CN114488269B - Proportional counter - Google Patents

Abstract

The invention belongs to the technical field of radiation dose measurement, and particularly relates to a proportional counter which is used for X-ray or gamma-ray pulse radiation measurement and comprises a cylindrical sealed cathode shell (3) arranged in a sealed shielding shell (6), an anode wire (1) arranged at the axis position of the cathode shell (3), a signal export interface (7) arranged at one end of the cathode shell (3), and a high-voltage power supply input interface (8) arranged at the other end of the cathode shell (3). The invention uses the metal shielding shell (6) to be grounded to form the electromagnetic shielding environment without interference to the internal structure of the proportional counter, the positive high voltage is provided by the anode wire (1), the induced charges generated during ionization and proportional multiplication charge drift are collected by the cathode shell (3) and form current signal output, and the space charge effect and the pulse accumulation effect of the conventional proportional counter in the high-count rate measurement and pulse radiation measurement scenes can be effectively avoided.

Description

Proportional counter

Technical Field

The invention belongs to the technical field of radiation dose measurement, and particularly relates to a proportional counter.

Background

The proportional counter is a gas nuclear radiation detector, and the working voltage of the proportional counter is in a proportional area, so that the proportional counter can be used for X-ray and gamma-ray measurement and is widely applied to radiation dose measurement, site radiation monitoring and other application occasions.

The proportional counter is mostly cylindrical in structure, the center is an anode filament, the shell of the cylindrical barrel is a cathode, and the working gas is a mixture of inert gas and a small amount of electronegative gas. The incident particles collide with the gas atoms in the cartridge to ionize the atoms, producing electrons and positive ions. Under the influence of the electric field, the electrons move towards the central anode wire and the positive ions drift towards the cathode at a much slower rate than the electrons. Electrons are accelerated by a strong electric field near the anode wire to obtain energy, so that atoms can be ionized again. The output pulse from the anode wire is of a larger amplitude and proportional to the initial ionization. In general, the anode wire of the proportional counter is at positive polarity potential, the counter shell is at negative polarity potential, an electric field is formed in the sensitive volume so that electrons generated by ionized charges drift towards the anode and electron multiplication occurs near the anode, the drift and multiplication of the electrons generate induced charges Q at the anode wire, the induced charges Q are output to the preamplifier through the blocking capacitor by the anode wire, the proportional counter generally adopts a charge sensitive preamplifier, as shown in fig. 1, the output voltage V=Q/C, wherein C is the feedback capacitor of the charge sensitive preamplifier and is usually in the pF magnitude. In general, the output of the preamplifier is a negative exponentially decaying voltage signal, and the intensity measurement of X and gamma rays, namely the measurement of the radiation quantity such as the air absorption dose, the surrounding dose equivalent and the like can be completed by counting the output pulse signal after the output signal is processed by a subsequent circuit.

Along with the wide establishment and use of medical X-ray machines, medical CT, medical electron linear accelerators, medical proton accelerators, research stacks or accelerators and the like, the ionizing radiation generated during the work of the medical X-ray machines, the medical CT, the medical electron linear accelerators and the research stacks or accelerators is different from the conventional continuous radiation field, usually a pulse radiation field, and the medical X-ray machines, the medical CT, the medical electron linear accelerators and the research stacks or accelerators have the characteristics of short duration, large single pulse radiation fluence rate and the like. At this time, the gain of the proportional counter is poor due to the space charge effect at the anode wire, a plurality of radiation photons are simultaneously incident to generate a single 'peak-combining' output signal, the rear-end nuclear electronic circuit generates the phenomena of pulse accumulation, even blocking and the like, the pulse signal count is greatly lower than the expected result, the measurement result in the pulse radiation field is seriously lower or even unresponsive, thus the use requirement of radiation protection cannot be met, and the health and safety of radioactive staff are threatened.

Disclosure of Invention

In order to solve the problems that in the conventional proportional counter, the phenomenon that the actual output pulse signal amplitude, the counting rate and the like have larger deviation or no reaction with the expected deviation due to the space charge effect of anode wires, the counting saturation of a pulse stacking and back-end nuclear power readout circuit, and the like in the pulse radiation field measurement, the invention aims to provide the proportional counter working in a current mode and used for the X-ray and gamma-ray pulse radiation measurement, wherein the output current or total charge quantity of the proportional counter is proportional to the radiation field intensity, and the proportional counter can be suitable for the conventional X-ray and gamma-ray continuous radiation measurement and also can be used for the X-ray and gamma-ray pulse radiation measurement, so that the problem that the conventional proportional counter cannot be applied to the pulse radiation field is solved.

In order to achieve the purpose, the technical scheme adopted by the invention is that the proportional counter is used for X-ray or gamma-ray pulse radiation measurement, wherein the proportional counter comprises a cylindrical sealed cathode shell arranged in a sealed shielding shell, an anode wire arranged at the axis position of the cathode shell, one end of the cathode shell is provided with a signal export interface, and the other end of the cathode shell is provided with a high-voltage power supply input interface.

