US2186636A - Cathode ray tube - Google Patents

Description

Jan. 9, 1940. P. GRLxcH CATHODE RAY TUBE Filed Nov. 1o, 19737 I l l +500 -IDD +500 Patented Jan. 9, 1940 UNITED STATES cArnonE my TUBE Paul Grlich, Dresden, Germany, assignor to Zeiss Ikon Aktihaft, Dresden, Germany Application November 10, 1937, Serial No. 173,889 In Germany November 12, 1936 GCIamS.

The invention relates to improvements in cathode ray tubes and in particular to amplier tubes operating according to the principle of ionization by means of electronic propulsion.

It is known that an electron current may be amplified by its own ionizing effect. If, for the purpose of amplifying an electron current, which initially was generated in a highly evacuated space or was passed therethrough, this current is conducted into the ionizing chamber, it is necessary to seal the opening between the ionizing chamber and the high vacuum space in such manner that the high vacuum in the last named space is continually maintained. Up to now, this seal of the ionizing chamber against the high vacuum. chamber was formed by a window pane applied to the opening through which the ionizing chamber communicated with the high vacuum chamber, said window pane consisting for instance of a thin Celluloid foil cemented over the opening.

Such a seal, however, has various defects.

The most important defects are that the foil can easily be destroyed and has a relatively short life, because the heat generated when the electrons strike the foil is very detrimental and shortens the life of the foil considerably. Another disadvantage of. this seal is that the electronsiwhen passing through the foil suier losses in energy, whereby their ionizing effect is reduced.

It is an object of the present invention to eliminate these disadvantages by a proper selection of the dimensions of the opening between the ionizing chamber and the high vacuum chamber in respect to the length of the path of the gas molecules. The dimensions of the opening measures in any direction are selected to be not greater than the mean free length of distance through which the gas molecules have to travel, but they may be smaller than the mean free length of this distance. When this method of dimensioning of the opening is properly carried out, a pressure equalization between the ionizing chamber and the high vacuum chamber does not take place. Those molecules only will enter the high vacuum chamber whose direction of movement at the very instant at which they arrive directly in front of the aperture is straight towards the opening. At thispoint, however, the molecules may be rendered harmless easily by getter material placed in the high vacuum chamber.

Another object of the invention is to arrange the opening between the high vacuum chamber and the ionizing chamber in a wall which constitutes an anode of the cathode ray tube.

(Cl. Z50-162) Still another object of the invention is to employ an opening in the form of an electric lens between the high vacuum chamber and the ionizing chamber.

This invention also has the object of producing 6 a pre-ionization of the gases within the ionizing' chamber.

Other objects of the invention will be apparent or will be specifically pointed out in the following lo more detailed description.

The drawing illustrates by way of example one embodiment of the invention.

Fig. 1 shows diagrammatically a longitudinal i sectional view of an image dissector tube;

Fig. 2 shows in cross-section and in an enlarged 15 scale a fragment of the wall separating the high vacuum chamber from the ionizing chamber, and

Figs. 3 and 4 show modifications. Referring .to Fig. 1 the image dissector tube l contains the photoelectric cathode 2 the output m electrode 3 and the apertured anode 4. The anode 4 divides the interior of the tube envelope into two chambers, namely a high vacuum chamber 5 and an ionizing chamber 6 in which the amplification takes place. discharged from the image elements of the electron image on the photocathode 2 traverses the high vacuum chamber 5 and enters the ionizing chamber 6 through the aperture 1 in the anode 4.

The electron beam '5 The electron image in well known manner is moved back and forth over the aperture 1 by deecting fields, the aperture 1 thus constituting a stationary scanning aperture. The ionizing chamber 6 is lled with gas of a composition and of a pressure selected in accordance with the requirements of the particular cases, as speed of electrons, degree of amplification desired, etc. The ionizing chamber 6 is of conventional construction. An electric field is applied in known manner between the anode t and the output electrode 3, the latter, in the embodiment illustrated, having an annular shape.

The aperture 1 in the anode 4 through which the electrons enter the ionizing chamber 6 is shown to be conical with the smaller diameter directed towards the high vacuum chamber 5. Owing to the inclination of the annular wall 8 (Fig. 2) confining this aperture 1, the ions which strikethe wall 8 will not enter the high vacuum chamber 5, but as a rule will be deflected rearwardly into the ionizing chamber 6.

