RU2360357C1 - Pulse generator - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: present invention relates to generation of electronic beams and X-rays, and can be used in applied physics researches, such as material-radiation interaction, high-speed processes, laser pumping, as well as in plasma chemistry, radiochemistry, biology etc. The generator of pulses of ultrashort avalanche electron beams contains coaxially fitted in a case (1), a power source with a step up pulse transformer on an open coaxially symmetrical magnetic core (2), peaker discharger (3), the housing of which forms with the housing of the generator, a short line with oil insulation, and a gas diode (5), the cathode holder (4) of which is connected to the high-voltage lead of the discharger. For uniform distribution of induced electric potential the inner part of the ferrite magnetic core is partitioned by dielectric insertions. The peaker discharger works in the first half-wave of charging voltage. The short line provides for duration of the high-voltage pulse on half-height of not more than 0.5 ns.

EFFECT: generation of high-energy (hundreds of keV) subnanosecond streams of electrons and X-ray quanta with pulse duration less than 0,2 ns in a gas diode at atmospheric pressure or higher.

3 cl, 1 dwg

Description

The invention relates to the field of generation of electron beams and x-rays and can be used in applied physical research, such as the interaction of radiation with matter, fast processes, pumping lasers, as well as in plasma chemistry, radiation chemistry, biology, etc.

A device is known for producing nanosecond beams of fast electrons in vacuum with its output through a foil based on a small-sized pulse-periodic high-current power source with a resonant transformer on an open magnetic circuit and a forming line combined with it [1]. High-voltage nanosecond pulses in this device are formed using a step-up pulse transformer with subsequent aggravation of the front by means of a surge arrester. The step-up pulse transformer is assembled on an open cylindrical magnetic circuit. This device allows you to receive voltage pulses with a duration of half maximum 5 ns.

The disadvantage of this device is the inefficient use of magnetic flux due to the geometry of the magnetic circuit and the large electric length of the forming line.

A device for producing nanosecond beams of fast electrons in vacuum with its output through a foil based on a small-sized pulse-periodic high-current power source with a resonant transformer on an open magnetic circuit and a forming line combined with it [2]. An open magnetic circuit of a pulse transformer consists of an external and internal magnetic circuit located coaxially in the transformer. Such a transformer has a higher coupling and transformation ratio. With a storage power line capacity of 55 pF, the total electrical length of the forming line is no more than 2 ns.

A disadvantage of the device for producing short-pulse modes is the large electric length of the forming line.

Closest to the claimed invention is a small-sized high-current electron generator of the RADAN series [3]. The generator contains a high voltage pulse transformer with an open magnetic circuit. The presence of an external magnetic circuit allows you to place the transformer in a metal case, almost completely shielding interference. The design of the transformer, combined with the forming line and having a coaxial open magnetic circuit, makes it possible to obtain a coupling coefficient between the windings close to unity. The primary winding of the step-up transformer is wound with four turns of paper-insulated copper foil. The secondary winding contains 400 turns of PESHO brand wire wound around a thin-walled conical frame. This device allows you to receive voltage pulses with a duration of about 1.5-2 ns.

The disadvantages of this device are the increased requirement for the dielectric strength of the insulation of the forming line gap, the insulator of the high-voltage surge arrester during operation of the pulse transformer at the second half-wave of the charging voltage, the inability to receive pulses of electron beams and X-ray radiation of subnanosecond duration in vacuum sealed electron and x-ray tubes based on this generator .

The technical task of the present invention is the formation of high-energy (hundreds of keV) subnanosecond electron and X-ray fluxes with a pulse duration of less than 0.2 ns pulse generator with a gas diode of atmospheric pressure and above.

The solution to the technical problem is achieved by the fact that in a pulse generator of ultrashort avalanche electron beams containing coaxially in the housing a power supply with a step-up pulse transformer on an open coaxially symmetric magnetic circuit, an aggravated arrester, the housing of which forms a short forming line with oil insulation with the generator housing, and a diode, the cathode holder of which is connected to the high-voltage output of the spark gap, according to the invention, in a pulse transformer, the magnetic circuit is made in e ferrite two coaxial cylinders which are electrically connected to the low voltage side of the transformer and by the open-loop peaking of the arrester, wherein the inner magnetic core portion is partitioned dielectric inserts and diode has a gas filling.

In addition, in the pulse generator, the short forming line has a length that provides a voltage pulse duration at half maximum of no more than 0.5 ns.

In addition, in the pulse generator, the anode of the gas diode is made of metric foil with a large atomic number.

The implementation of the inner part of the ferrite magnetic core by sectioned dielectric inserts allows you to evenly distribute the induced electric potential, which allows to obtain high electrical strength of the pulse transformer, to reduce its overall dimensions, in conjunction with an sharpener, to obtain a short forming line loaded with a gas diode with the lowest possible inductance, to obtain ultrashort avalanche electron beams and x-rays.

