US2886726A - Target for x-radiation and the like - Google Patents

Target for x-radiation and the like Download PDF

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Publication number
US2886726A
US2886726A US697823A US69782357A US2886726A US 2886726 A US2886726 A US 2886726A US 697823 A US697823 A US 697823A US 69782357 A US69782357 A US 69782357A US 2886726 A US2886726 A US 2886726A
Authority
US
United States
Prior art keywords
lead oxide
substrate
target
oxide
radiation
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
US697823A
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English (en)
Inventor
Berger Harold
John E Jacobs
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.)
General Electric Co
Original Assignee
General Electric 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 NL233423D priority Critical patent/NL233423A/xx
Priority to NL113476D priority patent/NL113476C/xx
Application filed by General Electric Co filed Critical General Electric Co
Priority to US697823A priority patent/US2886726A/en
Priority to GB33213/58A priority patent/GB902572A/en
Priority to FR779637A priority patent/FR1217077A/fr
Priority to DEG25773A priority patent/DE1279236B/de
Application granted granted Critical
Publication of US2886726A publication Critical patent/US2886726A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
    • H01J29/02—Electrodes; Screens; Mounting, supporting, spacing or insulating thereof
    • H01J29/10—Screens on or from which an image or pattern is formed, picked up, converted or stored
    • H01J29/36—Photoelectric screens; Charge-storage screens
    • H01J29/39—Charge-storage screens
    • H01J29/45—Charge-storage screens exhibiting internal electric effects caused by electromagnetic radiation, e.g. photoconductive screen, photodielectric screen, photovoltaic screen
    • H01J29/458—Charge-storage screens exhibiting internal electric effects caused by electromagnetic radiation, e.g. photoconductive screen, photodielectric screen, photovoltaic screen pyroelectrical targets; targets for infrared or ultraviolet or X-ray radiations
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
    • G03G5/00—Recording members for original recording by exposure, e.g. to light, to heat, to electrons; Manufacture thereof; Selection of materials therefor
    • G03G5/02—Charge-receiving layers
    • G03G5/04—Photoconductive layers; Charge-generation layers or charge-transporting layers; Additives therefor; Binders therefor
    • G03G5/08—Photoconductive layers; Charge-generation layers or charge-transporting layers; Additives therefor; Binders therefor characterised by the photoconductive material being inorganic
    • G03G5/082—Photoconductive layers; Charge-generation layers or charge-transporting layers; Additives therefor; Binders therefor characterised by the photoconductive material being inorganic and not being incorporated in a bonding material, e.g. vacuum deposited
    • G03G5/08207—Selenium-based
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors

