Flux-motion induced bolometer based on ceramic superconductive elements

• US 4,978,853 A
• Filed: 03/17/1989
• Issued: 12/18/1990
• Est. Priority Date: 03/17/1989
• Status: Expired due to Fees

• Current Assignee: International Superconductor Corp.
• Original Assignee: International Superconductor Corp.
• Inventors: Hilal, Mohamed A.
• Primary Examiner(s): FIELDS, CAROLYN
• Application Number:
  US07/325,658
• Time in Patent Office: 641 Days
• Field of Search: 250/336.2, 505/848, 505/849, 374/176
• US Class Current: 250/336.2
• CPC Class Codes: G01J 5/20 using resistors, thermistors or semiconductors sensitive to radiation, e.g. photoconductive devices
• CPC Class Codes: H10N 60/203 comprising high-Tc ceramic materials
• CPC Class Codes: Y10S 505/849 Infrared responsive electric signaling

Abstract

A novel high sensitivity superconductive bolometer is presented in which the detector is kept in its superconducting state during the functional phase. Operation is based on detecting an induced fluxoid motion following a temperature rise caused by impinging infrared radiation. The superconductive-flux-motion-induced bolometer consists of a superconductive film and a pick-up film which are electrically insulated from each other. As the temperature of the current carrying film rises, fluxoid motion is triggered, sweeping through both films so that a voltage is detected in the pick-up film. The superconductive-flux-motion-induced bolometer has higher sensitivity for detection of infra-red radiation than any bolometer known heretofore.

Claims

1. A bolometer, comprising:

a magnetic-flux-passing substrate having opposite surfaces;

a pick-up, superconductive film on one of said surfaces for exposure to infrared radiation to be measured;

flux-responsive indicating means along the other of said surfaces flux-coupled to said pick-up superconductive film through said substrate;

an electric current source connectable in circuit with said pick-up superconductive film for passing an electric current therethrough;

means connected across said flux-responsive indicating means for measuring voltage generated therein as a result of flux motion induced by infrared irradiation of said pick-up film; and

means for cooling said film to a temperature below a critical temperature of the superconductive film.

2. The bolometer defined in claim 1 wherein said flux-responsive indicating means along the other of said surfaces includes a coil positioned to intercept magnetic flux traversing said substrate.

3. The bolometer defined in claim 2 wherein said coil is a coil formed by a metallic film.

4. The bolometer defined in claim 2 wherein said coil is a coil formed by a superconductive film.

5. The bolometer defined in claim 4 wherein said coil is formed by a type-II superconductive film on said other surface.

6. The bolometer defined in claim 1 wherein said flux-responsive indicating means along the other of said surfaces includes a superconductive film.

7. The bolometer defined in claim 6 wherein said film on said other surface is formed by a type-II superconductive film on said other surface.

8. A method of measuring infrared radiation, comprising the steps of:

(a) providing on opposite sides of a substrate capable of passing magnetic flux, a pick-up superconductive film and an indicating superconductive film;

(b) passing an electric current through said pick-up superconductive film;

(c) cooling said films to a temperature below the critical temperatures thereof;

(d) exposing said pick-up superconductive film to infrared radiation, thereby inducing flux motion in magnetic flux generated by said pick-up superconductive film, traversing said substrate and inducing a voltage in said indicating superconductive film; and

(e) measuring the voltage induced in said indicating superconductive film.

9. The method defined in claim 8 wherein said indicating superconductive film is formed as a type-II superconductor and said pick-up film is formed as an oxide-ceramic superconductor.