High intensity atomic spectral lamp with interchangeable cathode

Claim 2

A high intensity atomic spectral lamp having a hollow body, a first set of electrodes located in said body including a primary cathode comprising a selected element adapted to produce a primary electric discharge which gives rise to an atomic vapour of said element by cathodic sputtering from the primary cathode; a second set of electrodes located in said body adapted to produce a secondary electric discharge which passes through said atomic vapour, to excite the atoms in the vapour to emit radiation characteristic of said element; a window in said body to allow the passage of said radiation out of the lamp, said window being placed in front of and substantially parallel to the operative surface of the primary cathode; a gas inlet and outlet means in said body to pass a stream of inert gas through said body of said lamp transversely across and substantially parallel to the operative surface of the primary cathode and between the primary cathode and the window in such a manner as to sweep away from the area between the primary cathode surface and the window atomic species formed by said primary discharge.

Claim 3

A lamp as claimed in claim 1, wherein the window is substantially parallel to the operative surface of the primary cathode and the gas stream also passes substantially parallel to that surface.

Claim 4

A lamp as claimed in claim 1, which includes demountable cathode support means to permit ready removal and replacement of the primary cathode.

Claim 5

A lamp as claimed in claim 1, comprising an elongate, generally tubular body portion having the primary cathode mounted in the wall of the body portion; the secondary cathode and common anode being mounted within the body portion and arranged to direct the second discharge across and through a region in front of the primary cathode; and gas inlet and outlet means arranged to pass a stream of gas through said region in a generally axial direction with respect to the body portion and in the direction of the secondary discharge.

Claim 6

A lamp as claimed in claim 1, comprising: a generally tubular body portion having gas inlet and outlet means to allow a flow of gas through the body portion in a generally axial direction; a cathode compartment located in the wall of the body portion; primary cathode means located in said compartment and comprising a primary cathode and demountable primary cathode support means adapted to allow the primary cathode to be readily removed from and replaced in said compartment; window means attached to the wall of the body portion, said window means comprising a chamber in open communication with an aperture in the wall of the body portion diametrically opposite the cathode compartment and an optical window at the end of the chamber remote from the aperture; a secondary cathode located within the body portion and spaced away from the cathode compartment; a common anode located within the body portion and spaced away from the cathode compartment in the opposite direction to the secondary cathode.

Claim 7

A lamp as claimed in claim 5, wherein the body portion is of reduced diameter in at least part of those portions of the body which lie between the cathode compartment and the secondary cathode and anode respectively.

Claim 8

A lamp as claimed in claim 5, wherein the optical window is of substantially longer diameter than said aperture of the primary cathode.

Claim 9

A lamp as claimed in claim 5, wherein the primary cathode has a substantially flat front face and the arrangement of the cathode compartment and supporting means is such that in use the flat face of cathode is substantially flush with the inside wall of the body portion adjacent the cathode compartment.

Claim 10

A lamp as claimed in claim 5, wherein the primary cathode consists of a disc plate or pellet of said element attached to or held in the supporting means.

Claim 11

A lamp as claimed in claim 1, wherein the secondary cathode is of the electrically heated (filament) type and/or is coated with a thermionically emissive material.

Claim 12

A lamp as claimed in claim 10, wherein the cathode coating material is lanthanum hexaboride.

Claim 13

A lamp as claimed in claim 10, wherein the secondary cathode is supported on supporting means which can be removed from and replaced in the body portion.

Claim 14

In a high intensity atomic spectral lamp comprising a body containing a first set of electrodes including a primary cathode comprising a selected element adapted to produce a primary electric discharge which gives rise to an atomic vapour of said element by cathodic sputtering from the primary cathode; a second set of electrodes adapted to produce a secondary electric discharge which passes through the said atomic vapour, to excite the atoms in the vapour to emit radiation characteristic of said element; and having a window placed in front of the operative surface of the primary cathode to allow the passage of said radiation out of the lamp, the improvements which comprise: (a) at least a part of the body being in the form of a relatively narrow elongated tube; (b) the primary cathode being positioned in a compartment located in said part of the body; (c) said window being located diametrically opposite to and essentially parallel with the operative surface of the primary cathode, said window being of substantially greater diameter than either the primary cathode or said part of the body and being located at one end of a chamber, the other end of which is in open communication with said part of the body; (d) said secondary cathode and a common anode being located in said part of the body one on each side and spaced away from the cathode compartment; (e) gas inlet and outlet means being located at or near opposite ends of said part of the body to allow a flow of gas to be passed axially through said part close to and across the operative surface of the primary cathode and between the primary cathode and the window in such a manner as to sweep away from the vicinity of the primary cathode surface atomic species formed by said primary discharge.

Claim 15

In a high intensity atomic spectral lamp comprising a body containing a first set of electrodes including a primary cathode comprising a selected element adapted to produce a primary electric discharge which gives rise to an atomic vapour of said element by cathodic sputtering from the primary cathode; a second set of electrodes adapted to produce a secondary electric discharge which passes through the said atomic vapour, to excite the atoms in the vapour to emit radiation characteristic of said element; and having a window placed in front of the operative surface of the primary cathode to allow the passage of said radiation out of the lamp, the improvements which comprise: (a) at least a part of the body being in the form of a relatively narrow elongated tube; (b) the primary cathode being positioned in a compartment located in said part of the body; (c) said window being located diametrically opposite to and essentially parallel with the operative surface of the primary cathode, said window being of substantially greater diameter than either the primary cathode or said part of the body and being located at one end of a chamber, the other end of which is in open communication with said part of the body; (d) said secondary cathode and a common anode being located in said part of the body one on each side and spaced away from the cathode compartment; (e) gas inlet and outlet means being located at or near opposite ends of said part of the body to allow a flow of gas to be passed axially through said part close to and across the operative surface of the primary cathode and between the primary cathode and the window in such a manner as to sweep away from the vicinity of the primary cathode surface atomic species formed by said primary discharge.

Claim 16

In a high intensity lamp as claimed in claim 13, the further improvement which comprises demountable primary cathode support means adapted to allow the primary cathode to be readily removed from and replaced in said compartment.

Claim 17

In a high intensity lamp as claimed in claim 13, the further improvement which comprises demountable secondary cathode support means adapted to allow the secondary cathode to be readily removed from and replaced in the body portion.

Claim 18

In a high intensity lamp as claimed in claim 13, the further improvement which comprises sections of reduced diameter being located in said part of the body, which sections lie between the cathode compartment and the secondary cathode and anode respectively.