Further, insulators are respectively arranged at two ends of the cathode shell, and the insulators enable the cathode shell not to contact with the shielding shell; the insulator is made of polytetrafluoroethylene, nylon or PEEK.

Further, the cathode shell is filled with working gas, first insulation terminals are arranged at the axle center positions of the two ends of the cathode shell, and the anode wire is fixedly arranged at the axle center position of the cathode shell through the first insulation terminals; the top end of the anode wire penetrates through the cathode shell and is connected with the high-voltage power supply input interface; the tail end of the anode wire is not in contact with the cathode casing and is insulated from the cathode casing.

Further, the cathode shell is made of stainless steel or hard aluminum.

Further, the shielding shell is grounded and used for providing an electromagnetic shielding environment for the inside of the shielding shell.

Further, the anode wire is a metal wire with the diameter of 2.5-20 mu m, and the material comprises copper or silver.

Further, interfaces are reserved at two ends of the shielding shell, the signal lead-out interface and the high-voltage power supply input interface extend out of the shielding shell through the interfaces, and a second insulating terminal is arranged on the interfaces to prevent the signal lead-out interface and the high-voltage power supply input interface from being in contact with the shielding shell.

Further, the high-voltage power supply input interface is connected and conducted with the anode wire and is used for being connected with a high-voltage power supply to provide working high voltage for the anode wire, and the voltage of the working high voltage is +800V to +3000V; the signal lead-out interface is connected with the cathode shell and is used for connecting an external preamplifier; the cathode shell is used for collecting ionization charges in the proportional counter, and signals of the ionization charges are output to the preamplifier in a direct current coupling output mode.

Further, the shielding shell is made of metal, and the first insulating terminal and the second insulating terminal are made of ceramic; the type of the high-voltage power supply input interface comprises an SHV connector or an MHV connector; the type of signal derivation interface includes a BNC connector or an SMA connector.

Further, the working gas is composed of an inert gas and a electronegative gas; the inert gas is argon, krypton or hernia; the electronegative gas is methane.

The invention has the beneficial effects that:

The shielding shell 6 made of metal is grounded to provide a non-interference electromagnetic shielding environment for the internal structure of the proportional counter, positive high voltage is provided for work by the anode wire 1, induced charges generated when ionization and proportional multiplication charge drift are collected by the cathode shell 3 and form current signal output, so that the space charge effect and the pulse accumulation effect of the conventional proportional counter in the high-count rate measurement and pulse radiation measurement scenes can be effectively avoided, and meanwhile, the accumulation and blocking phenomena caused by the conventional back-end nuclear electronics dead time can be avoided by adopting a current reading and related matched nuclear electronics circuit.

Drawings

FIG. 1 is a schematic diagram of the structure and operation principle of a proportional counter according to the prior art;

FIG. 2 is a schematic diagram of a proportional counter according to an embodiment of the present invention;

FIG. 3 is a schematic diagram illustrating the operation of a proportional counter according to an embodiment of the present invention;

In the figure: 1-anode wire, 2-working gas, 3-cathode shell, 4-first insulation terminal, 5-insulator, 6-shielding shell, 7-signal export interface, 8-high voltage power supply input interface.

Detailed Description

The invention is further described below with reference to the drawings and examples.

As shown in fig. 2, the proportional counter provided by the invention is used for measuring the pulse radiation of X or gamma rays, and comprises a cylindrical sealed cathode shell 3 arranged in a sealed shielding shell 6, an anode wire 1 arranged at the axis position of the cathode shell 3, a signal leading-out interface 7 arranged at one end of the cathode shell 3, and a high-voltage power supply input interface 8 arranged at the other end of the cathode shell 3.

Insulators 5 are respectively arranged at two ends of the cathode shell 3, and the insulators 5 prevent the cathode shell 3 from contacting with the shielding shell 6 to prevent contact conduction; the insulator 5 is made of high-insulation materials such as polytetrafluoroethylene, nylon or PEEK.

The cathode shell 3 is filled with working gas 2, first insulating terminals 4 are arranged at the axle center positions of the two ends of the cathode shell 3, and the anode wire 1 is fixedly arranged at the axle center position of the cathode shell 3 through the first insulating terminals 4 in a welding way (the working gas 2 in the cathode shell 3 is ensured not to leak); the top end of the anode wire 1 passes through the cathode shell 3 and is connected with a high-voltage power input interface 8; the tail end of the anode wire 1 is not in contact with the cathode casing 3 and is insulated from the cathode casing 3.

The cathode casing 3 is made of stainless steel or duralumin.

The shield enclosure 6 is grounded (i.e., zero potential) for electrostatic shielding to provide an electromagnetically shielded environment for the interior of the shield enclosure 6.

The anode wire 1 is a metal wire with the diameter of 2.5-20 mu m, and the material comprises copper or silver.