The aperture 1 in the anode 4 may also be constructed as an electric lens, in a manner as similar to that described in the U. S. patent specification No. 2,160,672 issued May 30, 1939. Such an electric lens as designated with 8, 9 and i0 in Fig. 3 is particularly useful for television purposes, and permits a ready adjustment of the size oi' the image point and in particular a reduction of the same to a very small size.

In order to accomplish a pre-ionization of the gases within the ionizing chamber a source of electrons, as for instance an electron emitting I incandescent iilament may be disposed in said field within the ionizing chamber from moving through the aperture of the anode.

It is believed obvious that numerous other forms of the invention will suggest themselves to an expert in this art, and the invention, therefore, is not limited to the particular forms illustrated and described.

What I claim is:

1. A cathode ray tube provided with an envelope and with a partition dividing the tube into a high vacuum chamber and an ionizing chamber, including means within said high vacuum chamber for emitting a beam of electrons, said partition being provided with an aperture for permitting said electron beam to enter said ionizing chamber, the lateral dimensions of said aperture being not larger than the mean free length of travel of the gas molecules in said ionizing chamber so as to prevent a pressure equalization between said ionizing chamber and said high vacuum chamber, said aperture having a conical shape with the larger end directed toward said ionizing chamber, the conical wall of said aperture being effective for reiiecting the gas molecules striking the same back into said ionizing chamber.

2. A cathode ray tube including within an envelope, an apertured anode dividing said envelope into a high vacuum chamber and an ionizing chamber, a photocathode in said high vacuum chamber, said photocathode converting an optical image projected onto the same into an electron image, a collecting electrode in said ionizing chamber, the aperture in said anode being provided for scanning the electron image on said photocathode, the lateral dimensions of f said scanning aperture being not larger than the mean free length of travel of the gas molecules in said ionizing chamber so as to prevent a pressure equalization between said ionizing chamber and said high vacuum chamber. l

3. A cathode ray tube including within an envelope, an apertured anode dividing said envelope into a high vacuum chamber and an ionizing chamber, a photocathode rin said high vacuum i ,matassa l chamber, said photocathode converting an'optical image projected onto the same into an electron ge, a collecting electrode in said ionizing chamber, the aperture i said anode being provided for scanning the electron image on said' photocathode, the lateral dimensions of said scanning aperture being smaller than the mean tree length of travel of the gas molecules in said Y ionizing chamber so as to prevent a. pressure equalization between said ionizing chamber and saidhigh vacuum chamber.l

4. A cathode ray tube including within an envelope, an apertured anode dividing said envelope into a high vacuum chamber and an ionizing chamber, a photocathode in said high vacuum chamber, said photocathode converting an optical image projected onto the same into an electron image, a collecting electrode in said ionizing chamber, the aperture in said anode being provided Ior scanning the electron image on said photocathode, scanning aperture being not larger than the mean Vfree length oi' travel of the gas molecules in said ionizing chamber, said aperture having a conical shape with ionizing chamber so as to prevent a pressure equalization between said ionizing chamber and said high vacuum chamber.

5. A cathode ray tube including within an envelope, an apertured anode dividing said envelope into a. high vacuum chamber and an inizing chamber, a photocathode in said high vacuum chamber, said photocathode converting an optical image projected onto the same into an electron image, a collecting electrode in said ionizing chamber, the aperture in said anode being provided for scanning the electron image on said photocathode, the dimensions of said scanning `aperture being not larger than the mean free length of travel of the gas molecules in said ionizing chamber so as to prevent a pressure equalization between said ionizing chamber and said high vacuum chamber, said apertured anode being formed and adapted to be used as an electrical ens.

6. A cathode ray tube including within an envelope, an apertured anode dividing said envelope into a high vacuum chamber and an ionizing chamber, a photocathode Y in said high lvacuum chambensaid photocathode converting an optical image projected onto the same into an electron image, a collecting electrode and means eiecting a pre-ionization oi.' the gas in said ionizing chamber, the aperture in said anode being provided for scanning the electron image on said photocathode, the lateral dimensions of said scanning aperture being not larger than the mean free length of travel of the gas molecules in said ionizing chamber so as to prevent a pressure equalization between said ionizing chamber and lsaid high vacuum chamber.

' PAUL GORLICH.

the lateral dimensions oi.' `said

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