the measured neutron flux at a neutron detector located in the neutron beam where the object to be scanned passes between the neutron source and the neutron flux detector.
Such a detector would only need to be installed at one position on each conveyor track. Neutron detectors may be of the Helium 3 type or any other gas or solid state type that may be assessed as appropriate for the application. It is also feasible and more costly to reduce to practice the more complex electrode structures of US Pat. Neutrons are emitted isotropically. There is an increased intensity from the central core defined by the cathode cage structure.
Unwanted neutrons are mitigated by making sections of the cathode grid not a grid structure but simply a cylindrical rod 74 which is firmly welded to the cage structures. This also provides benefit by reducing the electrical high voltage power consumption. On long segmented cathode assemblies high voltage stand-off components 76 made of Al 2 O 4 ceramic may be used. In sections or segments where neutron emission is required, there is usually a requirement to shield or block neutrons emitted in directions where they are not required so as to decrease the radiation hazard and interference.
Such shielding 75 may surround most of the neutron generator chamber. An aperture or hole 77 in such shielding will be a simple collimator to permit neutrons to emerge with minimal scattering energy loss. Note that the angles of the sides of the hole and the topology of the hole can be varied to suit the application and desired cone or fan angles. The non point or 2D line topology of the neutron emission can be considered in the design of the aperture.
The higher flux part of this beam would be with a cone angle of approximately 90 degrees with the apex 78 set back on the edge of the zone of greatest neutron emission. The thickness of the moderator in the radial direction will be determined by the inelastic scattering required to reduce the neutron energy. Such high aspect ratio collimation will be governed by the size of neutron emission zone.
Baffling of the neutron emission zone will reduce the apparent source intensity. The system again relies on a sensor data multiplexing architecture to accumulate the brief data set per letter transit at each sensor location so as to acquire statistically significant data of the measured elemental abundance ratios for each letter. Anomalous letters would be diverted for additional inspection by slower x-ray or chemical analysis techniques.
Such letter bombs would have to potential of causing serious damage to hands and face as well as increasing terror. The system is comprised of a linear neutron source 90 preferably of the type disclosed in WO with a length of 1 to 5 metres is surrounded be neutron moderator 91 material such as pure polyethylene so as to achieve a flux of thermal neutrons of an average energy deemed suitable for neutron interrogation.
The neutron moderator 91 may be constructed so that the average thermal neutron energy emitted at various positions along its length changes for the objective of optimizing the sensitivity of efficacy of the neutron interrogation techniques.
A postal letter conveyancing mechanism 92 is wrapped around the neutron moderator 91 so as to form a spiral which maximizes the transit time of each letter through the neutron field. The postal letter conveyancing mechanism means will be familiar to one skilled in the art. It will include means to regulate the speed and synchronize the transit of a letter past each sensor position.
The entire assembly may be mounted vertically or horizontally. The sectional view is set at an angle so that the cylindrical neutron generator 90 and moderator 91 appear elongated. A segment of the letter 95 conveyancing mechanism 92 is shown with representations of the locations of support structures for rollers and similar devices An overall neutron and gamma shield plus housing in not shown. Other embodiments of the linear geometry may be envisaged in order to suit specific applications. It will be apparent that the broad teachings of the present invention can be profitably applied to specific embodiments and applications far beyond what is set forth above for the purposes of illustration.
While the invention has been shown and described with reference to certain embodiments thereof, it will be understood by those skilled in the art that various changes hi form and detail may be made therein without departing from the scope of the invention as defined by the appended claims. The preferred features of the invention are applicable to all aspects of the invention and may be used in any possible combination.
Throughout the description and claims of this specification, the words "comprise" and "contain" and variations of the words, for example "comprising" and "comprises", mean "including but not limited to", and are not intended to and do not exclude other components, integers, moieties, additives or steps.
The system is comprised of several linear neutron source units which may have continuous or segmented electrode neutron emission zones. The multiple reaction chambers are connected together by a vacuum manifold which allows the free movement of the reactant gas. The reaction chambers may have any relative orientaion and may be aligned in non-linear arrangements such as for a curved baggage conveyor belt. The gas storage and pressure regulation device 45 is also hermetically attached to the combined vacuum chamber manifold at any convenient location.
The positions of the neutron emission units and the gamma detectors plus neutron shielding is determined by a detailed optimization analysis. The high voltage cables are connected to a high voltage poer supply and distribution switch unit which can be utilized to operate each neutron emission unit separately or in tandem.
Economic benefit is achieved by the reduction of power supply and supporting control electronics to one set. In particular there is a minimization of the inventory of reactant gas, which may be subject to radioactive material regulations, within the system because only one common getter pump unit 45 is necessary. One common control unit automation computer can manage the entire system. It is obvious that there is a wide range of permutations of such a system configuration. FIG 9 shows the utilization of the linear neutron generator in a mobile application on a railway carriage Calculations indicate that a level of neutron emission that is consistent with the achievable specific performance of linear neutron generator is sufficient to enable a total exposure of neutrons on a small segment of track where a bomb may be hidden to enable a statistically significant indication of a gamma spectral anomaly caused by the explosive.
