CN111683450B

CN111683450B - Target chamber device for producing radioactive isotope by gas cooling accelerator

Info

Publication number: CN111683450B
Application number: CN202010224009.6A
Authority: CN
Inventors: 张宇皓; 姜冲
Original assignee: Xi'an Maisi Topology Technology Co ltd
Current assignee: Xi'an Maisi Topology Technology Co ltd
Priority date: 2020-03-26
Filing date: 2020-03-26
Publication date: 2022-10-04
Anticipated expiration: 2040-03-26
Also published as: CN111683450A

Abstract

The invention relates to a target chamber device for producing radioactive isotopes by an accelerator, in particular to a target chamber device for producing radioactive isotopes by a gas cooling accelerator. The problems of low cooling efficiency, sample target oxidation, corrosion and possible explosion in the sample target cooling process when the radioactive isotope is produced by using the photonuclear reaction of an electron accelerator are solved, and the device mainly comprises a shell, a gas path assembly body, a vacuum pipeline and a target sheet assembly body; the gas circuit assembly body is positioned in the shell, and the target sheet assembly body is positioned in the cavity of the gas circuit assembly body; one end of the vacuum pipeline penetrates into the shell, and the other end of the vacuum pipeline is communicated with the vacuum pipeline of the electron accelerator; the electron beam in the vacuum pipeline bombards the target sheet assembly in the direction perpendicular to the target sheet, and the cooling gas in the gas circuit assembly cools the target sheet assembly. The invention has higher cooling efficiency aiming at the sample target and can not oxidize the sample target.

Description

Target chamber device for producing radioactive isotope by gas cooling accelerator

Technical Field

The invention relates to a target chamber device for producing radioactive isotopes by an accelerator, in particular to a target chamber device for producing radioactive isotopes by a gas cooling accelerator.

Background

When producing radioactive isotope by using photonuclear reaction of electron accelerator, the electron beam is first converted into bremsstrahlung X ray by converting target, and the X ray is then mixed with sample target element (such as ¹⁰⁰ Mo) to produce a radioisotope (e.g. a radioisotope) ⁹⁹ Mo). In both physical reactions, the electron beam from the accelerator deposits a significant portion of the energy of the electron power as heat into the conversion target and the sample target, thereby rapidly raising the temperature of the conversion target and the sample target to hundreds of degrees or even higher, which can destroy the performance and structure of the sample target and its surrounding devices. Sample target size, structure and radioisotopes (e.g., produced by the method) ⁹⁹ Mo) yield and specific activity are limited and affected by the thermal properties of the sample target. The design and cooling of the sample target chamber apparatus becomes especially important. Cooling of the sample target is typically by reducing the sample target temperature with a coolant such as water, oil or gas. Air is generally used as a coolant, which may cause oxidation reaction with the container and the cooling object, causing corrosion of the container and the cooling object, and the cooling effect is not good. Water (typically deionized or distilled) is the most convenient and economical coolant. In order to improve the cooling efficiency, the contact area of the coolant with the sample target is generally increased. In the production of radioisotopes by means of electron accelerator photonuclear reactions or the like, the sample target is made up of several or even tens of thin disks or plates of a certain thickness in order to increase the cooling efficiencyThe target sheet assembly is formed by stacking the flaky target bodies, and a certain gap is formed between two adjacent sheets in the target sheet assembly, so that deionized water passes through the gap to greatly improve the cooling efficiency of the target. However, this water cooling method also has a serious disadvantage in that the coolant water is oxidized to generate black residues and the like due to the oxidation caused by strong radicals and peroxides formed by radiation cracking under the irradiation of very high radiation level, thereby destroying and affecting the performance of the sample target. And the nuclides produced in the cooling water (e.g. are detected ⁹⁹ Mo), the sample target is not only oxidized but also eroded by the cooling water. Meanwhile, the cracking of water by high-level radiation may generate some hydrogen, and the hydrogen and the oxygen are mixed to reach a certain proportion, so that the explosion problem is easily caused, the target system is damaged, even more seriously, the vacuum system of the accelerator is damaged, and the consequence is serious. Concentrating ¹⁰⁰ The high cost of Mo strongly requires in production ⁹⁹ The Mo process does not attack and damage the sample target, and also eliminates the risk of possible explosions.

