US4570106A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Plasma electron source for cold-cathode discharge device or the like
Assignee: Philips Medical Systems Technologies Ltd
•
Filing: 1984-03-20
•
Granted: 1986-02-11
•
Expires: 2004-03-20
Abstract
Abstract A plasma electron source has an apertured cathode, and a housing for defining a cavity behind the aperture. A trigger electrode, in communication with the cavity, is responsive to a short-duration trigger pulse for establishing plasma in the cavity. The plasma is sustained in the cavity subsequent to the termination of the trigger pulse by a bias circuit, which biases the cavity at a relatively low voltage with respect to the cathode for a period of time much longer than the duration of the trigger pulse.
Inventors
- 👤 A. Robert Sohval
- 👤 Gerald Cooperstein
- 👤 David Fleischer
- 👤 Shyke A. Goldstein
- 👤 David R. Hearn
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 04:27
CPC Classifications
H; H01; H01J; H01J27/00; H01J27/02; H01J27/022; H01J37/00; H01J37/32; H01J37/32009
Claims Analysis
Total Claims: 43
Claim 1
Independent Claim
113 words
An X-ray source including a plasma electron source for a vacuum device comprising: (a) a cathode having a front surface and a rear surface; (b) anode means spaced apart from the front surface of the cathode; (c) aperture means in said cathode between said front surface and said rear surface; (d) a housing defining a cavity behind said aperture means; (e) means for establishing plasma in the cavity; (f) means for applying a positive voltage to the anode means sufficient to generate X-rays when electrons in said plasma are drawn through the aperture means in the cathode and impact on the anode means; and (g) means for confining the plasma to the cavity.
Claim 2
Dependent Claim
113 words
An X-ray source including a plasma electron source for a vacuum device comprising: (a) a cathode having a front surface and a rear surface; (b) anode means spaced apart from the front surface of the cathode; (c) aperture means in said cathode between said front surface and said rear surface; (d) a housing defining a cavity behind said aperture means; (e) means for establishing plasma in the cavity; (f) means for applying a positive voltage to the anode means sufficient to generate X-rays when electrons in said plasma are drawn through the aperture means in the cathode and impact on the anode means; and (g) means for confining the plasma to the cavity.
Claim 3
Dependent Claim
18 words
An X-ray source according to claim 1, wherein the aperture means in the cathode constitutes a single aperture.
Claim 4
Dependent Claim
19 words
An X-ray source according to claim 1 wherein the aperture means in the cathode constitutes a plurality of apertures.
Claim 5
Dependent Claim
26 words
An X-ray source according to claim 1 including means for focusing electrons that are drawn through the aperture means of the cathode onto the anode means.
Claim 6
Dependent Claim
34 words
An X-ray source according to claim 4 wherein the means for focusing operates to create a potential well in the space between the means and the cathode in the vicinity of the aperture means.
Claim 7
Dependent Claim
28 words
An X-ray source according to claim 4 wherein the means for focusing includes a conductor on the surface of the cathode in the vicinity of the aperture means.
Claim 8
Dependent Claim
20 words
An X-ray source according to claim 4 wherein the means for focusing includes a non-conductor associated with said aperture means.
Claim 9
Dependent Claim
33 words
An X-ray source according to claim 1 wherein said establishing means comprises a trigger electrode in communication with the cavity, and responsive to a short-duration trigger pulse for establishing plasma in the cavity.
Claim 10
Dependent Claim
24 words
An X-ray source according to claim 8 including means for sustaining the plasma in the cavity subsequent to the termination of the trigger pulse.
Claim 11
Dependent Claim
38 words
An X-ray source according to claim 9 wherein the means for sustaining the plasma includes means for driving current through the plasma for a period of time relatively long as compared to the duration of the trigger pulse.
Claim 12
Dependent Claim
45 words
An X-ray source according to claim 10 including an intermediate electrode disposed between and electrically insulated from both the cathode and the trigger electrode, and wherein the means for sustaining the plasma includes a bias circuit for biasing the intermediate electrode relative to the cathode.
Claim 13
Dependent Claim
29 words
An X-ray source according to claim 11 wherein the bias circuit includes a pulse-forming network that biases the intermediate electrode at a negative voltage with respect to the cathode.
Claim 14
Dependent Claim
20 words
An X-ray source according to claim 12 wherein the bias relative to the cathode is in excess of 100 volts.
Claim 15
Dependent Claim
21 words
An X-ray source according to claim 13 wherein the duration of the trigger pulse is of the order of 1 microsecond.
Claim 16
Dependent Claim
21 words
An X-ray source according to claim 14 wherein the duration of the bias voltage is of the order of 50 microseconds.
Claim 17
Dependent Claim
29 words
An X-ray source according to claim 10 wherein the means for driving current through the plasma includes means for rapidly and repeatedly applying trigger pulses to said trigger electrode.
Claim 18
Dependent Claim
52 words
An X-ray source according to claim 11 wherein said trigger electrode is associated with an insulator that has a surface separating the trigger electrode from the intermediate electrode, and across which surface flashover takes place when a trigger pulse is applied to said trigger electrode for generating a plasma in the cavity.
