US2866114A

US2866114A - Beryllium window x-ray tube

Info

Publication number: US2866114A
Application number: US436922A
Authority: US
Inventors: Hardenberg Jan Jesa Christiaan
Original assignee: US Philips Corp
Current assignee: US Philips Corp; North American Philips Co Inc
Priority date: 1953-06-12
Filing date: 1954-06-15
Publication date: 1958-12-23
Anticipated expiration: 1975-12-23
Also published as: FR1102271A; CH319763A; GB761702A

Description

1958 J. J. c. HARDENBERG 2,866,114

BERYLLIUM WINDOW X-RAY TUBE Filed June 15. 1954 I. I'll. 'IIIIIII'I "I". '11-'11. 'IIIIIIII VIIIIIIIIIII'IIIIIIIIIIIIIII w sm I ......m...... .......................n..

INVENTOR A Jn Jsayas, C/W/Lsf/aa/Y Harde/ze y AGENT United States Patent i 2,866,114 BERYLLIUNI WINDOW X-RAY TUBE Jan .l'esayas Chrisfiaan Hardenberg, Eindhoven, Netherlands, assignor, by mesne assignments, to North American Philips Company, Inc., New York, N. Y., a corporation of Delaware Application June 15, 1954, Serial No. 436,922 Claims priority, application Netherlands June 12, 1953 4 Claims. (Cl. 313-59) This invention relates to devices containing radiationtransparent windows, and in particular to X-ray tubes containing a beryllium window.

It is known to use X-rays in a manner such that the long-wave part of the X-ray spectrum is utilised. A suitable choice of the voltage between the anode and the cathode of the X-ray tube ensures the major portion of the ray output to have the required wavelength. However, if the requirement is to be satisfied that the wavelength exceeds 4 A., in which case the applied voltage is approximately 5 kv. in order to obtain a maximum ray output, difficulties arise. X-rays having such a wavelength are highly attenuated when they penetrate the very thin layer of material which forms the partition between the evacuated space in the tube and the environment and the effect of this detrimental phenomenon increases with increase in the wavelength. Consequently the need for ever thinner windows made of a material absorbing a minimum amount of rays arises. The most suitable material is beryllium. A-n X-ray tube has already been manufactured comprising a window of this material 200,11. thick. The tube had to be connected permanently to the vacuum pump since the beryllium plate arranged in the ray window did not form a completely airtight seal.

This circumstance interferes with the development of the art of photographic registration of tissue structures by means of X-rays. It was found that the examination of such objects includes a region in which the resolving power of the light microscope is not sufficient. The fineness of the tissue structure requires a resolving power preferably exceeding 1 micron which can be approximated to by a contact registration by means of X-rays. Registrations of tissue layers 30 1. thick have already been made.

The invention relates to an X-ray tube comprising a radiation-transparent metal window of slight thickness in order to seal the radiation aperture in an airtight manner, which window is made of beryllium. According to the invention the beryllium window is less than 100 microns thick for part of its surface area. Technical difficulties apparently did not allow the manufacture of windows passing X-rays of a wavelength exceeding 4 A. in a sufficient degree. These difiiculties have been overrated and according to the invention it was found that a very careful treatment allowed the manufacture of windows which were 100p. thick or even thinner while starting from known methods. If sufficient care is taken the desired result is obtained in that the window is rubbed along a flat surface with the use of a small amount of very fine grinding powder. Thus the resultant window of beryllium has a ground portion less than 100 microns thick that is air-tight or vacuum-tight.

In most cases a radiation field of small size is sufficient to make a registration since this can be enlarged several times optically for examination. If only that part of the window which passes the useful rays has to creases the resistance of the window to the atmospheric pressure.

From a calculation of the X-ray absorption it was found that in the case of an absorption in the tissue layer of from 20 to the lowest absorption limit indicating the difference in intensity which can just be observed, the wavelength is 4 to 8 A, with a 20 1 tissue. With 10y. tissue this value is 5 to 10 A. and with 5 tissue the wavelength would have to be 6 to 12 A. The invention permits the examination to be extended to cover these tissue layers since the ray window sufficiently passes the required wavelength spectrum.

The drawing shows an embodiment of an X-ray tube according to the invention.

The X-ray tube is connected to the end of a high tension supply cable 1. A current supply conductor 2 of the cable 1 is secured to the anode hood 3 of the X-ray tube. The anode hood 3 together with a glass cylinder 4 to which it is sealed anda cylindrical metal part 5 sealed to the other end of the glass cylinder 4 forms the wall of the X-ray tube envelope. The tube is surrounded by a metal sheath 6 which forms an integral structure with the earthed cable sheath 7. The anode 8 is secured to the anode hood 3. It extends close to a window 9 secured to the cylindrical part 5. The window hermetically seals the cylinder aperture. The vacuum space within the tube wall also contains a focusing member 10 and a thermionic cathode 11. The cathode is held by a current supply wire 12 and a cathode support 13. Electrons emitted from the cathode 11 strike the end face 15 of the anode 8 and are focused thereon into a small focal point by means of the focusing member 10. The X-rays penetrate the window 9 in the direction of the tube axis.

The window 9 is made of ground beryllium foil the thickness of which is so slight that soft X-rays are absorbed to a small extent. The window is less than 0.1 mm. thick and the X-ray tube produces a radiation of such slight hardness that a field of examination which is highly important to medical science can be considerably extended.

What is claimed is:

1. A discharge device comprising an envelope containing an atmosphere different from the outside atmosphere, cathode and anode electrodes, and a radiationtransparent window in said envelope, said window comprising vacuum-tight beryllium foil having a ground portion of a thickness less than microns.

2. An electron discharge device comprising an evacuated envelope, cathode and anode electrodes, and a radiation-transparent window in said envelope, said window comprising vacuum-tight beryllium foil having a ground portion of a thickness less than 100 microns.

3. A device as set forth in claim 2 wherein the lessthan-lOO-microns-thick foil portion is surrounded by a beryllium portion of greater thickness for strengthening purposes.

4. An X-ray tube comprising an evacuated envelope, cathode and anode electrodes, and an X-radiation-transparent window in said envelope and capable of transmitting X-rays of a wavelength exceeding 4 Angstroms, said window comprising vacuum-tight beryllium foil having a ground portion of a thickness less than 100 microns.

References Cited in the file of this patent UNITED STATES PATENTS 1,942,007 Slack Ian. 2, 1934 2,332,426 Atlee Oct. 19, 1943 2,394,984 Claussen Feb. 19, 1946 2,440,348 Root Apr. 27, 1948 2,665,391 Bleeksma Jan. 5, 1954

Claims

1. A DISCHARGE DEVICE COMPRISING AN ENVELOPE CONTAINING AN ATMOSPHERE DIFFERENT FROM THE OUTSIDE ATMOSPHERE, CATHODE AND ANODE ELECTRODES, AND A RADIATIONTRANSPARENT WINDOW IN SAID ENVELOPE, SAID WINDOW COMPRISING VACUUM-TIGHT BERYLLIUM FOIL HAVING A GROUND PORTION OF A THICKNESS LESS THAN 100 MICRONS.