NL2025411B1 - Radiation monitoring device and inspection system. - Google Patents
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- NL2025411B1 NL2025411B1 NL2025411A NL2025411A NL2025411B1 NL 2025411 B1 NL2025411 B1 NL 2025411B1 NL 2025411 A NL2025411 A NL 2025411A NL 2025411 A NL2025411 A NL 2025411A NL 2025411 B1 NL2025411 B1 NL 2025411B1
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Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
- G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
- G01T1/02—Dosimeters
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- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
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- Spectroscopy & Molecular Physics (AREA)
- Measurement Of Radiation (AREA)
Abstract
Radiation monitoring device and inspection system 5 A radiation monitoring device comprises a radiation sensitive optical fibre (20) together with a photon source (31) and an optical receiver (32). Said photon source (31) is coupled to said optical fibre (20) to transmit light through said optical fibre (20) to said optical receiver (32). Said optical receiver (32) is coupled to signal processing means (40) that process an output signal of said optical receiver according to a mathematical algorithm to determine optical 10 distortions within the optical fibre that are induced by radiation impinging on said optical fibre. Said algorithm allows said processing means (40) to determine said optical distortions as a function of a position along said optical fibre (20). As said optical fibre is layed out over a detection area (10) according to a determined trajectory said processing means may translate said positions and an incidence of said distortions to spatial coordinates within said detection 15 area. An inspection system contains at least one such monitoring device. Fig. 1
Description
Radiation monitoring device and inspection system The present invention relates to a radiation monitoring device, comprising a radiation sensitive optical fibre, a photon source and an optical receiver, wherein said photon source is coupled to said optical fibre to transmit light through said optical fibre to said optical receiver and wherein said optical receiver is coupled to signal processing means that process an output signal of said optical receiver according to a mathematical algorithm to determine optical distortions within the optical fibre that are induced by radiation impinging on said optical fibre.
Generally the invention relates to a detector for detecting a particular dose of radiation to which it has been exposed, particularly ionizing radiation such as X-ray and gamma radiation.
Several types of such detectors are known in the art.
The most common among these are gas filled detectors, scintillation detectors and semiconductor detectors.
Gas filled detectors operate by exploiting the ionization produced by incident radiation as it passes through a gas.
Such a counter consists of two electrodes to which a certain electrical potential is applied.
The electrodes are placed in a cylindrical chamber that is filled with a gas like helium, neon or an argon-methane mixture.
When ionizing radiation passes through the chamber, electron-ion pairs are generated in the space between said electrodes which then move under the influence of the electric field.
This induces a current on the electrodes which may be measured and related to the incident radiation level.
Scintillation detectors detect radiation upon induction of luminescence in a scintillator cell.
The scintillator cell is made of a material, which can be a solid (such as anthracene crystals or sodium iodide crystals), liquid, or a gas, that produces sparks or scintillations of visible light when ionizing radiation passes through it.
By means of a photocathode, which is a light-sensitive material that absorbs photons and emits photo-electrons, an occurrence of this light that is generated light is detected.
As the amount of light produced in the scintillator is comparatively small, it is amplified before it is recorded as a pulse or in any other way.
The amplification of the scintillator's light is achieved with a photo-multiplier tube which allows for an amplification or gain by the order of a million.
Semiconductor detectors are solid state devices which essentially operate as ionization chambers filled with a solid semiconductor material.
In semiconductor detectors, an electrical field is established that depends on the distinct properties of n-type and p-type doped
-2- semiconductor material. An energy transfer from the incident radiation to the semiconductor material produces a freed electron and a hole {vacancy} that move to the anode and cathode respectively. The sensitive region of the counter occupies only a few millimetres and the speed of electrons and holes is such that the charge carriers can cross the sensitive region and be collected in times of the order of tens of microseconds. As a result semiconductor detectors have a comparatively fast response time. In addition, since a relatively small amount of energy is required to produce an electron-hole pair in a semiconductor, these detectors exhibit low statistical fluctuations for any given radiation energy and have a linear response over a wide range of energies.
A monitoring device as described in the opening paragraph uses a radiation sensitive fibre as a sensor for impinging radiation to which it is exposed. Such detector is for instance known from US patent USP 10,317,539. This known radiation monitoring device comprises a light source at one end of the optical fibre and a photon detector at the opposite end. It uses radiation induced optical changes in said fibre to measure a total radiation dose of specific ionizing radiation, specifically of high energy photons or neutrons. Said dose is determined by measuring optical attenuation changes as a function of time and temperature that are delivered to the optical fibre by incident radiation.
