US2258149A

US2258149A - Device for producing rapidly flying ions

Info

Publication number: US2258149A
Application number: US269452A
Authority: US
Inventors: Schutze Werner
Original assignee: Fides Gesellschaft fuer die Verwaltung und Verwertung von Gewerblichen Schutzrechten mbH
Current assignee: Fides Gesellschaft fuer die Verwaltung und Verwertung von Gewerblichen Schutzrechten mbH
Priority date: 1938-04-23
Filing date: 1939-04-22
Publication date: 1941-10-07
Anticipated expiration: 1958-10-07
Also published as: NL52790C; BE433960A; FR853171A

Description

Oct. 7, 1941. w. scHUTzE 2,258,149

DEVICE FOR PRODUCING RAPIDLY FLYING IONS Filed April 22, 1939 123 F/Z a' NON-MAGNETIC 9 man/[77c P016 PIECE POLE PIECE merited Oct. 7, 1941 Werner Schiitae, Berlin-Pankow,.

signer to Fides-Gesellschait liir Germany, al-

die Verwaltnng 11nd Verwertnng yon gewerblichen Schntarechten mit beschrankter Battling, Berlin, Germany, acorporationof Germany 7 Application April 22, 1939, Serial No. 269,452

8 Claims.

This invention relates to adischarge device for producing ions of high velocity.

In a known arrangement of this type, the ions are produced in a gas-filled discharge chamber whence they pass at a given velocity through a relatively narrow aperture into a vacuum chamber in which they are further accelerated. When using such iontubes it has been found that the production of highly accelerated ions-in proportion to the input of the tube, 1. e.- the efliciency,

is lower than expected, and that the anode struc- Germany April 23, 1938 aperture 2 of both chambers. A cathode of such design isdescribed in the application of Curt Hailer, Serial No. 222,607, filed August 2, 1938.

It has been found that the ions produced in the anode chamber are already accelerated within the anode to relatively high velocities and fly in the direction towards the aperture 2. When flying, the ions often recombine with the electure of the tube is liable to be overheated, particularly in local areas.

, The main object of the present invention is to eliminate or greatly reduce these drawbacks. To this end, in a discharge device for the production of rapidly flying ions having an ion source consisting of a gas-filled discharge chamber as-' sociated with an evacuated acceleration chamber, a magnetic field is caused to act upon the ions in the neighborhood of the cathode aperture and to prevent the electrons released at the cathode from reaching the anode aperture opening.

The invention will be understood from the following description of the devices shown in the drawing in which Fig. 1 represents a? longitudinal section through the electrode arrangement of a discharge device according to the present invention, the magnetic energization and hence the ,above-mentioned magnetic field being not in operation.

Fig. 2 shows substantially the same arrangement, the magnetic field being operative.

Fig. 3 shows diagrammatically a part-sectional side elevation of a complete discharge device employing an electrode arrangement similar to those of Figs. 1 and 2.

Fig. 4 is a diagrammatic illustration of electric magnetic means for producing the magnetic field above referred to, and

Fig. 5 shows a top view of the cathode structure of the arrangement shown in Fig. 2.

In Fig. 1, i denotes a gas-filled discharge chamber in which the ions are produced, 2 is a narrow aperture forming an outlet for the ions produced in chamber I, 3 is the highly evacuated vessel portion in which the ions are accelerated to very high velocities before passing through the aperture 6 of the cathode 4 and before bein trons present inside the anode chamber to form neutral gas particles which, however, continue to fly approximately at the velocity of the accelerated ion. Most of these neutral gas particles pass through the aperture 2 into the vacuum chamber and fly in the latter in the direction of the cathode.. The neutral gas particles fly in different directions owing to the prevailing speed distribution, and afocussing oi the neutral particles does not take place so that a large number of them impinge .with'great force upon the surface of the cathode 4, where secondary electrons are released which are considerably accelerated in the direction towards the anode. At the same time the stream of electronstowards the anode is focussed, and the secondary electrons released at the surface portions I and 8 of the cathode reach the aperture 2 in the form of a dense stream, part of which passes through its aperture into the anode chamber I. This inverse electron current represents a loss. Besides, a large portion of the stream of electrons impinges upon a very small surface of the anode, thus heating it locally to a considerable temperature.

Fig. 2 shows the conditions which prevail in the same electrode arrangement if a magnetic field is produced in the neighborhood of the cathode. The cathode 4 is composed of two magnetic pole pieces l3 and I H which produce a steady magnetic field represented by the lines of force IS. The intermediate sections 9 and H of the cathode (Fig. 5) consist of non-magnetic metal. If now secondary electrons are released in the above-described manner at the surface of the cathode 4, they are magnetically influenced in the very neighborhood of the cathode where they have not yet attained a high speed and thus are scattered from their original direction of flight into different directions depending upon the initial direction and speed of the electrons. The electrons emitted from the cathode surface,

therefore, either fly back to the cathode or they reach the anode along more or less spiral-shaped paths (as indicated by the arrowed lines l6, l1 and I8) without being able to form a dense stream of electrons due to the iocussing action of the electric lens. The points of the anode 5 upon which the electrons impinge are therefore disstream of ions I! however, remains practically .unbiased, since the ions have already a very great speed when entering the effective range of the magnetic field and since the field exerts a slighter efiect on the ion current than on the electron current.

The magnetic'fleld about the cathode may be produced in any suitable manner. Thus, for instance, two pole pieces l3 and I may be magnetized by an electric energizing coil or-by a permanent magnet. The two pole pieces, for instance, may be connected with each other by a suitable yoke and form with the latter a permanent magnet. The pole pieces may also be arranged in a difierent manner, for instance slightly above the cathode surface facing the anode, the only essential requirement being that the mag netic field be eifective in the immediate neighborhood of this surface.

