RU2794236C1 - Complex for measuring the light yield of scintillation strips - Google Patents

Abstract

FIELD: measurement technology.

SUBSTANCE: complex for measuring the light yield of scintillation strips contains a two-channel block for analysing signal scans, an electronic computer and a light-insulated box for placing a tested scintillation strip, inside which a particle source positioning device is fixed and a photodetector of optical signals of the scintillation strip is installed.

EFFECT: reduced time for measuring the light yield of a scintillation strip.

8 cl, 2 dwg

Description

The field of technology to which the invention belongs

The invention relates to the field of measurement technology, namely to scintillation detectors of ionizing radiation, and can be used to test and study the characteristics of thin scintillation strips (strips) before installing them in coordinate-tracking detection systems, including muon hodoscopes.

State of the art

Coordinate track detectors are widely used in solving problems in various fields of physics (nuclear physics, particle physics, space and astrophysics, etc.). A separate subclass is coordinate-tracking detectors based on plastic scintillators.

As a rule, coordinate track scintillation detectors are made on the basis of narrow thin scintillation strips (strips) laid in one plane, often called the coordinate layer. If a charged elementary particle passes through such a layer, a scintillation flash is generated in the corresponding strip, which is recorded by a photodetector. Thus, by actuation of the photodetector, the number of the actuated strip is determined, which is converted into a coordinate. If the instrument alternates coordinate layers with mutually perpendicular arrangement of scintillation strips, then it is possible to restore the charged particle track.

Recently, muon scintillation hodoscopes, consisting of a large number of coordinate layers and thousands of scintillation strips, have been used to conduct various applied studies in the field of muon diagnostics of large-scale objects and natural phenomena.

Strips for coordinate track detectors are made of plastic with the addition of scintillating agents. Light collection is carried out from the end of the strip, so the amplitude of the recorded signal strongly depends on the distance between the photodetector and the place where the particle passes. In addition, the magnitude of the signal depends on the optical properties of the plastic. To improve light collection, spectrum-shifting optical fibers are often used, which are glued into the strip along its entire length; in addition, scintillation strips are coated with various reflective paints.

Since the optical properties of plastics, the quality of adhesives, fibers and paints can vary significantly from batch to batch, it is necessary to test scintillation strips in order to determine the parameters of their responses to charged particles.

In the embodiment of the invention from patent RU 2461903 09/20/2012, a device for calibrating muon hodoscopes is described, consisting of two horizontal coordinate detectors, a controller, a coincidence circuit and a computer. The hodoscope to be calibrated is placed between two parallel horizontal coordinate detectors. The outputs from all layers of the muon hodoscope are connected to the controller inputs. The outputs of both coordinate detectors are connected to the inputs of the coincidence circuit. The output of the coincidence circuit is connected to the same controller. When a muon passes through the coordinate detectors, the coincidence circuit is triggered, the signal from which is transmitted to the controller. When the controller receives a signal from the coincidence circuit, it reads the coordinates of the passed muon from all layers of the hodoscope. The controller transmits to the computer information about the track of the muon that passed through the coordinate detectors and the corresponding information from the hodoscope. The computer evaluates the efficiency of operation of individual channels of the hodoscope, and also plots the spatial-angular distributions of the muon flux passing through the coordinate planes and compares them with the distributions obtained from the muon hodoscope.

The main disadvantage of the described device is the fact that it calibrates the hodoscope strips after its assembly, and if low-quality strips are found in the hodoscope, it becomes necessary to dismantle them from the already assembled device.

From the patent for invention RU 2664928 08/23/2018, a device for monitoring the parameters of a scintillation detector is known. The device consists of two auxiliary particle detectors, a circuit for measuring and digitizing the pulse amplitude, a coincidence circuit, a controller, and a computer. The scintillation detector under test, consisting of a scintillator and a photodetector, is placed between the auxiliary particle detectors. In this case, it is possible to move the auxiliary detectors along the coordinate axis. The output of the scintillation detector from the photodetector is connected to the input of the circuit for measuring and digitizing the pulse amplitude. Auxiliary detectors are connected through a coincidence circuit to the second of the inputs of the circuit for measuring and digitizing the pulse amplitude. The output of the circuit for measuring and digitizing the pulse amplitude is connected through the controller to the computer. The device works as follows. When a muon flies through the auxiliary detectors and the scintillation detector, the signal from the output of the photodetector arrives at the circuit for measuring and digitizing the pulse amplitude, as well as from the coincidence circuit. The digitized value of the signal amplitude of the scintillation detector is fed to the computer through the controller. The disadvantage of this device is the use of relativistic particles (atmospheric muons) as a source, such a device has a low rate of statistics collection and requires a long time for measurements.