These known dosimeter systems have in common that they register a total dosage of captured radiation over a duration of time. A field of use of such devices are for in stance X-ray systems that are used for X-ray inspection. These X-ray systems perform a non-destructive inspection of optical hidden features during electronics manufacturing processes. By means of X-ray inspection, extremely high magnified images of micron level features may be displayed that reveal more detail than less sophisticated optical methods. In fact X-ray inspection appears the only practical solution to inspect high complexity printed circuit boards and high density semiconductor components, particularly integrated circuits, microprocessors and solid state memory devices such as flash-memory. A danger, however, is that during inspection or after repeated inspection certain components may become highly radiated or even over-radiated.
This may, in itself, cause physical damage to those components if the radiation dose exceeded a certain safety limit. Accordingly it is important to be able to monitor the radiation dose received by each component.
-3- The known dosimeters, however, have the disadvantage that they only provide an indication of the average dose that was received over the testing area during exposure to said radiation. Especially X-ray radiation fields are not uniform over the entire inspection area so that some components may have been exposed more heavily than others. There is, accordingly, a need for a more precise monitoring device that provides a more accurate radiation dose for each position over the testing area. The present invention has inter alia for its object to provide such a radiation monitoring device and an inspection system in which such a more radiation accurate monitoring device has been implemented.
In order to meet said object, a radiation monitoring device of the type as described in the opening paragraph, according to the present invention, is characterized in that said algorithm allows said processing means to determine said optical distortions as a function of a position along said optical fibre, in that said optical fibre is layed out over a multi-dimensional detection area according to a determined non-linear trajectory, and in that said processing means translate said positions and an incidence of said distortions to spatial coordinates within said detection area. The invention thus uses a radiation sensitive optical fibre together with an optical transmitter and optical receiver that are coupled to said fibre to detect radiation induced changes along said the fibre. Based on the mathematical algorithm that is executed by said processing means, the processing means are capable of calculating the position and incidence, i.e. total occurrence, of these changes as a measure of the radiation dose received at that position along the fibre. Because the trajectory of the fibre over the detection area is known, this linear position along the fibre can be translated into spatial coordinates within said detection area, particularly 2D Cartesian coordinates within that detection area.
The radiation monitoring device of the invention, as a result, does not only provide an indication of a total dose over the entire detection area but also specific knowledge of the particular dosage that was received at each such position. This may then be mapped with (an image of) the object that was exposed to provide information on the dosage at each location of said object, for instance to reveal the particular dosage that was received by specific components residing at those location in a printed circuit board, semiconductor device or any other object or subject that has been exposed to said radiation, including medical applications like X-ray tomography.
-A- A particular embodiment of the radiation monitoring device according to the invention is characterized in that said fibre is a doped optical fibre, in that said optical distortions are optical attenuation changes within the optical fibre that are induced by said radiation impinging on said optical fibre, and in that that said algorithm allows said processing means to determine said optical attenuation changes as a function of a position along said optical fibre, particularly as a distance to said receiver, and in that said processing means translate said positions of said optical attenuation changes to spatial coordinates within said detection area.
In this embodiment a doped optical fibre is used to detect and measure incident ionizing radiation.
This ionizing radiation causes local point defects in the fibre that, in turn, give rise to attenuation changes of a laser pulse that is being sent through the fibre.
The position and magnitude of those attenuation changes may then be derived by said processing means.
A preferred embodiment of the radiation monitoring device according to the invention is characterized in this respect that said photon source is a pulsed photon source, emitting said light as a sequence of consecutive pulses having a limited pulse duration, and in that said optical fibre comprises a distributed optical fibre sensor {DOFS) and in that said optical receiver comprises an optical reflectometer, particularly an optical time domain reflectometer (OTDR). More particularly, a further preferred embodiment of the monitoring device according to the invention is thereby characterized in that said photon source comprises a pulsed laser diode and in that said receiver comprises a photo diode that is sensitive to laser light emitted by said laser diode.
By using Optical Time Domain Reflectometry (OTDR) both size and location of the radiation can be measured.
The photon source, such as the laser diode, launches a sequence of comparatively short pulses into the fibre.
The fibre defects, that are caused by the radiation, act as a reflector.
