US1735302A - Lenard ray tube - Google Patents

Lenard ray tube Download PDF

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Publication number
US1735302A
US1735302A US272194A US27219428A US1735302A US 1735302 A US1735302 A US 1735302A US 272194 A US272194 A US 272194A US 27219428 A US27219428 A US 27219428A US 1735302 A US1735302 A US 1735302A
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US
United States
Prior art keywords
window
glass
envelope
tube
electrons
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US272194A
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English (en)
Inventor
Slack Charles Morse
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Westinghouse Lamp Co
Original Assignee
Westinghouse Lamp Co
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority to NL27580D priority Critical patent/NL27580C/xx
Application filed by Westinghouse Lamp Co filed Critical Westinghouse Lamp Co
Priority to US272194A priority patent/US1735302A/en
Priority to GB12028/29A priority patent/GB310329A/en
Priority to FR673624D priority patent/FR673624A/fr
Priority to DEW82409D priority patent/DE615705C/de
Application granted granted Critical
Publication of US1735302A publication Critical patent/US1735302A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J33/00—Discharge tubes with provision for emergence of electrons or ions from the vessel; Lenard tubes
    • H01J33/02—Details
    • H01J33/04—Windows

Definitions

  • This invention relates to a Lenard ray tube of the type in which the electrons are projected at high velocities through a wall of the tube into the open air so as to be available for various purposes, such as effecting chemical reactions or for germicidal and sterilizing efiects.
  • Lenard ray tubes have been produced with metallic windows for the projection of an electron stream into the open air.
  • Lenard as early as 1891 provided a vacuum tube with a small window of aluminum ioil of extreme thinness against which cathode rays were shot at a sufiiciently high velocity to pass completely therethrough and to excite phosphorescence in the air a few millimeters away. Due to the low velocity of the electrons and the small quantity thereof obtainable from this tube, is remained only a laboratory experiment.
  • improvements have been made in the Lenard ray tube among others, by O. Eisenhut (Heidelberg Dissertations May 1921),
  • Metal of this degree of thinness is extremely fragile and if of any appreciable area, it must be supported by a heavier metallic structure to which it is necessary to secure the foil in a gas tight manner.
  • This metallic structure in turn, must be sealed to the glass portion of the envelope also in a gas tight manner.
  • One of the objects of the present invention is to overcome the difficulties inherent in the use of metal windows and to employ a portion of the glass envelope of the device as the window ghrough which the cathode rays are proecte
  • Another object is to produce a novel window for a Lenard ray tube in which there will be a low loss of energy of the cathode ray in passing through the window.
  • a still further object is to produce a window for a Lenard ray or ion tube which is of low density and which may be made extremely thin while retaining'sufficient strength to resist the external atmospheric pressure.
  • the loss of energy of cathode rays in passing through a material increases with and is proportional to the square root density of the material and the square root thickness thereof.
  • Molybdenum has been considered the most practical metal for this service due to its ductility and high elastic limit. The density of molybdenum is rather high, however. so that the energy which is lost in passage of the cathode rays through the window is relatively large.
  • Aluminum has a much lower density and the energy loss therein is much less than that for molybdenum, but its strength is low and it is necessary to employ heavier foil. 'Aluminum, moreover, does not seal readily with glass or other metals and increases the difiiculty of producing gas tight conditions in the tube.
  • the oathode rays can be transmitted directly through the glass wall of the device.
  • Ordinary glass as used for the envelope of high voltage devices, such as X-ray tubes, cathode ray tubes, etc. is ordinarily about 1 mm. in thickness in order to give the requisite strength to resist handling and support of the heavy electrode structure.
  • this thick- 'ness of glass is opaque to cathode rays.
  • the critical voltage required to just pass through the glass is about 52,000 volts.
  • the energy absorption in the glass at potentials of 100,000 volts between the electrodes corresponds to a decrease in inter-electrode potential of only about 16,000 volts and at 200,000 volts there is a loss of energy corresponding only to a decrease of about 8,000 volts between the electrodes.
  • the window through which the cathode rays are transmitted may be made by drawing in or blowing out a restricted portion of the envelope to form a bulbous portion.
  • the drawn-in window may be made thinner for the same strength, than the blown-out window since in the former case, the atmospheric pressure exerts a tensional instead of a bending or buckling strain force.
  • This drawn-in bulb has the further advantage of being protected by the heavy surrounding portion of the envelope.
  • the chief advantage of the blown-out window is that it enables the window to be brought closer to the material to be treated.
  • the cathode rays are drawn over from the cathode by an anode maintained at a high potential and having an aperture through which the electrons pass at high velocity.