From the articles of N.V. Ampilogova et al. “Use of the URAGAN muon hodoscope for calibrating charged particle detectors”, Izvestiya RAN. Physical series, 2015, vol. 79, no. 3., pp. 420-422 and O.I. Likiy et al. “Investigation of the characteristics of the scintillation detectors of the NEVOD-SHAL facility”, Experimental Instruments and Techniques. 2016. No. 6. S. 5-13 known device for studying the characteristics of detectors of charged particles. The device consists of a muon hodoscope, a controller, a signal sweep analysis unit, and an electronic computer. The planes of the hodoscope are connected to the controller, the output of the controller is connected to an electronic computer. The signal sweep analysis unit is also connected to an electronic computer. In addition, there is a synchronization line from the controller to the signal sweep analysis unit. The investigated detector of charged particles is mounted on the muon hodoscope and connected to the signal sweep analysis block. The atmospheric muon passes first through the detector being tested, and then through the hodoscope. In this case, the controller transmits a clock signal to the signal sweep analysis unit, upon receipt of which the signal sweep analysis unit transmits the digitized sweep to the electronic computer. The controller at this time also transmits data to the electronic computer, according to the hodoscope data, the electronic computer reconstructs the muon track and calculates the point at which the muon crosses the tested detector. The measurements are repeated many times, resulting in the dependence of the response of the tested detector of charged particles on the coordinates of the passage of the particle. The disadvantage of this device is the low speed of the measurements, since atmospheric muons pass through one square centimeter approximately once every two minutes. Thus, it takes 2-3 days to conduct a complete examination of the detector.

In the patent for invention RU 2647222, March 14, 2018, a device for controlling the output of scintillations and photoluminescence of powdered scintillators and phosphors is described, consisting of a source of ²⁴¹ Am alpha particles, a wire frame for attaching the sample and an alpha source, a photomultiplier, a spectrometric amplifier, a multichannel amplitude analyzer and Teflon reflector. A test sample of a powdered scintillator or phosphor is mounted on a wire frame, and a source of alpha particles is fixed opposite it. The frame is covered with a Teflon light reflector, the volume of which is viewed by a photomultiplier tube, the output of the photomultiplier tube is connected to the input of a spectrometric amplifier, the output of the spectrometric amplifier is connected to the input of a multichannel amplitude analyzer. An alpha particle emitted by ^{the 241} Am isotope with an energy of 5.5 MeV enters the test sample of the scintillator, causing a glow in it, flash photons are recorded by a photomultiplier, the signals of which are amplified by a spectrometric amplifier and processed by a multichannel amplitude analyzer. This device has two disadvantages: firstly, it is intended for testing samples of powdered scintillators and phosphors several centimeters in size and, in the proposed form, cannot be used to test scintillation strips several meters long, and secondly, the proposed device uses heavy nonrelativistic alpha particles, the effect of which on the scintillator differs from the effect of light relativistic muons and electrons.

The closest analogue (prototype) to the claimed invention is the device described in the article by A.I. Teregulov "Stand for testing scintillation strips", Proceedings of the 10th Baksan Youth School of Experimental and Theoretical Physics, 2010, vol. 2, 277-286. The device consists of a light-isolated box, a photodetector of optical signals from a scintillation strip, a two-channel block for analyzing signal sweeps, an electronic computer, a coincidence circuit, a positioning device, and a muon telescope consisting of two small scintillation counters. The tested scintillation strip is fixed inside the light-insulated box, the end of the strip is in contact with the photodetector of optical signals of the scintillation strip, the output of which is connected to the first input of the two-channel signal sweep analysis unit, which is connected by a data bus to an electronic computer. A muon telescope is fixed on the muon telescope positioning device installed inside the box. The muon telescope positioning device allows you to manually move the muon telescope along the test scintillation strip. The outputs of the scintillation counters included in the muon telescope are connected to a coincidence circuit, the output of which is connected to the second input of the two-channel signal sweep analysis unit. The muon telescope is located above the test strip, the near-vertical atmospheric muon first crosses the scintillation counters, and then the test scintillation strip. The signals from the counters of the muon telescope are fed to the coincidence circuit, which generates a clock signal that arrives at the second input of the two-channel block for analyzing signal sweeps. When a muon passes through the test scintillation strip, a scintillation flash is generated, the photons of which fall on the photodetector of the optical signals of the scintillation strip, the signal from the photodetector arrives at the first input of the two-channel block for analyzing signal sweeps. With repeated repetition of measurements, a response histogram is formed, after processing which the average value of the response of the tested scintillation strip to a muon with known coordinates is calculated. Then, with the help of the muon telescope positioning device, the position of the muon telescope is changed and the measurement cycle is repeated. The disadvantage of the prototype is the long measurement time, since the muon telescope allows you to select only a few particles per minute from the atmospheric muon stream, so the prototype needs more than a day to fully measure the light output of the scintillation strip.