The reflected light is detected by the optical receiver, such as the photodetector, that is coupled with the processing means.
These processing means may comprising fast sampling electronics.
The timing of the reflected light indicates the location of the defect, whereas the amount of reflected light indicates the size.
By using this technique, the radiation monitoring device according to the invention can create a 2D dose map of incident dose over the entire detection area.
This may, for instance, provide a realtime 2D dose map of received radiation by each component on a printed circuit board or other object that is being inspected
-5- by X-ray exposure and this map can be updated at every cycle of such X-ray inspection process, particularly providing an mGray dose range for the individual components.
Optical Time Domain Reflectometry {OTDR) basically consists in injecting a short and high-peak power optical pulse into an optical fiber and measuring the backscattered Rayleigh power as a function of time. If the group velocity of the optical pulse in the fibre is known, it is straightforward to convert the time scale into the fibre-length scale. The spatial information can therefore be obtained from the pulse round-trip time between the fibre input and a given position along the fibre. OTDR is an optical pulse- echo technique that can be considered as a one-dimensional radar.
Using Optical Time Domain Reflectometry , temporal variations of the Rayleigh backscattered power level allow to measure local losses throughout the fibre. This provides detail about local loss information throughout the fibre and this information can be used to calculate the attenuation coefficient. Due to non-zero losses in the fibre, the power associated with the launched light pulses is gradually attenuated along the fiber and, consequently, the backscattered power is attenuated relative to the input. While light propagates into the fibre, optical pulses encounter Fresnel reflections and Rayleigh scattering locations resulting in a fraction of the signal travelling back, i.e. in the opposite direction.
The optical power received by the optical receiver will be proportional to the optical power pulse at that reflecting location and this information may be used to calculate the position of the site of reflection along the fibre. An advantage of this technique is that it only requires access to the fibre at a single end of the fibre. In a further preferred embodiment, the radiation monitoring device according to the invention is, hence, characterized in that said photon source and said optical receiver are coupled to a same end of said optical fibre, particularly outside the detection area. Particularly, both the optical transmitter and optical receiver may be placed at a same position outside the detection area in order to be shielded from incident radiation.
In principle many types of optical fibres may be used in the monitoring device according to the invention. Particularly doped silica based optical fibres lend themselves as intrinsic distributed optical fibre sensors in the device according to the invention. As dopants, Germanium {Ge}, Phosphorus (P} and Nitrogen {N) may be used to increase the glass refractive index, while
-6- Fluorine (F) or Boron {B) may be used to decrease said refractive index. A particular embodiment of the radiation monitoring device according to the invention is characterized in this respect in that optical fibre comprises a phospho-silicate (P doped Si0O,) optical fibre.
In order to improve the spatial resolution of the detection by the monitoring device it is beneficial that the trajectory of the optical fibre provides a proper coverage over the detection area. To that end, a further preferred embodiment of the device according to the invention is characterized in that said optical fibre is layed out according to a trajectory chosen from a group comprising a flat meander and a flat spiral that substantially covers said detection area.
The windings of such a spiral or turns of a meander may be packed closely together to provide a high sensing density within the detection area. A further embodiment of the device according to the invention is thereby characterized in that said optical fibre is layed out according to a flat meander having alternating turns and elongated portions, in that said elongated portion extend in the detection area lying closely next to one another, and in that said turns are located outside said detection area. In this manner, the packing density within the detection area is served by the elongated, particularly straight portions of the optical fibre, while the turns are made outside the detection area to allow sufficient radius without sacrificing detection density.
In order to properly translate a linear position along the fibre to a spatial coordinate within the detection area, it is important that the optical fibre is layed out according to the intended trajectory. To facilitate this, a further preferred embodiment of the monitoring device according to the invention is characterized in that said optical fibre is supported by a support member that is substantially transparent to said radiation and that comprises guide means that guide said optical fibre into said trajectory, and more particularly in that said guide means comprise a channel in said support member that accommodates said optical fibre. The guidance provided by the support member fixates the optical fibre according to the intended, predetermined trajectory and, as such, ensures, a correct translation between a one dimensional distance along the fibre into two dimensional or three dimensional spatial coordinates within the detection area.