Disclosure of Invention

In order to solve the problems of low cooling efficiency, sample target oxidation, corrosion and possible explosion in the sample target cooling process when the radioactive isotopes are produced by the photonuclear reaction of an electron accelerator, the invention provides a target chamber device for producing the radioactive isotopes by using a gas cooling accelerator, and the device takes rare inert gas such as helium as a coolant, thereby not only ensuring the stability of the sample target in the cooling process, but also greatly improving the cooling efficiency of the target.

The technical scheme of the invention is to provide a target chamber device for producing radioactive isotopes by using a gas cooling accelerator, which is characterized in that: mainly comprises a shell, a gas circuit assembly body, a vacuum pipeline and a target sheet assembly body;

the gas circuit assembly body comprises a cavity, a blind plate, and a gas inlet pipeline and a gas outlet pipeline which are respectively communicated with the left side wall and the right side wall of the cavity in a sealing way; the cavity is positioned in the shell, the upper end of the cavity is opened, and the opening end of the cavity extends out of the shell and is fixed on the shell; the blind plate is detachably fixed at the opening end of the cavity in a sealing manner; the air inlet pipeline and the air outlet pipeline extend out of the shell and are connected with an external helium cooling loop system;

the target sheet assembly body is positioned in the cavity of the gas circuit assembly body, one end of the target sheet assembly body is fixedly connected with the blind plate, the other end of the target sheet assembly body is used for fixing the target sheet assembly body, and a single target sheet in the target sheet assembly body is parallel to the central axes of the gas inlet pipeline and the gas outlet pipeline, so that cooling gas in the gas pipeline is ensured to be blown into each gap of the target sheet assembly body;

one end of the vacuum pipeline penetrates into the shell, and the other end of the vacuum pipeline is communicated with the vacuum pipeline of the electron accelerator; the central axis of the vacuum pipeline is vertical to the central axes of the air inlet pipeline and the air outlet pipeline, and the electron beams in the vacuum pipeline bombard the target sheet assembly in the direction vertical to the target sheet.

Further, two sections of vacuum pipelines are included; one end of the vacuum pipeline is a vacuum window, the material of the vacuum window is standard beryllium, the thickness of the vacuum window is 0.25-0.50mm, and the vacuum window of one section of the vacuum pipeline is opposite to the front side wall of the cavity of the gas circuit assembly body; the vacuum window of the other section of vacuum pipeline is opposite to the rear side wall of the cavity of the gas circuit assembly body; in order to avoid collision between the vacuum pipeline and the gas circuit assembly body, a gap is formed between the vacuum window and the front side wall and the rear side wall of the cavity of the gas circuit assembly body, and the width of the gap can be 2-5mm. The electron beam in the vacuum pipeline sequentially penetrates through the vacuum window and the front side wall and/or the rear side wall of the cavity of the gas circuit assembly body to bombard the target sheet assembly in the direction vertical to the target sheet.

Furthermore, the vacuum pipeline can be integrated with the cavity, namely the vacuum pipeline comprises two sections of tubular vacuum pipelines; one end of one section of vacuum pipeline is hermetically connected with the front side wall of the cavity of the air path assembly body; one end of the other section of vacuum pipeline is hermetically connected with the rear side wall of the cavity of the gas circuit assembly body. The materials of the cavity and the target window are selected from heat-resistant and corrosion-resistant alloy chromium-nickel-iron alloy or Inconel (Inconel: nickel 80%, chromium 14% and iron 6%), maraging steel (Maraging steel) and the like. The electron beam in the vacuum pipeline sequentially penetrates through the front side wall and/or the rear side wall of the cavity of the gas circuit assembly body to bombard the target sheet assembly body in the direction vertical to the target sheet.

Further, because the front side wall and/or the rear side wall of the cavity of the air channel assembly directly faces the target sheet assembly, the part is defined as a target window; in order to weaken the attenuation degree of the target window to the electron beam and simultaneously avoid the target window from generating a large amount of heat, the target window is designed into a convex-concave lens structure, and the concave direction points to the inside of the cavity; the concave surface contacts air or vacuum, and the convex surface cools heat generated when the electron beam passes through the concave surface, so that uneven heat distribution generated by the target window is reduced, thermal stress of the target window is enhanced, and the service life of the target window is prolonged. The convex surface may be ellipsoidal, spherical or planar in shape. The target window is thinnest at the center, preferably 0.25-0.5mm thick.

