Electronic dosimeters for generating alarms in pulsed radiation fields

Abstract

A portable electronic dosimeter is described, comprising: a plurality of detectors, each detector being configured to detect a type of ionizing radiation, wherein each detector is associated with an amplifier and an event counter, the amplifier being configured to generate an output in response to a plurality of detected photons of the ionizing radiation, and the event counter being configured to generate one or more counts in response to the detected photons of the ionizing radiation within an integration time; and a processor being configured to receive the one or more counts from each of the counters and to determine whether there is overlap among the one or more counts of all of the detectors, wherein if there is overlap, the processor is configured to provide an out-of-range alarm signal.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of priority to U.S. Patent Application No. 62 / 720,277, filed on August 21, 2018. The disclosure of the foregoing application is incorporated herein by reference. Technical Field

[0003] The presently described invention generally relates to electronic personal radiation dosimeter devices and methods for use in pulsed radiation fields. Background Art

[0004] As the use of pulsed ionizing radiation sources increases, the safety of personnel in the presence of these pulsed ionizing radiation sources becomes more important. As used herein, the term "radiation dosimeter" generally refers to a device that measures exposure to ionizing radiation. Such devices play an important role for workers in certain industries where there is conventional radiation exposure. For these workers, it is important to monitor the cumulative dose over time to ensure that their exposure does not exceed a safe level. There are many types of radiation dosimeters available for use, which are divided into two major categories.

[0005] The first type is referred to as a "passive" dosimeter, which is sensitive to ionizing radiation and records a value for the cumulative radiation dose (sometimes also referred to as an "effective dose" or "equivalent dose" value in a biological context, which may include a unit measurement of "Sievert" (Sv) or a unit measurement of "Gray" (Gy) in a physical context). Typical embodiments of passive dosimeters do not have the ability to communicate dose values ​​directly to the user, nor do they have the ability to warn the user of immediate radiation hazards. Passive dosimetry devices, such as thermoluminescence dosimeters (TLDs), are widely used to monitor exposure to radiation. Typical embodiments of passive dosimeter devices provide cumulative exposure readings that represent the dose received over an extended period of time. In some cases, exposure readings are provided weeks or months after actual exposure to ionizing radiation.

[0006] The second type of dosimeter is referred to as an "active" dosimeter, which may include an "electronic personal radiation dosimeter" that continuously measures and provides communications reporting dose values ​​to the user. Because it is monitoring dose values ​​in real time, it may also provide dose rates (e.g., Sv / h) that passive dosimeters cannot provide. Likewise, many embodiments of electronic personal radiation dosimeters typically include an alarm function that provides the user with an audible and / or visual and / or tactile (e.g., vibration) indication that a threshold dose or dose rate value has been reached. Similarly, many embodiments of electronic personal radiation dosimeters typically include a dose history record that provides the user with an indication of the received dose over time. True active dosimetry provides significant benefits over passive dosimetry because the user can be notified in "real time" when the user has entered a radiation field that may be dangerous to the user, thereby providing the user with an opportunity to avoid harm. The term "real time" as used herein generally refers to reporting, depicting, or reacting to an event at the same rate as the event occurs, and sometimes at the same time as the event occurs (e.g., within seconds or fractions of a second), rather than reporting it with a long delay.

[0007] In the following description, "counting mode" is used to mean "pulse counting mode", as described in Chapter 17-II of Glenn / Knoll, Radiation Detection and Measurement, Fourth Edition, which is incorporated herein by reference in its entirety for all purposes. Currently available electronic personal radiation dosimeters are typically operated in counting mode. For example, in a typical embodiment of a counting device, radiated photons are detected and processed into a signal. If the signal matches appropriate parameters (e.g., amplitude, shape, etc.), it is counted as an event corresponding to an increment of the dose (also referred to as a "count"). Typical embodiments also use dead time correction (as described in Glenn / Knoll, Chapter 4-VII, incorporated by reference above). Therefore, the event counting device is able to provide real-time alarms (e.g., audible alarms, visual alarms, or tactile vibration alarms) when the count rate is very high or when the cumulative count reaches a preset level. In this example, counts are collected, and one or more dose equivalents are calculated and displayed based on these counts.

