CN104505135A - Shielding device and method of electron linear accelerator - Google Patents

Abstract

The invention provides a shielding device and a shielding method of an electron linear accelerator. The shielding device of the electron linear accelerator includes: a target ray shielding, the front end of the accelerator can be arranged inside, and a movable block with an X-ray exit slit is installed inside. It also has: tube ray shielding, the acceleration tube of the accelerator can be arranged inside it; X-ray outlet shielding, arranged at the front end of the target ray shielding, has an outlet opening larger than the X-ray outlet slit; power source inlet The shielding is installed at the position corresponding to the power source of the tube ray shielding, the X-ray exit shielding, the target ray shielding and the tube ray shielding are sequentially configured as a whole, and the electron linear accelerator can be arranged in a the space they surround. The present invention obtains the thickness dimension of each shielding component according to the three-dimensional dose distribution of X-rays obtained by the Mont-Card method. The invention can avoid partial thickening or thinning of partial shielding, and effectively reduce or even cancel additional additional shielding.

Description

A shielding device and shielding method for an electron linear accelerator

technical field

The present invention relates to the field of accelerator X-ray shielding, in particular to a shielding device and shielding method for an electron linear accelerator (hereinafter referred to as an accelerator).

Background technique

In the prior art, a shielding device is provided for the X-rays generated by the accelerator, so that the X-ray leakage radiation level meets the requirements of relevant national standards. There are two main source term parameters related to accelerator shielding design: one is X-ray yield and the other is X-ray energy. The greater the X-ray output and the higher the energy, the more difficult it is to shield. In addition, after the accelerated electrons hit the target, the X-ray yield and energy generated by the X-rays are distributed in three-dimensional space. Therefore, the shielding requirements of different parts are also different.

In the past, shielding designs of accelerators were designed and calculated by empirical methods. It was difficult to fully consider the X-ray yield and energy in three-dimensional space. In the design, some places were shielded too conservatively, while other places were too conservative. Insufficient shielding, and finally, in order to compensate for the lack of shielding, a large amount of additional shielding has to be added around the periphery of the accelerator. Figure 1(a) and (b) are diagrams of accelerator shielding devices based on the prior art, as shown in Figure 1(a), (b), the existing accelerator shielding devices are not optimal accelerators in terms of structure and cost shielding device.

In addition, the current three-dimensional dose calculation program based on the Monte Carlo (hereinafter referred to as Monte Carlo) simulation method has been able to accurately give the dose distribution of accelerator X-rays in the shielding body. For the existing shielding design, it can directly reflect the shielding Weaknesses of the structure. Figure 2 is a diagram of the dose distribution of accelerator X-rays in the shielding body. In Figure 2, the horizontal axis is the height direction (in meters), and the vertical axis is the ray direction (in meters). As shown in Fig. 2, for the existing accelerator shielding, based on the accelerator dose distribution calculated by three-dimensional dose, the shielding weak points and conservative positions can be clearly known.

Contents of the invention

The present invention was made to solve the above-mentioned problems, and an object of the present invention is to provide an electron linear accelerator shielding device and a shielding method capable of accurately shielding X-rays.

In the present invention, based on three-dimensional dose Monte Carlo calculation, for example, an optimized shielding device is designed for 6MeV electron linear accelerator X-rays, the shielding thickness and size of the main shielding structure are clarified, and the additional shielding of the accelerator is determined according to the structural characteristics of the accelerating tube. Shielding thickness and size to ensure the optimization of the structure and size of the entire shielding device.

The invention provides a shielding device for an electron linear accelerator, which is characterized in that,

Equipped with: target ray shielding, used to shield the X-rays generated by the target of the accelerator, the shape is cylindrical and the front end of the accelerator can be arranged inside it, and the X-ray from the accelerator is installed inside. The live block of the X-ray exit slit where the ray exits.

In addition, in the present invention, also have:

Tube ray shielding, used to shield the X-rays generated in the accelerating tube of the accelerator and part of the X-rays generated by the target, the shape is cylindrical and the accelerating tube of the accelerator can be arranged inside it;

an X-ray exit shield disposed at the front end of the target ray shield and having an exit opening larger than the X-ray exit slit; and

The power source inlet shield is installed at the position corresponding to the power source of the tube radiation shield, and is used to shield the direct and scattered X-rays from the power source inlet,

The X-ray exit shield, the target beam shield, and the tube beam shield are sequentially arranged integrally, and the electron linear accelerator can be arranged in a space surrounded by them.

In addition, in the present invention, the movable block is detachably installed inside the target radiation shield.