Further, the inlet duct is the same with the structure of the pipeline of giving vent to anger, all includes trunk line and horn mouth, the main aspects and trunk line sealing connection of horn mouth, trunk line and the access & exit sealing connection of outside gas cooling loop system, the tip and the gas circuit assembly body cavity left and right sides wall sealing connection of horn mouth communicate with each other, preferentially, and the tip of horn mouth is the rectangle opening. The preferred gas is helium, which has not only better cooling performance compared with other inert gases, but also has light atomic weight and small absorption of rays, so helium is selected as the cooling gas. The pressure of the helium gas was 2MPa, the flow rate at 300psi was 300g/s, and the inlet temperature was 20 ℃.

Furthermore, the material of inlet duct and outlet duct is 316L stainless steel, and the internal diameter of trunk line is 50mm, and the wall thickness is 4mm.

Furthermore, the shell is a square shell, second openings are formed in the upper side wall, the lower side wall, the left side wall and the right side wall of the shell, and the size of each second opening can ensure that the gas circuit assembly body can be taken out of the shell; the upper side wall, the left side wall and the right side wall are provided with gas circuit fixing flanges at the positions of the holes, and the lower side wall is provided with a bottom plate flange at the position of the hole;

an end flange is arranged on the lower end face of the blind plate of the gas circuit assembly body, a flange hole of the end flange is matched with the cross section shape of the cavity, and one end of the cavity penetrates through the flange hole of the end flange and is fixedly connected with the blind plate; the end flange is positioned on the upper end face of the gas circuit fixing flange on the upper side wall of the shell and is fixedly connected with the gas circuit fixing flange; the air inlet pipeline and the air outlet pipeline are fixed with the shell by the air path fixing flanges on the left side wall and the right side wall of the shell.

Further, in order to improve the sealing performance of the cavity, a sealing ring is arranged between the blind plate and the end flange.

Further, the gas circuit fixing flange is composed of two half flanges.

Further, the target assembly comprises a first target clamping plate, a second target clamping plate and a screw; the first target slice clamping plate and the second target slice clamping plate have the same structure;

the first target slice clamping plate sequentially comprises an end head, a clamping plate section and a target slice fixing part along the length direction of the target slice assembly body; the end head is fixedly connected with the blind plate; a through groove with a semicircular cross section is formed in the target sheet fixing part, and the length direction of the through groove is consistent with the width direction of the target sheet assembly body; a plurality of gaps for fixing single target pieces are arranged along the wall of the semicircular through groove, and the plurality of gaps are axially arranged along the circumferential direction of the groove wall;

insert each breach respectively with a plurality of target sheets and just form the target sheet assembly, the rethread screw is fixed with first target sheet splint and second target sheet splint.

Furthermore, the target sheet assembly is formed by combining 30 single target sheets, and the diameter of each single target sheet is 20mm, and the thickness of each single target sheet is 1.0-2.0mm; the axial clearance between two adjacent notches is 0.5-1.0mm.

Further, the target sheet assembly is a dual-function target of bremsstrahlung and photonuclear reaction. This dual function target is disclosed in patent No. 201910769344.1. The thickness of the first 10 target pieces on the two sides is 1.0mm, and the axial clearance between the first 10 adjacent gaps on the two sides is 1.0mm; the thickness of the middle 10 target plates is 1.5mm, and the axial clearance between the middle 10 adjacent notches is 0.5mm.

Further, in order to detect the temperature of the cooling gas, temperature sensors are arranged in the air inlet pipeline and the air outlet pipeline so as to detect the temperature of the air flow at the inlet and the outlet.

The beneficial effects of the invention are:

1. the invention has higher cooling efficiency aiming at the sample target, and the sample target can not be oxidized; the invention utilizes the gas circulation system to cool the sample target, and the gas is directly blown into the gap between the adjacent target plates in the target plate assembly, thereby greatly improving the cooling efficiency of the target. And simultaneously, the device can ensure that the device does not have reactions such as corrosion, oxidation and the like with the container and the sample target under the irradiation of a high radiation level. In addition, even if the target window fails, the accelerator vacuum system breaks down, and the inert gas helium does not damage the cathode of the very sensitive accelerator.

2. The invention can simultaneously improve the yield and specific activity of the radioisotope produced by the electron accelerator photonuclear reaction;

the invention can use the electron beams of two accelerators to simultaneously irradiate into the target body from two sides of the sample target respectively, and simultaneously improve the yield and specific activity of the electron accelerator for producing the radioactive isotope by the photonuclear reaction.