[0008] Traditionally, active dosimetry for ionizing radiation has focused on measurements known as "personal dose equivalents." As used herein, the term "personal dose equivalent" generally refers to an amount of ionizing radiation that represents a safe threshold for exposure, which is the dose equivalent in tissue at a depth (d) below a specific point on the body recommended by the International Commission on Radiation Units and Measurements (ICRU). Examples of personal dose equivalents include what is known as H P (10) The deep dose (e.g. for chest exposure) equivalent safety threshold is called H P(3) Eye dose equivalent safety threshold, and approximately H P (0.07) is a surface dose (e.g., for skin exposure) equivalent safety threshold. One of ordinary skill in the relevant art will appreciate that it is advantageous to monitor dose equivalent values ​​for personnel who may be regularly exposed as part of their occupation, such as those working in the fields of interventional radiology and cardiology, as well as the nuclear power and aviation industries.

[0009] Unlike passive dosimeters, active dosimeters always have an upper limit on dose rate. For example, certain radiation fields are very strong (sometimes referred to as "high fields" or "high intensity fields") and may exceed the range of the detection elements used to count active dosimeters, and need to be detected by the instrument to immediately warn the user ("out-of-range detection") of a potentially dangerous condition. For example, an event counting electronic personal radiation dosimeter may include detection elements, such as one or more sensors, signal processors, and / or counting electronics that typically operate linearly. This can result in missed event counts (sometimes referred to as "dead time"), and in some cases, high fields can cause one or more detection elements to saturate, where the count rate saturates or even decreases while the field strength increases (sometimes referred to as "folding"). Conventionally, the deviation of the measured count rate from a linear dependence on the radiation field strength can be corrected by applying a dead time correction formula. In this example, the limit of the detection range of the current event counting active dosimeter can be demonstrated by the saturation of the count rate at dose rate levels above about typically 1 to 10 Sv / h. However, such dead time correction may only work correctly if the radiation field is of a continuous nature over the analyzed time interval.

[0010] However, currently available counting electronic personal radiation dosimeters are known to have limited performance with respect to so-called pulsed radiation fields, where the dose rate in a radiation pulse may be very high (e.g. too high for proper registration in the instrument), while the dose rate averaged over a macroscopic time (e.g. one second or one minute) is well within the specified dose rate measurement range. Typical examples of such pulsed radiation fields are medical X-ray devices with radiation pulse widths of a few milliseconds or pulsed linear accelerators (LINACs) with pulse widths of typically a few microseconds or X-ray flash instruments with pulse widths of typically 10 to 50 nanoseconds. For a detailed discussion of the effects of pulse width and repetition rate on active electronic dosimeters, see "CONSIDERATIONS CONCERNING THE USE OF COUNTING ACTIVE PERSONAL DOSEMETERS IN PULSED FIELDS OF IONISING RADIATION," Radiation Protection Dosimetry (2010), pp. 1-11, published on January 18, 2010, which is incorporated herein by reference in its entirety for all purposes.

[0011] For pulsed radiation scenarios where the pulse length is much longer than the pulse length of the electronic signal of the active dosimeter, reducing the time interval (time resolution) can solve the problem of insufficient dead time correction or undetected over-range conditions. For example, the Thermo Fisher Scientific FH 40GL-10 instrument allows the counting interval to be set to 1 millisecond. In other words, for pulsed fields in the millisecond range, the pulsed radiation can be processed as continuous radiation and correctly determined as long as the maximum dose rate specified in the pulse is not exceeded.

[0012] It will be appreciated that high intensity fields may exhibit durations significantly shorter than a specified interval that an event counting device is capable of measuring. These ultra-short duration events, where the radiation pulse duration is comparable to or even much smaller than the signal resolution time (or dead time) of the counting device, are often referred to as "radiation flashes". These radiation flashes cannot be accurately measured by currently available active dosimeters and present serious problems to users exposed to them. This has become increasingly important, for example, due to the increased use of pulsed fields in linear accelerator (LINAC) and non-destructive testing (NDT) applications. It will be generally appreciated that for safety considerations of personnel at risk of exposure, it is necessary to accurately measure exposure to such pulsed fields.

[0013] Some embodiments of radiation dosimeters utilize so-called "ionization chambers" that are better suited for detecting pulsed radiation. However, in order to correctly integrate the dose even at low dose rates, a large number of ionization chambers are required. Therefore, the use of ionization chambers is limited to larger devices that cannot be easily carried or worn by the user.

