Abstract:
An electron microprobe including a magnetic objective lens for focusing an electron beam upon a specimen, and means for cooling the lens to a temperature below about - 20*. It is found that operating results are greatly improved by maintaining the lens cold and the specimen warm. Contamination of the specimen, particularly by carbonaceous materials, can be reduced by more than an order of magnitude without compromise with the operational features of the instrument.
Abstract:
1,225,579. Electron - beam apparatus. APPLIED RESEARCH LABORATORIES Inc. 17 July, 1969 [17 July, 1968], No. 36119/69. Heading HID. In order to remove contaminants from an electron microprobe of the kind having a lens positioned closely adjacent to the specimen, the lens structure is cooled to a temperature below about - 20 C. In the microprobe shown, an election beam impinges on a small area of the specimen 14 to cause emission of X-rays which are subjected to analysis. Contaminants are caused to condense on the surface 10 of a lens 12 which is cooled by means of a refrigerant circulated in a coil 24 surrounding the winding 16. A conventional refrigerant is used for temperatures down to- 40 C. and below this, liquid nitrogen is used. The coil 24 may be included in the cooling circuit of a diffusion pump for the apparatus and the temperature of the lens may be regulated by means of an adjustable valve in a by-pass circuit. The specimen 14 may be heated by means of a coil 27. Temperature sensors 26, 28 may be used in automatic regulating circuits for both cooling and heating.