Apparatus and method for detection of vacuum ultraviolet radiation
Vacuum ultraviolet radiation detection apparatus ( 10 ) comprises a radiation detector ( 30 ) in a chamber ( 12 ). The detector ( 30 ) receives ultraviolet radiation from a radiation source ( 36 ). The chamber is evacuated using a dry vacuum pump ( 18 ) to a relatively poor vacuum of no less than 5 Pa. UV transparent gas is supplied from a gas supply ( 26 ), into the chamber ( 12 ) at a relatively low flow rate (around 0.1 liters/minute) so as to provide an overall pressure in the chamber ( 12 ) of between 100 and 1,000 Pa. The use of a relatively inexpensive pump coupled with a lower gas flow rate provides significant cost savings.
1. Vacuum ultraviolet radiation detection apparatus, comprising;
a radiation detector arranged to receive ultraviolet radiation from a radiation source,
a chamber in which said detector is disposed,
a dry vacuum pump arranged to evacuate the chamber to a pressure substantially equal to or greater than 5 Pa (0.05 mbar), and
a gas supply means arranged to supply a substantially UV transparent gas into the chamber through a chamber inlet port while the chamber is being evacuated, wherein the overall pressure in the chamber is below atmospheric pressure.
2. Apparatus according to claim 1 , wherein the UV transparent gas is arranged to be supplied to the chamber at a substantially continuous rate.
3. Apparatus according to claim 1 , wherein the inlet port comprises a valve arranged to control the flow of the UV transparent gas.
4. Apparatus according to claim 1 , wherein, during operation, the vacuum pump is arranged to remove the UV transparent gas in the chamber to atmosphere at such a rate, and/or the gas supply means is arranged to supply the gas at such a rate, so as to cause the overall pressure within the chamber to be substantially equal to or greater than 100 Pa (1 mbar).
5. Apparatus according to claim 4 , wherein the vacuum pump is arranged to remove the UV transparent gas in the chamber to atmosphere at such a rate, and/or the gas supply means is arranged to supply the gas at such a rate, so as to cause the overall pressure in the chamber to be no more than 10,000 Pa (100 mbar).
6. Apparatus according to claim 4 , wherein the gas supply means is arranged to cause gas flow into the chamber at about 0.1 liters/minute.
7. Apparatus according to claim 1 , wherein the vacuum pump is a dry diaphragm vacuum pump.
8. Apparatus according to claim 1 , wherein the UV-transparent gas is argon, nitrogen, or a combination of argon and nitrogen.
9. Apparatus according to claim 1 , wherein the radiation detection apparatus comprises an optical spectrometer.
10. Apparatus according to claim 9 , wherein the spectrometer is arranged to detect vacuum ultraviolet radiation and radiation in another waveband.
11. Apparatus according to claim 1 , wherein the chamber comprises a window arranged to allow radiation to pass therethrough for detection by the radiation detector.
12. An apparatus according to claim 1 , wherein the gas supply means is a non-recirculating gas supply means.
13. An apparatus according to claim 1 , wherein the flow rate of the UV transparent gas and the pumping rate of the pump are each greater than zero but sufficiently low so that an overall pressure of between 100 and 10,000 Pa (1 to 100 mbar) is maintained in the chamber.
14. Vacuum ultraviolet radiation detection apparatus, comprising:
a radiation detector arranged to receive ultraviolet radiation from a radiation source;
a chamber in which said detector is disposed;
a pump arranged to evacuate the chamber; and,
a gas supply means arranged to supply a substantially UV transparent gas into the chamber through a chamber inlet port, the flow rate of the UV transparent gas and the pumping rate of the pump each being greater than zero but sufficiently low that an overall pressure in the chamber of between 100 and 10,000 Pa (1 to 100 mbar) is maintained.
15. A method of detecting vacuum ultraviolet radiation using a radiation detector disposed in a chamber, said method comprising;
evacuating the chamber to a pressure of substantially equal to or greater than 5 Pa (0.05 mbar),
supplying a substantially UV-transparent gas into the chamber while the chamber is being evacuated, such that the overall pressure in the chamber is below atmospheric pressure, and
detecting UV radiation impinging on the radiation detector.
16. A method according to claim 15 , wherein the UV-transparent gas is supplied to the chamber at such a rate, and/or the chamber is evacuated at such a rate, that the overall pressure in the chamber is substantially equal to or greater than 100 Pa (1 mbar) during the vacuum pump's operation.
17. The method of claim 16 , wherein the UV transparent gas is supplied to the chamber at such a rate, and/or the chamber is evacuated at such a rate, that the overall pressure in the chamber is no more than 10,000 Pa (100 mbar).
18. The method of claim 14 , wherein the gas is supplied to the chamber at a rate of about 0.1 liters/minute.
19. A method of detecting vacuum ultraviolet radiation using a radiation detector disposed in a chamber, said method comprising:
evacuating the chamber;
supplying a substantially UV transparent gas into the chamber while the chamber is being evacuated, the flow rate of the UV transparent gas and the rate of evacuation of the chamber each being greater than zero but sufficiently low that the pressure in the chamber is maintained between 100 Pa and 10,000 Pa (1 and 100 mbar); and
detecting UV radiation impinging on the radiation detector.
20. A method according to claim 15 , wherein the UV-transparent gas is removed from the chamber by the vacuum pump.