[0014] Compared to ionization chamber radiation dosimeter devices, electronic personal radiation dosimeters have the advantage of achieving comparable sensitivity with a much smaller detector and thus allowing the overall device to be significantly smaller. The international standard IEC 61526 for active dosimeters specifies a maximum size of 15 cm x 3 cm x 8 cm and a maximum weight of 300 g. For the convenience of the wearer, actual electronic dosimeters on the market are usually significantly smaller and lighter.

[0015] Some embodiments of electronic personal radiation dosimeters may include so-called "PIN diode" type detectors, such as embodiments of electronic personal dosimeters described in GB-A-2,255,177B, filed May 7, 1991, entitled "Improvements in or relating to personal radiation dose in indicators," which is hereby incorporated by reference in its entirety for all purposes. The term "PIN diode" (sometimes also referred to as a "p-type, intrinsic, n-type diode") is generally understood by those skilled in the relevant art to include a diode having a wide region of undoped intrinsic semiconductor material contained between a p-type semiconductor and an n-type semiconductor. Advantageously, a PIN diode can be operated in a counting mode or as an ionization chamber, as described in "Determination of X-Ray Flux Using Silicon PIN Diodes," which is hereby incorporated by reference in its entirety for all purposes. For example, while a typical PIN diode detector operated in counting mode can correctly integrate dose even at dose levels close to background (e.g., less than 0.1 μSv / h), a corresponding PIN diode operated in ion chamber mode only provides current at about 1 pA at a dose rate of mSv / h. Because electronic personal radiation dosimeters need to operate correctly at low dose levels, it is advantageous to operate a PIN diode detector in counting mode.

[0016] Compared to passive dosimeters and ionization chambers, current electronic personal radiation dosimeters have the following disadvantages: once the maximum dose rate of continuous radiation is exceeded, the pulsed dose cannot be correctly captured. As long as the dose per X-ray pulse is less than the dose per count in continuous radiation, the electronic personal radiation dosimeter can correctly measure the dose of short-duration (usually < a few microseconds) pulsed X-rays. However, there are certain situations where users are exposed to dose rates that are too large for the correct dose indication in the electronic personal radiation dosimeter. In such cases, due to the fact that the electronic personal radiation dosimeter cannot accurately calculate the measurement of the dose based on the exposure, the electronic personal radiation dosimeter is generally unable to warn the user of danger. For example, the user may be exposed to the direct beam of an industrial X-ray flash generator, which produces a pulsed radiation field that exceeds the measurement capabilities of the electronic personal radiation dosimeter worn by the user.

[0017] Therefore, there is a need for an electronic personal radiation dosimeter system and method that achieves real-time response to pulsed radiation fields or even single x-ray flashes. In addition, it is advantageous and important that the device can immediately warn the operator once the dose rate is too large for the correct dose indication in the device. Systems, methods and products that address these and other needs are described herein with respect to illustrative, non-limiting embodiments. Various alternatives, modifications and equivalents are possible. Summary of the invention

[0018] A portable electronic dosimeter according to a first aspect of the invention is defined in claim 1. It comprises: a plurality of detectors, each detector being configured to detect a type of ionizing radiation, wherein each detector is associated with an amplifier and an event counter, the amplifier being configured to generate an output in response to a plurality of detected photons of the ionizing radiation, and the event counter being configured to generate one or more counts in response to the detected photons of the ionizing radiation within an integration time; and a processor being configured to receive the one or more counts from each of the counters and to determine whether there is overlap in the one or more counts of all the detectors, wherein if there is overlap, the processor is configured to provide an out-of-range alarm signal.

[0019] In some embodiments, the types of ionizing radiation include gamma radiation, beta radiation, neutron radiation, and x-ray radiation. Additionally, in some embodiments, each detector operates in a counting mode. Some embodiments may include 2 or 3 detectors, and in some embodiments, an over-range alarm signal may indicate that a high-intensity pulsed radiation field has been detected. In some cases, at least one detector includes more than one threshold, wherein at least one of the thresholds is greater than a normal signal level from an x-ray.