Disclosure of the essence of the invention

The technical result of the invention is to reduce the time of measuring the light output of the scintillation strip many times over.

The specified technical result is achieved due to the fact that the complex for measuring the light output of scintillation strips, containing a two-channel block for analyzing signal scans, an electronic computer and a light-insulated box for placing the tested scintillation strip, inside which a particle source positioning device is fixed and a photodetector of optical signals of the scintillation strip is installed, the output of the photodetector of the optical signals of the scintillation strip is connected to the first input of the two-channel block for analyzing signal sweeps, which is connected to the electronic computer by a data bus, the complex includes a fixed-energy electron source installed on the particle source positioning device, and the particle source positioning device is additionally equipped with an electric drive and a controller for automating control of the position of the particle source, while the electric drive is in functional communication with the controller, which is connected to an electronic computer, the output of the fixed energy electron source is connected to the second input of the two-channel signal sweep analysis unit, while the fixed energy electron source consists of a housing , inside which a beta-emitter, a deflecting magnet, a scintillation fiber and a triggering photodetector are fixed, in the lower part of the fixed energy electron source housing there is a collimating hole, the scintillation fiber is fixed above the collimating hole, and the end of the scintillation fiber is in optical contact with the triggering photodetector.

In a particular case, the ⁹⁰ Sr isotope is used as a beta emitter.

In another particular case, the ⁹⁰ Y isotope is used as a beta emitter.

In another particular case, the ¹³⁷ Cs isotope is used as a beta emitter.

In a particular case, a vacuum photomultiplier tube is used as a photodetector of optical signals from a scintillation strip.

In another particular case, a silicon photomultiplier is used as a photodetector of the optical signals of the scintillation strip.

In a particular case, a vacuum photomultiplier is used as a triggering photodetector.

In another particular case, a silicon photomultiplier is used as a triggering photodetector.

Brief description of the drawings

On FIG. 1 shows a schematic diagram of a complex for measuring the light yield of scintillation strips. The numbers in Fig. 1 marked:

1 - light-insulated box;

2 - tested scintillation strip;

3 - photodetector of optical signals of the scintillation strip;

4 - two-channel block for analyzing signal sweeps;

5 - electronic computer;

6 - source of electrons of fixed energy;

7 - device for positioning the source of particles;

8 - electric drive;

9 - controller.

On FIG. 2 discloses a schematic diagram of a fixed energy electron source (item 6 in FIG. 1). The numbers in Fig. 2 marked:

10 - body of a fixed energy electron source;

11 - collimating hole;

12 - beta emitter;

13 - deflecting magnet;

14 - scintillation optical fiber;

15 - triggering photodetector.

Implementation of the invention

As shown in FIG. 1, in accordance with the present invention, the complex for measuring the light output of scintillation strips contains a light-insulated box 1, inside which the tested scintillation strip 2 is placed, a photodetector of optical signals of the scintillation strip 3 is leaned against the end of the tested scintillation strip 2, the output of which is connected to the first input of the two-channel scan analysis unit signals 4. The two-channel block for analyzing signal scans 4 is connected to an electronic computer 5 by a data bus. Inside the light-insulated box 1, a particle source positioning device 7 is fixed, equipped with an electric drive 8 and a controller 9 for automating control of the particle source position, the controller 8 is in functional communication with the controller 9, which is connected to an electronic computer 5. A source is installed on the particle source positioning device 7 fixed-energy electrons 6, connected to the second input of the two-channel signal sweep analysis block 4. As shown in FIG. 2, the fixed energy electron source 6 consists of a fixed energy electron source housing 10, in the lower part of which there is a collimating hole 11, a beta emitter 12, a deflecting magnet 13, a scintillation fiber 14 and a triggering photodetector 15 are fixed inside the fixed energy electron source housing 10. The scintillation fiber 14 is fixed above the collimating hole 11, the end of the scintillation fiber 14 is in optical contact with the trigger photodetector 15. The output of the trigger photodetector 15 is the output of a fixed energy electron source 6.

