CN103528547B - A kind of device and method measuring electron linear accelerator focal spot size - Google Patents

Abstract

The invention discloses a method for measuring the focus size of an electron linear accelerator, comprising step 1: placing a collimator with two collimation slits directly in front of the accelerator focus f, the two collimation slits are arranged symmetrically; the two collimation slits The included angle with the centerline of the collimator is β, and the symmetry axis of the two collimation slits coincides with the center of the accelerator beam; a detector is respectively installed at the end of the two collimation slits; Step 2: Move the collimator and the detector , when a sudden change in the detector value is observed, record the position of the collimator at this time as 2; Step 3: Continue to move the collimator and detector in the same direction, and when a sudden change in the detector value is observed again, the collimator The position of the collimator is recorded as position 3; step 4: measure the distance S ₂₃ between position 2 and position 3 of the collimator, and the angle β of the collimation slit; step 5: calculate the size of the accelerator focus f. The invention observes the change of the value of the detector and measures the moving distance of the collimator through the transverse scanning mode, so as to calculate the size of the focal point.

Description

A device and method for measuring the focal point size of an electron linear accelerator

technical field

The invention relates to the field of ray sources, in particular to a device and method for measuring the focus size of an electron linear accelerator.

Background technique

Electron linear accelerators have the characteristics of high ray energy, strong penetrating power, large dose rate, small focus, high detection precision, and faster detection speed. Non-destructive testing and quality evaluation. It meets the special non-destructive testing needs of large-scale equipment in aerospace, national defense and military industries, transportation, iron and steel metallurgy, geology, petroleum and other industries. It is an indispensable and important means to ensure the quality and safety of these special products, and has huge social value. and application value.

The size of the focal point of the electron linear accelerator is one of the key technical indicators of the electron linear accelerator. It has a significant impact on the geometric unsharpness of radiography, real-time imaging, and the spatial resolution of industrial CT. Smaller focus sizes produce less geometric unsharpness and sharper images. The measurement methods of the focus size of electron linear accelerator mainly include pinhole imaging method, line penetrometer method and slit method. Often used is the gap method or "sandwich" method. However, due to the high energy of the accelerator rays and the small focus, the measurement methods currently used have large errors, and it is difficult to meet the measurement requirements.

For example, the "sandwich" used in the standard GB/ _T20129-2006 is to use copper or lead sheets with a thickness of _h1 and plastic sheets with a thickness of h2 to form a "sandwich" with a length of about 300mm, clamped with steel plates to form a sandwich focus measuring device. When measuring, place the laminated block at the X-ray output port of the accelerator, as close as possible to the target. When X-rays pass through the laminated block, the copper foil will block the rays, and the rays will pass through the corresponding slits of the plastic sheet to make the film placed at the other end of the stacked block sensitive. After exposure, several black stripes will appear on the exposed film. The part is relatively dark, and the blackness on both sides is small, and the number n of black bars whose blackness is greater than 50% of the blackness in the center is taken. The focus f size is calculated by the formula f=n×(h ₁ +h ₂ ).

From the above measurement methods, it can be seen that the measurement results of the "sandwich" method are susceptible to many subjective and objective factors such as the inhomogeneity of the accelerator ray field, the exposure time of the film, the quality of the developed film, the distance between the stack and the focus of the accelerator, and visual misreading by personnel. , so the measurement error is large.

Contents of the invention

In view of this, the present invention discloses a device for measuring the focus size of an electron linear accelerator by using the angle translation method, and also discloses a measuring method for measuring by using the above-mentioned device. The device observes the change of the detector value by scanning horizontally, and measures the moving distance of the collimator, so as to calculate the size of the focal point.

One of the objectives of the present invention is achieved by the following technical solutions: a device for measuring the focal point size of an electron linear accelerator, comprising a collimator with a first collimation slit, and a collimator is arranged at the end of the first collimation slit Detector, the angle between the first collimating slit and the collimator is β, and the collimator allows the chief ray emitted by the accelerator to pass through the collimating slit, so that the detector collects incident photons; Slits the ray photons and converts them into a measurable signal, which is used to measure the intensity of the ray.

Further, the collimator is also provided with a second collimation slit, a detector is arranged at the end of the second collimation slit, the angle between the second collimation slit and the collimator is β, and the second collimation slit The slit is arranged symmetrically with the first collimating slit, and the symmetry axis of the two collimating slits coincides with the center of the accelerator ray beam.

Further, the collimator is made of lead, tungsten or tungsten alloy.

Further, the first collimation slit and the second collimation slit are less than or equal to 0.2mm.

Two of object of the present invention is to provide a kind of method utilizing above-mentioned device to measure the focal point size of electron linear accelerator, comprising the following steps:

Step 1: Place a collimator directly in front of the accelerator focus;

Step 2: Move the collimator and detector, and record the position of the collimator as 2 when a sudden change in the value of the detector is observed;

Step 3: Continue to move the collimator and detector in the same direction, and when you observe a sudden change in the value of the detector,

The position of the straightener is marked as position 3;

Step 4: Measure the distance S ₂₃ between position 2 and position 3 of the collimator, and the angle β between the collimator slit and the collimator;

Step 5: Calculate the size of the accelerator focus by the formula f=tanβ×S ₂₃ .