[0020] Also in some embodiments, coincidence is determined by at least 2 counter values ​​being equal. In the same or alternative embodiments, coincidence of the detector signals is detected by analog coincidence circuitry in a time range of 0.1 to 10 μs. The integration time is in a range of 0.1 ms to 1 s.

[0021] According to a second aspect of the present invention, there is provided a method as claimed in claim 11. The method comprises: detecting a plurality of photons of ionizing radiation using a plurality of detectors, each detector being capable of being used for a type of ionizing radiation; generating an output from each of the detectors in response to a plurality of detected photons; generating one or more counts in response to the detected photons of the ionizing radiation within an integration time; and determining whether there is overlap in the one or more counts of all the detectors.

[0022] The above-mentioned embodiments and embodiments are not necessarily mutually inclusive or exclusive, and whether or not they are presented in combination with the same or different embodiments or embodiments, the embodiments and embodiments can be combined in any manner that does not conflict and is otherwise possible. The description of an embodiment or embodiment is not intended to be restrictive with respect to other embodiments and / or embodiments. Moreover, in alternative embodiments, any one or more functions, steps, operations or techniques described elsewhere in this specification may be combined with any one or more functions, steps, operations or techniques described in the content of the present invention. Therefore, the above-mentioned embodiments and embodiments are illustrative and non-restrictive. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The above and other features will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. In the drawings, like reference numerals indicate like structures, elements, or method steps, and the leftmost digit of a reference numeral indicates the number of the figure in which the referenced element first appears (e.g., element 100 first appears in Figure 1 However, all of these conventions are intended to be typical or illustrative rather than limiting.

[0024] Figure 1 is a functional block diagram of one embodiment of an electronic personal radiation dosimeter and user including an optional wireless receiver;

[0025] Figure 2 is a simplified graphical representation of one embodiment of an X-ray apparatus having a hazardous area or exclusion zone in which short duration high dose rate pulses are present;

[0026] Figure 3 yes Figure 1 A functional block diagram of one embodiment of an electronic personal radiation dosimeter;

[0027] Figure 4 yes Figure 1 A simplified graphical representation of one embodiment of a circuit for an electronic personal radiation dosimeter;

[0028] Figures 5A to 5D is located in the direct beam of the X-ray flash generator. Figure 1 A simplified graphical representation of one embodiment of a detection signal measured by a detector of a dosimeter; and

[0029] Figure 6 is a functional block diagram of one embodiment of a method for providing an out-of-range alert.

[0030] Like reference numerals refer to corresponding parts throughout the several views of the drawings. DETAILED DESCRIPTION

[0031] As will be described in more detail below, embodiments of the described invention include an active electronic personal radiation dosimeter that includes multiple detectors and alarms configured to issue an excessive radiation warning if the dose in a short duration radiation pulse is greater than the instrument can handle accurately enough.

[0032] Figure 1 A simplified illustrative example of a dosimeter 100 typically worn on a user 110 is provided. Figure 1 Also illustrated is a receiver 130 that receives one or more wireless communications from the dosimeter 100 and, in some embodiments, can provide real-time information of the radiation dose detected by the dosimeter 100 to the user 110 based on the received communications. In some embodiments, the receiver 130 can include a smart phone, a tablet computer, other general purpose device with wireless capabilities, or any receiver type device known in the field of active dosimetry. The term "close proximity" as used herein with reference to the spatial relationship between the dosimeter 100 and the user 110 generally refers to a position within a range where the user 110 can clearly identify a signal from the dosimeter 100 and respond accordingly. For example, the acceptable range can depend on the type and / or strength of the signal provided by the dosimeter 100 or a combination of signals, such as auditory, visual, or mechanical (e.g., vibration) signals. The arrow pointing from the dosimeter 100 to the user 110 indicates the direction of the information flow, which includes digital information about the accumulated dose, the current dose rate, and various immediate alarm notification means, which can include optical signals, auditory sounders, and tactile vibration alarms. The measured data and alarm status can be transmitted to an optional wireless receiver.

[0033] Likewise, in some embodiments, the dosimeter 100 may be configured to interface with a central base station when not in use by the user 110. Embodiments of the central base station may provide the dosimeter 100 with charging capabilities, as well as a network connection that provides the dosimeter 100 with the ability to transmit data to other computing devices via a network and / or receive information such as software updates, test parameters, security identification codes, etc. In addition, some or all embodiments of the central base station may include a processor or microprocessor and data storage elements, which may be particularly useful if a consistent network connection is not available.

