US2442493A - Electric discharge device comprising an exhaust system - Google Patents

Description

June 1, 1948.

F. A. HEYN ELECTRIC DISCHARGE DEVICE COMPRISING AN EXHAUST SYSTEM Filed Feb. 27, 1945 INVENTOR- ATTORNEY Patented June 1, 1948 ELECTRIC DISCHARGE DEVICE COMPRIS- ING AN EXHAUST SYSTEM Frans A. Heyn, Eindhoven, Netherlands, assignor to Hartford National Bank and Trust Company, Hartford, Conn., as trustee Application February 27, 1943, Serial No. 477,490 In the Netherlands March 10, 1941 Section 1, Public Law 690, August 8, 1946 Patent expires March 10, 1961 4 Claims. 1

Certain electric discharge tubes, such as dis charge tubes in which a high velocity beam of electrically charged particles is generated for the transmutation of atoms, must be continuously connected to an exhausting system during the operation of the tube.

Tubes of the foregoing type generally comprise two separate sections, i. e. a section in which an electric discharge in a gas takes place and a section in which the gas ions produced thereby are accelerated by an electric field. A device of this kind is described in the Journal Physica of February 1937 and illustrated therein on page 153; additional description of this type of apparatus may be found in the following patents and publications: U. S. Patent 2,243,941; Proc. Roy. Soc. 141, 259 (1933); Ann. Physik 23, 137 (1935); Phys. Rev. 25, 452 (1925); Z. Phys. 4, 195 (1921); Proc. Roy. Soc. 136, 619 (1932); Radiology 22, 163 (1934) and Philips Tech. Rev. 1, 6, (1936').

In the section in which the ions are accelerated there must prevail a pressure considerably lower than in that in which they are produced. Since both sections communicate with each other it is necessary to simultaneously exhaust the section in which acceleration of the charged particles takes place and to constantly admit gas into the section in which the charged ions are generated.

To increase the effect of the beam of charged particles, the potential drop in the accelerating section, as well as the intensity of the rays may be increased. The one as well as the other renders the maintenance of the difierence in pressure more difficult, which will appear from the following explanation.

It is desirable that the end of the accelerating section wherein the charged particles are received should be connected to earth, in order that this end and the parts connected thereto may be approached and touched even when the tube is operative. This requires that the'exhaust plant, which has also earth potential, be connected to the same end of the tube. In the case ofa short tube, such as described in the above-mentioned publication, the mouth of the channel through which the two sections are in communication with each other, lies closely to the end of the accelerating section which is connected to earth. In a tube for a much h h r I voltage the path to be traversed by the ions is much longer, so that the gas to be carried oil has also to traverse a much longer path to reach the pump.

' The intensity of the beam of rays is increased by rendering the channel communicating between the two sections wider and shorter, but this also necessitates a higher exhaust speed.

In a high-power accelerating device, especially in one mounted vertically, a direct connection of the pump to the tube, i. e. a connection without intermediary conduit, is no longer possible because of the large dimensions required for the pump to develop sufficient capacity.

The present invention provides a solution of this difiiculty. It can in general be applied to high-tension discharge devices having a corpuscular beam of rays, in which the electrically charged particles, after having traversed a section wherein they are accelerated, enter into a receiving device. According to the invention, two or more difiusion pumps are arranged in line with the accelerating device beside the centrally arranged receiving device and directly secured ,to the bottom of the accelerating section. In this arrangement the receiving device remains well accessible and a saving of space is obtained. In a connecting conduit a loss of pressure would always occur so that, if such a conduit were used and if it were even possible to exhaust the accelerating section through this conduit to a suflicient extent, it would be necessary to use a much larger plant than in the case of direct connection of a certain number of pumps according to the invention.

These pumps need not directly maintain the high-vacuum relatively to the atmospheric pres-v sure, but they may cooperate with an exhaust device which produces a preliminary vacuum. A particularly advantageous device is obtained by arranging four high-vacuum pumps in a square and connecting them two by two with av preliminary vacuum pump.

In order that the invention may be more clearly understood and readily carried into effect, it will be explained more fully by reference to the accompanying drawings showing, by way of f example, one embodiment thereof.

