US2232030A - Device for the generation of large amounts of negative ions - Google Patents

Description

Feb 1941- HARTMUT ISRAEL KALLMANN, ,030

F0 ERLY KNOWN AS HARTM KALLMANN ETAL DEVI FOR THE GENERATION OF LAR%E lesgNTS 0F NEGATIVE IONS Filed F Wu e/vvbom.

III-IIIIIIIJIIIIIIII l I 11111111111111 l Patented Feb. 18, 1941 UNITED STATES DEVICE FOR. THE GENERATION OF LARGE AMOUNTS OF NEGATIVE IONS Hartmut Israel Kallmann, formerly known as Hartmnt Kallmann, Berlin Charlottenburg,

and Ernst Kuhn, Berlin, Germany, assign to I. G. Farbenindustrie Aktiengesellschaft, Frankfort-on-tbe-Main, Germany Application February 6, 1939, Serial No. 254,948

In Germany February 8, 1938 9 Claims.

In a canal ray the positively charged ions are neutralised when traversing a gas-filled space by collisions with uncharged gas molecules, the positive ions passing into the uncharged state by taking up electrons without any essential loss of energy. These so formed neutral particles can further be transformed either into positive ions or, may be, also into negative ions by such collisions. After said particles have traversed in the gas a path of sufficient length, a state of equilibrium arises. Thus for example a hydrogen canal ray having a speed of 20 kva, consists of 1 about two thirds of neutral particles and of about one third of positive ions. There are only from one to two percent of negative ions. The relative number of ions increases a little with increasing voltage, whereas the relative number of neutral particles increases with decreasing voltage. s The output of negative ions. can be increased by an addition of water, mercury or an organic vapor to the gas of the discharge space. It is further known that ions impinging at glancing incidence on a metal surface are highly reflected 25 and it is probable that nearly every reflection is associated with a neutral-isation. If, therefore, a beam of ions passes through a narrow metal channel the equilibrium between different sorts of ions and neutral particles arises within a con- 80 siderably shorter path than is the case if only a gas space is traversed. This phenomenon has, however, been observed hitherto only with positive ions and neutral particles.

Experiments have shown us that negative ions are not only formed within a gas space, but are also generated by quickly moving positive ions or neutral particles impinging on surfaces. The physical cause of this formation of negative ions has not yet been fully explained, but it seems that 40 negative ions are formed from positive ions directly by exchange of charge on the surface, or that first neutral particles are formed which then are transformed into negative ions.

In accordance with the present invention, a 45 beam of positive ions is directed onto a surface in such a manner that the positive ions are reflected, The reflected particles partly consist of negative ions formed from positive ions during the process of reflection. The proportion of these 50 negative ions is the larger, the smaller the angle is between the direction of the positive ion beam and the surface.

The invention will be now more fully explained with the aid of the accompanying drawing in 55 which Figure 1 shows diagrammatically and by way of example a form of apparatus which embodies a' device according to the invention, and Figure 2 is a geometrical representation of a particularly suitable form of the conical canal in which the negative ions are formed. 5

' From a source I of positive ions a narrow penoil of ions enters into a bore of the electrode 2. This bore is long in proportion to its entrance aperture, and is conically enlarged in the direction of the beam of positive ions. In order to 10 provide that the largest possible portion ofthe ions impinge on the wall of the bore in the electrode 2, the angle of the conical aperture may be smaller than the angle of divergency of the ion beam, which is conditioned by the shape of 15 the electrode of the ion source.

It has been found that with baked out walls the formation of negative ions from positive ions proceeds only with comparatively small output. In order to enlarge the output, according to this invention at least those portions of the wall upon which the ions impinge are laden with a gas.

In order to inhibit the travelling about and the neutralisation of 'thesnegative ions in the canal an electric field from outside the electrode 2 draws the negative ions out of the canal as quickly as possible. It may under circumstances be advantageous for the just mentioned purpose to broaden the canal at its exit side, thus to enable the electric field to penetrate somewhat deeper into the an canal, By this field the positive ions are prevented from leaving the canal and are driven back thereinto so that again a possibility for neutralisation is established for them. By an appropriate design of the counter-electrode 6 the extension of the electric field into the aperture can likewise be favoured. V

Figure 1 shows an apparatus in which the device for a source of negative ions according to the invention is used for generating a beam of positive ions of very high velocity.