[0034] As described above, in the case of short duration pulses at high intensity (e.g., those occurring in the direct beam of certain X-ray sources), the amplifiers of the detectors of an electronic dosimeter may be driven into saturation. This is because within the amplifier integration time of typically a few microseconds, several photons ionize the sensitive volume of the detector. For a given photon energy up to the saturation of the amplifier, the resulting amplifier output signal may have a much higher amplitude than that produced by a single ionization event. Such high dose rate short pulses may produce synchronous signals (sometimes also referred to as coincidence) in all detector channels, such as a signal of one count per X-ray flash in each detector channel.

[0035] Figure 2 An illustrative example is provided of an X-ray source 200 (e.g., which may include an X-ray flash generator) having an exclusion zone 207, which is typically defined by the manufacturer of the X-ray source 200 as an area where no human beings may be present during exposures. The purpose of an active dosimeter according to the present disclosure is to:

[0036] a) Correctly integrate the received dose from the X-ray source 200 outside the regions 207 and 215

[0037] b) correctly accumulate the received dose from the X-ray source 200 in the region 207 and provide a warning during the extended stay in this region

[0038] c) Providing an immediate warning to the user in the zone 215. During the relevant short-term exposure (typically a few seconds), until the person is able to react and leave the danger zone 215, the dose can eventually be fully registered.

[0039] Moreover, as described above, electronic personal radiation dosimeters typically use PIN diodes as detectors operating in a counting mode. For example, an embodiment of the dosimeter 100 may include at least two detectors, each of which may have one or more signal processing elements, which in some embodiments may include one or more amplitude detectors configured to detect different types of radiation. However, it will also be understood that the dosimeter 100 may include three or more detectors as will be described in more detail below. Therefore, this example should not be considered limiting.

[0040] Figure 3 An illustrative example of an embodiment of a dosimeter 100 capable of providing an excessive radiation warning using at least two sensors, each of which is configured to detect a different type of ionizing radiation. Figure 3 Event count sensors 307 and 309 are illustrated, each of which is capable of measuring a particular aspect of the radiation field 300 in a complementary manner. Figure 3 Also illustrated are additional components of the dosimeter 100, such as amplifiers 317 and 319, which are configured to operate with the event count sensors 307 and 309. However, it will be appreciated that additional signal processing components (e.g., comparators, etc.) known to those of ordinary skill in the art may also be included. Figure 3 In the example of , amplifiers 317 and 319 each receive an output from its corresponding event counting sensor 307 or 309 and provide a measure of the dose of events detected from the radiation, which is then provided to a corresponding embodiment of a counter 327 or 329. An embodiment of a counter 327 or 329 integrates the number of events detected over an integration time (e.g., which may include a range between 1 ms and 1 second) and communicates a measure, such as a count rate, to a processor 340 (e.g., an average number of detected events per unit time, such as counts per second "cps").

[0041] Also in Figure 3In an example of, the processor 340 may include one or more processors and / or microprocessors coupled to a system memory 341, the system memory including one or more data storage elements that may include solid-state storage technology known in the relevant art. In the described embodiment, the processor 340 uses control logic (e.g., a software program, including program code) stored in the system memory 341. The control logic causes the processor to perform the functions described herein when executed by the processor 340. For example, the processor 340 implements software that executes a processing algorithm that receives input from event counters 327 and 329 and sends information to / receives information from the user interface 350. In addition, the alarm device 380 may include one or more elements that are configured to signal an event or condition to the user 110, the event or condition may include but is not limited to a sounder, a vibration element, and / or an optical alarm indicator.

[0042] Figure 3 An embodiment of a wireless device 360 ​​that may include a radio element and a wireless antenna is further illustrated. The wireless device 360 ​​may communicate with the receiver 130 via any wireless technology known to a person of ordinary skill in the relevant art, and may depend at least in part on various standards. The standards may include, but are not limited to, transmission range, data security, power requirements, physical dimensions of the radio and / or antenna, one-way or two-way communication, or other standards. For example, direct device-to-device communication may be achieved using a technology commonly referred to as "Bluetooth," which has become a standard for exchanging data over short distances using short wavelength UHF radio waves. Alternatively, the wireless device 360 ​​may communicate with the receiver 130 via an intermediary. Some examples of communication intermediaries using an intermediary device include so-called Wi-Fi that communicates via a wireless router device and cellular-based communications (e.g., text-based communication standards (also referred to as "Short Message Service" (SMS)) utilizing cellular communication points supported by telecommunications providers.