-7- The present invention further relates to an inspection system for inspection of an object by means of radiation, comprising a radiation source for generating a radiation beam and a target area for receiving said object for exposing said object to said radiation beam, wherein at least one radiation monitoring device according to the invention is provided, having its detection area crossing a path of said radiation beam of said radiation source. In a particular embodiment the inspection system according to the invention is thereby characterized in that a first radiation monitoring device is positioned between said radiation source and said target area. This first radiation monitoring device gives a realtime reading of the amount of radiation that is received by each calculated position in the detection area to provide information regarding the exposure of individual locations on the object. To that end, the detection area of the monitoring device preferably extends over the entire target area where the object is received.
A preferred embodiment of the inspection system according to the invention is characterized in that a second monitoring device is positioned downstream of said target area, said second monitoring device having its detection area aligned with the detection area of said first monitoring device, and in that said first radiation monitoring device and said second radiation monitoring device are coupled to processing means that comprise subtraction means to calculate a radiation dose difference between said detection area of said first radiation monitoring device and said detection area of said second radiation monitoring device for said spatial coordinates. By deriving the difference between the output data of the first monitoring device and the output data of the second monitoring device, information is obtained about the actual amount of absorption at every location of the object. This information may be used to secure the integrity and/or safety of the object by protecting it against over exposure. Moreover, also data from muftiple inspections on the same object can be added together to achieve a full total dose map of the end-product, even when those inspection were conducted at different production sites in a production line. To that end a further embodiment of the inspection system according to the invention is characterized in that electronic storage means are provide that store said incidence difference at said spatial coordinates together with an identification of said object, particularly in a database. By storing the output data of consecutive measurements, particularly in a database, the date can be linked to the object that
-8- has been inspected and shared with different manufacturers and/or end-users. This gives the unprecedented opportunity to follow the accumulated dose that an object has received throughout its production cycle. The invention will now be explained in further detail with reference to a specific embodiment and an accompanying drawing. In the drawing: figure 1 shows a plan view of a first example of a radiation monitoring device according to the invention; figure 2 shows a plan view of a second example of a radiation monitoring device according to the invention; figure 3 shows a plan view of a third example of a radiation monitoring device according to the invention; figure 4 shows a cross section of a part of one of the examples of a radiation monitoring device according to the invention; figure 5 shows a cross section of a part of an alternative example of a radiation monitoring device according to the invention; figure 6 shows a schematic view of processing means that can be used in conjunction with a radiation monitoring device according to the invention; and figure 7 shows a schematic representation of an inspection system in accordance with the present invention. It should be noticed that the figures are purely schematic and not drawn to scale. Particularly, certain dimension may have been exaggerated to a higher or lesser extent in order to highlight specific features. Same parts are generally allotted a same reference numeral throughout the drawing.
Figures 1-4 show several embodiments of a radiation monitoring device according to the present invention. Each of the devices of figures 1-3 comprises a support member 10 with a sheet like carrier body 11, see figures 4 and 5, of a material that is substantially transparent to the radiation that is being used, like in these examples a sheet 11 of polymethyl-methacrylate (PMMA). The sheet 11 is provided with a one or more channels or slots at a detection area to accommodate a radiation sensitive optical fibre 20. The channel(s) or slot(s) 15 may be cut or moulded into the material of said support body and guides the fibre into an intended, predetermined trajectory, as shown in the plan views of figures 1-3. The fibre is coupled to an optical interface 30, comprising a photon source 31 and an optical receiver 32 that are mounted to the same sheet 11 or integrated therein. Alternatively to a sheet for supporting the fibre 20, like in these examples, the fibre might also be supported otherwise, like for instance by a surrounding frame in which the fibre is suspended while being spatially spread to provide a 2D detection area.
The fibre 20 may be provided lying bare at the surface of the carrier sheet 11 or may be covered by a top sheet 12 that is also transparent to the radiation that is being used. In this example the cover is made of PMMA, like the bottom sheet, and is glued together with the bottom sheet 11 while enclosing the fibre 20. Instead of PMMA, also other plastics, like for instance polycarbonate and polystyrene, and other materials that are not affected by X-ray radiation may be used for the support body 10. This forms a protective enclosure to the fibre 20, while the fibre is kept precisely in place within one or more of the channels or slots 15. In order to create a proper coverage of said detection area said fibre may be forced into a spiral, meander or other spatial configuration in this manner, as shown in figure 1-3. The curved bends B of the meandering fibre 20 may optionally be provided outside the detection area 10 to allow a sufficient radius, while the straight, elongated portions S of the fibre 20 are accommodated at a short pitch close to one another within the detection area 10 to provide more resolution.
