288 Classified Abstracts 710--711

25 : 17 Cryopumping. See Abstr. No. 693.

25 : 17 Compact cryogenic refrigerators for special purposes. See Abstr. No. 692.

26. Automatic Protective and Control Equipment 26

710. A technique for the safe handling and controlled opening of sealed glass bulbs containing gas at a pressure of 280 lb in.-L (Great Britain) A. R. Blake and R. A. Redford, J. Sci. Instrum., 40 (4), April 1963, 199-200.

27. L e a k Detectors and Leak Detection 27

711. Improvement of performance of halogen leak detectors.

Germany. Halogen leak detectors depend on the catalysing effect of a halogen tracer gas on the emission of positive ions from an incandescent anode. The author points out that the composition of the residual atmosphere existing in the circuit to which the leak detector is attached has a marked effect on its performance. In order to ensure consistency combined with sensitivity, it is essential that a minimum amount of oxygen should be present in the detector itself. This can be ensured by providing a suitable artificial leak in the circuit which is blocked before the test starts, w . s . s .

E. Meurer, Le Vide, 17 (100), July/Aug. 1962, 375-378.

28. Heating Equipment and Thermometers 28 : 37

Present and future possibilities of electronic bombardment. See Abstr. No. 753.