The maximum speed of the track may be approximately kilometer per hour approximately Clearly this is a function of many parameters which include the specific neutron output, the neutron flux at or just under the rails, the effective length of the neutron source , detector efficiency and other factors which will effect the neutron delivery to the region under the rails. In such a case the long neutron source brings economic benefit through its lower total cost compared to many separate neutron sources. Comparison of results achievable with typical neutron fluxes and neutron generator output levels indicates that approximately 30 seconds of neutron exposure would be necessary to obtain a statistically significant indication of the presence of fissile material or shielding material.
The array of detectors may be organized to provide crude resolution of the location of a suspicious object within the container as illustrated in the conceptual display where colour coding would inindicate the position within the container to focus further non-invasive scanning techniques. Design analysis will determine the optimal neutron source characteristics for penetration and interaction with the interior contents in order to yield as many gamma photons to be detected by the array. Various schemes such as oscillation of the field of view of detectors or the direction of the neutron slit beam may be envisaged to enhance the production of useful interrogation information.
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A common industrial neutron interrogation screening requirement is that a high throughput rate be accommodated by the screening system. If the subject 14 passes through a neutron beam, with a strictly limited time window for exposure, the flux must be sufficient to accumulate the required statistics. The level of neutron flux necessary may exceed the cost effective limits of the selected neutron source means Exposure time window dilation is disclosed through a class of system configurations which become practical for reduction to practice by utilization of linear neutron source topology neutron generators.
This disclosure is concerned with example embodiments which utilize the length, width, thickness and segmentation of the source emission zone within an appropriate neutron source Application No. A process as claimed in 1, wherein the plurality of objects must pass through or pass by the screening or probing or interrogation system without being stopped for exposure and data collection. A process as claimed in 1, wherein the plurality of objects are contained within a larger object which is of a size and mass so great that it is optimal to move the exposure and measurement apparatus concurrent with the large object so as to mitigate stop-start movements of the container relative to the operating neutron interrogation system.
A process as claimed in 1, wherein the neutron source is comprised of a plurality of points of origin of neutrons which occupy a volume of three dimensional space so that the extent of the neutron source is not a unitary or near unitary point source of approximately 10 mm mean diameter or less. A process as claimed in 1, wherein the neutron emission volume or zone is elongated so as to be described as a planar or linear whereby planar implies that the dimensions in two of the three orthogonal axes are approximately equal while the dimension in the third orthogonal axis is relatively short, and whereby linear implies the converse of two relatively short orthogonal axes and a third relatively long orthogonal axis.
A process as claimed in 1, wherein the number of elongated neutron sources used in combination may be greater than one arranged end to end or in parallel or in an array and which may be segmented so that neutrons are emitted only from segments rather than the entire length and these active segments correspond with the scanning station sensors within a neutron interrogation system. A process as claimed in 1, wherein the relationship between the flux level of neutrons passing through an object being interrogated and the duration of the transit through the flux field, sometimes referred to as dose or expsure, is set with respect to the available neutron intensity or strength of the neutron source so that a specific neutron emission rate per unit of length in the transit direction or measurement zone, can be integrated or summed to be equivalent or greater than the dose accumulated from a collimated beam from a single point source of much greater intensity.
A process as claimed in 1, wherein the objects to be interrogated in defined industrial production or recycling applications will be essentially identical as is the case with a product on a production line where the uniform product is produced in batches of which the individual units can be passed in series through the subject neutron interrogation system and where there is a predefined standard acceptance pattern of characteristic interrogation data for the automated anomaly recognition means which can be an implementation of so called pattern recognition algorithms based on well known or emerging computational technologies for real-time comparison and detection of anomalies that may be caused by contaminant material and foreign objects.
A process as claimed in 1, wherein the objects to be interrogated are all diverse such as the application of baggage or consolidated cargo security screening where the non standard characteristics must be measured in order to enhance the automated anomaly recognition means which can be an implementation of so called pattern recognition algorithms based on well known or emerging computational technologies for real-time comparison and detection of anomalies that may be caused by presence of fissile material, explosives or contraband materials within the luggage unit.
An apparatus as claimed in 10, wherein the practical achieved levels of performance, endurance and cost of neutron sources such as radionuclides or neutron generators practically limits the specific neutron emission per mm and necessitates the extension of length of the source and associated power supply capability in the case of the preferred embodiments that use linear topology neutron generators.
An apparatus as claimed in 10, wherein it is apparent that the effective highest attainable flux neutron field immersion time for a certain neutron source of point or quasi point source topology is approximately equivalent to that of an elongated neutron source with approxiamately ten times less specific neutron output flux but approximately ten times greater effective length and furthermore it is apparent that effective elongated source lengths of approximately times the mean transit length of collimated point sources are readily able to be manufactured using available technology.
An apparatus as claimed in 10, wherein a relatively long linear topology neutron source with a specific performance that is ten to one hundred times that of a comparable point source will enhance the neutron interrogation function or neutron interrogation performance so as to produce more useful information per unit of time of effective scanning and furthermore it is apparent that elongated and distributed neutron sources with such specific performance can be obtained at a cost that is less than that for higher intensity neutron point sources.
Murphy et al. I really enjoyed the courses. Solar neutrons are produced through interactions between energetic ions and the solar atmosphere. Chronicon Thomae, altro heart' sett in solid-liquid book minutes. Conference Archive.
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