In figure 4 only one side of the carrier body is provided with one or more channels or slots 15 to guide the fibre. A similar system of channels 15 may, however, also be provided at both sides of the support body 11 to accommodate a single fibre at both surfaces of said support body 10 as shown in figure 5. Please note that the slots 15 of the back site lie interlaced in between the channels 15 at the front side, when looking in plan view. This significantly improves the effective packing density of the fibre 20 over the total detection area 10 and thereby the spatial resolution of the monitoring device. The fibre 20 of these examples has typically has a length of the order of 5 to 20 metre, but may be as long as several hundreds of metre with a more narrow pitch, at a diameter of the order of 0,5 millimetre and covers a total detection surface that is typically of the order of 600x600 millimetre in this case. Slots 15 of about 0,6x0,6x0,6 millimetre are cut in the plate 11 to provide some tolerance to the fibre. The support plate typically can have a thickness of the order of 15 millimetre if used single sided as in figure 4 or 30 millimetre if the fibre is routed at both sides of the plate 11.
-10- The fibre 20 of these examples is a phospho-silicate {P doped SiO.) optical fibre that is sensitive to X-ray ionizing radiation. This doped optical fibre is used an inspection system according to the invention to measure a dosage of impinging ionizing radiation. lonizing radiation causes local point defects in the fibre. These defects cause attenuation of a laser pulse sent through fibre. By using Optical Time Domain Reflectometer (OTDR) both size and location of the radiation can be measured. Figure 6 shows a typical setup of an OTDR system as used with the device according to the invention. A laser diode 31 is driven by an electrical pulse generator 41 that produces a train 25 of short optical pulses. The fibre defects caused by the radiation act as a reflector. A photodiode 32 is used to detect the backscattered optical power from the fibre 20 through a directional coupler
33. The timing of the reflected light indicates the location of the defect, while the amount of reflected light indicates the size, which will be proportional to the captured radiation dose. The photodetector 32 is coupled with processing means 40 that process an output signal of said optical receiver 32 according to a mathematical algorithm to determine optical distortions within the optical fibre 20 that are induced by radiation impinging on said optical fibre. These processing means consist of fast sampling electronics to real-time analyse the reflected light. The detected waveform of the optical signal is first amplified by an amplifier 42 and then digitized through an analogue-to-digital-convertor {ADC) 43. The digital output of the ADC 43 is analysed by a fast digital-signal processing (DSP) unit 44. The timing of the DSP 44 is synchronized with the source 31 of the optical pulses so that the propagation delay of each backscattered pulse can be precisely calculated. The losses in the optical fibre 20 may be caused by several mechanisms, most of these effects being non-uniform along the fibre. Therefore, the fibre attenuation coefficient is a function of the location along the fibre. Shorter pulses deliver higher spatial resolutions but carry less energy and require a broader receiver bandwidth. The fast electronics 40 that is applied to investigate the signal, is capable of generating nano-second pulse-times and has sufficient bandwidth for ultra-fast processing of the return pulses. By iteration and averaging the measurement over a number (N) pulses the signal-to-noise ratio (SNR) may be enhanced significantly to create a high dynamic range despite short measuring pulses, resulting in a high spatial resolution within a centimetre to millimetre range. This linear location within the fibre 20 is translated into 2D spatial coordinates within the detection area 10 to give an indication of
-11- the local radiation flux that may be monitored on a screen 45 or other convenient output device. By using this technique the system can, hence, create 2D dose map over the entire detection area 10.
A specific application of such a radiation monitoring device is depicted in figure 7 and involves an inspection system that operates on basis of intrusive radiation. The system comprises a radiation source 60 and a target area 65 to receive an object 1 to be inspected. The target area 65 is part of a table that is substantially transparent to the radiation that is being used in order no to have a significant influence on the measurement. In this case the inspection system is used for X-ray inspection of a sophisticated printed circuit board (PCB) 1 and the table 65 is made of PMMA at the location of the target area 65. The radiation source 60 is a conventional, state of the art X-ray generator that is not further detailed here as a skilled person is presumed to be sufficiently familiar with this technique. The system further comprises imaging means 70 to deliver an X-ray transmission image of the object under inspection.