  • This aperture is disposed opposite the bulbous window in such manner and should be of such size that the electrons emerging therefrom strike the window substantially normal to the surface thereof.
  • the interior surface of the window may be coated with an exceedingly thin metallic film electrically connected to the anode, so as to prevent the accumulation of a negative charge on the window and the danger of discharges between the glass window and the highly positively charged anode. This, however, in most cases is un necessary as the intense ionization produced by the rays allows this charge to leak off.
  • the cathode stream after passing through the window is dispersed by collison with gas molecules in the air. These deflected electrons may bombard the outside surface of the bulbous window, in the case of the drawn-in Window, causing undesirable heating and danger of destruction of the window if the operation of the tube is prolonged.
  • This heating may be reduced by coating the exterior of the side walls of the bulbous window with a protective material of such thickness that the electrons will not readily penetrate therethrough to the glass.
  • a coating of shellac may be applied to the glass for this purpose.
  • This shielding coating serves also device, as at 12.
  • Fig. 1 is a side view, partly in section, of a Lenard ray tube embodying my invention
  • FIG. 2 is a fragmentary View similar to Figure 1 showing modified form of anode construction
  • Fig. 3 is a fragmentary view showing a modified form of window.
  • the tube shown in Figure 1 comprises a glass envelope 1 having a relatively heavy wall and containing a filamentary cathode 2 and an anode 3.
  • the cathode end 4 of the tube has a reentrant glass stem 5 termiiiating in a press 6 through which the leading-in conductors 7 for the cathode, are sealed.
  • the cathode 2 may be of any suitable electron emitting material, but preferably I construct it of tungsten or tantalum in the form of a coil mounted within a focusing cup 8, as is usual in X-ray tube construction.
  • An electro-static' shield 9 surrounds the cathode and protects the seal from puncturing. It also prevents sharp point sparking from the cathode.
  • This shield may take the form of a split metal tube of nickel, Monel metal, chrome-iron of other metal, held in place on the reentrant stem 5 by friction. Obviously, other convenient methods of support may be readily devised.
  • the anode consists of a tube 10 preferably of copper and is provided with a leading-in conductor 11 sealed through the wall of the
  • the tubular anode is sup ported in the envelope by a split collar 13 of chrome-iron or other suitable metal which fits snugly into the glass envelope and is secured to the anode in any suitable manner as by pins, screws, friction, soldering, etc.
  • the tubular anode is arranged with its axis aligned with the axis of the electron stream from the cathode so that the electrons drawn over by the anode pass there through and are projected against the window 14.
  • the tubular anode also serves as a shield to prevent the electrons striking undesired portions of the envelope. For this purpose, the end 15 adjacent the cathode may be enlarged.
  • the end 16 of the envelope adjacent the anode may be reduced in diameter where the window 14 is formed therein.
  • the window 14 is formed in the closed end of a short length of tubing which is subsequently sealed to the reduced portion of the envelope.v
  • the window 14 may preferably have a thickness of from 0.0001 to 0.005 inches. Since the center of the closed endof the tube is heated to the highest temperature it becomes the thinnest part of the bulb, the walls gradually increasing in thickness from such central section to the outer edge of the bulbous portion where it joins the end of the tubular part 16 of the envelope. This strengthens the bulbous end of the envelope while enabling the central portion through which the cathode rays are projected, to be very thin.
  • the bulbous window may be further thinned to the desired thickness by etching with a weak solution of hydrofluoric acid.
  • a convenient method of determining the thickness of the window is by the voltage required to cause 'cathrode rays to pass through the glass window.
  • the voltage required between the electrode of the tube in order to cause a florescence of the coating on the window is a measure of the thickness of the glass.
  • the outer end 17 of the envelope may be enlarged in order to accommodate a bulbous portion 14 of a diameter somewhat larger than the opening 18 in the tubular anode 3, so that all portions of the window opposite the opening 18 will be substantially normal to the direction of travel of the cathode rays and therefore, so that the thickness of glass traversed by the electrons will be substantially uniform. If the electrons were permitted to strike the glass obliquely to the surface of the bulbous portion, the energy loss in the greater thickness of glass encountered would cause undesirable heating with danger of causing destruction of the window or limiting the period of operation of the tube.
  • FIG 2 a modification is shown in which the tubular anode 3 is replaced by a cup shaped anode 19 having an aperture 20 through which the cathode rays emerge.
  • the anode is supported by a sleeve 21 engaging the inner wall of the envelope.
  • the inner surface of the window 14 may be coated with an exceedingly thin film of conductive material 22 which is in electrical connection with the anode 19, whereby the accumulation of a negative charge on the window due to the electrons striking the same, is prevented.