3. The reliability of the method for producing the radioactive isotope is high;

the invention not only improves the yield and the specific activity of the radioactive isotope, but also improves the reliability of the production and the supply of the radioactive isotope by a double-accelerator system, and the two parts are backup for each other. If one accelerator system fails, the other accelerator can still continue to produce, and the continuity of production and supply is guaranteed.

4. The invention has convenient and simple operation;

according to the invention, the end head is reserved at the upper end of the target sheet assembly body, the end head is fixedly connected with the blind plate, the target sheet assembly body can be assembled and disassembled by opening the blind plate 22, and the target sheet can be conveniently and quickly taken out after irradiation. Furthermore, the target is composed of 30 separate sheets, which are easier and faster to dissolve and handle than a single target of the same weight.

5. The special section design of the target window not only greatly reduces the attenuation of the electron beam in the passing process, improves the yield and specific activity of the radioisotope of the target sheet, but also reduces the uneven heat distribution generated by the target window, enhances the thermal stress of the target window, improves the safety of the target window and prolongs the service life of the target window.

Drawings

FIG. 1 is a general view of a helium cooling target chamber arrangement of the present invention;

FIG. 2 is a first cross-sectional view of the helium cooling target chamber assembly taken along the beam current direction;

FIG. 3 is a second cross-sectional view of the helium cooling target chamber assembly taken along the beam current direction;

FIG. 4 is a first cross-sectional view of the helium cooling target chamber apparatus taken along the gas path;

FIG. 5 is a second cross-sectional view of the helium cooling target chamber device along the gas path direction;

FIG. 6 is a schematic view of the housing structure;

FIG. 7 is a schematic view of a gas circuit assembly;

FIG. 8 is a schematic cross-sectional view of a gas circuit assembly;

FIG. 9 is a schematic cross-sectional view of a target window;

FIG. 10 is a schematic view of a target assembly;

FIG. 11 is a cross-sectional view of a target holder;

FIG. 12 is a cross-sectional view of a vacuum line;

FIG. 13 is a schematic diagram showing the relationship between electron beam energy deposition (mostly converted to heat) and target depth when three electron beams with different energies bombard a Mo target;

FIG. 14 shows the temperature values of target pieces when 50MeV electron beams bombard a target assembly consisting of 42 Mo pieces;

FIG. 15 shows single and double side irradiation ¹⁰⁰ Produced from Mo targets ⁹⁹ Comparing Mo yield;

the reference numbers in the figures are: 1-a shell, 2-a gas path assembly body, 3-a target sheet assembly body and 4-a vacuum pipeline;

11-a first opening, 12-an upper side wall, 13-a lower side wall, 14-a left side wall, 15-a right side wall, 16-a second opening, 17-a gas path fixing flange, 18-a bottom plate flange, and 19-a first screw;

21-cavity, 22-blind plate, 23-air inlet pipeline, 24-air outlet pipeline, 25-second screw, 26-end flange, 231-main pipeline, 232-horn mouth and 27-target window;

31-a first target plate clamping plate, 32-a second target plate clamping plate, 33-a third screw, 34-a target plate combination body, 311-an end, 312-a clamping plate section, 313-a target plate fixing part, 314-a through groove and 315-a notch.

Detailed Description

The invention is further described below with reference to the accompanying drawings and specific embodiments.

With reference to fig. 1 to 5, it can be seen that the helium cooling target chamber device of the present invention is mainly composed of a housing 1, a gas path assembly 2, a target assembly 3, and a vacuum pipeline 4, wherein the vacuum pipeline 4 in the figure is connected to an accelerator vacuum pipeline.

The following examples select helium as the cooling gas because helium has not only better cooling performance, but also light atomic mass and small absorption of radiation, compared to other inert gases.