A first radiation monitoring device S1 according to the invention ís positioned, upstream of the target area 65, between the X-ray source 60 and the object 1 to be investigated. This first detector S1 is coupled to processing means 40 as described above to deliver a 2D map of the X-ray flux to which the sample 1 is exposed. A second monitoring device S2 according to the invention is placed at the downstream side of the target area 65 with the sample 1 to receive the radiation that is transmitted through the sample. This second detector S2 is aligned with the first detector S1 and likewise coupled to similar processing means 40 to deliver a comparable 2D map of the X-ray flux passing through the sample 1. By subtracting the latter figures from those of the first detector 51 for each location, a 2D-map of the actual absorbed dose by each component on the PCB 1 is thus obtained. This information may be represented on a screen 45 or other output device, but is moreover stored in a database and updated at every cycle of X-ray inspection process together with a unique identification of the sample 1. The invention provides a unique manner of acquiring information and knowledge about the spatial distribution of the radiation that is being used. By monitoring the actual amount of exposure and particularly the actual absorption of radiation for each vulnerable spot of the object to be inspected, an unprecedented level of valuable information may thereby be created to safeguard the integrity of the object that was inspected. Although the invention has been
-12- explained in detail with reference to merely a number of embodiments, it will be appreciated that the invention is by no means limited to those examples.
On the contrary many more variations and embodiments are feasible to a skilled person with the scope and spirit of the present invention as emanating from the claims below.
Claims (14)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NL2025411A NL2025411B1 (en) | 2020-04-23 | 2020-04-23 | Radiation monitoring device and inspection system. |
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| NL2025411A NL2025411B1 (en) | 2020-04-23 | 2020-04-23 | Radiation monitoring device and inspection system. |
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Citations (3)
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|---|---|---|---|---|
| JPS62257078A (en) * | 1986-05-01 | 1987-11-09 | Fujikura Ltd | Distribution type radiation measuring system |
| US10317539B2 (en) | 2017-04-14 | 2019-06-11 | Jefferson Science Associates, Llc | Radiation monitor based on wavelength-dependent optical absorption in fused silica optical fibers |
| US20190310381A1 (en) * | 2016-07-08 | 2019-10-10 | Fibermetrix | Device for determining a deposited dose and associated method |
-
2020
- 2020-04-23 NL NL2025411A patent/NL2025411B1/en not_active IP Right Cessation
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS62257078A (en) * | 1986-05-01 | 1987-11-09 | Fujikura Ltd | Distribution type radiation measuring system |
| US20190310381A1 (en) * | 2016-07-08 | 2019-10-10 | Fibermetrix | Device for determining a deposited dose and associated method |
| US10317539B2 (en) | 2017-04-14 | 2019-06-11 | Jefferson Science Associates, Llc | Radiation monitor based on wavelength-dependent optical absorption in fused silica optical fibers |
Non-Patent Citations (3)
| Title |
|---|
| DI FRANCESCA D ET AL: "Distributed Optical Fiber Radiation Sensing in the Proton Synchrotron Booster at CERN", IEEE TRANSACTIONS ON NUCLEAR SCIENCE, IEEE SERVICE CENTER, NEW YORK, NY, US, vol. 65, no. 8, 1 August 2018 (2018-08-01), pages 1639 - 1644, XP011688981, ISSN: 0018-9499, [retrieved on 20180816], DOI: 10.1109/TNS.2018.2818760 * |
| SABATIER CAMILLE ET AL: "6-MeV Electron Exposure Effects on OFDR-Based Distributed Fiber-Based Sensors", IEEE TRANSACTIONS ON NUCLEAR SCIENCE, IEEE SERVICE CENTER, NEW YORK, NY, US, vol. 65, no. 8, 1 August 2018 (2018-08-01), pages 1598 - 1603, XP011688972, ISSN: 0018-9499, [retrieved on 20180816], DOI: 10.1109/TNS.2018.2804663 * |
| ZAGHLOUL MOHAMED A S ET AL: "High Spatial Resolution Radiation Detection Using Distributed Fiber Sensing Technique", IEEE TRANSACTIONS ON NUCLEAR SCIENCE, IEEE SERVICE CENTER, NEW YORK, NY, US, vol. 64, no. 9, 1 September 2017 (2017-09-01), pages 2569 - 2577, XP011660195, ISSN: 0018-9499, [retrieved on 20170913], DOI: 10.1109/TNS.2017.2735546 * |
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