In addition, in the present invention, the shielding of the tube radiation includes: the shielding of the first half of the accelerating tube, which is connected to the shielding of the target radiation; the shielding of the second half of the accelerating tube, which is connected to the shielding of the first half of the accelerating tube; The shield is fitted with the shield of the second half of the acceleration tube.

In addition, in the present invention, the material for shielding the target radiation is tungsten, the shielding thickness in the axial direction is greater than or equal to 160 mm, the shielding thickness in the vertical axis direction is greater than or equal to 140 mm, and the shielding thickness at a 45-degree angle relative to the axial direction is greater than or equal to 170 mm.

In addition, in the present invention, the material for the shielding of the target radiation is lead, and its shielding thickness in the axial direction is greater than or equal to 250 mm, the shielding thickness in the vertical axis direction is greater than or equal to 214 mm, and the shielding thickness at a 45-degree angle relative to the axial direction is greater than or equal to 255 mm.

In addition, in the present invention, the first half of the acceleration tube shield is a tungsten shield with a thickness greater than or equal to 84 mm in the vertical axis direction or a lead shield with a thickness greater than or equal to 120 mm in the vertical axis direction, and the second half of the acceleration tube shield is a tungsten shield with a thickness in the vertical axis direction of A lead shield with a thickness greater than or equal to 100mm, and the tail shield is a tungsten shield with a thickness greater than or equal to 130mm or a lead shield with a thickness greater than or equal to 180mm.

In addition, in the present invention, the X-ray exit shielding material is lead, which is located on both sides of the X-ray exit, and its main structure has a trapezoidal cross-section, with a bottom width greater than or equal to 75 mm, a top width greater than or equal to 35 mm, and a length greater than or equal to 120 mm. , the exit opening is more than 7mm larger than the X-ray exit slit.

In addition, in the present invention, the material of the power source inlet shield is lead, the thickness of the side is greater than or equal to 15mm, and the total thickness of the top is greater than or equal to 40mm.

In addition, the present invention provides an electron linear accelerator X-ray shielding method, which is characterized in that it has:

The step of obtaining the three-dimensional dose distribution of X-rays;

A step of obtaining the thickness dimension of each shielding component according to the obtained three-dimensional dose distribution of X-rays; and

A step of arranging a shielding component having the thickness dimension at a corresponding position of the electron linear accelerator.

Furthermore, in the present invention, the Monte Carlo method is used in the step of obtaining the three-dimensional dose distribution of X-rays.

As mentioned above, according to the invention of the present application, the shielding structure of the main body of the accelerator is optimized to avoid the situation that the local shielding is too thick or too thin; the use of loose parts in the accelerator shielding structure facilitates the modification of the slit width of the accelerator ray exit, avoiding the The replacement of the shielding structure; the optimization of the X-ray exit shielding structure effectively shields the influence of the exit scattered rays on the radiation level of the whole system; the use of power source entrance shielding strengthens the weak link of the entire accelerator shielding, which can effectively reduce, Even cancel the application of additional additional shielding.

Description of drawings

FIG. 1 is a diagram of an accelerator shielding device based on the prior art.

Fig. 2 is a diagram of the dose distribution of accelerator X-rays in the shielding body.

Fig. 3 is a schematic structural view of the electron linear accelerator shield of the present invention.

Fig. 4 is a cross-sectional view of the structure of the electron linac shield of the present invention.

Fig. 5 is a perspective view of the structure of the electron linac shield of the present invention.

Detailed ways

Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. In addition, in the present invention, the shielding device of a 6 MeV electron linear accelerator is described as an example, but it is not limited thereto, and of course it can also be applied to the shielding of electron accelerators of other energies.

Figure 3 is a schematic structural view of a 6MeV electron linear accelerator shield of the present invention, wherein (a) is a horizontal cross-sectional view of the central axis, (b) is a vertical cross-sectional view, and Figure 4 is a shield of a 6MeV electron linear accelerator of the present invention, for example A cross-sectional view of the structure, FIG. 5 is a perspective view of the structure of, for example, a 6MeV electron linear accelerator shield of the present invention. As shown in Figure 3(a) and (b), the shielding device of the 6MeV electron linear accelerator of the present invention includes target ray shielding, tube ray shielding, tail shielding, X-ray exit shielding and power source entrance shielding.

In the present invention, firstly, the three-dimensional dose distribution of 6MeV electron linear accelerator X-rays in the shielding body is calculated based on the three-dimensional dose Monte Calculation, and then, the thickness of each part of the accelerator shielding is optimized according to the calculated three-dimensional dose distribution.