[0043] In the described embodiments, the counting sensors 307 and 309 may include any type of event counting sensor known in the field of active dosimetry. For example, each of the event counting sensors 307 and 309 may be enabled to detect one or more of gamma radiation, beta radiation, neutron radiation, and X-ray radiation. The specific sensor technology may depend at least in part on the type of radiation that the embodiment of the dosimeter 100 is designed to measure. In the present example, some embodiments may include so-called photodiodes, which may include a "PIN diode detector" capable of measuring at least gamma radiation and X-ray radiation. Moreover, the various components of the dosimeter 100 receive power from a power supply 370, which may include one or more batteries, which in some embodiments may be rechargeable. Similarly, the user interface 350 may include a display (e.g., a liquid crystal display, a touch screen including a graphical user interface (GUI), or other types of display interfaces known in the relevant art) and / or one or more buttons. In some embodiments, the alarm device 380 may include a speaker interface for auditory communication (e.g., an alarm message or alarm), one or more visual alarm indicators, and / or a tactile alarm indicator.

[0044] Figure 4 A schematic illustration of an exemplary embodiment of a circuit design implemented by a dosimeter 100 is provided, which uses three PIN diode detectors (415, 417, 419). Ionizing radiation, including photons or beta particles, deposits charge in the intrinsic regions of the diodes of detectors 415, 417, 419, which produces charge pulses that are amplified by amplifiers 425, 427, 429 and provide "detector amplifier outputs" denoted as A1, A2, and A3. The signal is then amplitude discriminated (sometimes referred to as a "discriminator") by one or more threshold comparators (435a, 435b), (437a, 437b), (439a, and 439b). The signal from each threshold comparator is counted by a separate counter (445a, 445b), (447a, 447b), (449a, and 449b) and transmitted to processor 340. In the presently described example, each photon that interacts in the sensitive volume of the detector is counted and then corrected for dead time losses. The number of dead time corrected counts from each detector is multiplied by the dose per count factor for each counting channel and then summed to yield a detected dose value.

[0045] continue Figure 4In an example of a PIN diode detector 415, 417, or 419, each embodiment is configured to detect a specific type of radiation. For example, PIN diode detector 415 may be configured to detect so-called "hard gamma" radiation, PIN diode detector 417 may be configured to detect so-called "soft gamma" radiation, and PIN diode detector 419 may be configured to detect so-called "beta" radiation. Each PIN diode detector may be combined with an appropriate filter to allow detection of a specific radiation energy. Processor 340 performs counter readouts at regular intervals, which may include 1 ms intervals or other interval periods that may be used for a particular application.

[0046] In typical operation of the dosimeter 100, two or more of the counter embodiments may output a value equal to one count, indicating that the detected radiation rate of the associated embodiment of the PIN diode detector has exceeded the range of the detector (e.g., the detector is saturated). However, the random occurrence of all embodiments of counters 445, 447, or 449 outputting a value equal to one count is highly unlikely because the threshold of at least one counter embodiment is set high enough so that the range of the channel is not exceeded by normal radiation levels, even at relatively high dose rates. As used herein, the term channel generally refers to the path from one of the PIN diode detectors (e.g., PIN diode detector 415, amplifier 425, comparator 435, counter 445) to the processor 340. For example, it is highly desirable that the channel with the highest threshold can only be exceeded by high energy photons (e.g., from Cs-137 or by a pileup of several lower energy X-ray photons at very high dose rates within the amplifier integration time, as they occur during an X-ray flash pulse). Thus, a random occurrence where all counters (e.g., 2 counters, 3 counters, 6 counters, etc., according to an embodiment) transmit a value equal to one count is considered to be the result of, for example, a high intensity pulsed field event (e.g., from an X-ray flash pulse, which presents a potential hazard to the user 110). In the embodiments described herein, in this situation, the dosimeter 100 may not provide an accurate dose accumulation, however, it is clearly associated with a potentially harmful level of radiation and is therefore used to trigger the alarm function of the dosimeter 100.