As shown in fig. 4 and 5, the key parts of the air channel assembly 2 are located inside the housing 1, and mainly include a cavity 21, a blind plate 22, an air inlet pipe 23 and an air outlet pipe 24; in the embodiment, the cavity 21 is a rectangular cavity, the upper end of the cavity is an open end, the target sheet assembly 3 can be arranged in the cavity 21 from the open end, the blind plate 22 is buckled at the open end, one end of the target sheet assembly 3 is fixedly connected with the blind plate 22, the other end of the target sheet assembly is positioned at the bottom of the cavity, and the target sheet assembly 34 is fixed; the air inlet pipeline 23 and the air outlet pipeline 24 are respectively communicated with the left side wall and the right side wall of the cavity 21, and the ports of the air inlet pipeline and the air outlet pipeline are respectively connected with an external helium cooling loop system. The pressure of the high-pressure helium flow in the gas circuit assembly body 2 is 2MPa, the flow rate is 300g/s, the inlet temperature is 20 ℃, the cooling gas of the gas inlet pipeline 23 takes away the heat on the target plate through the gap of the target plate assembly 34 and flows out from the gas outlet pipeline 24, and temperature sensors can be arranged in the gas inlet pipeline and the gas outlet pipeline to detect the temperature of the gas flow at the inlet and the outlet. Referring to fig. 2, 3 and 6, the housing 1 is provided with a first opening 11 through which the vacuum pipe 4 can penetrate, the vacuum pipe 4 penetrates into the housing 1 and is opposite to the front and rear side walls of the cavity of the gas circuit assembly 2, and the length direction of the vacuum pipe is perpendicular to the length directions of the gas inlet pipe 23 and the gas outlet pipe 24. The end of the vacuum tube 4 is a very thin disc, called a vacuum window, which ensures a vacuum tight seal when the electron beam passes through it. The electron beam loses a very small portion of its energy when passing through the vacuum window. The vacuum window is made of standard beryllium and has the thickness of 0.25-0.50mm. In order to avoid collision, a gap with the width of 2-5mm is formed between the vacuum window and the front side wall and the rear side wall (namely the target window 27) of the cavity of the gas path assembly. The electron beam current passes through the vacuum window of the vacuum pipeline to enter the atmosphere, and then immediately passes through the target window to bombard the target sheet assembly in the direction vertical to the target surface. The electron beam can be provided from one vacuum pipeline on one side for unidirectional targeting, and two electron beams can be provided from the vacuum pipelines on two sides for targeting the sheet assembly.

The vacuum pipeline 4 can also be arranged integrally with the cavity 21, wherein one end of one section of the vacuum pipeline is hermetically connected with the front side wall of the cavity of the gas circuit assembly body; one end of the other section of vacuum pipeline is hermetically connected with the rear side wall of the cavity of the air path assembly body. The materials of the cavity and the target window are selected from heat-resistant and corrosion-resistant alloy chromium-nickel-iron alloy or Inconel (Inconel: nickel 80%, chromium 14% and iron 6%), maraging steel (Maraging steel) and the like. The electron beam in the vacuum pipeline sequentially penetrates through the front target window and/or the rear target window of the cavity of the air passage assembly body to bombard the target sheet assembly body in the direction vertical to the target sheet.

The portion of the side of the gas circuit assembly cavity 21 opposite the vacuum window (i.e., the target window 27) is the path for the targeted electron beam and therefore attenuates the beam intensity while generating heat and therefore is not too thick, but not too thin and must withstand helium pressures up to 2 MPa. According to fluid mechanics, a special section design is carried out on a target window, so that the influence of high-pressure helium flow on the target window is minimized, the target window is optimized to be of a convex-concave lens-like structure, and the concave direction points to the inside of a cavity; the concave surface is exposed to air or vacuum, and the convex surface cools heat generated when the electron beam passes through it, and the shape of the convex surface may be an ellipsoid, a sphere or a plane. The target window is thinnest at the center, preferably 0.25-0.5mm thick.

The gas circuit assembly body 2 can be detached from the shell body 1, so that the structure and the installation of the shell body 1 and the gas circuit assembly body 2 need special design. With reference to fig. 4 and fig. 6, it can be seen that the housing 1 of this embodiment is a square housing, the upper side wall 12, the lower side wall 13, the left side wall 14 and the right side wall 15 of the housing are all provided with second openings 16, and the size of the second openings 16 can ensure that the air channel assembly 2 is taken out of the housing 1; the upper side wall 12, the left side wall 14 and the right side wall 15 are provided with air path fixing flanges 17 at the hole opening positions, and the lower side wall 13 is provided with a bottom plate flange 18 at the hole opening position; all the gas circuit fixing flanges 17 are formed by two half flanges.

