Demountable sputtering cathode for atomic absorption spectroscopy

Claim 2

Apparatus for providing an atomic vapour for spectrochemical analysis from a sample area on the surface of a sample body, the sample area in use forming the cathode of a sputtering discharge, comprising a vacuum chamber having an apertured wall, an anode lying inside the chamber and below the wall aperture, and apertured sample locating means lying outside the chamber around the wall aperture and comprising an outer annular portion adapted in use to abut the surface of the sample body and an inner annular portion electrically insulated from the outer portion and the anode, adapted in use to lie opposite the surface of the sample body but spaced therefrom a short distance to form an annular gap surrounding the sample area, the gapwidth being large enough to electrically isolate the opposed surfaces thereof but smaller than the width of the cathode dark space for the sputtering discharge.

Claim 3

Apparatus as claimed in claim 1 in which the gapwidth is about 0.2 millimetre.

Claim 4

Apparatus as claimed in claim 1 in which the vacuum chamber includes means whereby a stream of gas may be introduced into the vacuum chamber while vacuum is maintained by a vacuum pump, such that impurity atoms and molecules may be swept out of the chamber while the sputtering discharge is operating.

Claim 5

Apparatus as claimed in claim 3 in which the sample locating means is provided with at least one internal gas passage for directing at least part of the stream of gas into the region of the sputtering discharge so that sputtered atoms are thereby carried away from the discharge region towards the body of the vacuum chamber to facilitate spectrochemical analysis.

Claim 6

Apparatus as claimed in claim 4 in which the sample locating means has a gas circulation passage into which at least part of the stream of gas may be directed, and at least one gas outlet duct leading into the aperture in the sample locating means.

Claim 7

Apparatus as claimed in claim 4 in which the sample locating means has a gas circulation passage into which at least part of the stream of gas may be directed, and at least one outlet duct leading into the annular gap between the sample locating means and the surface of the sample body.

Claim 8

Apparatus for spectrochemical analysis of a sample by means of a sputtering discharge comprising in combination; a vacuum chamber having an apertured wall; an anode lying inside the chamber and below the wall aperture; a disc-shaped centrally apertured sample locating means disposed outside and around the wall aperture having a surface facing the sample with an outer annular portion abutting the surface of the sample and an inner annular portion electrically insulated from the outer annular portion and the anode, stepped away from the sample surface a distance large enough to electrically isolate the opposed surfaces of the gap so formed but smaller than the width of the cathode dark space for the sputtering discharge; a sealing member in the form of an O-ring disposed around the periphery of the sample locating means and between the sample and the vacuum chamber wall so as to effect a vacuum seal therebetween; means to evacuate the vacuum chamber; means to initiate and maintain the sputtering discharge between the anode and the sample through the aligned apertures in the wall and the sample locating means; a spectral lamp providing light containing at least one spectral line characteristic of an element under analysis; and photodetector means for providing an indication of the degree to which the characteristic spectral line is absorbed by atoms sputtered from the sample by the discharge.

Claim 9

Apparatus for spectrochemical analysis of a sample by means of a sputtering discharge comprising in combination; a vacuum chamber having an apertured wall; an anode lying inside the chamber and below the wall aperture; a disc-shaped centrally apertured sample locating means disposed outside and around the wall aperture having a surface facing the sample with an outer annular portion abutting the surface of the sample and an inner annular portion electrically insulated from the outer annular portion and the anode, stepped away from the sample surface a distance large enough to electrically isolate the opposed surfaces of the gap so formed but smaller than the width of the cathode dark space for the sputtering discharge; a sealing member in the form of an O-ring disposed around the periphery of the sample locating means and between the sample and the vacuum chamber wall so as to effect a vacuum seal therebetween; means to evacuate the vacuum chamber; means to initiate and maintain the sputtering discharge between the anode and the sample through the aligned apertures in the wall and the sample locating means; a spectral lamp providing light containing at least one spectral line characteristic of an element under analysis; and photodetector means for providing an indication of the degree to which the characteristic spectral line is absorbed by atoms sputtered from the sample by the discharge.

Claim 10

Apparatus for spectrochemical analysis of a sample as claimed in claim 7 in which the degree of absorbance is determined by measuring the fluorescent light re-emitted by the sputtered atoms.

Claim 11

Apparatus for spectrochemical analysis as claimed in claim 7 including means whereby a stream of gas may be introduced into the vacuum chamber while vacuum is maintained by a vacuum pump such that impurity atoms and molecules may be swept out of the vacuum chamber while the sputtering discharge is operating.

Claim 12

Apparatus as claimed in claim 9 in which the sample locating means is provided with at least one internal gas passage for directing at least part of the stream of gas into the region of the sputtering discharge so that sputtered atoms are thereby carried away from the discharge region towards the body of the vacuum chamber to facilitate spectrochemical analysis.