US1559715A - High-vacuum tube - Google Patents

Description

Nov. 3, 1925' 1,559,715 J. E. LILIENFELD Y r I men VACUUM TUBE Filed Sept. 9, 1921 Patented blow. 3, i225.

area

JULIUS LE. mmnnrnnn, or new GARDENS, NEW roan.

HIGH-VACUUM TUBE.

Application filed September 29, 1921.. Serial No. 504,088;

vacuum tubes of the type described. in my application Serial No. 364,215 filed March 8, 1920, in which an electronic discharge is started and maintained'between cold electrodes in close proximity to each other, the vacuum being so high that ionization is substantially excluded.

It has been observed with tubes of this character that in order to prevent the formation of too small focal areas, which would cause the fusion and evaporation of the anodic surfaces before a very heavy "millif amperage has been applied, itis desirable to use hollow anodic surfaces.

If the anode has a cavity opposite the cathodically active point, then the cathode beam is distorted by the electric field and no harmful concentration upon single points can take place, e. no exceedingly small and relatively overloaded focal spots are likely to be formed.

It is the general object of this invention to make use of this observation to better adapt high-vacuum tubes of the character referred to for various purposes to be more particularly pointedout.

For a full understanding of the invention reference is made 'to the accompanying drawings in which 1 Fig. 1 is a fragmentary View partly in section showing one embodiment of the invention;

Fig. 2 is a bottom plan view of the electrode arrangement shown in Fig. 1.-

Fig. 3 is a more of-less schematic view of another form of device embodying the invention.

vacuum tube of the general character above referred to 10 is the anode which is provided with aplurality of cavities 11, 12 and 13. A like plurality of cathodes 14., 15 and 16 are so disposed that their active points 14!, 15 and 16 are each oppositeone of the said cavities. In practice the stems of the cathodes approach the anode laterally and the ends are bent to pointsubstan tially' axially into the respective cavities. a I a By varyingthe distance of the cathodically active points 14*, 15 and 16 from.

their respective cavities 11, 12 and 13, assumlng the geometrical characteristics of the-said points to be identical, X-rays of different degrees of hardness can be produced. l

Conversely by varying the shape of the cathodically active points, other things-being substantially equal, the degree of hard ness of the X-rays will vary accordingly.

In the drawings the cathodica-lly active points have difierent shapes for the purpose just mentioned.

It may be stated that the cavities must be larger in tubes operating under high tension than in tubes'for the regular diagnos,-

tic work, because cathodic rays of considerable velocity require a larger cavity, to be distorted.

The size of the cavity may also be determined by other considerations. Pin hole camera pictures show that not only the'spots of impact of the primary cathode rays but also the Whole cavity radiates secondary elec trons filling the cavity. :Thus for radiographic purposes the size of the cavity must be made to correspond to the size, of the focus capable of producing sufliciently sharp pictures. I

Figs. 3 and 4 represent an arrangement particularly adapted for radiographic purposes. As above mentioned, it is. important for suchpurposes to limit the origin of the -X-rav emanation to a relatively small surface which then acts as-a focus to produce shadow pictures of good definition. For most practical purposes a sharp definition is obtained with cavities whose mouth or orifice is approximately 5-6 mm. and whose p depth is about 3-4 mm. The cathode may consist of a wire of about 2 mm. diameter having as active point a cone the apex angle of which may be 10" ing harder rays suitable for therapeutic work more obtuse angles, (130 or more) may be resorted to. J

The cavity 21 in the lower facevof the anode 20 vmay be oval i. e. the axis on of the cavity may be directed at an angleto the For producanode. Thecathode 22 terminates in a more or less sharp point 23 closely approaching v the cavity or even slightly extending 1nto it as may be found desirable.

X-ray emanation may take place in the form of a ray cone defined ,by the angle n, the procast by it.

It "is a particular. advantage of the just describederrangement that X-ray emanations from surfaces other than the cavity the cathode is shown in Fig. 5.

are practically avoided. This is due, no doubt, to the fact that the electrons tending to pass out of the cavity are restrained by the intense field between the mouth of the 'cavity.and the cathode point.

' Another form for still more effectively eliminating the possibility ofv a .shadow due. to the interception of the useful X-rays by In this form the angular disposition of the cavity relatively to the axis of the anticathode may be similar to the arrangement shown in Fig.

3 or maybe like in Figs. land 2. The cavity, however, is not disposed within the planes defined by the' sides of the, anticath'ode but is intersected by one side. The disposition of the cavity 25 and the cathode point 26 is such that the cone of X-ray emanation is projected clear of the cathode point. Within the. zone delimited by the angle 7' there is undisturbed radiation.

For the purposes of illustration I have may be any desired plurality of groups of cavities andeathodically active points differing from each other in various respects to produce rays of different degrees ofhard ness, as pointed out in connection with Figs.

- 1 and 2.

" and also by the distance and general rela- .tionship of the two.

It is understood that various other modifications may be'made within the scope of the mvention.

. The surfaces of the cavities hereinbefore' referred to are preferably,- although not necessar ly, surfaces of revolution.

I claim '1. In hlgh-vacuum devices of the charac- 'ter described, a device for limiting X-ra v emanations -to'a predetermined area, which By the particular arrangement shown the imity thereto.

comprises an anode having a cavity whoseorificecorresponds to the said'area and a cathodic point directed into said cavity and inclose proximity thereto.

2. In high;vacuum devices of thecharacter described, a device adapted for radiographic purposes and having a predeter mined focalarea, comprising an anode having a cavity whose orifice corresponds'to the said area and a cathodic point directed into the area and in close proxmity thereto.

3. In high-vacuum devices of the "char acterdescribed, a device for producing an unobstructed zone of X ray' emanations, which comprises an anode having a cavity extending obliquely relatively to the axis of the anode and a cathodic point directed into the cavity and in close proximity thereto.

4.. In a high-vacuum X-ray apparatus, an anode having a cavity whose surface is a surface 'of revolution and whose. projected area corresponds to a predetermined focal area, and a oath de point directed into said cavity and in clfise proximity thereto. 5. In a high-vacuum X-ray apparatus, an anode having a-cavity whose surface is a surface of revolution about an axis inclined. to. the axis'of the anode and whose -projected area corresponds to a predetermined focal area, and a cathode point directed into said cavity and in close proximity thereto.

6. In a high-vacuum X-ray apparatus, an N anode having in one edge a cavity whose, surface is a surface of revolution about an axis inclined to the axis of the anode and whose projected area corresponds to a predetermined focal area, and a cathode point directed .into said cavity and in close prox- 7.'In high-vacuum devices of the charactor described, a device comprising an anode having a cavity and a cathode whose active end is directed toward the cavity, the remaining part being bent out of the range v of the useful X-ray emanations' 8. In high-vacuum devices of the character described, a device comprising an anode having a cavity extending obliquely a relatively to the axis of the anode and a cathode whose active end is directed toward the cavity, the remaining part being bent out of the range of the useful .I-rny emanations.

9. In high-vacuum devices of the Icharactcr described, a device comprising an anode having a cavity in one edge and a cathode vWhose active end is directed 'toward the cavity, the remaining part being bent out of the range of the useful X-ray emanations. In testimony whereof, I afiix my signature.

JULIUS

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