With reference to fig. 7 and 4, an end flange 26 is disposed on a lower end surface of the blind plate 22 of the gas circuit assembly, a flange hole of the end flange 26 is matched with the cross-sectional shape of the cavity 21, and one end of the cavity 21 penetrates through the flange hole of the end flange 26 and is fixedly connected with the blind plate 22; and the end flange 26 is positioned on the upper end surface of the gas circuit fixing flange 17 of the upper side wall 12 of the shell and is fixedly connected with the gas circuit fixing flange; the air channel fixing flanges 17 of the left side wall 14 and the right side wall 15 of the shell fix the air channel fixing flanges and the shell 1 from the side surfaces of the air inlet pipeline 23 and the air outlet pipeline 24. In order to improve the sealing performance of the cavity, a sealing ring is arranged between the blind plate 22 and the end flange 26.

As shown in fig. 7, the inlet duct 23 and the outlet duct 24 both include a main duct 231 and a bell mouth 232, and the small end of the bell mouth 232 is a rectangular opening. The main pipe 231, the bell mouth 232, the cavity 21 and the end flange 26 are welded together by argon arc welding, so that the high-pressure sealing performance is ensured. Wherein the main pipeline 231 is welded with the big end of the horn mouth 232, and the left and right side walls of the air channel assembly cavity 21 are welded with the small end of the horn mouth 232. The maximum working pressure of the high-pressure helium gas circuit is 2MPa, so that a 316L stainless steel pipeline with the inner diameter of 50mm and the wall thickness of 4mm is selected as the main pipeline, the pressure of 4MPa can be borne, and the safety of the gas cooling system is ensured. The flow rate of the high-pressure helium gas at 2MPa is 300g/s.

The target assembly 3 is used for fixing, mounting and dismounting a target assembly 34 (i.e. a sample target), and is located in the cavity 21 of the air channel assembly 2, as shown in fig. 10, the target assembly 3 includes a first target clamping plate 31, a second target clamping plate 32 and a third screw 33; the first target plate clamping plate 31 and the second target plate clamping plate 32 have the same structure, and the first target plate clamping plate 31 sequentially comprises an end 311, a clamping plate section 312 and a target plate fixing part 313 along the length direction of the target plate assembly 3; the end 311 is fixedly connected with the blind plate 22, and the target assembly 3 can be assembled and disassembled by opening the blind plate 22 of the gas circuit assembly. The end is reserved at the upper end of the target assembly body, and the mechanical arm can clamp the end to lift out or put in the target assembly body. The target fixing part 313 is provided with a through groove 314 with a semicircular cross section, and the length direction of the through groove 314 is consistent with the width direction of the target assembly 3; a plurality of notches 315 for fixing single target pieces are formed along the groove wall of the semicircular through groove 314, and the plurality of notches 315 are axially arranged along the circumferential direction of the groove wall; and respectively inserting a plurality of target plates into the notches to form a target plate assembly 34, and fixing the first target plate clamping plate and the second target plate clamping plate through screws.

The target sheet assembly 34 is composed of 30 target sheets with the diameter of 20mm and the thickness of 1.0-2.0mm, and the installation gap between two adjacent target sheets is 0.5-1.0mm. The mounting gap is also a high pressure helium gas passage. Helium gas under high pressure flows through the gap of the target assembly to provide cooling to the target. Considering only the circular area of the target, the total area of 30 target pieces is 188cm ² In an amount of 0.8kW/cm per unit ² The high pressure helium gas flow may provide a maximum of 150kW of cooling power.

Since the electron beam is on the Mo target ¹⁰⁰ The energy deposition of Mo by photonuclear reactions is not uniformly distributed but is a function of the depth of the target. We simulated the calculations using the Monte Caro program, and the results are shown in FIGS. 13 and 14. FIG. 13 shows the energy deposition (mostly converted to heat) of the electron beam as a function of the target depth for three different electron beams bombarding a Mo target. Energy deposition is plotted on the ordinate versus depth of target in d/RL, depth d (cm), RL radiation length (cm). When the electron beam energy is 50-60MeV, RL is 0.95-0.98cm. It can be seen that the 60MeV energy is deposited primarily in the middle front (0.0-7.0 mm) of the target. FIG. 14 shows the temperature values for each target plate when a 50MeV electron beam bombards a target assembly consisting of 42 Mo plates. Wherein each target plate has a thickness of 0.5mm and a gap of 0.25mm. The results also show that the heat is distributed primarily in the front middle (0.0-9.0 mm) of the target assembly, substantially in accordance with figure 13.