Interfaces are reserved at two ends of the shielding shell 6, the signal lead-out interface 7 and the high-voltage power supply input interface 8 extend out of the shielding shell 6 through the interfaces, and a second insulating terminal is arranged on the interfaces to prevent the signal lead-out interface 7 and the high-voltage power supply input interface 8 from contacting with the shielding shell 6.

The shielding shell 6 is made of metal, and the first insulating terminal 4 and the second insulating terminal are made of ceramic; the type of high voltage power input interface 8 includes an SHV connector or an MHV connector or other high voltage connector; the type of signal derivation interface 7 comprises a BNC connector or an SMA connector or other type of connector.

The working gas 2 is composed of an inert gas and a (small amount of) electronegative gas; the inert gas is argon, krypton or hernia; the electronegative gas is methane.

The high-voltage power supply input interface 8 is electrically connected and conducted with the anode wire 1 and is used for connecting a high-voltage power supply to provide working high voltage for the anode wire 1, wherein the voltage of the working high voltage is +800V to +3000V; the signal lead-out interface 7 is connected and conducted with the cathode shell 3 and is used for connecting an external preamplifier; the cathode shell 3 is used for collecting ionized charges in the proportional counter, and a signal of the ionized charges is output to the preamplifier in a direct current coupling output mode; when the high-voltage power input interface 8 is connected with the working high voltage of +800V to +3000V, the proportional counter is in a current output mode, electric charge signals generated by ionization are subjected to proportional amplification and then are induced in the cathode shell 3 to generate current signals, the current signals are output by the cathode shell 3 through the signal output interface 7, the wide-range current signal measurement is completed through the direct-current coupled preamplifier (high-speed logarithmic amplifier), the working principle is as shown in figure 3, and at the moment, the output current signals are proportional to the intensity of X and gamma rays in the incident proportional counter; by measuring the current signal value, the sensitivity of the proportional counter obtains the intensity of the incident radiation (e.g., air absorption dose, ambient dose equivalent, etc.).

The device according to the invention is not limited to the examples described in the specific embodiments, and a person skilled in the art obtains other embodiments according to the technical solution of the invention, which also belong to the technical innovation scope of the invention.

Claims (8)

1. A proportional counter for use in X or gamma ray pulsed radiation measurements, characterized by: the cathode comprises a cylindrical sealed cathode shell (3) arranged in a sealed shielding shell (6), an anode wire (1) is arranged at the axis position of the cathode shell (3), a signal export interface (7) is arranged at one end of the cathode shell (3), and a high-voltage power supply input interface (8) is arranged at the other end of the cathode shell (3); the cathode shell (3) is filled with working gas (2), first insulation terminals (4) are arranged at the axle center positions of two ends of the cathode shell (3), and the anode wire (1) is fixedly arranged at the axle center position of the cathode shell (3) through the first insulation terminals (4); the top end of the anode wire (1) passes through the cathode shell (3) to be connected with the high-voltage power supply input interface (8); the tail end of the anode wire (1) is not contacted with the cathode shell (3) and is insulated from the cathode shell (3); the high-voltage power supply input interface (8) is connected and conducted with the anode wire (1) and is used for connecting a high-voltage power supply to provide working high voltage for the anode wire (1), and the voltage of the working high voltage is +800V to +3000V; the signal lead-out interface (7) is connected with the cathode shell (3) and is used for connecting an external preamplifier; the cathode shell (3) is used for collecting ionization charges in the proportional counter, and signals of the ionization charges are output to the preamplifier in a direct current coupling output mode.

2. A proportional counter as in claim 1 wherein: insulators (5) are respectively arranged at two ends of the cathode shell (3), and the insulators (5) enable the cathode shell (3) not to be in contact with the shielding shell (6); the insulator (5) is made of polytetrafluoroethylene, nylon or PEEK.

3. A proportional counter as claimed in claim 2, wherein: the cathode shell (3) is made of stainless steel or hard aluminum.

4. A proportional counter as claimed in claim 3 wherein: the shielding shell (6) is grounded and is used for providing an electromagnetic shielding environment for the inside of the shielding shell (6).

5.A proportional counter as in claim 4 wherein: the anode wire (1) is a metal wire with the diameter of 2.5-20 mu m, and the material comprises copper or silver.

6. A proportional counter as in claim 5 wherein: interfaces are reserved at two ends of the shielding shell (6), the signal lead-out interface (7) and the high-voltage power supply input interface (8) extend out of the shielding shell (6) through the interfaces, and a second insulating terminal is arranged on the interfaces to prevent the signal lead-out interface (7) and the high-voltage power supply input interface (8) from being in contact with the shielding shell (6).

7. A proportional counter as in claim 6 wherein: the shielding shell (6) is made of metal, and the first insulating terminal (4) and the second insulating terminal are made of ceramic; the type of the high voltage power input interface (8) comprises an SHV connector or an MHV connector; the type of signal derivation interface (7) comprises a BNC connector or an SMA connector.

8. A proportional counter as in claim 7 wherein: the working gas (2) is composed of inert gas and electronegative gas; the inert gas is argon, krypton or hernia; the electronegative gas is methane.