[0047] In some embodiments, the likelihood of random alarms may be further reduced by providing a so-called coincidence circuit that may be implemented in hardware, firmware, or some combination thereof. Figure 4 The circuit of includes an AND gate 451, which is a basic digital logic gate that acts according to a set of rules.

[0048] As described herein, AND gate 451 can provide so-called "coincidence" that can be used by processor 340 (see Glenn / Knoll, 4th edition, Chapter 17-B2, incorporated by reference above). In a typical embodiment, if a synchronous event is detected in all detector channels, the output of AND gate 451 provides a signal to processor 340. In other words, when all counters (e.g., counters 415, 417, and 419) provide equal values ​​(e.g., one count) for an event that includes multiple pulses within an integration period (e.g., one second), processor 340 determines that there is a coincidence. For example, AND gate 451 receives detector amplifier outputs A1, A2, and A3 from each of threshold comparators 435, 437, and 439 and generates a coincidence time that is approximately the width of the analog pulse, which can be approximately 5 μs.

[0049] Other methods of determining coincidence events may also be employed, including, for example, reading the counters at relatively large intervals (up to one second intervals) and determining that all counters have an equal condition as a criterion for a pulsed radiation event. The advantage of this method is that the processor 340 can remain dormant most of the time to reduce energy consumption and increase battery life, and can be implemented on the instrument by changing the firmware without changing the hardware components. However, this method is limited to applications with continuous radiation levels near the background, because at the typical sensitivity of the PIN diode detectors used in electronic personal dosimeters (about 5nSv per detected pulse), occasional random coincidences may occur at dose rates approaching a count rate of 1 count per readout interval. Another method may include speeding up the readout to a smaller time interval, such as a readout interval of about 1ms. This will increase the useful operating range of the continuous radiation dose rate by about 1000 times compared to reading at relatively large intervals. In addition, the AND gate 451 may include a more complex circuit that only observes the leading edge of the pulse, and the coincidence time may be provided in accordance with the X-ray pulse flash magnitude (e.g., <500ns; see the method described below). Figure 5D leading edge of the signal in ).

[0050] Yet another method includes using at least one of the detector thresholds with a high threshold level. For example, the high threshold channel is triggered only by high energy photons (e.g., from Cs-137 or by the accumulation of several lower energy X-ray photons at very high dose rates within the amplifier integration time, as they occur during an X-ray flash pulse). This method can be advantageously combined with the first three methods, and avoids random coincidence of all continuously radiated X-ray levels.

[0051] Figure 5A , 5B, 5C and 5D each provide an illustrative example of amplifier output pulses (e.g., A1, A2 and A3) from three detectors (e.g., PIN diodes 415, 417 and 419) with increasing dose per X-ray pulse. Specifically, Figure 5A The example shows detection signals 510, 520 and 530 measured by the detector of a dosimeter located in the direct beam of a Golden Industries Model XR200 X-ray flash generator at a distance of 10 m, which is produced by an approximately 0.02 μSv dose pulse. At these dose values ​​per X-ray flash pulse, the amplitude of the detector amplifier varies with the number of photons interacting in the active detector volume and the total charge deposited during the pulse duration. Each X-ray flash produces a different amplifier output signal and can be registered or unregistered based on the simulated pulse exceeding the threshold.

[0052] As the dose per X-ray flash increases, the amplitude of the amplifier output pulse increases and becomes equal for all detectors regardless of the photon energy, because a large number of photons ionize the active detector volume during the integration time, and the resulting pulse amplitude becomes independent of the energy of the individual photons because it is averaged over a large number of photons. Figure 5B , 5C 5D illustrates that as the pulse dose increases, signals 510, 520, and 530 gradually converge. In this example, Figure 5B The response to a dose of about 0.02 μSv is shown, and Figure 5C The response to a dose of about 0.06 μSv is shown. Figure 5D Amplifier output signals 510, 520 and 530 are shown resulting from a high dose pulse equal to or greater than about 0.1 μSv during the charge collection time. Importantly, the shapes of the signals 510, 520 and 530 are the same even though they are generated by different PIN diodes with different filtering and different sizes.

