JPS5848770Y2 - micro channel plate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a microchannel plate in which the inner surface of the channels is coated with a material that emits secondary electrons.

Microchannel plates with internal electron emission in the form of thin flat parallel plates are known.

This channel is parallel to the normal pressure and is located on the main or end surface of the microchannel plate (reference numeral 11 in the drawing).
and 12, whose surfaces are perpendicular to the channel direction.

) are connected to each other. The surface area of the connected microchannels amounts to, for example, 67% of the total surface area at their end faces.

Meanwhile, the remaining 33% is directed southward by the channel wall.

For example, in optoelectronic devices in which an intensifying element in the form of a microchannel plate is used, a portion of the primary electrons emitted by the photocathode impinge on the end faces of the channel walls at the input of the channel plate.

These electrons have sufficient energy for secondary electron formation to occur.

The preferred orientation of these secondary electrons away from the edge, ie the direction in which most of the electrons are emitted from the channel plate, is perpendicular to said surface or edge.

Therefore, there are a large number of electrons that do not contribute to the image intensifier, ie they disappear in said direction.

As a result, the enhancement factor of the image intensifier tube is reduced.

The aim of the invention is to recover at least some of the electrons lost on the input of known microchannel plates due to channel walls.

These recovered electrons can contribute to intensifying.

For this purpose, the homogeneity of the glass structure, both in terms of volume and surface, is not affected in order to avoid the appearance of parasitic signals that arise due to field effects that appear when the glass structure is modified or deformed. However, by uniformizing this glass structure in this region, the dimensions of the channel walls on the input of the microchannel plate are modified.

That is, each channel is provided with a funnel-shaped inlet portion without destroying the channel plate structure and without having sharp edges or the like.

The invention is based on the recognition of the fact that on the output of the microchannel plate the light spot corresponding to the secondary electrons from the channels is always substantially broadened.

Said extent corresponds, for example, to a lateral dimension of 15 channels.

Therefore, the secondary electrons generated by collision with the wall of the associated channel on the input side of the microchannel plate are
If caught en route by an adjacent channel due to the oblique direction of motion, said secondary electron changes very little with respect to the first light spot considered, as far as its lateral dimensions are concerned. This will result in a light spot on the output.

That is, electrons reflected from the entrance surface of the channel plate re-enter the channel plate at other positions, and the change in position is largely reduced by the funnel-shaped entrance of the channel.

By stimulating said interception, ie en route capture, the effectiveness of electronic intensification will be increased without a substantial reduction in resolution.

In other words, more electrons, all due to the funnel shape,
Acceptable and few local changes occur.

According to the invention, this is achieved by rounding off the ends of the channel walls on the input side of the microchannel plate.

That is, when the channel wall of the microchannel plate is viewed in cross section in its length direction, the end of the channel wall on the input side of the microchannel plate is formed in an arc shape.

As a result, the vertical direction at said end corresponds to an oblique direction with respect to the input surface of the channel.

That is, furthermore, the primary electrons oriented vertically at the input surface are incident on the rounded end of the wall according to the inclined direction.

So here it is just the fact that only a very small part of the entrance surface (that is the channel wall edge) is oriented perpendicular to the channel direction and thus perpendicular to the direction of electron entry. .

Almost all inlet surfaces are beveled due to the funnel shape of the channel ends.

The importance of the aforementioned properties is twofold.

That is, on the one hand, the secondary electron emission is thus strongest in the case of a perpendicular collision of the primary electrons, and the secondary electrons thus formed are easily facilitated by the adjacent channels due to their tilted direction with respect to the input surface. Caught on the way.

That is, the funnel causes almost no electrons to be incident perpendicularly to its walls, thus reducing its reflection.

On the other hand, however, the degree of emission of the secondary electrons is increased by the less inclined direction of incidence of the primary electrons at the channel wall.

The present invention is useful for various applications in which the microchannels described above can be used for the direct detection of ultraviolet electromagnetic radiation, X-ray radiation, Geimer radiation or particle radiation such as alpha particles, or ions, instead of for the detection of primary electrons. Offers the same benefits when boards are used.

In all embodiments of microchannel plates with rounded channel ends, it is possible to enhance entrapment and increase detection effectiveness on the input of the microchannel plate.

That is, more electrons are accepted by the funnel and also produce an output signal.

In the present invention, in order to give the desired rounded shape to the end of the microphone channel, for example, the microchannel plate is heated to a temperature close to the softening temperature of glass, and then the input surface of the microchannel plate is heated to a high output temperature. It is heated by a relatively short bombardment with an electron beam carrying energy of .