Definitions

  • lead oxide photoconductive material Ihas been applied to a substrate material such as aluminum, aluminum being capable of good X-ray transmission.
  • a substrate material such as aluminum
  • aluminum being capable of good X-ray transmission.
  • the oxide of aluminum has very high electrical resistance and the processing techniques which we desire to use have been such as to produce in a non-uniform formation of aluminum oxide between the substrate and the lead oxide coating, resulting in undesirable variation of photoconductivity characteristics from point to point.
  • the present invention seeks to improve the target by use of ka substrate which has at least its surface composed of stainless steel or one of a number of other metal whose oxides have electrical resistance of th'e order of 10 ohm-cm. or less, a good degree of electrical conductivity between the substrate surface and the lead oxide being assured, and uniformity enhanced.
  • the substrate desirably comprises a heavy metal relatively opaque to X-radiation, whereby to filter out soft scattered radiation and produce sharper images than are otherwise obtainable.
  • the heavy metal intensites the photoconductive signal by means of photoemission from the substrate material, particularly at high X-ray energy in excess of 100 kvp.
  • Stainless steel is ideal, but it is necessary to select an alloy having a co-ecient of expansion sufficiently close to that of the coating to preclude peeling.
  • AISI type 430 is the most suitable alloy presently known.
  • the preferred embodiments of the invention are made by electroplating or otherwise coating with a thin film of stainless steel a base plate of aluminum or other light metal which is a good electrical conductor and not unduly X-ray opaque.
  • coatings essentially comprising copper, nickel or chromium or alloys thereof.
  • stainless steel is preferred, particularly in medical applications.
  • lead oxide vapor is condensed and subsequently baked to convert it to a yellow crystalline form of lead oxide.
  • the baking will oxidize the heavy metal face of the substrate at the interface and it is important that the oxide of the substrate metal should should match that of the lead oxide sutliciently so that there will be no peeling of the lead oxide layer.
  • the substrates herein disclosed have all of these properties and, additionally, are easily worked, relatively non- ICC magnetic, and have good X-ray transmission. Additionally, the preferred stainless steel substrate facing in particular is sufficiently heavy to act as an electron intensifier.
  • the target plate area has been found to be notably free of the spots or blemishes found in prior target plates of this type. i
  • Fig. 1 is a diagrammatic view showing a greatly enlarged fragmentary cross section of a target embodying the invention.
  • Fig. 2 is a diagrammatic view showing in greatly enlarged fragmentary cross section a preferred embodiment of a target incorporating the invention.
  • Fig. 3 is a ow diagram of steps of the preferred method for producing a target as shown in Fig. 2.
  • Fig. 4 is a diagrammatic view showing in cross section apparatus used to coat the substrate with lead oxide.
  • the substrate 5 comprises a sheet of stainless steel or chromium or nickel of just sucient thickness to be form sustaining. Upon this is a layer 6 of an oxide of the metal of sheet 5 and a photoconductive deposit 7 of yellow crystalline lead oxide.
  • the substrate supporting sheet 8 is aluminum or other lightweight electrically conductive metal upon which is bonded a thin deposit 50 of stainless steel preferably produced by plating or spraying it upon the substrate ply, as it is usually too thin to be self supporting. Heavier plies may be laminated to the sheet 8 by rolling.
  • Upon the facing 50 is an oxide coating on which the lead oxide layer or layers 9 and 10 are applied.
  • the oxide formed at the surface and contacted by the lead oxide should have electrical resistance very materially less than that of the lead oxide (which is l01l ohm-cm). It has been found satisfactory to use as the interface portion of the substrate a metal whose oxide has a resistance of the order of 1()6 ohm-cm. or less. This insures proper electrical conductivity between the substrate and the deposit of lead oxide and gives results greatly superior to those achieved when the lead oxide is in contact with aluminum oxide or the like, the aluminum oxide having resistance greater than that of the lead oxide.
  • AISI type 430 is the preferred material used at l5 in Fig. 1 and 8 in Fig. 2 to provide the substrate surface.
  • AISI type 430 is a preferred example principally because its co-etlcient of expansion so nearly-matches that of lead oxide that no separation occurs during heating or coating.
  • the lead oxide contains a large percentage of the red form of lead oxide. It has been found that the yellow crystalline leadoxide gives faster response to X-radiation than the red form of lead oxide.
  • the preferred method of applying the photo-conductive layer and its conversion to the desired yellowcrystalline form of lead oxide is as follows, reference being made to Fig. 3.
  • the substrate plate generically designated by reference character 12 may comprise the sheet 5 of Fig. l or the supporting sheet 8 and surface lm 50 of Fig. 2.
  • the plate 12 is placed in a vacuum chamber 13 and over it is placed a heater 14 of the electrical resistance type having current supply leads 15 and 16. Gas is thereupon withdrawn from the chamber 13 through the pipe 17 of vacuum is not critical, it has been found appropriate to draw a vacuum of 10-4 mm. Hg to 10-5 mm. Hg. Dry oxygen is then introduced through the pipe 18 in such manner as to maintain a pressure of 3 to 5 microns within the chamber. After the oxygen pressure has remained stable for 5 to 10 minutes, the substrate heater 14 is energized and the target plate 12 is raised thereby a temperature of 360 to 380 C. This temperature 1s allowed to stabilize for about 30 minutes before the coating operation is commenced.