Claim 19
Dependent Claim
40 words
An X-ray source according to claim 17 wherein the cavity is defined, at least in part, by a cylindrical conductive member that constitutes the intermediate electrode, said trigger electrode being a rod that is coaxial with the cylindrical conductive member.
Claim 20
Dependent Claim
29 words
An X-ray source according to claim 18 wherein the cavity is defined, at least in part, by a cylindrical non-conductive member interposed between the intermediate electrode and the cathode.
Claim 21
Dependent Claim
35 words
An X-ray source according to claim 18 wherein the cavity is defined, at least in part, by a conductive cup-shaped member electrically isolated from the cathode and interposed between the non-conductive member and the cathode.
Claim 22
Dependent Claim
20 words
An X-ray source according to claim 17 wherein said trigger electrode has an enlarged head that tapers toward the insulator.
Claim 23
Dependent Claim
23 words
An X-ray source according to claim 17 wherein the head of the trigger electrode sits in a countersunk recess in the intermediate electrode.
Claim 24
Dependent Claim
20 words
An X-ray source according to claim 22 wherein the countersunk recess has a conical surface that tapers towards the insulator.
Claim 25
Dependent Claim
31 words
An X-ray source according to claim 8 wherein the means for confining the plasma to the cavity is a baffle located in the cavity in the vicinity of the aperture means.
Claim 26
Dependent Claim
28 words
An X-ray source according to claim 24 wherein the projected area of the baffle on the cathode comprehends an area larger than the area of the aperture means.
Claim 27
Dependent Claim
25 words
An X-ray source according to claim 8 wherein the aperture means includes a plurality of apertures inclined relative to the front surface of the cathode.
Claim 28
Dependent Claim
57 words
An X-ray source according to claim 11 wherein the bias circuit includes an active element having a control terminal for controlling the state of the elements, the active element being connected between the intermediate electrode and a negative voltage for applying the latter to the intermediate electrode when a control signal is applied to the control terminal.
Claim 29
Dependent Claim
17 words
An X-ray source according to claim 12 wherein the pulse-forming network produces a pulse of uniform amplitude.
Claim 30
Dependent Claim
19 words
An X-ray source according to claim 12 wherein the pulse-forming network produces a pulse whose amplitude varies with time.
Claim 31
Dependent Claim
20 words
An X-ray source according to claim 11 wherein the secondary of a pulse transformer is coupled to said trigger electrode.
Claim 32
Dependent Claim
16 words
An X-ray source according to claim 11 wherein a capacitor is coupled to said trigger electrode.
Claim 33
Dependent Claim
22 words
An X-ray source according to claim 17 wherein each of the electrodes have free ends that engage said surface on said insulator.
Claim 34
Dependent Claim
28 words
An X-ray source according to claim 32 wherein the cathode defines a surface, and said surface on said insulator is non-parallel to the surface defined by the cathode.
Claim 35
Dependent Claim
23 words
An X-ray source according to claim 33 wherein said surface on said insulator is substantially perpendicular to the surface defined by the cathode.
Claim 36
Dependent Claim
40 words
An X-ray source according to claim 34 wherein the free ends of the trigger electrode and the intermediate electrode define a pair of opposite faces, the spacing between which increases in a direction away from said surface on said insulator.
Claim 37
Dependent Claim
61 words
An X-ray source according to claim 35 including an auxiliary electrode in the cavity, and wherein the intermediate electrode has a curved portion adjacent the auxiliary electrode, one of the last-mentioned electrodes being electrically connected to said bias circuit whereby the arc produced in the cavity subsequent to flashover stabilizes in the space between said curved portion and said auxiliary electrode.
Claim 38
Dependent Claim
17 words
An X-ray source according to claim 36 wherein the bias circuit is connected to the intermediate electrode.
Claim 39
Dependent Claim
17 words
An X-ray source according to claim 36 wherein the bias circuit is connected to the auxiliary electrode.
Claim 40
Dependent Claim
30 words
An X-ray source according to claim 36 wherein the auxiliary electrode has a plurality of components connected to respective ones of a plurality of bias circuits that are selectively actuatable.
Claim 41
Dependent Claim
41 words
An X-ray source according to claim 36 wherein the auxiliary electrode and the curved portion of the intermediate electrode are constructed and arranged so that the stabilized arc is oriented, generally, in a direction parallel to said surface on the cathode.
Claim 42
Dependent Claim
25 words
An X-ray source according to claim 40 wherein the aperture means in the cathode overlies said space between said curved portion and said auxiliary electrode.
Claim 43
Dependent Claim
66 words
A CT scanner comprising a plurality of X-ray sources according to claim 1 mounted on a source ring whose axis defines the axis of the scanner, and a plurality of detectors mounted on a rotatable detector ring with a diameter smaller than the source ring for receiving X-rays produced by the sources, the detector ring having an axis colinear with the axis of the source ring.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1989-02-10 | 1989-08-12 | 1990-02-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-02-10 | 1993-08-12 | 1994-02-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-02-10 | 1997-08-12 | 1998-02-11 | $7700.00 | Window Closed / Lapsed |