That is, to produce a microchannel plate with rounded input ends of the channels at the input surface, the input surface of the glass microchannel plate is heated to a temperature close to, but below, the softening temperature of the glass; This heated beam carries an energy of 100-200 W/cm2 for a time sufficient to round the input ends of the channel walls of the microchannel plate to enhance en route trapping of radiation when at high temperatures. Impact the input surface of the microchannel board.

This is the magazine Glass and Refractories Vol. 23, No. 6, No. 693-697 published in November-December 1969.
It represents an improvement on the known method of polishing glass described on page 1.

According to the invention, the described type of microchannel plate is characterized in that the ends of the walls of each channel are rounded.

In other words, in a microchannel plate in which the inner wall surface of the channel is coated with a material that emits secondary electrons, when the channel wall of the microchannel plate is viewed in cross section in its length direction, the input end of the microchannel plate The end portion of the channel wall is formed in an arc shape.

The invention also relates to the use of such microchannel plates in image intensifiers, photomultipliers or particle detection devices.

A number of preferred embodiments of the present invention will now be described in detail with reference to the drawings.

The known channel plate shown in FIG.
, 14. Channel 17°18 with 15 and 16
and 19.

It comprises an input major surface 11 and an output major surface 12.

The boundaries of these walls coincide with the output and input surfaces of the microchannel plate.

Both end faces of the microchannel plate are coated with a metal layer (not shown) to apply an electric field across the microchannel plate.

Primary electrons 10 move toward, for example, a wall 14 and are projected onto point A on this wall.

The directional distribution for the secondary electrons emitted from this point A is indicated by a circle 9' (see FIG. 1).

If electrons are incident at the position of point A, the probability of secondary electron emission is maximum in the direction perpendicular to the microchannel plate surface 11 at point A.

Electrons emitting in this direction, e.g. electrons 8, do not contribute to intensifying.

In Figure 2, which shows a cross-section of the microchannel plate according to the invention, walls 13, 14, 15 and 1 on the side of the input surface are shown.
6 is seen in cross section and the end of its wall is in side view 21.22.
The corners are rounded to have 23 and 24.

That is, when the channel wall of the microchannel plate is viewed in cross section in its length direction, the end of the channel wall on the input side of the microchannel plate is formed in an arc shape.

Electron 9 collides with wall 14 at point B.

For this point, circle 4 represents the directional distribution of secondary electron emission.

The probability of secondary electron emission is now given by electron 9 with respect to the input surface.
is maximized by direction 5, which in the drawing tends towards the direction of normal incidence.

That is, the reflected (or secondary) electrons leave this relevant surface which is normally perpendicular to the relevant surface, which is direction 5.

The two electrons 6 and 7 emitted in the aforementioned direction can be caught en route by the channels 18 and 19,
In this way, it can contribute to intensifying.

For example, for the reasons already mentioned for the expansion of the light spot on a luminescent screen that occurs per channel on the output of a microchannel plate, the resolution or resolution of an instrument with such a channel plate is limited by detection and intensification. Indica) effectiveness increases, whereas it does not substantially decrease.

That is, it is strongly reduced by the funnel having the shape according to the present invention.

Due to the polarization of the electrons across the entrance surface, a light spot, ie a so-called high illumination or image point, is emitted and this light spot is thus enlarged or dilated.

FIG. 3 schematically shows an apparatus illustrating the method of manufacturing such a channel plate.

This device is placed in a space (not shown) that maintains a vacuum between, for example, IQ'mmHg and IQ'mmHg.

This figure shows a microchannel plate 30 with flat channel walls to be rounded on the input side.

For example, an electron beam 33 provided by a pierce-type electron gun 34 is focused onto the input surface of the microchannel plate, comprising for example a focusing coil and a deflection coil 35 for said electron beam.

Additionally, the apparatus may include a furnace for preheating the microchannel plate to bring the glass to a temperature near and slightly below the softening temperature.

Said preheating can also be provided by a dispersed electron beam.

After the above preheating is completed, the deformation temperature of the glass is approximately 500℃.
℃, whereas this glass has a temperature of, for example, 450°C.

The surface of the microchannel plate is then scanned by a focused high power electron beam.

In tests carried out on microchannel plates with a diameter of 25 mm and a thickness of 2 mm, the applied energy amounted to approximately 140 W/cm 2 and said power was applied for approximately 0.7 seconds.

The microchannel plate is then slowly cooled to avoid thermal shock.