An example of a specific implementation of the invention. The test scintillation strip 2, 3000 mm long, 10 mm wide and 7 mm thick, is placed inside a light-insulated box 1, which is 4000 mm long, 400 mm wide and 400 mm high and is made of 12 mm plywood painted with black paint to improve light isolation. The end face of the tested scintillation strip 2 is pressed against the photodetector of optical signals of the scintillation strip 3; in this case, the photodetector of optical signals of the scintillation strip 3 is the FEU-115M vacuum photomultiplier. The anode output of the photomultiplier is connected by means of a coaxial cable to the first input of the two-channel block for analyzing signal scans 4. To maintain light insulation, the coaxial cable enters the wall of the light-insulated box through the cable gland. In this case, a two-channel digital oscilloscope with a scanning ADC is used as a two-channel signal sweep analysis unit 4, having a sampling rate of 2.5 Gsamples/s, which makes it possible to measure the shape of the photomultiplier signals with good accuracy. The two-channel signal sweep analysis unit 4 is connected to an electronic computer 5, which in this case is a personal computer. The digital oscilloscope and the personal computer are connected to each other by a USB bus.

On the inner side of the light-insulated box 1, along one of its long walls, a particle source positioning device 7 is fixed, to which a fixed-energy electron source 6 is attached. to it with a source of electrons of fixed energy 6. The carriage is equipped with an electric drive 8, made in this case on the basis of a stepper motor. The position of the carriage is controlled by a controller 9 connected to a personal computer 5 via a USB bus.

In this case, the fixed energy electron source 6 has a length of 120 mm, a width and a height of 60 mm each. The housing of the fixed energy electron source 10 is made of aluminum with a thickness of 5 mm. This thickness of the hull is sufficient to protect the operators of the complex from beta rays. A beta emitter 12 is fixed inside the body of the fixed energy electron source 10. In this case, the ⁹⁰ Sr isotope with an activity of 200 Bq is used as the beta emitter. Also, inside the housing of the fixed energy electron source 10, a deflecting magnet 13 is fixed, which directs a part of the electrons emitted by the beta emitter with a certain energy into the collimating through hole 11, located in the lower part of the housing of the fixed energy electron source 10 and having dimensions of 2x2 mm. In this case, a permanent ferrite magnet is used as the deflecting magnet 13. Above the collimating hole 11, a scintillation fiber 14 is fixed, which in this case has a diameter of 2 mm. The end of the scintillation fiber 14 is in contact with the triggering photodetector 15. In this case, a silicon photomultiplier with photocathode dimensions of 3x3 mm ² is used as the triggering photodetector 15; to ensure optical contact, the end face of the scintillation fiber 14 is preliminarily polished. The output of the triggering photodetector 15 is connected by means of a coaxial cable to the second input of the two-channel block for analyzing signal sweeps 4. To maintain light insulation, the coaxial cable passes through the wall of the light-insulated box 1 through the cable gland.

The complex works as follows. After the test scintillation strip 2 is installed, the light-insulated box 1 is closed and power is supplied to the photodetectors 3 and 15. The electronic computer 5 sets the measurement mode of the two-channel block for analyzing signal sweeps 4 "synchronization by the second input", and also transmits a command to the controller 9, which, using an electric drive 8, moves the carriage with a fixed energy electron source 6 to the end of the scintillation strip 3 opposite from the optical signal photodetector .

