TECHNICAL FIELD

The subject disclosure relates, but is not limited, to field of irradiation processing, and in particular to an electron beam focusing device.

BACKGROUND

There may be two types of sources of radiation for radiation processing. One may be a source of a radioactive isotope such as cobalt. The other may be an accelerator for accelerating charged particles such as electrons. An electron accelerator is advantageous as follows. Energy is controllable. A beam of electrons may essentially act on a product illuminated by the beam with high utilization. There is no issue of processing a source of radioactive waste. No electricity is consumed during shutdown. There is barely any pollution to the environment during the entire production except for a trace of ozone being produced. Consequently, more users tend to employ an electron accelerator in radiation processing.

During transmission of a beam of electrons accelerated in an electron accelerator, the greater a transverse envelope and a longitudinal envelope of the beam are, the greater a beam restraining loss, and the poorer the transmission performance of the beam restraining. In some cases, once production of an electron beam focusing device completes, then a performance parameter for the device to perform beam restraining on a beam of electrons is determined, failing to meet demands of focusing a beam of electrons in different application scenes.

SUMMARY

In view of this, at least one embodiment herein provides a system of electron irradiation.

A system of electron irradiation includes an electron accelerator and an electron beam focusing device.

The electron accelerator is arranged for emitting and accelerating a beam of electrons.

The electron beam focusing device is located at a rear end of the electron irradiation. The electron beam focusing device includes a beam restraining rail and 2n+1 sets of magnetic poles.

The beam restraining rail forms a beam restraining channel through which the beam of electrons are to pass.

The 2n+1 sets of magnetic poles are installed on the beam restraining rail. The 2n+1 sets of magnetic poles are distributed at different locations of the beam restraining channel. An nth set of magnetic poles of the 2n+1 sets of magnetic poles are arranged for performing, on the beam of electrons, focusing in a first direction. An (n+1)th set of magnetic poles of the 2n+1 sets of magnetic poles are arranged for performing, on the beam of electrons, focusing in a second direction. The second direction is perpendicular to the first direction. The n is a positive integer.

The 2n+1 sets of magnetic poles may include a first set of magnetic poles, a second set of magnetic poles, and a third set of magnetic poles.

The first set of magnetic poles may be arranged for performing, on the beam of electrons, first-time focusing in the first direction.

The second set of magnetic poles may be arranged for performing, on the beam of electrons, focusing in the second direction.

The third set of magnetic poles may be arranged for performing, on the beam of electrons, second-time focusing in the first direction.

At least part of the 2n+1 sets of magnetic poles may be movably installed on the beam restraining rail, with a spacing between any two neighbor sets of magnetic poles being adjustable.

Of the 2n+1 sets of magnetic poles, a second set of magnetic poles and/or a third set of magnetic poles may be movably installed on the beam restraining rail.

Different locations of the second set of magnetic poles on the beam restraining rail may correspond respectively to different first spacings between the second set of magnetic poles and a first set of magnetic poles of the 2n+1 sets of magnetic poles.

And/or, different locations of the third set of magnetic poles on the beam restraining rail may correspond respectively to different second spacings between the third set of magnetic poles and the second set of magnetic poles.

Different spacings between a first set of magnetic poles and a last set of magnetic poles of the 2n+1 sets of magnetic poles may correspond respectively to different lengths of a drift space in the beam restraining channel in which the beam of electrons drift.

The sets of magnetic poles may be sets of quadrupole magnetic poles.

The sets of quadrupole magnetic poles may be composed of permanent magnets.

The permanent magnets may be made from NdFeB.

A permanent magnet of the 2n+1 sets of magnetic poles may be installed on the beam restraining rail through a yoke ring.

The yoke ring may be made by connecting multiple yokes. Different connection locations between two neighbor yokes may correspond respectively to different diameters of the yoke ring.

The system may further include an electron beam detecting device arranged for detecting the beam of electrons.

The electron beam detecting device may include an electron collecting device, a sampling box, a communicating box, and a controller.

The electron collecting device may be located, together with the electron accelerator, inside a shield room. The electron collecting device may be arranged for acquiring a first signal by detecting a strength of the beam of electrons radiated by the electron accelerator.

The sampling box may be located inside the shield room. The sampling box may be connected to the electron collecting device. The sampling box may be arranged for receiving the first signal and converting the first signal into a second signal which is an optical signal that reflects a degree of uniformity of irradiation of the beam of electrons.

The communicating box may be located outside the shield room. The communicating box may be connected to the sampling box through an optical fiber. The communicating box may be arranged for receiving the second signal through the optical fiber and converting the second signal into a third signal which is an electric signal.

The controller may be located outside the shield room. The controller may be connected to the communicating box. The controller may be arranged for receiving the third signal and controlling detection of the beam of electrons.

The communicating box and the controller may be located inside a control room. A metal shield wall may be provided between the control room and the shield room.

A perforation through which the optical fiber is to pass may be provided on the metal shield wall.

The sampling box may include a current to voltage converting circuit, a digital to analog converter, a sampling chip, and a photoelectric converting circuit.

The current to voltage converting circuit may be connected to the electron collecting device. The current to voltage converting circuit may be arranged for receiving the first signal, which is a current signal, and converting the current signal into a voltage signal.

The digital to analog converter may be connected to the current to voltage converting circuit. The digital to analog converter may be arranged for converting the voltage signal, which may be an analog signal, into a digital signal.

The sampling chip may be connected to the digital to analog converter. The sampling chip may be arranged for converting the digital signal into a third signal that reflects the degree of uniformity of irradiation of the beam of electrons,

The photoelectric converting circuit may be connected to the sampling chip. The photoelectric converting circuit may be arranged for converting the third signal into the second signal which is the optical signal.

The system may further include an electron collecting scaffold and a driving device.

The driving device may be connected to the electron collecting device.

The driving device may be arranged for providing the electron collecting device with a driving force.

The electron collecting device may be installed on the electron collecting scaffold. Driven by the driving force, the electron collecting device may move based on the electron collecting scaffold.

The electron collecting scaffold may include an electron collecting rail.

The electron collecting device may be movably installed on the electron collecting rail. The electron collecting device may be allowed of a one-dimensional movement along the electron collecting rail.

The driving device may include a stepper motor.

The electron collecting scaffold may be movably installed on an installation location of an irradiation processing production line.

If the electron collecting scaffold is located at a first location, the electron collecting device may be located on a processing location of the irradiation processing production line, and may be arranged for detecting the strength of the beam of electrons for irradiation processing. The processing location may be where a product is to be processed.

If the electron collecting scaffold is located at a second location, the electron collecting device may be located off the processing location.

With an electron beam focusing device according to at least one embodiment herein, an odd number of sets of magnetic poles may be installed on a beam restraining rail. Any set of magnetic poles of an odd ordinal number may focus the beam of electrons in a direction different from a direction in which any set of magnetic poles of an even ordinal number may focus the beam of electrons. As there may be an odd total number of sets of magnetic poles, a subsequent set of magnetic poles may focus the beam of electrons again to at least partially cancel out defocusing effect in the focusing direction of the set of magnetic poles under consideration brought about by a prior set of magnetic poles, thereby improving focusing effect of the electron beam focusing device, ultimately improving focus performance of the beam of electrons.