The double electron accelerators have the advantages of increasing total beam incidence on a single system, improving total yield, generating relatively uniform isotope distribution in the target body and improving the specific activity of the radioactive isotopes. According to the characteristic Radiation Length (RL) of Mo is 0.97 cm, and in early research work, the Mo dual-function target (Mo disc is a conversion target and a sample target, and the patent: 201910769344.1) is optimized to have the thickness of 2.0RL-3RL, so that the yield and the specific activity of the sample are optimal. We chose a practical thickness of the bifunctional target of 3.0cm. In order to effectively dissipate heat, the sample target is made into a series of target plates with the thickness of 1.0-2.0mm and the interval of 0.5-1.0mm to form a target plate assembly, and high-pressure helium flow passes through the gap of the target plate to cool the whole target plate assembly.

To this end, we studied the Monte Caro kernel simulation program separately from ¹⁰⁰ Generated when Mo target is irradiated on one side or two sides ⁹⁹ Mo yield. ¹⁰⁰ The Mo sample target consisted of 30 target pieces 1.0mm thick and 1.0mm apart. The results are shown in FIG. 15. The results show that the yield and specific activity of 99Mo in the two-side irradiated sample target is superior to that of the one-side irradiation. According to the simulation calculation, a target assembly consisting of 30 targets is designed for the purpose of irradiation from two sides, wherein the first 10 targets on two sides are 1.0mm thick and have a gap of 1.0mm, and the middle 10 targets are 1.5mm thick and have a gap of 0.5mm.

Claims

1. A target chamber device for producing radioactive isotopes through a gas cooling accelerator is characterized in that: comprises a shell (1), a gas circuit assembly body (2), a vacuum pipeline (4) and a target assembly body (3);

the gas circuit assembly body (2) comprises a cavity (21), a blind plate (22), and a gas inlet pipeline (23) and a gas outlet pipeline (24) which are respectively communicated with the left side wall and the right side wall of the cavity (21) in a sealing way; the cavity (21) is positioned in the shell (1), the upper end of the cavity (21) is open, and the open end extends out of the shell (1) and is fixed on the shell (1); the blind plate (22) is detachably fixed at the opening end of the cavity (21) in a sealing manner; the air inlet pipeline (23) and the air outlet pipeline (24) extend out of the shell (1) to be connected with an external helium cooling loop system;

the target sheet assembly body (3) is positioned in the cavity (21) of the gas circuit assembly body (2), one end of the target sheet assembly body (3) is fixedly connected with the blind plate (22), the other end of the target sheet assembly body is used for fixing the target sheet assembly body, a single target sheet in the target sheet assembly body is parallel to the central axis of the gas inlet pipeline (23) and the central axis of the gas outlet pipeline (24), and cooling gas in the gas inlet pipeline (23) is ensured to be blown into each gap of the target sheet assembly body;

one end of the vacuum pipeline (4) penetrates into the shell (1), and the other end of the vacuum pipeline is communicated with the vacuum pipeline of the electron accelerator; the central axis of the vacuum pipeline is vertical to the central axes of the air inlet pipeline (23) and the air outlet pipeline (24), and the electron beams in the vacuum pipeline bombard the target piece combination body in the direction vertical to the target piece.

2. The target chamber apparatus for radioisotope production from a gas-cooled accelerator as recited in claim 1, wherein: comprises two sections of vacuum pipelines (4); one end of the vacuum pipeline (4) is a vacuum window, and the vacuum window of one section of the vacuum pipeline is opposite to the front side wall of the cavity (21) of the gas circuit assembly body; the vacuum window of the other section of vacuum pipeline is opposite to the rear side wall of the cavity (21) of the gas circuit assembly body; a gap is formed between the vacuum window and the front side wall and the rear side wall of the cavity of the gas circuit assembly body.

3. The target chamber apparatus for radioisotope production from a gas-cooled accelerator as recited in claim 1, wherein: comprises two sections of tubular vacuum pipelines (4); one end of one section of vacuum pipeline is hermetically connected with the front side wall of the air channel assembly body cavity (21); one end of the other section of vacuum pipeline is hermetically connected with the rear side wall of the cavity (21) of the air passage assembly body.