The importance of the invention will be readily apparent if it is considered that in the known arrangements the neutral gas particles may assume a very high velocity, for instance of-50 kv., suflicient to release a current of electrons at the cathode greater than the current of ions produced. The force with which this electron current impinges upon the anode is so great as to produce intensive X-rays. In the case of an electron current of only 1 ma., a magnitude which may easily be reached or surpassed, and an anode voltage of 1000 kv., every 7 mm. of surface have to carry a wattage of 1 kw. if the diameter of the stream of electrons amounts to 3 mm. This wattage is converted into heat upon the impinging of the electrons. However, by employing' a magnetic field this waste heat and its distributing eifects are virtuallyeliminated according to the invention.

Fig. 3 exemplifies the construction of a complete arrangement according to the invention.

The discharge vessel has a porcelain'wall 2|, in

which is arranged the anode structure 30, whereas the cathode 23 is secured to the bottom 24 of the vessel. The cathode 23 is designed in the manner shown in Figs. 1 and 2. It consists of the two magnetic pole pieces 25 and 26 magnetically connected with each other by a yoke 2! and energized by

coils

28 and 29, as shown in Fig. 4. The ions produced in the gas chamber 22 of the anode fly through the anode aperture 'and through the aperture of the cathode 23 into the chamber 3| in which the material 33 to be treated is placed on the bottom of a Faraday cage 32. The acceleration voltage for the ions is applied between the terminals 34 and 35. The portion of the chamber of the vessel to be evacuated-i. e. the entire vessel chamber with the exception of the gas-filled ion producing chamber 30-is evacuated by a high-vacuum pump connected to the suction conduit 36. The intensity of the ion current may be measured by means of an ammeter 31.

What is claimed is:

1. A discharge device for producing ions of high velocity, comprising a vacuum chamber, an anode having a gas-filled chamber forming the source of the ions and provided with an aperture for the passage of the ions into said vacuum chamber, a cathode in said vacuum chamber for accelerating the ions, and non-focussing magnetic means associated with said cathode for producing a dispersing magnetic field effective at the surface of said cathode so as to prevent electrons released at said cathode from forming a directed beam impinging on said anode.

2. A discharge device for producing ions of high velocity, comprising a vacuum chamber, an

anode having a gas-filled chamber forming the source of the ions and provided with an aperture for the passage of the ions into said vacuum chamber, a cathode'in said vacuum chamber for accelerating the-ions, said cathode comprising ferromagnetic pole pieces for producing a dispersing magnetic field effective at the surface of said cathode so as to prevent electrons released at said cathode from forming a direc beam impinging on said anode.

3. A discharge device for producing ions of high velocity, comprising a vacuum chamber, an anode having a gas-filled chamber forming the source of the ions and provided with an aperture for the passage of the ions into said vacuum chamber, a cathode in said vacuum chamber for accelerating the ions, said cathode having a central aperture for the passage of the ions, and comprising two ferromagnetic pole pieces bordering said cathode aperture and arranged diametrically opposite each other, and means for energizing said pole pieces to produce a dispersing magnetic field eflective at the surface of said cathode so as to.unfocus electrons released at said cathode to prevent them from forming a directed beam impinging on said anode.

4. A discharge device for producing ions of high velocity, comprising a vacuum chamber, an anode having a gas-filled chamber forming the source of the ions and provided with an aperture for the passage of the ions into said vacuum chamber, a cathode in said vacuum chamber for accelerating the ions, said cathode having a central aperture for the passage of the ions, and comprising two ferromagnetic pole pieces bordering said cathode aperture and arranged diametrically opposite each other, a ferromagnetic yoke connecting said pole pieces with each other, and an electric energizing coil disposed on said yoke for magnetizing said pole pieces.

5. A discharge device for producing ions of high velocity, comprising a vacuum chamber, an anode having a gas-filled chamber forming the source of the ions and provided with an aperture for the passage of the ions into said vacuum comprising two ferromagnetic pole pieces bordering said cathode aperture and arranged diametrically opposite 'each other, a permanent magnet structure including said pole pieces for producing a magnetic field effective at the surface of said cathode so as to unfocus electrons released at said cathode to prevent them from forming a directed beam impinging on said anode.

6. A discharge device for producing ions of high velocity, comprising a vacuum chamber, an anode having a gas-filled chamber forming the source of the ions and provided with an aperture for the passage of the ions, into said vacuum chamber, a cathode in said .vacuum chamber for accelerating the ions, said cathode having a central aperture for the passage of the ions, and comprising two ferromagnetic pole pieces bordering said cathode aperture and ar ranged opposite each other, intermediate pieces of non-magnetic metal also bordering said aperture and connecting said pole pieces with each other, and means for energizing said pole-pieces so as to assume opposite magnetic polarities to produce a magnetic field for diverting electrons released at said cathode to prevent them from forming a directed beam impinging upon said anode.

'7. A discharge device for producing ions of high velocity, comprising a vacuum chamber, an anode having a gas-filled chamber forming the source of the ions and provided with an aperture for the passage of the ions into said vacuum chamber, a cathode in said vacuum chamber for accelerating the ions, said cathode comprising ferromagnetic elements of different magnetic polarity so as to produce a dispersing magnetic field for preventing electrons released at said cathode from reaching said anode as a directed beam.

8. A discharge device for producing ions of high velocity, comprising a vacuum chamber, an anode having a gas-filled chamber forming the source of the ions and provided with an aperture for the passage of the ions into said vacuum chamber, a cathode'in said vacuum chamber for accelerating the ions, and non-focussing magnetic means for producing at the surface of said cathode a dispersing magnetic field whose lines of force extend substantially perpendicularly to the direction of moz ement of the ions flying through said aperture towards said cathode.

\ WERNER