  • the lead oxide coating material is placed in a crucxble 20 and arrangement is made for heating it by induction through the energization of the coil 21.
  • the crucible temperature is raised slowly over a period of l to 20 minutes.
  • the lead oxide commences to vaporize. Desirably the temperature is raised to a maximum of about 980 C., which is maintained for approximately minutes.
  • the induction heater 21 is then deenergized and the target plate 12 is allowed to cool gradually in the oxygen atmosphere'for about 30 minutes. Thereupon the chamber 13 is opened by removing its cover 22 and whenthe target plate 12 is removed, it will have a velvety appearing red oxide coating of a red orange color and composed of a random orientation of red and yellow crystals.
  • the target is placed immediately in a 600 C. oven and baked in air for about 90 minutes.
  • the lead oxide is thereby converted to the yellow crystalline form.
  • the target is then replaced in the vacuum chamber 13, the cover 22 is sealed over it, and the coating operation is repeated to provide a second layer of lead oxide as shown at in Fig. 2.
  • the procedure is identical with that above described, including baking in air for about 90 minutes after removal of the target plate from the vacuum chamber.
  • the combined thickness of the two layers 9 and 10 of lead oxide is of the approximate order of 0.2 mm. and the color, in consequence of the air bake, is now yellow.
  • the yellow crystalline lead oxide has a resistance of 1l)11 ohm-cm. and gives a faster response to X-radiation than the red form.
  • the resistivity of the lead oxide coating is lower a'nd the image decay time is higher. The latter is particularly important, as there is a pronounced reduction in decay time as the substrate temperature during lead oxide deposit is increased to and above 200 C. A reduced decay time reduces blurring and facilitates X-ray observation of moving objects.
  • the baking of the lead oxide and its conversion to the yellow crystalline form necessarily results in the oxidation of the substrate material at the interface. Consequently itis important that the selected substrate metals be metals whose oxides are so formed as to provide the desired uniformity of distribution and have the desired relatively high electrical conductivity, whereby to achieve the objectives of the present invention.
  • I mase are less persistent and blurring of images of movmg objects is eliminated or greatly reduced. Moreover, the images are intensied by photo emission from the substrate as pointed out above.
  • a target for converting X-radiation into an electrical signal bypmeans of photo-conductivity comprising a substrate plate of electrically conductive metal having a face portion and a photoconductive layer of lead oxide adherent to said face portion, the electrical conductivity of the said face portion being greatly in excess of the conductivity of the photoconductive layer.
  • a support plate comprising relatively light metal of self-supporting'thickness and good electrical conductivity having stainless steel bonded to one of its faces in a layer too thin to be self-supporting in use, and a layer of lead oxide on an exposed face of the stainless steel and forming a photoconductor, the coeicient of thermal expansion of the lead oxide and the stainless steel beingso nearly identical as to avoid cracking o the lead oxide in the course of changes of temperature aecting the target.
  • a plate providing mechanical support and comprising relatively light metal of good electrical conductivity, said plate having a facial coating of a heavier metal uniformly superlicially oxidized, and a layer of photoconductive yellow lead oxide on the superficial oxide ofheavier metal, the oxide of the heavy coating metal becoming very substantially more conductive electrically than the yellow lead oxide and having approximately the same co-efiicient of thermal expansion, relative conductivity of the oxidized surface of the heavier metal coating and the oxide being substantially uniform throughout the interface therebetween.
  • the target .of claim 4 in which the coating of heavier metal is less conductive to X-radiation than the support plate and filters soft and scattered rays of X-radiation, thereby intensifying the photoconductive response of the yellow lead oxide layer when the target is subjected to X-radiation.
  • the method of making a target plate for converting X-radiation into photo-conductive action comprises plating a substrate of lightweight and selfsustaining thickness and capable of good X-ray transmission with a ply of materially heavier metal to a. thickness inadequate for self-support, whereby the plated ply is dependent on the substrate for support, and subsequently applying lead oxide to the surface of said ply, and baking the substrate and said ply and coating, producing an oxide on the said ply which has materially greater electrical conductivity than the lead oxide, and concurrently converting the lead oxide to yellow lead oxide.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Chemical & Material Sciences (AREA)
  • Inorganic Chemistry (AREA)
  • General Physics & Mathematics (AREA)
  • Physical Vapour Deposition (AREA)
  • Image-Pickup Tubes, Image-Amplification Tubes, And Storage Tubes (AREA)
  • Photoreceptors In Electrophotography (AREA)
US697823A 1957-11-21 1957-11-21 Target for x-radiation and the like Expired - Lifetime US2886726A (en)

