Method for generating subnanosecond electron beam

FIELD: cathode-luminescent analysis of materials, plasmochemistry, quantum electronics, and the like.

SUBSTANCE: proposed method designed for shaping high-energy (hundreds of keV) subnanosecond (t ≤ 1 ns) charged particle beams whose current density amounts to tens of amperes per cm2 in gas-filled gap at atmospheric and higher pressure involves following procedures. Volumetric pulsed discharge is effected in gas-filled electrode gap and electron beam is shaped during breakdown of discharge gap as soon as parameter U/(p x d) is brought to value sufficient for shaping runaway electron beam between front of plasma propagating from cathode and anode and volumetric discharge plasma moving to anode is shaped by pre-ionization of gap with fast electrons formed across voltage pulse wavefront due to intensifying field on anode and/or on cathode plasma spots, where U is voltage, V; p is gas pressure, torr; d is gas-filled gap, mm.

EFFECT: enhanced energy and current density of generated subnanosecond electron beams.

1 cl

 

The invention relates to the field of forming and generating charged particle beams and can be used in cathodoluminescence the analysis of matter, plasma, quantum electronics and so on

A method of obtaining an electron beam in a gas discharge [1]. The method consists in the fact that in the gas-filled space between electrodes exercise volume pulsed high-voltage discharge at atmospheric pressure in which is formed a beam of runaway electrons (RES). The beam occurs in the near-cathode region of the discharge. This type of discharge is implemented in a high overvoltage, i.e. discharge voltage in the interval many times greater than the voltage of the static breakdown. The electric field in the discharge gap is non-uniform and is much stronger near the cathode. In the near-cathode area ratio of field strength to the gas pressure (E/P) is comparable with the maximum energy loss. In this field there is a transition of low-energy electron discharge mode of escape, with the result that they, speeding, leaving the near-cathode region, and is forming a beam of high-energy electrons.

The closest solution we have chosen for the prototype is a patent for a method of obtaining an electron beam [2]. In the prototype between the electrodes of the gas-filled gap osushestvlyaetsya pulsed high-voltage discharge with the formation in it of the electron beam. The formation of the electron beam is carried out by avalanche multiplication of the initial electron beam in a discharge at a pressure of about atmospheric discharge current, the value of which is chosen from the condition of ensuring the compensation of the space charge, resulting in a discharge at the development of electronic avalanches, and the electric field is chosen from the condition of a threshold value necessary for the development lavigne runaway electrons.

The method is based on theory of the occurrence of the avalanche of runaway electrons in strong electric fields. It is assumed that the initial runaway electrons are produced either as a result of the processes in the discharge or injections in the discharge region from the outside. The electric field of the discharge occurs avalanche multiplication of the initial runaway electrons and is formed by a beam of high-energy electrons. Avalanche multiplication of runaway electrons develops not just in the electric field and the gas discharge. The flow of discharge current can compensate for space charge. In an electric field without discharge compensation does not occur, and the charge is accumulated, stopping the process of acceleration of high-energy component of secondary electrons. The electric field E in this invention is determined by the ratio E/P=E/R)CR. Here P is the gas pressure in the discharge gap. The value of e(E/R)CR equal to the minimum value of the resistance forces acting on runaway electrons in this gas from atoms and molecules. The generation time of the beam is limited by the pulse duration of the injected electrons and (or) development of the instability of the discharge volume.

The disadvantage of the prototype is the restriction on the formation of electron flow (t>40 NS) during pulse discharge and the tension in the gas gap, which must be not less than a critical value.

The technical result of the invention is the formation of high-energy (hundreds of Kev) subnanosecond flow of electrons (t≤1 NS) current density tens of amperes per cm2in the gas between atmospheric pressure and above.

The technical result is achieved that the gas-filled gap between the electrodes exercise volume pulse discharge with the formation in it of the electron beam, new, according to the invention is that the formation of the electron beam is carried out on-stage breakdown of the discharge gap in the achievement of the values of the parameter U/(p× (d)sufficient for formation of a beam of runaway electrons between front propagating from the cathode plasma and the anode, and that the plasma of the discharge lines, moving to the anode, is formed by the preionization mode period of fast electrons formed on the front of the pulse voltage by increasing the field on the cathode and / or the cathode plasma lesions (spots). Where U is the voltage (V), R is the gas pressure (Torr), d is the gap of the gas gap (mm).

The formation of subnanosecond electron beam is at the front of nanosecond voltage pulse, the beam is formed between the moving front pulsed volume discharge and anode. The velocity distribution of the plasma from the cathode is determined by fast electrons emerging from the cathode due to the enhancement of the field at the cathode and cathode spots.

The method is based on the fact that in pulsed volume discharge the main part of the runaway electrons with low initial values of the parameter E/p~0.1 kV/cm×Torr is formed in the space between the plasma, which is formed at the cathode and anode. Cathode plasma with high speed distributed to the anode, due to the redistribution of the electric field in the portion of the gas diode is achieved critical value of E/p, including due to the geometric factor.