  • Such negative charge if allowed to accumulate may cause a discharge to the anode and consequent destruction of the window.
  • the bulbous window 24 is formed externally of the side walls of the en- Velope. This form, while not as strong as the drawn-in window, is satisfactory for high voltage tubes in which heavier windows may be employed. It has the advantage that the window may be brought closer to the material being treated and is subject to less bombardment by deflection of electrons in the air.
  • a tubular shield 25 surrounds the window and protects the same from mechanical shock.
  • This shield is shown composed of glass but may be of any other suitable material, as metal, fiber, bakelite, etc.
  • the electrodes should be thoroughly degasified in accordance with the practice followed in the construction of X-ray tubes. Briefly, such degasification may be carried out by heating the metal parts to a red heat in a vacuum furnace prior to assembly in the envelope to effect a removal of the major portion of the occluded gases. After assembly, the electrodes and associated parts are sealed into the tube, a high vacuum is created therein and a final degasification of the electrodes effected by electronic bombardment and high frequency induction heating while the tube is on the exhaust pumps. After this final degasification, the tube may be sealed off from the pumps and due to the relatively small mass of metal therein, such vacuum is maintained without the use of gas absorbing ma.- terials within the tube and liquid air.
  • a small pressure of from 1 to 10 microns of monatomic gas such as neon may be admitted to the envelope.
  • a Lenard ray tube operable in the absence of appreciable gas ionization within the tube to project cathode rays into the atmosphere comprising an envelope, a source of electrons therein, an anode having an aperture therein, and a window transparent to cathode rays disposed opposite said aperture, said window being composed of vitreous material.
  • a Lenard ray tube comprising an envelope, a source of electrons therein, a bulbous window in said envelope composed of vitreous material and an anode for projecting a stream of high velocity electrons against said window, said window having a thickness of from 0.0001 to 0.005 inches.
  • a Lenard ray tube comprising an envelope, a bulbous window therein having a central dome portion of a thickness of not over a few thousandths of an inch, a source of electrons within the envelope, an anode disposed between said window and said source of elec' trons, said anode having an aperture therein through which electrons are directed against said window, and shielding means on the exterior of a portion of said bulbous window to protect the same from stray electrons.
  • a Lenard ray tube operable in the absence of appreciable gas ionization within the tube, comprising an envelope, an electron emitting cathode extending from one end thereof, a vitreous bulbous shaped window at the opposite end of the envelope permeable to high speed electrons and an anode for directing cathode rays upon the window at a sufiiciently high rate to pass through the same.
  • a window for an ion tube permeable to high velocityions comprising a bulbous body of low density glass having at the dome portion a thickness of from 0.0001 to 0.005' inches.
  • a Lenard ray tube comprising an envelope having a vitreous wall and containing an electron emitting cathode therein and an anode, for directing a stream of electrons at high velocity against the vitreous wall of said envelope, said wall at the region of impact of said'electrons having a thickness of from about one ten thousandth to five thousandths of an inch.
  • a window permeable to high velocity ions comprising a bulbous body of vitreous material having at the dome portions a thickness of from about 0.0001 to 0.005 inches.
  • a window permeable to high velocity ions comprising a substantially bulbous body of relativel heavy glass having a concentric re-entrant bulbous portion, sald re-entrant portion having at the center a thickness of rom about 0.0001 to 0.005 inches.
  • a window permeable to high velocity ions said window being composed of vitreous material of a thickness of from 0.0001 to 0.005 inches.
  • a Lenard ray tube comprising an envelope, a bulbous window therein having a central dome portion of a thickness of from 0.0001 to 0.005 inches, means within said envelope for projecting a stream of high velocity electrons against said window and means for confining said stream of electrons substantially to said dome portion.
  • a Lenard ray tube operable in the absence of appreciable gas ionization within the tube to project cathode rays into the atmosphere comprising an envelope, 9. source of electrons within said envelope, a vitreous window in said envelope of a thickness of from 0.0001 to 0.005 inches, an anode for directing a stream of high velocity electrons against said window and a thin conducting coating on one side of said window for preventing the accumulation of a negative charge thereon.
  • a Lenard ray tube operable in the 'absence of appreciable gas ionization within the tube to project cathode rays into the atmosphere comprising an enve ope, a source of electrons within said envelope, a vitreous window in said envelope of a thickness of from 0.0001 to 0.005 inches, an anode for directing a stream of electrons against said window and a thin conductive coating on one side of said window in electrical connection with said anode,