Priority Applications (6)

Application Number Priority Date Filing Date Title
NL233423D NL233423A (US06262066-20010717-C00315.png) 1957-11-21
NL113476D NL113476C (US06262066-20010717-C00315.png) 1957-11-21
US697823A US2886726A (en) 1957-11-21 1957-11-21 Target for x-radiation and the like
GB33213/58A GB902572A (en) 1957-11-21 1958-10-17 Improvements in photoconductive devices and their methods of manufacture
FR779637A FR1217077A (fr) 1957-11-21 1958-11-20 écran pour rayons chi et analogues
DEG25773A DE1279236B (de) 1957-11-21 1958-11-21 Verfahren zur Herstellung einer als Roentgenaufnahmeroehre verwendbaren Elektronenroehre

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US697823A US2886726A (en) 1957-11-21 1957-11-21 Target for x-radiation and the like

Publications (1)

Publication Number Publication Date
US2886726A true US2886726A (en) 1959-05-12

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ID=24802711

Family Applications (1)

Application Number Title Priority Date Filing Date
US697823A Expired - Lifetime US2886726A (en) 1957-11-21 1957-11-21 Target for x-radiation and the like

Country Status (5)

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US (1) US2886726A (US06262066-20010717-C00315.png)
DE (1) DE1279236B (US06262066-20010717-C00315.png)
FR (1) FR1217077A (US06262066-20010717-C00315.png)
GB (1) GB902572A (US06262066-20010717-C00315.png)
NL (2) NL233423A (US06262066-20010717-C00315.png)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2974064A (en) * 1958-03-03 1961-03-07 Monsanto Chemicals Process for the production of boron phosphide
US3263026A (en) * 1965-05-12 1966-07-26 Kihs Josef Karl Wire stand-off
US3289024A (en) * 1963-03-12 1966-11-29 Philips Corp Photo-sensitive device including layers of different conductivity types
US3500099A (en) * 1967-03-31 1970-03-10 Emi Ltd Lead oxide photoconductive members and method of producing such members
US3546515A (en) * 1964-07-23 1970-12-08 Philips Corp Photocathode control of electron flow through lead monoxide,bombardment-induced conductivity layer
US4940633A (en) * 1989-05-26 1990-07-10 Hermansen Ralph D Method of bonding metals with a radio-opaque adhesive/sealant for void detection and product made

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US747132A (en) * 1903-03-10 1903-12-15 Emil Tyden Pedestal-extension-table lock.
US2169840A (en) * 1936-11-28 1939-08-15 Hazeltine Corp Cathode-ray signal-generating tube

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE918098C (de) * 1936-08-21 1954-10-25 Siemens Ag Reduktionshalbleiter mit kuenstlicher Sperrschicht

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US747132A (en) * 1903-03-10 1903-12-15 Emil Tyden Pedestal-extension-table lock.
US2169840A (en) * 1936-11-28 1939-08-15 Hazeltine Corp Cathode-ray signal-generating tube

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2974064A (en) * 1958-03-03 1961-03-07 Monsanto Chemicals Process for the production of boron phosphide
US3289024A (en) * 1963-03-12 1966-11-29 Philips Corp Photo-sensitive device including layers of different conductivity types
US3546515A (en) * 1964-07-23 1970-12-08 Philips Corp Photocathode control of electron flow through lead monoxide,bombardment-induced conductivity layer
US3263026A (en) * 1965-05-12 1966-07-26 Kihs Josef Karl Wire stand-off
US3500099A (en) * 1967-03-31 1970-03-10 Emi Ltd Lead oxide photoconductive members and method of producing such members
US4940633A (en) * 1989-05-26 1990-07-10 Hermansen Ralph D Method of bonding metals with a radio-opaque adhesive/sealant for void detection and product made

Also Published As

Publication number Publication date
FR1217077A (fr) 1960-05-02
NL233423A (US06262066-20010717-C00315.png)
GB902572A (en) 1962-08-01
NL113476C (US06262066-20010717-C00315.png)
DE1279236B (de) 1968-10-03

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