RU2387042C2 - Electron flux amplifier - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: electron flux amplifier for electron-optical converter comprises conducting plate coated on both sides with metal film with periodically arranged through holes, besides specified conducting plate comprises at least sections of surface that consist of conducting diamond film, at the same time primary flow of electrons falls normally to its surface to create secondary emission of electrons on reverse side of plate. Specified holes are arranged in the form of slots arranged to surface of specified plate at optimal angle α defined experimentally and providing for highest secondary emission for dropping flux of electrons, besides thickness of plate H and width of slot h are related with ratio h=H cosα, besides specified sections of surface consisting of conducting diamond film are represented by inner surface of slots, and specific resistance of specified conducting plate is not more than 0.1 Ohm·cm, and surface resistance of metal on plate surface is not more than 0.01 Ohm/□.

EFFECT: increased amplification ratio due to higher energy of dropping electrons.

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Description

The invention relates to vacuum electronics and can be used in klystrons, high-power microwave lamps and protection devices from high-power microwave pulses.

Known microchannel plate night vision devices Daedalus - 200 [1] and Darcos NGB / 1 [2], used as amplifiers of the electron beam in electron-optical converters

Electron flux amplifiers (UEP) [3] are a microchannel plate (MCP) with through microchannels in which the incident electron flux gives rise to secondary electrons under the action of the field, which provide amplification of the electron flux by (100-1000) times, but such amplification is achieved only when very low current densities, not more than 10 ^-4 A / cm ² .

Closest to the claimed technical solution is an electron beam amplifier [4], made on a conductive diamond film. The design of the electron beam amplifier is shown in FIG. On the silicon frame 1 is a diamond film 2. In the diamond film are periodically located holes 3 micron size. When a primary electron stream falls on a diamond film 2 (see Fig. 1), the electrons of this stream give rise to secondary electrons [5]. An accelerating electric field applied between the film 2 and the electrode 4 penetrates through the holes 3 to the side of the film from which the secondary electrons exit, and through the holes 3 it draws the secondary electrons to the side of the film facing the electrode 4, thereby creating an enhanced secondary stream of electrons. With this amplifier design and an initial electron energy of 1 keV, a gain of 30 is obtained. However, with a further increase in the electron energy, the gain decreases rapidly.

This is explained by the fact that secondary electrons are generated at a greater depth and less and less secondary electrons reach the film surface due to the finite diffusion length, which in polycrystalline diamond films can be a fraction of a micron. The production of secondary electrons at great depths also has the disadvantage that secondary electrons require more time to reach the film surface, and this sharply affects the frequency characteristics of microwave devices in which it is proposed to use an electron beam amplifier.

The aim of the invention is to increase the gain by increasing the energy of incident electrons (or to obtain the maximum gain of electrons with a certain energy E).

This goal is achieved by the fact that in the electron beam amplifier for an electro-optical transducer comprising a conductive plate coated on both sides with a metal film and periodically arranged through holes, said conductive plate containing at least surface portions consisting of a conductive diamond film, the primary stream of electrons normally falls onto the plate to its surface, creating a secondary emission of electrons from the back of the plate, it is provided that uyuschee:

these holes are made in the form of slots located to the surface of the specified plate under an experimentally determined optimal angle α, which provides the greatest secondary emission for the incident electron flux, and the plate thickness H and the width of the slit h are related by the relation h = H cosα, while the above-mentioned surface sections consisting of a conductive diamond film, is the internal surface of the slots, the specific resistance of the specified conductive plate is not more than 0.1 Ohm · cm, and the surface resistance of the metal on overhnosti plate not more than 0.01 ohms / □.

Thus, these drawbacks can be overcome if the primary electron with energy E is directed to the surface emitting secondary electrons at an optimal angle α, at which the maximum electron multiplication coefficient for a given energy E.

A constructive solution to the problem is presented in figure 2.

Figure 2 shows the design of the electron beam amplifier, where:

1 - KEF 4.5 silicon wafer with a thickness of H from tens to hundreds of microns;

2 - metal film Cr with a thickness of 1 μm, forming an ohmic contact to silicon;

3 - periodically located identical slots of width h from a few microns to tens and having an inclination to the surface of the plate at an angle α, with h = HCosα;

4 - p-type diamond film covering the walls of the slit;

5 - walls of the slit of the minimum thickness achieved with the used technology of manufacturing an electron beam amplifier.

The design of the electron beam amplifier is shown in FIG. In a silicon wafer 1, covered on both sides by a layer of chromium 2, identical and periodically located slots 3 are formed, inclined at an angle α that is optimal for a given electron energy E, and the slot width h, the plate thickness H, and the angle α are related by the relation h = HCosα. The walls of the slots 5 are covered with a diamond film of 4 p-type conductivity.