Landscapes

  • Manufacture Of Electron Tubes, Discharge Lamp Vessels, Lead-In Wires, And The Like (AREA)
  • Vessels, Lead-In Wires, Accessory Apparatuses For Cathode-Ray Tubes (AREA)
US272194A 1928-04-23 1928-04-23 Lenard ray tube Expired - Lifetime US1735302A (en)

Priority Applications (5)

Application Number Priority Date Filing Date Title
NL27580D NL27580C (enrdf_load_html_response) 1928-04-23
US272194A US1735302A (en) 1928-04-23 1928-04-23 Lenard ray tube
GB12028/29A GB310329A (en) 1928-04-23 1929-04-18 Improvements in cathode ray and like tubes
FR673624D FR673624A (fr) 1928-04-23 1929-04-20 Perfectionnements apportés aux tubes à rayons cathodiques
DEW82409D DE615705C (de) 1928-04-23 1929-04-21 Verfahren zur Herstellung von Lenardfenstern

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US272194A US1735302A (en) 1928-04-23 1928-04-23 Lenard ray tube

Publications (1)

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US1735302A true US1735302A (en) 1929-11-12

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Application Number Title Priority Date Filing Date
US272194A Expired - Lifetime US1735302A (en) 1928-04-23 1928-04-23 Lenard ray tube

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US (1) US1735302A (enrdf_load_html_response)
DE (1) DE615705C (enrdf_load_html_response)
FR (1) FR673624A (enrdf_load_html_response)
GB (1) GB310329A (enrdf_load_html_response)
NL (1) NL27580C (enrdf_load_html_response)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2418202A (en) * 1941-07-07 1947-04-01 Gen Electric Fluorescent lamp and method of manufacture
US2617953A (en) * 1949-06-28 1952-11-11 Electronized Chem Corp Window structure for cathode-ray tubes
US2702863A (en) * 1949-07-12 1955-02-22 Koch Jorgen Method of treating optical elements
US2903613A (en) * 1955-05-13 1959-09-08 Sam Robbins Inc Apparatus for and method of wave guide energy transmission modulation, control and cut-off
EP1775752A3 (de) * 2005-10-15 2007-06-13 Burth, Dirk, Dr. Herstellung eines Elektronenaustrittsfensters mittels eines Ätzprozesses

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR829048A (fr) * 1937-11-05 1938-06-03 Fernseh Ag Construction d'anode pour tubes à rayon cathodique, en particulier pour tubes de braun à très hautes tensions de travail

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2418202A (en) * 1941-07-07 1947-04-01 Gen Electric Fluorescent lamp and method of manufacture
US2617953A (en) * 1949-06-28 1952-11-11 Electronized Chem Corp Window structure for cathode-ray tubes
US2702863A (en) * 1949-07-12 1955-02-22 Koch Jorgen Method of treating optical elements
US2903613A (en) * 1955-05-13 1959-09-08 Sam Robbins Inc Apparatus for and method of wave guide energy transmission modulation, control and cut-off
EP1775752A3 (de) * 2005-10-15 2007-06-13 Burth, Dirk, Dr. Herstellung eines Elektronenaustrittsfensters mittels eines Ätzprozesses
US20090160309A1 (en) * 2005-10-15 2009-06-25 Dirk Burth Electron beam exit window

Also Published As

Publication number Publication date
FR673624A (fr) 1930-01-17
DE615705C (de) 1935-07-11
GB310329A (en) 1930-01-09
NL27580C (enrdf_load_html_response)

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