Further, the collimator is made of lead, tungsten or tungsten alloy.

Further, the collimation slit is less than or equal to 0.2mm.

Beneficial technical effects:

1. The present invention does not need to use film for photosensitization, which reduces the errors that are difficult to control in the steps of film exposure and film processing, making the measurement results more accurate.

2. The present invention observes the change of the value of the detector and measures the moving distance of the collimator by means of horizontal scanning, so as to calculate the size of the focal point.

3. It avoids the influence of many subjective and objective factors such as the inhomogeneity of the accelerator ray field, the distance between the lamination and the accelerator focus, and the visual misreading of personnel in the "sandwich" method.

Description of drawings

In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be described in further detail below in conjunction with the accompanying drawings, wherein:

Fig. 1 is the measuring schematic diagram of measuring the focal point size of electron linear accelerator;

Figure 2 is the count diagram of the detector.

detailed description

The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings; it should be understood that the preferred embodiments are only for illustrating the present invention, rather than limiting the protection scope of the present invention.

A device for measuring the focus size of an electron linear accelerator, comprising a collimator 2, the collimator has a first collimation slit 1, the collimation slit passes through the collimator, and a collimator is arranged at the end of the first collimation slit Detector 3, the angle between the first collimating slit and the collimator is β, and the collimator allows the chief ray emitted by the accelerator to pass through the collimating slit, so that the detector collects incident photons; Ray photons from the slit are collimated and converted into a measurable signal, which is used to measure the intensity of the ray.

As an improvement to this embodiment, the collimator is further provided with a second collimation slit 4, and setting two collimation slits can further ensure the accuracy of measurement.

A detector is arranged at the end of the second collimating slit, the angle between the second collimating slit and the collimator is β, the second collimating slit is arranged symmetrically with the first collimating slit, and the two collimating slits The axis of symmetry coincides with the center of the accelerator beam.

The first collimating slit and the second collimating slit are less than or equal to 0.2mm. The collimator is made of lead, tungsten or tungsten alloy.

A method for measuring the focus size of an electron linear accelerator by using the above-mentioned device, comprising the following steps:

Step 1: Place a collimator directly in front of the accelerator focus;

Step 2: Move the collimator and detector, and record the position of the collimator as 2 when a sudden change in the value of the detector is observed;

Step 3: Continue to move the collimator and detector in the same direction, and when a sudden change in the detector value is observed, the position of the collimator at this time is recorded as position 3;

Step 4: Measure the distance S ₂₃ between position 2 and position 3 of the collimator, and the angle β between the collimator slit and the collimator;

Step 5: Calculate the size of the accelerator focus by the formula f=tanβ×S ₂₃ .

The invention does not need to use film for photosensitization, reduces the errors that are difficult to control in the steps of film exposure and film processing, and makes the measurement result more accurate. Since the focus size of the accelerator is generally relatively small, direct scanning measurement will make the scanning accuracy difficult to control and the error will be large; the present invention observes the change of the detector value and measures the moving distance of the collimator to calculate the focus size by means of horizontal scanning the size of. In the "sandwich" method, the influence of many subjective and objective factors such as the inhomogeneity of the accelerator ray field, the distance between the lamination and the focus of the accelerator, and visual misreading by personnel is avoided.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and equivalent technologies thereof, the present invention also intends to include these modifications and variations.

Claims (3)

1. A method for measuring the focal point size of an electron linear accelerator, the device used to measure the focal point size of an electron linear accelerator comprises a collimator with a first collimating slit, and a detector is arranged at the end of the first collimating slit , the angle between the first collimating slit and the collimator is β, and the collimator allows the chief ray emitted by the accelerator to pass through the collimating slit, so that the detector collects incident photons; the detector collects and passes through the collimating slit The photon of the ray and convert it into a measurable signal for measuring the intensity of the ray, is characterized in that: comprising the following steps: Step 1: Place a collimator directly in front of the accelerator focus; Step 2: Move the collimator and detector, and record the position of the collimator as 2 when a sudden change in the value of the detector is observed; Step 3: Continue to move the collimator and detector in the same direction, and when a sudden change in the detector value is observed, the position of the collimator at this time is recorded as position 3; Step 4: Measure the distance S ₂₃ between position 2 and position 3 of the collimator, and the angle β between the first collimation slit and the collimator; Step 5: Calculate the size of the accelerator focus by the formula f=tanβ×S ₂₃ . 2. A method for measuring the focal point size of an electron linear accelerator according to claim 1, wherein the collimator is made of lead, tungsten or tungsten alloy. 3. A method for measuring the focal point size of an electron linear accelerator according to claim 2, wherein the first collimation slit is less than or equal to 0.2 mm.