As shown in Figures 3 to 5, the target radiation shielding structure is cylindrical and used to shield the X-rays generated by the target. Specifically, the outer shape of the target ray shield is cylindrical and the front end of the 6MeV electron linac (that is, the end of the 6MeV electron linac where the target is arranged) can be arranged inside it. The block of the X-ray exit slit for emitting the X-rays from the accelerator (ie, the ray exit slit block shown in FIG. 4 ). In addition, the thickness of the shield varies depending on the material used for the shield.

In addition, regarding the shielding material of the target ray, when the shielding material is tungsten, the shielding thickness in the axial direction is greater than or equal to 160mm, the shielding thickness in the vertical axis direction is greater than or equal to 140mm, and the shielding thickness in a 45-degree angle relative to the axial direction is greater than or equal to 170mm. The axis direction mentioned all refers to the axis direction of the cylinder constituting the target ray shielding.

In addition, when the shielding material is lead, the shielding thickness in the axial direction is greater than or equal to 250mm, the shielding thickness in the perpendicular axis direction is greater than or equal to 214mm, and the shielding thickness at a 45-degree angle relative to the axial direction is greater than or equal to 255mm.

In addition, by installing a movable block structure inside the target radiation shield, such as the ray exit slit block shown in FIG. 4 , the width of the X-ray exit slit can be changed by replacing the movable block.

In addition, the tube radiation shielding structure is cylindrical and the accelerating tube of the accelerator can be arranged inside it, which is used to shield the X-rays generated in the accelerating tube and part of the X-rays generated by the target. Furthermore, the tube ray shielding includes the first half shield of the accelerating tube arranged in contact with the target ray shield, the second half shield of the accelerating tube arranged in contact with the first half shield of the accelerating tube, and the tail shield fitted with the second half shield of the accelerating tube . The X-ray exit shield, the target ray shield and the tube ray shield are sequentially arranged as a whole, and the 6MeV electron linear accelerator can be arranged in the space surrounded by them.

According to the above-mentioned three-dimensional dose distribution results based on three-dimensional dose Monte Carlo calculations, the shielding of the first half of the accelerating tube is tungsten shielding with a thickness greater than or equal to 84mm in the vertical axis direction or lead shielding with a thickness greater than or equal to 120mm in the vertical axis direction, and the second half of the accelerating tube is The shield is a lead shield with a thickness greater than or equal to 100mm in the vertical axis direction, and the tail shield is a tungsten shield with a thickness greater than or equal to 130mm or a lead shield with a thickness greater than or equal to 180mm.

In addition, the shielding body of the X-ray exit is made of lead material, which is used to shield the X-rays scattered by the X-ray exit of the accelerator. The horizontal section of the main structure is trapezoidal, the bottom width is greater than or equal to 75mm, the top width is greater than or equal to 35mm, and the length is greater than 120mm, and the size of the exit opening is more than 7mm larger than the above-mentioned X-ray exit slit.

In addition, the shielding body of the power source entrance is made of lead material, which is used to shield the direct and scattered X-rays from the power source entrance. The power source inlet shield is installed at the position corresponding to the power source of the tube ray shield, and its side is made of lead with a thickness greater than or equal to 15mm, that is, except for necessary openings, all four sides are lead with a thickness greater than or equal to 15mm, and the total amount of lead on the top The thickness is greater than or equal to 40mm. In addition, in order to facilitate installation and achieve a better shielding effect, as shown in Figure 4, the top shielding is divided into three layers according to the structural characteristics of the power source. The opening to its interior, the second layer determines the position according to the needs, and the third layer is the power source entrance labyrinth.

As shown in Figures 3 to 5, the X-ray exit shield, target ray shield, power source entrance shield, tube ray shield and tail shield are sequentially arranged as a whole, and the 6MeV electron linear accelerator can be arranged in the space surrounded by them, thereby Well shielded from X-rays from 6MeV electron linacs.

As mentioned above, according to the invention of the present application, the shielding structure of the main body of the accelerator is optimized to avoid the situation that the local shielding is too thick or too thin; the use of loose parts in the accelerator shielding structure facilitates the modification of the slit width of the accelerator ray exit, avoiding the The replacement of the shielding structure; the optimization of the X-ray exit shielding structure effectively shields the influence of the exit scattered rays on the radiation level of the whole system; the use of power source entrance shielding strengthens the weak link of the entire accelerator shielding, which can effectively reduce, Even cancel the application of additional additional shielding.