The drawing shows a General view of the accelerator. The generator housing (1) contains: a pulsed resonant transformer assembled on an open ferrite coaxial-symmetric magnetic circuit (2), an sharpener (3), the high-voltage output of which is connected to the cathode of a gas diode (4), a gas diode (5) filled with atomic , molecular gas or gas mixture. The magnetic circuit (2) is made of ferrite and has a gap in the high voltage part. In order to distribute the induced electric potential, the inner part of the magnetic circuit is partitioned and consists of six ferrite rings separated by polyester paper insulators (7). The primary winding (8) of the pulsed step-up transformer is wound with copper tape on a cardboard sleeve, and the secondary winding (9) is wound on a thin-walled frame (10) made of caprolon and has a low inductive electrical connection with the sharpening arrestor (3). The metal shell of the spark gap (3) and the metal case (1) of the generator form a forming line and at the same time a high-voltage capacitor, in which the transformer oil is a dielectric medium. The high voltage terminal (4) of the arrester is elongated and is the cathode holder of the gas diode. The chamber (5) of the gas diode is made of caprolon, on the outer surface of which a charging inductance (11) is wound. The anode (6) of the gas diode is made of aluminum foil with a thickness of 50 μm. The high-voltage block of the accelerator and the gas diode are made in coaxial geometry. The minimum possible inductance of the generator is provided by the coaxial geometry of the device.

The device operates as follows. The secondary winding of the pulse transformer charges the forming line formed by the outer shell of the sharpening arrestor (3) and the housing (1) of the generator. After switching on the sharpening spark gap 3, the generated voltage pulse is supplied to the cathode of the gas diode by means of a transmission line formed by the output of the spark gap, a cathode holder (4) and a generator housing (1). The formation of the electron beam occurs at the front of the applied voltage pulse, the beam is formed between the moving front of the pulsed volume discharge and the anode. In this case, the plasma propagation velocity is determined by fast electrons arising at the cathode due to field amplification at the cathode and cathode spots.

Using a pulse generator that generates voltage pulses with a front duration of not more than 0.4 ns, performing the inductance of the discharge circuit and the surface of the insulator of the gas diode is minimally sufficient for the voltage supplied to the gas diode and using an sharpening arrester with a response time of less than 1 ns and a cathode rolled up with a thin-walled tube of rolled stainless steel with a thickness of 100 microns, allows you to effectively form an ultra-short stream of electrons and x-rays in gaseous atmospheres osfernogo pressure or higher. In this design, in a volume pulsed discharge, the bulk of runaway electrons at low initial parameters E / p ~ 0.1 kV / cm · Torr (E is the electric field strength, p is the gas pressure) is formed in the space between the plasma that formed on the cathode, and anode. The cathode plasma propagates at high speed to the anode, while due to the redistribution of the electric field in the part of the gas diode, a critical value of E / p is achieved, including due to the geometric factor.

The generator contains in a coaxial circuit a source of high voltage pulses and a gas diode filled with air. Voltage pulses of ~ (150-160) kV with a half-maximum duration of ~ 0.5 ns with a rise front of ~ 0.3 ns were applied to the gas diode in which the point-to-plane two-electrode system is located. The cathode was in the form of a thin-walled tube with a diameter of 6 mm, rolled from a foil (100 μm) of stainless steel. Anode is a plane of aluminum foil 50 microns thick. The electron beam was extracted through the anode window. The optimal anode-cathode distance was 12 mm. An electron beam with a current amplitude of ~ 20 A and a pulse duration at half maximum of ~ 100 ps was obtained.

Information sources

1. Belkin N.V., Kolesov V.I., Khudyakov L.N. Generators of nanosecond pulses of fast electrons with energies up to 500 keV. PTE No. 5, 1981, p.145.

2. Month G.A. High current electron beams in technology. Publishing house "Science" of the Siberian Branch of the Academy of Sciences of the USSR, Novosibirsk, 1983, p.125-129.

3. Zagulov F.Ya., Kotov A.S., Shpak V.G., Yurike Y.Ya., Yalandin M.I. RADAN - small-sized high-current electron accelerators of pulse-periodic action. PTE No. 2, 1989, p.146.

4. Alekseev S.B., Orlovsky V.M., Tarasenko V.F. Generator of subnanosecond electron beams. Patent for the invention of the Russian Federation No. 2222062.

5. Zheltov K.A., Malygin A.V., Rozov V.I., Shalimov V.F. A nanosecond high-current electron accelerator with a stable energy of 1 MeV. PTE, No. 5, 1981, pp. 23-26.

6. Alekseev S.B., Orlovsky V.M., Tarasenko V.F. A method of obtaining a subnanosecond electron beam. Patent for the invention of the Russian Federation No. 2244361.

Claims (3)

1. Pulse generator of ultrashort avalanche electron beams, containing a power source coaxially in the housing with a step-up pulse transformer on an open coaxially symmetric magnetic circuit, an sharpening arrester, the housing of which forms a short forming line with oil insulation with the generator housing, and a diode whose cathode holder is connected to a high-voltage output spark gap, characterized in that in a pulse transformer the magnetic circuit is made in the form of two coaxial ferrite cylinders, an electric cally interconnected by the low-voltage side of the transformer, and open from the peaking surge arrester, the interior of the magnetic partitioned dielectric inserts and diode has a gas filling. 2. The pulse generator according to claim 1, characterized in that the short forming line has a length that ensures the duration of the voltage pulse at half maximum not more than 0.5 ns. 3. The pulse generator according to claim 1 or 2, characterized in that the anode of the gas diode is made of metric foil with a large atomic number.