In the beta emitter 12, the reaction of beta decay of the strontium-90 nucleus occurs, as a result of which the yttrium-90 nucleus is formed and an electron is emitted. The maximum possible energy of an electron from the beta decay of strontium-90 does not exceed 0.54 MeV, and this electron is directed by a deflecting magnet 13 into the wall of the housing of an electron source of fixed energy 10. The yttrium-90 nucleus has a half-life of 64 hours (significantly less than that of the parent strontium-90 nucleus). 90, whose half-life is 28.8 years), therefore, in the beta-emitter containing strontium-90, beta decays of the resulting yttrium-90 nuclei are constantly going on. As a result of the beta decay of yttrium-90 nuclei, electrons with energies up to 2.28 MeV are formed. Most of these electrons are deflected by the magnet 13 and they enter the wall of the housing of the fixed energy electron source 10. However, part of the electrons emitted by yttrium-90 are directed by the deflecting magnet 13 into the collimating hole 11, while crossing the scintillation fiber 14. The geometry of the location of the beta-emitter 12 deflecting the magnet 13 and the collimating hole 11 are selected in such a way that electrons with an energy of 1.8 ± 0.1 MeV fly out from the source of electrons of a fixed energy 6. When the electrons cross the scintillation fiber 14, photons are generated in it, which, through the scintillation fiber 14, enter the photocathode of the triggering photodetector 15. As a result, a signal appears on the anode of the triggering photodetector 15, which is fed via a coaxial cable to the second input of the two-channel block for analyzing signal scans 4.

The electron released from the source of fixed energy electrons 6 hits the tested scintillation strip 2, causing a scintillation flash in it, the photons of which fall on the photodetector of optical signals of the scintillation strip 3, as a result of which a signal is formed on its anode, which is fed through the cable to the first input of the two-channel unit analysis of signal sweeps 4.

The signal from the photodetector of the optical signals of the scintillation strip 3 and the signal from the triggering photodetector 15 are fed to the two-channel signal sweep analysis unit 4 with a time difference of 10-20 ns. After the appearance of a signal at the second input, the two-channel block for analyzing signal scans 4 via the USB interface transmits a digitized scan to an electronic computer 5, where the amplitude and charge of the signal recorded from the tested scintillation strip 2 are stored at a given position of a fixed energy electron source. After the completion of the event processing, the electronic computer 5 sends a command to the two-channel signal sweep analysis unit 4 to start a new measurement.

In this case, with the same position of the fixed energy electron source, the measurements are repeated at least 1000 times and take about 1 minute in time. As a result, the amplitude and charge histograms are collected in the electronic computer 5, after processing which data appear on the average amplitude and average charge of the response of the tested scintillation strip at a given position of the fixed energy electron source 6. After that, the electronic computer 5 sends a command to the controller via the USB data bus. 9, which, with the help of an electric drive 8, moves the carriage with a fixed-energy electron source 6 fixed on it to a new position, and the measurement cycle is repeated.

With a strip length of 3000 mm and a light output measurement every 500 mm, measurements take about 10 minutes.

Thus, the proposed invention makes it possible to measure the light output of a scintillation strip in less time compared to the prototype, and thereby increases productivity when creating coordinate-tracking detection systems, including muon hodoscopes.

Claims (8)

1. A complex for measuring the light output of scintillation strips, containing a two-channel block for analyzing signal sweeps, an electronic computer and a light-insulated box for placing the test scintillation strip, inside which a particle source positioning device is fixed and a photodetector of optical signals of the scintillation strip is installed, the output of the photodetector of optical signals of the scintillation strip is connected to the first input of a two-channel block for analyzing signal sweeps, which is connected to an electronic computer by a data bus, characterized in that the complex includes a source of fixed energy electrons installed on the particle source positioning device, and the particle source positioning device is additionally equipped with an electric drive and a controller for automation of the control of the position of the particle source, while the electric drive is in functional communication with the controller, which is connected to an electronic computer, the output of the fixed energy electron source is connected to the second input of the two-channel signal sweep analysis unit, while the fixed energy electron source consists of a housing, inside which a beta-emitter, a deflecting magnet, a scintillation fiber and a triggering photodetector are fixed, and there is a collimating hole in the lower part of the body of the fixed energy electron source, while the scintillation fiber is fixed above the collimating hole, and the end of the scintillation fiber is in optical contact with the triggering photodetector. 2. The complex according to claim 1, characterized in that the ⁹⁰ Sr isotope is used as a beta emitter. 3. The complex according to claim 1, characterized in that the isotope ⁹⁰ Y is used as a beta emitter. 4. The complex according to claim 1, characterized in that the ¹³⁷ Cs isotope is used as a beta emitter. 5. The complex according to claim 1, characterized in that a vacuum photomultiplier tube is used as a photodetector of optical signals of the scintillation strip. 6. The complex according to claim 1, characterized in that a silicon photomultiplier is used as a photodetector of the optical signals of the scintillation strip. 7. The complex according to claim 1, characterized in that a vacuum photomultiplier is used as a triggering photodetector. 8. The complex according to claim 1, characterized in that a silicon photomultiplier is used as a triggering photodetector.

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