[0053] In the presently described invention, if Figure 5D As illustrated in , the occurrence of a synchronization signal response (e.g., coincidence) indicates that the output of each of the amplifiers has saturated due to multiple photons ionizing the detector, thereby determining that the X-ray flash dose is greater than the accurately accumulated X-ray flash dose. Therefore, when the synchronization signal appears in all discriminator channels, the dosimeter 100 generates an out-of-range warning for the user 110, which indicates a dangerous condition caused by the X-ray flash source.

[0054] Figure 6An example of a method for providing an out-of-range alarm is provided. For example, in step 610, the processor 340 reads a counter from each detection channel and determines in step 620 whether there is a signal coincidence (e.g., a synchronization signal). If the processor 340 determines that there is a signal coincidence, then as illustrated in step 630, the processor 340 issues an out-of-range alarm to the user 110, which may include one or more audible alarms, visual alarms, tactile alarms, or some combination thereof. The processor 340 determines the dose and dose rate values ​​to the user 110 as part of the normal operation of the dosimeter 100.

[0055] Various embodiments and implementations have been described, and it should be apparent to those skilled in the relevant art that the foregoing is illustrative and non-restrictive only, and is presented by way of example only. Many other schemes for allocating functions between the various functional elements of the illustrated embodiment are possible. In alternative embodiments, the functions of any element may be performed in various ways.

Claims

1. A portable electronic dosimeter, comprising: a plurality of detectors, each detector configured to detect a different type of ionizing radiation, wherein each detector is associated with an amplifier and an event counter, the amplifier being configured to generate an output in response to a plurality of detected photons of the ionizing radiation, and the event counter being configured to generate one or more counts in response to the detected photons of the ionizing radiation within an integration time; as well as A processor configured to receive the one or more counts from each of the counters and determine whether there is overlap in the one or more counts of all of the detectors, wherein if there is overlap, the processor is configured to provide an out-of-range alarm signal, wherein the overlap is determined by at least 2 counter values ​​being equal.

2. A dosimeter according to claim 1, wherein: Each detector was operated in counting mode.

3. The dosimeter according to claim 1, wherein: The plurality of detectors includes 2 detectors.

4. The dosimeter according to claim 1, wherein: The plurality of detectors includes three detectors.

5. The dosimeter according to claim 1, wherein: The out-of-range alarm signal indicates that a high intensity pulsed radiation field has been detected.

6. The dosimeter of claim 1, wherein: The integration time is in the range of 0.1 ms to 1 s.

7. The dosimeter according to claim 1, wherein: Said coincidence of the detector signal is detected by analog coincidence circuitry in a time range of 0.1 to 10 μs.

8. The dosimeter of claim 1, wherein: Such types of ionizing radiation include gamma radiation, beta radiation, neutron radiation, and x-ray radiation.

9. The dosimeter of claim 1, wherein: At least 1 detector includes more than 1 threshold.

10. A dosimeter according to claim 9, wherein: At least one of the thresholds is exceeded only by high energy photons.

11. A method comprising: using a plurality of detectors to detect a plurality of photons of ionizing radiation, each detector being capable of being used for a different type of ionizing radiation; generating an output from each of the detectors in response to a plurality of detected photons; generating one or more counts in response to said detected photons of said ionizing radiation during an integration time; as well as A determination is made as to whether there is an overlap in the one or more counts of all of the detectors, wherein the overlap is determined by at least two counter values ​​being equal.

12. The method according to claim 11, wherein: If there is an overlap, an out-of-range alarm signal is provided.

13. The method according to claim 11, wherein: Each detector was operated in counting mode.

14. The method according to claim 11, wherein: The plurality of detectors includes 2 detectors.

15. The method of claim 11, wherein: The plurality of detectors includes three detectors.

16. The method of claim 12, wherein: The out-of-range alarm signal indicates that a high intensity pulsed radiation field has been detected.

17. The method of claim 11, wherein: The integration time is in the range of 0.1 ms to 1 s.

18. The method of claim 11, wherein: Said coincidence of the detector signal is detected by analog coincidence circuitry in a time range of 0.1 to 10 μs.

19. The method of claim 11, wherein: Such types of ionizing radiation include gamma radiation, beta radiation, neutron radiation, and x-ray radiation.

20. The method of claim 11, wherein: At least 1 detector includes more than 1 threshold.

21. The method of claim 20, wherein: At least one of the thresholds is exceeded only by high energy photons.

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