Real design, which is implemented subnanosecond electron beam in discharge under atmospheric pressure, included a pulse generator with wave resistance is m 30 Ohm, the voltage at the agreed load ~200 kV, duration at half-height of ~3 NS pulse voltage of ~1 NS [3]. With this generator was used a gas chamber filled with air or nitrogen at a pressure of 760 Torr, and used two cathode. One cathode was a set of three cylinders of Ti foil thickness of 50 μm, is inserted into each other and mounted on aluminum substrate with a diameter of 36 mm, the Other the cathode was made of graphite in the form of tablets with a diameter of 29 mm, the edges were rounded and convex side facing towards the foil with a radius of curvature of 10 cm Graphite cathode was placed on a copper holder with a diameter of 30 mm, the electron beam extraction was carried out through the mesh with transparency ~50% or through l foil of a thickness of 45 μm. The optimal distance anode - cathode was 18-28 mm Electron beam at a pressure of one atmosphere was obtained in air, nitrogen, helium and a mixture of Co2-N2-Not as in the mode of single pulses, and the repetition rate to 10 Hz. The amplitude of the current in the air was 40 And Not 300 A. For the other gases also received the highest currents for similar conditions in the gas diode. The maximum distribution of the electron beam energy for the ring-shaped cathode when the air pressure in the diode (1 atmosphere) corresponded to the electron energy ~(90-110) Kev, the duration of the beam current dlesex subjects gases was less than 1 NS. For air at atmospheric pressure when using a generator with an impedance of 20 Ohms and a pulse voltage with an amplitude of up to 220 kV and duration at half-height of ~2 NS, when the pulse voltage is ~0.3 NS was obtained pulse duration of the beam current of 0.3 na current 70 A, the maximum of the energy distribution of the electrons was ~110 Kev [4].

Sources of information taken into account when drawing up the proposal

1. Lowthresh, Linguatula, Twico and Vasotran. Fast electrons and x-ray radiation of nanosecond pulsed discharges in gases at pressures of 0.1-760 Torr // Journal of technical physics, 1974, .XLIV, B.3, S-568.

2. Patent RU No. 2113033, publ. in B. I. No. 16 from 06.10.1998.

3. Alekseev S. B., Orlov V.M., Tarasenko V.F. / electron Beam formed in the gas-filled diode at atmospheric pressure air and nitrogen // technical physics Letters, 2003, vol. 29, VIP, p.29-35.

4. Tarasenko V.F., Yakovlenko S.I., Orlov V.M., Tkachev A.I., Shunailov S.A. / reception of powerful electron beams in dense gases // JETP Letters, 2003, vol 77, VIP, s-742.

A method of obtaining a subnanosecond electron beam at atmospheric pressures and above, namely, that in the gas-filled gap between the electrodes exercise volume pulse discharge with the formation in it of the electron beam, characterized in that the formation of the tion of the electron beam is carried out on-stage breakdown of the discharge gap in the achievement of the values of the parameter U/(p× d)sufficient for formation of a beam of runaway electrons between front propagating from the cathode plasma and the anode, and the fact that the plasma discharge volume, moving to the anode, is formed by the preionization mode period of fast electrons formed on the front of the pulse voltage by increasing the field on the cathode and / or the cathode plasma lesions (spots), where U is the voltage, V, p is pressure, Torr, d - clearance gas gap, mm



 

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FIELD: cathode-luminescent analysis of materials, plasmochemistry, quantum electronics, and the like.

SUBSTANCE: proposed method designed for shaping high-energy (hundreds of keV) subnanosecond (t ≤ 1 ns) charged particle beams whose current density amounts to tens of amperes per cm2 in gas-filled gap at atmospheric and higher pressure involves following procedures. Volumetric pulsed discharge is effected in gas-filled electrode gap and electron beam is shaped during breakdown of discharge gap as soon as parameter U/(p x d) is brought to value sufficient for shaping runaway electron beam between front of plasma propagating from cathode and anode and volumetric discharge plasma moving to anode is shaped by pre-ionization of gap with fast electrons formed across voltage pulse wavefront due to intensifying field on anode and/or on cathode plasma spots, where U is voltage, V; p is gas pressure, torr; d is gas-filled gap, mm.

EFFECT: enhanced energy and current density of generated subnanosecond electron beams.

1 cl

FIELD: electronic engineering.

SUBSTANCE: proposed method and device make use of triangular-wave generator that produces triangular-waveform current signal conveyed to scanning coil for electron beam displacement in first scanning direction Y and rectangular-wave generator that produces rectangular-waveform current pulse arriving at deflection coil for displacing electron beam in second scanning direction X perpendicular to first scanning direction Y. Triangular-waveform current signal produced by triangular-wave generator is modulated to eliminate hysteresis effect in scanning coil. In addition, leading edge of rectangular-waveform current signal is timed at definite offset relative to peaks of triangular-waveform current signal so as to distribute return points on electron beam route in second scanning direction.

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10 cl, 18 dwg

FIELD: quantum electronics, spectrometry, and plasma chemistry.

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4 cl, 5 dwg

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