Fig. 1 of this drawing shows a plant for very 3 high voltage which comprises a discharge device for high speed charged particles.

Fig. 2 shows a detail of this discharge device and a portion of the exhaust plant.

Fig. 3 is a cross-section through the device of Fig. 2 taken on the line I-I.

Fig. 1 shows a device I, constituted by condensers and rectifying tubes in cascade connection, for converting alternating current into direct current whilst increasing the voltage up to, for example, 1250 kilovolts.

article in the Journal Physica on page 158.

Between a pole body 3 of this generator and a pole body 4 of the discharge device 5 are provided two connecting resistances 2. The two pole bodies are directly connected to each other by one of the resistances. V a double conductor is used will be explained hereinafter.

The discharge device is constituted by three An illustration of a similar device is found in the beforementioned is a metal tube I4 which surrounds the discharge The reason why parts, a vertical tube 6, the section in which gas ions are accelerated by electric fields, a source 1 of charged particles (shown in dotted line), and a receiving device 8 which is connected to earth.

The accelerating section is subdivided into a pluraiity of sections. By means of six connecting resistances which are connected to tappings of the generator I, the accelerating voltage is uniformly divided over these sections. The pole body 4 is supported by columns Ii! of insulating material which, together with the tube '6, are placed on a metal fioor' II which has earth potential. The columns I8 are provided with a plurality of integral radially extending flanges 50 which serve to increase the exposed surface area of the columns and decrease electrical leakage. Beneath this floor is the operating room which contains, in addition to the receiving device 8, the exhaust plant and various operating devices and auxiliary apparatus.

The columns I0 may be hollow so that they may contain oil conduits (not shown) for the oil cooling of thesource I of charged particles and connecting rods (not shown) of insulating material in order that regulating devices (not shown) such as valves for regulating the amount and pressure of the ionizable gas introduced into the ion source I, which are'in the pole body 4 may be operated from the operating room.

A rectifier (not shown) for 50 kilovolts is arranged in the pole body 4 and serves as the voltage supply for the source I of the charged particles. Beside the generator column I are placed two columns I2 constituted by condensers which bridge the potential difference between the pole body 3 and earth and through which is supplied the alternating current for energizing the rectifier in the pole body '4. Integral radially extending flanges 5| are provided for. increasing the exposed surface area of the columns I 2 to thereby minimize electrical leakage. One of these columns is shown in Fig. 1, the other is located behind it and therefore does not appear in the drawing. Each of these columns is connected to one of the two connecting resistances 2, the first column with one resistance, the second column with the other. sistances lead inside the pole body 4 to the'rectifler above noted energizing the source of ions 1, the electrical energy being transmitted to the said resistance throughthe condensers in the columns I2. A similar circuit arrangement is shown in Fig. 5 of the above-mentioned article in the Journal Physica. In addition, one of The connecting rechannel. Between the edges of the consecutive metal tubes, i. e. for example between the edges I6. and I1, the ions are each time accelerated. Since definite disturbances may occur when loaded particles impinge on the wall I3, the latter is protected therefrom by a metal cylinder I5. The cylinders I4 and I5 overlap each other, owing to which the best possible protection of the wall is obtained.

Four oil diffusion pumps I8, I9, 20, 2| are arranged beneath the tube 6 in line therewith beside the section 3 in which the ions are received. Section 8 comprises a metal tube 22 which is connected to earth and cooled by a tubular conductor 23 which is traversed by water. After having traversed the tube 22, the charged particles pass a cock 24 and subsequently a glass intermediate piece 25 through which the beam may be observed because of its weakly luminous character. At last, the rays enter into a tube 26 which is closed at the lower end by a bottom 2'! on which a plate 28 may be provided of the material which is desired to be transformed by ion bombardment, during which neutrons may be generated. The bottom 2! is cooled by water which circulates in a channel 29 provided in the bottom and is carried on and off through tubes 30.