The amplifier is made as follows. In a KEF 4.5 silicon wafer with a thickness of 100-300 μm and a chromium layer 2 coated on both sides in some way (for example, by a laser beam), slots 3 with a width of 10-50 μm are formed at an angle a to the surface. Then, a silicon wafer is treated in an ultrasonic bath with a suspension of diamond powder, thereby creating centers of nucleation of the diamond film, after which a p-type 4 diamond film is formed in the CVD plasma method.

The optimal angle α for a given electron energy E and this technology for coating the walls of a diamond film is determined as follows. A diamond film is formed on the flat surface of the plate. Then the plate is placed in an electron microscope and achieved at a given energy of incident electrons E by changing the angle of incidence of the electrons of the highest brightness in secondary electrons. The angle at which the maximum brightness of the image of the plate is achieved is optimal. The principle of operation of the amplifier is the same as for the amplifier [4]. The difference is that the electron multiplication coefficient in this design reaches its maximum value for a given electron energy and this value is stored at incident current densities of up to 1.0 A / cm ² , which, with a gain of 10-100, allows the production of a secondary electron flux of 10- 100 A / cm ² . The optimality of the gain is achieved, firstly, due to the optimal angle α, and secondly, due to the ratio h = HCosα. Indeed, if h <HCosα, then secondary electrons will be born in the gap farther from the hole through which the electric field draws them to the side opposite to the side on which the primary electrons fall. Consequently, the efficiency of using secondary electrons will be lower. If h> HCosα, then part of the primary electrons will pass through the gap without generating secondary electrons, and, therefore, the multiplication coefficient of primary electrons will also decrease.

At primary current densities of 0.1 A / cm ² - 1.0 A / cm ² , measures must be taken so that there is no excessive heating of the amplifier, leading to its destruction. There is an inevitable heating associated with the dissipation of the energy of primary electrons and the birth of secondary electrons. In addition to this inevitable heating, the amplifier heats up due to the flow of current necessary to compensate for holes born in the p-type diamond layer. These losses must be eliminated or minimized, which is achieved by the plate resistance of not more than 0.1 Ohm · cm and the surface metal resistance on the plate surface of not more than 0.01 Ohm / □. Indeed, when a current I for dissipating power compensation holes per 1 cm ² of the plate will consist of power allocated to current flowing through the metal coating that is not more than 0.01I ^2/2 W, and the power allocated with the same current flowing perpendicularly to the surface of the plate with a thickness of not more than 300 microns, which is not more than 0.03I ² · 0.1. At the same time, the inevitable dissipation power caused by primary electrons is 2E _g KI / 3e (K-1), where E _g ≈ 5 eV is the diamond band gap, K is the electron flux gain, and e is the electron charge. Thus, the ratio of power inevitably allocated to power due to resistive losses is

Since I≈I _O, the resistive losses reach only 24% of the required loss in the worst case, where I _O ≈100 A / cm ^2. When I _o <10 A / cm ² they are less than 3%.

An advantage of the design is the obtaining of large amplification factors by increasing the electron energy E. Thus, at E≈3 keV, the gain can reach 100 and, therefore, when the density of the primary electron flux is 0.1 A / cm ² , an electron flux can be obtained at the output at 10 A / cm ² . In addition, the incidence of electrons at an optimal angle to the surface mainly ensures the production of secondary electrons in the diamond film at the same depth not exceeding the diffusion length, which means that with increasing current density the frequency response of the amplifier will not deteriorate, which is important when its use in microwave devices.

Information sources

1.http: //www.darkos.ru:8000/goggles/html.

2.http: //www.Arsenal.com.

3. A.G. Berkovsky. Electronic multipliers. “Electronics and its application” (results of science and technology), 1973, v.5, p. 43-85.

4. Patent RU No. 2222072 “Amplifier of electronic flow”, priority dated November 16, 2000 (prototype).

5. J. E. Yater, A. Schih, and R. Abraws. Electron transport and emission properties of diamond, J. Vac. Sci. Technol. A 16930, May / Jun 1998, pp. 913-918.

Claims (1)

An electron beam amplifier for an electron-optical converter, which is a conductive plate coated on both sides with a metal film and periodically spaced through holes, said conductive plate containing at least surface portions consisting of a conductive diamond film, and normal to on its surface, a primary electron flow falls, creating a secondary emission of electrons from the back of the plate, characterized in that these holes are filled in the form of slots located to the surface of the said plate under the experimentally determined optimal angle α, which provides the highest secondary emission for the incident electron flux, the thickness H of the plate and the width h of the slit being connected by the relation h = HCosα, while the above-mentioned surface sections consist of a conducting diamond film is the inner surface of the slits, and the resistivity of the aforementioned conductive plate is not more than 0.1 Ohm · cm, and the surface resistance of the metal on the surface of the plates s no more

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