The negative ions leaving the aperture 3 of the canal are accelerated by the potential difference p between the electrode 2 and the positively charged high-tension electrode 6. The accelerated negative ions enter the bore I of this electrode.

The pressure in the middle part of bore I is somewhat higher than in the surrounding space of the apparatus, as a stream of gas continually flows into the bore through a tube 8 of small cross-section. This gas, of course, also flows through bore 1 into the surrounding space of the apparatus. But the pressure in this space is very low as the tube is continually evacuated by a strong vacuum pump (not shown). I56

Iii

In the canal I of the high-tension electrode 8 the negative ions are transformed to positive ions, and after leaving bore 1 they are again accelerated by the potential diflerence between the electrode 8 and the collecting electrode 9 so that they impinge with very high speed upon the substance to be radiated, housed in the electrode [0.

The arrangement as shown and above de-. scribed is distinguished by its particularly simple arrangement in that only one insulator II is required even for very high potentials. The device necessary for regulating the gas pressure may be attached also to said insulator, whereas the source of ions and the collecting electrode as well as the vessel, can be grounded. Moreover the speed of the ions impinging upon the collecting electrode is just double that which corresponds to the used potential.

Instead of the discharge tube shown in the drawing, which entails the necessity to make use of high potentials in order to obtain an intense beam of ions, an arc-discharge (low-voltage-arc) may be used as source of the positive ions, this modification permitting operation with lower potentials and presenting, therefore, the advantage that the ions can be transformed more easily.

We claim:

1. A device for the generation of large amounts of negative ions comprising means providing positive ions and an electrode maintainable at a negative potential with respect to said means and positioned so that a beam of said positive ions is in grazing incidence with a surface of said electrode; whereby said positive ions are converted into negative ions. a

- 2. A device as defined in claim 1 wherein said electrode is provided with a passage extending substantially in the path of said beam of positive ions.

3. A device as defined in claim 1 wherein said electrode is provided with a passage extending substantially in the path of said beam of positive ions, said passage having a length substantially greater than its entrance aperture.

4. A device as defined in claim 1 wherein said electrode is provided with a passage extending substantially in the path of said beam of positive ions, said passage having alength substantially tially greater than its entrance aperture and diverging in the direction of motion of said beam at an angle smaller than the angle of divergence of said beam.

6. A device for the generation of large amounts of negative ions comprising means providing positive ions, an electrode maintainable at a negative potential with respect to said means and positioned so that a beam of said positive ions is in grazing incidence with a surface of said electrode, whereby said positive ions are converted into negative ions, and means providing an electric field adapted to accelerate the flow of negative ions from said electrode and to repel positive ions.

7. A device for the generation of large amounts of negative ions comprising means providing positive ions, an electrode maintainable at a negative potential with respect to said means and positioned so that a beam of said positive ions is in grazing incidence with a passage through said electrode, whereby said positive ions are con verted into negative ions, and means providing an electric field at the exit end of said passage adapted to accelerate the flow of negative ions from said electrode and to repel positive ions, the exit aperture of said passage being larger than the entrance aperture thereof to facilitate the penetration of said fieldinto said passage.

8. A device for the generation of large amounts of negative ions comprising means providing positive ions, an electrode maintainable at a negative potential with'respect to said means and positioned so that a beam of said positive ions is in grazing incidence with a surface of said electrode, whereby said positive ions are converted into negative ions, and a further electrode in substantial alignment with said firstnamed electrode and maintainable at a potential positive with respect to said first-named electrode whereby to accelerate the flow of negative ions from said first-named electrode.

9. A device for the generation of large amounts of nlegative ions comprising means providing positive ions and an electrode maintainable at a negative potential with respect to said means, said electrode being positioned so that a beam of said positive ions is in grazing incidence with a surface thereof which is laden with gas.

HAR'I'MU'I' ISRAEL KALLMANN, FORMERLY KNOWN AS HARTMUT KALLMANN. ERNST KUHN.

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