Photodiode

Claim 2

A photodiode device for far-uv radiation comprising: a radiation entry zone; a photocathode positioned at one end of said zone in the path of far-uv radiation entering from the other end and passing through said zone; and an anode positioned to collect electrons emitted by said photocathode; characterized in that: said radiation entry zone is neither evacuated nor filled with inert gas; the distance between said other end of said entry zone and said photocathode is sufficiently short that absorption of said radiation within said zone is no greater than 90% in the presence of oxygen-containing atmospheric gases; and the spacing between said photocathode and said anode is sufficiently small to allow the creation of field strength adequate for operation of said photodiode device with atmospheric gases filling said spacing.

Claim 3

The photodiode device of claim 1 further comprising a window at the other end of said radiation entry zone.

Claim 4

The photodiode device of claim 2 wherein said radiation path is less than 10 mm in length.

Claim 5

The photodiode device of claim 2 wherein said window is made of magnesium fluoride.

Claim 6

The photodiode device of claim 2 wherein said window filters out far-uv radiation with wavelengths shorter than 100 nanometers.

Claim 7

The photodiode device of claim 2 further comprising a high-temperature perfluoroethylene material as an insulating layer spacing said window from said anode or said anode from said photocathode.

Claim 8

The photodiode device of claim 1 wherein said photocathode is a cylindrical element and said anode is an annular element surrounding said photocathode.

Claim 9

The photodiode device of claim 7 wherein the spacing between said anode and photocathode is annular and a few thousandths of an inch in width.

Claim 10

A photodiode device of claim 1 wherein said photocathode is constructed of a metal that emits electrons predominantly in response to far-uv radiation of 140 nanometers or shorter wavelengths.

Claim 11

The photodiode device of claim 9 wherein said metal is nickel.

Claim 12

The photodiode device of claim 1 wherein said window and photocathode device material serve to make said photodiode sensitive predominantly to radiation in a wavelength range no greater than 100 to 140 nanometers.

Claim 13

The photodiode device of claim 1 wherein said distance between the other end of said entry zone and said photocathode is from 1-2 mm.

Claim 14

A gas chromatography detector comprising a source of far-uv radiation in the 100 to 140 nanometer wavelength range, a sample cell through which gases flow and said radiation passes, a photodiode device sufficient for detecting the far-uv radiation emerging from said cell, and means for positioning said photodiode device so that radiation emerging from said cell passes through said photodiode device, said photodiode device comprising a radiation entry zone; a photocathode positioned at one end of said zone in the path of far-uv radiation entering from the other end and passing through said zone; and an anode positioned to collect electrons emitted by said photocathode; characterized in that: said radiation entry zone is neither evacuated nor filled with inert gas; the distance between said other end of said entry zone and said photocathode is sufficiently short that absorption of said radiation within said zone is no greater than 90% in the presence of oxygen-containing atmospheric gases; and the spacing between said photocathode and said anode is sufficiently small to allow the creation of field strength adequate for operation of said photodiode device with atmospheric gases filling said spacing.

Claim 15

A gas chromatography detector comprising a source of far-uv radiation in the 100 to 140 nanometer wavelength range, a sample cell through which gases flow and said radiation passes, a photodiode device sufficient for detecting the far-uv radiation emerging from said cell, and means for positioning said photodiode device so that radiation emerging from said cell passes through said photodiode device, said photodiode device comprising a radiation entry zone; a photocathode positioned at one end of said zone in the path of far-uv radiation entering from the other end and passing through said zone; and an anode positioned to collect electrons emitted by said photocathode; characterized in that: said radiation entry zone is neither evacuated nor filled with inert gas; the distance between said other end of said entry zone and said photocathode is sufficiently short that absorption of said radiation within said zone is no greater than 90% in the presence of oxygen-containing atmospheric gases; and the spacing between said photocathode and said anode is sufficiently small to allow the creation of field strength adequate for operation of said photodiode device with atmospheric gases filling said spacing.