4. A target chamber apparatus for radioisotope production using a gas-cooled accelerator as claimed in claim 2 or 3, wherein: defining parts of the front side wall and the rear side wall of the cavity of the gas path assembly body bombarded by the electron beams as target windows; the target window is of a convex-concave lens structure, and the concave direction points to the inside of the cavity (21); the thickness of the center of the depression is smaller than that of the edge; wherein the convex surface is an ellipsoid, a spherical surface or a plane.

5. The target chamber apparatus for radioisotope production using a gas-cooled accelerator as claimed in claim 4, wherein: the structure of the air inlet pipeline (23) is the same as that of the air outlet pipeline (24), the air inlet pipeline (23) and the air outlet pipeline (24) respectively comprise a main pipeline (231) and a bell-mouth (232), the large end of the bell-mouth (232) is hermetically connected with the main pipeline (231), the main pipeline (231) is hermetically connected with an inlet and an outlet of an external air cooling loop system, and the small end of the bell-mouth (232) is hermetically connected and communicated with the left side wall and the right side wall of a cavity (21) of an air channel assembly body; wherein the gas is helium.

6. The target chamber apparatus for radioisotope production using a gas-cooled accelerator as claimed in claim 5, wherein: the shell (1) is a square shell, second openings (16) are formed in the upper side wall (12), the lower side wall (13), the left side wall (14) and the right side wall (15), and the size of each second opening (16) can ensure that the gas circuit assembly body (2) can be taken out of the shell (1); the hole positions of the upper side wall (12), the left side wall (14) and the right side wall (15) are all provided with gas circuit fixing flanges (17), and the hole position of the lower side wall (13) is provided with a bottom plate flange (18);

an end flange (26) is arranged on the lower end face of the blind plate (22) of the gas circuit assembly body, a flange hole of the end flange (26) is matched with the cross section shape of the cavity (21), and one end of the cavity (21) penetrates through the flange hole of the end flange (26) and is fixedly connected with the blind plate (22); the end flange (26) is positioned on the upper end surface of the gas circuit fixing flange on the upper side wall of the shell and is fixedly connected with the gas circuit fixing flange; the air inlet pipeline and the air outlet pipeline are fixed with the shell by the air path fixing flanges on the left side wall and the right side wall of the shell.

7. The target chamber apparatus for radioisotope production using a gas-cooled accelerator as claimed in claim 6, wherein: a sealing ring is arranged between the blind plate (22) and the end flange (26); the gas circuit fixing flange (17) is composed of two half flanges.

8. The target chamber apparatus for radioisotope production using a gas-cooled accelerator as claimed in claim 6, wherein: the target assembly (3) comprises a first target clamping plate (31), a second target clamping plate (32) and a third screw (33); the first target plate clamping plate (31) and the second target plate clamping plate (32) have the same structure;

the first target slice clamping plate (31) sequentially comprises a tip (311), a clamping plate section (312) and a target slice fixing part (313) along the length direction of the target slice assembly body (3); the end head (311) is fixedly connected with the blind plate (22); the target sheet fixing part (313) is provided with a through groove (314) with a semicircular cross section, and the length direction of the through groove (314) is consistent with the width direction of the target sheet assembly body (3); a plurality of gaps (315) for fixing a single target are formed along the groove wall of the semicircular through groove (314), and the plurality of gaps (315) are formed along the circumferential direction of the groove wall and are axially arranged;

and a plurality of target plates are respectively inserted into the notches to form a target plate assembly, and then the first target plate clamping plate (31) and the second target plate clamping plate (32) are fixed through a third screw (33).

9. The target chamber apparatus for radioisotope production using a gas-cooled accelerator as claimed in claim 7, wherein: the target sheet assembly (34) is formed by combining 30 single target sheets, the diameter of each single target sheet is 20mm, and the thickness of each single target sheet is 1.0-2.0mm; the axial clearance between two adjacent gaps (315) is 0.5-1.0mm.

10. The target chamber assembly of claim 9, wherein the gas-cooled accelerator comprises: the target sheet assembly (34) is a dual-function target of bremsstrahlung and photonuclear reaction;

the thickness of the first 10 target pieces on the two sides is 1.0mm, and the axial clearance between the first 10 adjacent gaps on the two sides is 1.0mm; the thickness of the middle 10 target pieces is 1.5mm, and the axial clearance between the middle 10 adjacent gaps is 0.5mm;

temperature sensors are arranged in the air inlet pipeline and the air outlet pipeline to detect the temperature of the air flow at the inlet and the outlet.