Method for selecting electrodes of neutron ionization chamber on basis of parameters of electrodes coverage

FIELD: electronics.

SUBSTANCE: method includes recording number of particles emitted by radioactive layer on basis of number of voltage or current pulses recorded by counting device, then to measuring detector a flow of ionizing radiation is directed from calibrating standard electrode and also registered is number of particles, position of covered electrode is change no less than two times, by turning it in horizontal plane around its axis for arbitrary angle, while repeating measurement of pulses number, while measurement time is selected to be such that number of recorded pulses was no less than 3600 pulses for each measurement position, and then selection of necessary number of electrodes is calculated for forming electrode system in chamber.

EFFECT: higher precision, higher safety.

 

The invention relates to the field of technical physics, or more precisely to the dimensions of the coverage settings using ionizing radiation, and can most effectively be used in the manufacture of neutron ionization chambers division.

One of the main tasks in the manufacture of neutron ionization chambers fission is the process of applying appropriate coatings on the electrodes.

The amount of substance deposited on the electrodes, is determined by weighing before and after coating (Malyshev E.K. and other gas-Discharge detectors for control of nuclear reactors. M.:Energoatomizdat, 1991, str and str).

This method cannot be used when the coating density of less than 0.1 mg/cm2because of the small gain on the background of the considerable weight of the electrode. Mechanical weighing cannot provide the required accuracy of determining the amount of coverage.

Known methods of measuring the amount of coating using ionizing radiation, such as a method of measuring the coating thickness of the electrode, which is exposed to a beam of radiation onto the object of control, excite characteristic radiation of this coating layer and determine its thickness, while additionally choose solid Etalon of the second substance from the surface layer with a thickness greater than the thickness of saturation, stir in Deut who m from the surface layer of the secondary characteristic radiation with the aid of the characteristic radiation layer controlled coating excite characteristic radiation of the massive pattern of radiation of the same energy that the characteristic emission layer controlled coating, register secondary characteristic radiation that has passed through the controlled coating, and the characteristic radiation of massive benchmark, we take the ratio of the intensities of the registered signals, the largest of which is judged on the thickness of the upper layer coating (patent RF №2107894, G 01 15/02).

Closest to the proposed method to the technical essence and purpose is a method of measuring the thickness of the sensitive region of the semiconductor silicon detector (RF patent No. 1373084, G 01 15/02). The known method is that the flux of ionizing radiation is directed to the calibration and the measuring detectors, register this radiation and determine the thickness of the sensitive area of the measured detector. To improve the accuracy of the measurement irradiation produce monoenergetic neutrons with energy E>Fthenwhere Ethenenergy threshold for the reaction28Si(n, α)25Mg, register linear energy spectrum of the pulses from charged particles formed in the sensitive area of the detector, allocate the peak of the energy spectrum of these particles, corresponding to the reaction28Si(n, α0)25

where f is the fluence of neutrons; S - the nameplate area sensitive area of the detector, and this curve determine the thickness of the sensitive area of the measured detector.

The disadvantages of the known methods using ionizing radiation is the need for a separate source of ionizing radiation.

The technical result that can be obtained with the implementation of the proposed method is to improve the accuracy of measuring the amount of coating of the electrodes and the increase in radiation safety by eliminating the source of ionizing radiation.

This technical result is achieved due to the fact that the method of selection electrodes neutron ionization chamber according to the parameters of the coating of the electrode for measuring the detector directs the flow of private ionizing radiation from radioactive coating of the electrode, record the number of particles emitted by a radioactive coating on the number of pulses of voltage or current registered conversion device, and then measuring the detector is directed flux is ionizing radiation from the calibration of the electrode pattern and also records the number of particles, change the position of the covered electrode is at least two times, rotating it in a horizontal plane around its axis by an arbitrary angle, the repeated measurement of the number of pulses of voltage or current, formed from interaction of the emitted particles with the detector, and the measurement time is chosen such that the number of registered pulses was not less than 3600 imp. at each position of measurement, and sample the required number of electrodes for forming the electrode system of the neutron ionization chamber dividing spend to run ratio

where Ncpi - the average rate of the i-th covered electrode in three dimensions; FFP - average rate calibration of the electrode pattern in three dimensions; n is the number of covered electrodes required for the formation of the electrode system of the neutron ionization chamber of the division.

Practically the method is as follows.

Coated electrode is placed in the holder device. The area of the sensitive part of the measuring radiation detector must be greater than the surface area of the electrode.

Using the detector registers the amount of particles emitted by a covered electrode, formed as a result of natural radioactive decay of a substance pokr is an event.

When the interaction of particles with the detector of ionizing radiation is formed impulse voltage (current), which is amplified by a preamplifier and, after forming, is logged to update the device.

Given the fact that at low counting rates, the pulses are distributed according to the Poisson law, and with confidence 0,99 error

(where N is the number of pulses in the measurements) should not exceed 5%, the measurement time number of pulses is selected so that the number of registered pulses was not less than 3600 imp.

To increase the accuracy and reliability of measurement specified process is repeated at least two times, changing the position of the covered electrode, rotating it in a horizontal plane around its axis by an arbitrary angle.

Is determined by the average count rate from each covered electrode for the three measurements for the entire set of covered electrodes.

Then is determined by the relative speed of each coated electrode as compared with a calibration electrode pattern. Using the calibration of the electrode-reference is necessary because the measurements are performed in air and the rate of the electrode depends on the temperature, humidity and atmospheric pressure environment.

Held in the Bork required number of covered electrodes for forming the electrode system of the neutron ionization chamber dividing thus, to execute the above ratio

where Ncpi - the average rate of the i-th covered electrode in three dimensions; FFP - average rate calibration of the electrode pattern in three dimensions; n is the number of covered electrodes required for the formation of the electrode system of the neutron ionization chamber of the division.

The calibration electrode-pattern is selected from a set of covered electrodes tested in this way and which will be collected neutron ionization chamber dividing verify its sensitivity to thermal neutrons. The calibration electrode-pattern is selected for each new batch of material used to cover the electrodes.

This set of essential features necessary and sufficient to achieve the technical result obtained using the proposed method.

Analysis of patent and scientific literature, with descriptions of similar technical solutions in this and related areas of technology allows us to conclude that the proposed technical solution is new and for specialists is not obvious from the prior art, involves an inventive step, industrial feasible and applicable in the specified scope, then e is th meets the criteria of the invention.

The method of selection electrodes neutron ionization chamber according to the parameters of the coating of the electrode, characterized in that the measuring detector directs the flow of private ionizing radiation from radioactive coating of the electrode, record the number of particles emitted by a radioactive coating on the number of pulses of voltage or current, registered conversion device, and then measuring the detector directs the flow of ionizing radiation from the calibration of the electrode pattern and also records the number of particles change position covered electrode is at least two times, rotating it in a horizontal plane around its axis by an arbitrary angle, the repeated measurement of the number of pulses of voltage or current, formed from interaction of the emitted particles with the detector, and the measurement time is chosen such that the number of registered pulses was not less than 3600 imp. at each position of measurement, and sample the required number of electrodes for forming the electrode system of the neutron ionization chamber dividing spend to run ratio

where Ncpi- the average speed of the i-th covered electrode in three dimensions; Nco- the average rate kalibrovochnoj the electrode pattern in three dimensions; n is the number of covered electrodes required for the formation of the electrode system of the neutron ionization chamber of the division.



 

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