By means of a common connecting tube (not shown), the pumps I8 and I9 are jointly connected to one of the preliminary vacuum pumps 32 (Fig. 1), the pumps 28 and ill being also connected to a preliminary vacuum pump 32 through a common connecting tube (not shown). To this end, the pumps are provided with outlet tubes 33, 34, 35 and 36, of which the first two extend into a common outlet tube 3'! which in turnconnects with one of said connecting tubes and the other two extend into a common outlet tube 38 which in turn connects with the other of said connecting tubes. The preliminary vacuum pumps may be of comparatively small size. The pumps I8, I9, 20 and 21 are mounted on a support 52 secured to the lower-most section of the accelerating tube 6.

To give the gas as wide a passage as possible,

care has been taken to see to it that the space' drogen, to flow continuously into the source of ions I and to maintain nevertheless in the ac celerating section 6 and in the receiving device 8 the low pressure for example lower than 10* mm. Hg, which is necessary for a free passage of the charged particles generated in the section 6 by ionisation of the gas at a pressure of, for example, 2.10- mm. Hg.

The preliminary vacuum may be increased by the pumps 32 up to 10' mm. Hg. These preliminary vacuum pumps may in turn be connected to a preliminary vacuum of, for example, 0.2 mm. Hg which may be supplied by a rotary pump.

I claim:

1. A high-tension electrical discharge device comprising a source of electrically charged particles derived from a gaseous atmosphere, an accelerating chamber for the charged particles having one end connected to said source, a receiving device for the accelerated charged particles connected to said accelerating chamber at a point remote from the source of charged particles and centrally arranged with respect to the axis of said accelerating chamber, and means to exhaust gases from said accelerating chamber. said means comprising plurality of diffusion pumps having their axes arranged parallel to the axis of the accelerating chamber, being directly secured thereto and'being positioned adjacent to said receiving device.

2. A high-tension electrical discharge device comprising a source of electrically charged particles derived from a gaseous atmosphere, an accelerating chamber for the charged particles having one end connected to said source, a receiving device for the accelerated charged particles connected to said accelerating chamber at a point remote from the source of charged particles and centrally arranged with respect to the axis of said accelerating chamber, and means to exhaust gases from said accelerating chamber, said means comprising four difiusion pumps having their axes arranged parallel to the axis of the accelerating chamber, being directly secured thereto, and being positioned adjacent to said receiving device with their axes symmetrically arranged about the axis of the said accelerating chamber.

3. A high-tension electrical discharge device comprising a source of electrically charged particles derived from a gaseous atmosphere, an accelerating chamber for the charged particles having one end connected to said source, said accelerating chamber comprising a plurality of electrically conductive tubular elements arranged along a common longitudinal axis with their end portions spaced apart and a plurality of electrically insulating tubular elements arranged along a common longitudinal axis, concentrically surrounding said electrically conductive elements and spaced therefrom, a receiving device for the accelerated charged particles connected to said from the space between said conductive and insulating elements to said difiusion pumps.

4. A high-tension electrical discharge device comprising a source of electrically charged particles derived from a gaseous atmosphere, an ac celerating chamber for the charged particles having one end connected to said source, said accelerating chamber comprising a plurality of electrically conductive cylindrical elements arranged along a common longitudinal axis with their end portions spaced apart, a plurality of electrically insulating cylindrical elements arranged along a common longitudinal axis, concentrically surrounding the electrically conductive elements and spaced therefrom to form a plurality of aligned annular spaces, and a plurality of annular-shaped partition members each interconnecting two adjacently positioned electrically insulating elements and fixedly securing one of said electrically conductive elements and each being provided with a plurality of apertures at its portion within the annular space so as to provide a passageway between the aligned annular spaces for gas molecules contained within the electrically conductive elements and the said annular spaces, a receiving device for the accelerated charged particles connected to said accelerating chamber at a point remote from the source of charged particles and centrally arranged with respect to the axis of said accelerating chamber, and means to exhaust gases from said accelerating chamber, said means comprising a plurality of diffusion pumps having their axes arranged parallel to the common axis of the electrically conductive elements and being positioned adjacent to said receiving device so as to provide free passage of gas molecules from said annular spaces to said difiusion pumps.

FRANS ADRIAAN HEYN.

REFERENCES CITED UNITED STATES PATENTS Name Date Kuhn et al. Oct. 22, 1940 Number

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