In addition, the present invention is not limited to 6MeV electron linear accelerators, and can also be used in other energies or other types of accelerators, as long as the three-dimensional dose distribution of accelerator X-rays in the shielding body can be obtained by using the Monte Carlo method, the method of the present invention can be applied, and Get the corresponding shielding device.

The structure of the shielding device for a 6 MeV electron linear accelerator and the specific data of each part have been described above, but the invention is not limited thereto, and the shielding thickness of each part of the shielding device can be set as required. In addition, the shape and material of each part of the shielding device are not limited to the shapes described above, as long as the X-ray shielding requirements can be met, other shapes and other materials can also be used.

Claims (11)

1. a shield assembly for electron linear accelerator, is characterized in that,

Possess: target alpha ray shield, for the X ray that the target shielding described accelerator produces, profile is that the front end of cylindrical and described accelerator can configure therein, and, the loose piece of the X ray exit slit with the X ray outgoing made from described accelerator is housed in inside.

2. the shield assembly of electron linear accelerator as claimed in claim 1, is characterized in that also possessing:

Pipe alpha ray shield, for shielding the partial x-ray that the X ray that produces in the accelerating tube of described accelerator and target produce, profile is that the accelerating tube of cylindrical and described accelerator can configure therein;

X ray exit curtain, is configured in the front end of described target alpha ray shield, has the exit opening larger than described X ray exit slit; And

Power source entry mask, is arranged on the position corresponding with power source of described pipe alpha ray shield, for shielding the X ray of direct projection from power source entrance and scattering,

Described X ray exit curtain, described target alpha ray shield and described pipe alpha ray shield are configured to entirety successively, described electron linear accelerator can be configured in the space surrounded by them.

3. the shield assembly of electron linear accelerator as claimed in claim 1 or 2, is characterized in that,

Described loose piece is arranged on described target alpha ray shield inside in the mode that can dismantle.

4. the shield assembly of electron linear accelerator as claimed in claim 3, is characterized in that,

Described pipe alpha ray shield comprises: accelerating tube first half section shields, and connects configure with described target alpha ray shield; The accelerating tube second half section shields, and shields to connect to configure with described accelerating tube first half section; Afterbody shields, and shields chimeric configuration with the described accelerating tube second half section.

5. the shield assembly of electron linear accelerator as claimed in claim 4, is characterized in that,

The material of described target alpha ray shield is tungsten, and its axis direction shielding thickness is more than or equal to 160mm, and vertical axis direction shielding thickness is more than or equal to 140mm, and relative axis direction miter angle shielding thickness is more than or equal to 170mm.

6. the shield assembly of electron linear accelerator as claimed in claim 4, is characterized in that,

The material of described target alpha ray shield is plumbous, and its axis direction shielding thickness is more than or equal to 250mm, and vertical axis direction shielding thickness is more than or equal to 214mm, and relative axis direction miter angle shielding thickness is more than or equal to 255mm.

7. the shield assembly of the electron linear accelerator as described in any one of claim 4 ~ 6, is characterized in that,

The shielding of described accelerating tube first half section is the lead shield that vertical axis direction thickness is more than or equal to the tungsten shielding of 84mm or vertical axis direction thickness and is more than or equal to 120mm,

Described accelerating tube second half section shielding is the lead shield that vertical axis direction thickness is more than or equal to 100mm,

The shielding of described afterbody is the lead shield that thickness is more than or equal to the tungsten shielding of 130mm or thickness and is more than or equal to 180mm.

8. the shield assembly of the electron linear accelerator as described in any one of claim 4 ~ 6, is characterized in that,

The material of described X ray exit curtain is plumbous, and its agent structure cross section is trapezoidal, and bottom width is more than or equal to 75mm, and top is more than or equal to 35mm, and length is more than or equal to 120mm,

Described exit opening 7mm more than larger than described X ray exit slit.

9. the shield assembly of the electron linear accelerator as described in any one of claim 4 ~ 6, is characterized in that,

The material of described power source entry mask is plumbous, and the thickness of side is more than or equal to 15mm, and top gross thickness is more than or equal to 40mm.

10. a screen method for electron linear accelerator X ray, is characterized in that, possesses:

Obtain the step of the 3-dimensional dose distribution of X ray;

3-dimensional dose according to obtained X ray distributes, and obtains the step of the gauge of each shield member; And

There is in the configuration of the relevant position of electron linear accelerator the step of the shield member of described gauge.

The screen method of 11. electron linear accelerator X ray as claimed in claim 10, is characterized in that,

Monte Carlo method is used in the step of 3-dimensional dose distribution obtaining X ray.