Under the influence of gravity and the surface stresses of the molten glass, the ends of the walls of each channel tend to assume a rounded shape.

The glass maintains the thus obtained rounded shape during cooling.

According to another method, surface heating by electron bombardment is replaced by heating by a laser beam, for example a carbon dioxide laser beam, scanning the input major surface of the microchannel plate.

In the same way as before, the assembly formed by the microchannel plates is first brought to a temperature near the softening temperature of the glass, for example in a furnace.

However, this assembly is a configuration of channels of a certain loft that are treated together.

It is not important what equipment is used to heat the surface of the microchannel plate, as long as only a relatively short period of time is required between substantial localized heating.

As mentioned above, the effects of the present invention are similar to known microchannel plates of this type, for example,
In the 3617 publication, even its FIG. 4 provides a kind of tapered channel.

The figure is shown to represent a plurality of independent tubes having an outer layer and an inner layer.

This fact necessitates a method in which each channel is first tapered (i.e., tapered) at the associated end and then provided with a second, i.e., outer layer, which is a secondary electron emissive layer. request.

A conductive coating 43a must be applied, such as by plating, to the ends of these tapered channels.

All these facts suggest that sharp edges pose difficult problems in electrical stability, causing spontaneous electron emission, poor uniform conductive coatings, etc. due to these sharp edges. This results in very expensive equipment.

To obtain the present invention, only the conventional channel plate has to be locally heated to a certain temperature within a limited time interval.

This conductive coating can typically be placed on a blunt sphere.

All this results in a very stable device with little additional cost.

In summary, the microchannel plate for secondary electron emission enhancement has channel walls that are rounded to enhance en route trapping of secondary electrons formed due to the incidence of primary electrons at the ends of the channel walls. have

In other words, the present invention provides a microchannel plate in which the inner wall surface of the channel is coated with a material that emits secondary electrons, and when the channel wall of the microchannel plate is viewed in a longitudinal section, the input side of the microchannel plate The end of the channel wall is formed into an arc shape.

It should be noted that in order to manufacture such a channel plate according to the invention, the channel wall material is softened by bombarding the glass of the input surface with a beam carrying high power energy for a very short period of time.

The glass of the wall at the input surface then assumes a rounded shape under gravity and the surface stress of the glass.

When implementing the present invention, the following terms can be set as conditions for implementation.

(1) In a method for manufacturing a microchannel plate in which the end of the channel wall on the input side of the microchannel plate is rounded, the inner wall surface of the channel is coated with a material that emits secondary electrons, the flat surface of the input surface of the microchannel plate is After heating a microchannel plate with an end on one input end face belonging to a coincident plane to a temperature close to the softening temperature of glass, the input face of the microchannel plate is heated at 100-200 W/cm2 in a relatively short time. It is characterized in that it starts from heating at its surface by impact with a beam carrying energy of an order of magnitude of power.

(2) The input surface of the microchannel plate is bombarded by an electron beam.

(3) The input surface of the microchannel plate is bombarded by a laser beam.

(4) The above-mentioned time is 0.7 seconds.

(5) A light-enhancing or image-enhancing photocell comprising a photocathode, a microchannel plate, and a luminescent screen, characterized in that the microchannel plate is bordered by a round channel wall on the input side.

(6) A microchannel plate emitting secondary electrons and an electron detection device, characterized in that the electrode radiation or particle radiation is directed towards the input of the microchannel plate, the channel walls of which are rounded on the side of said input. Includes a radiation detection tube.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the structure of a known microchannel plate, FIG. 2 is a sectional view showing the structure of a microchannel plate according to the present invention, and FIG. 3 is a sectional view showing a manufacturing method for obtaining an embodiment of the present invention. FIG. 4...circle, 5...electrons emitted in a direction that is now inclined with respect to the input surface, 6, 7...electrons emitted in an inclined direction with respect to the input surface, 8... Electrons emitted perpendicular to surface A1, 9'... Circle,
9JO...Primary electron, 1T...Input main surface, 12...Output main surface, 13, 14, 15.
16...Channel wall, 17,18.19...
...Channel, 21.22,23゜24...
...Side view, 30...Microchannel board,
33...electron beam, 34...electron gun, 35...deflection coil for electron beam 33.

Claims (1)

[Scope of utility model registration request] In a microchannel plate where the inner wall surface of the channel is coated with a material that emits secondary electrons, when the channel wall of the microchannel plate is viewed in a longitudinal section,
A microchannel board characterized in that an end of a channel wall on an input side of the microchannel board is formed in an arc shape.