(19)

(11)

EP 0 176 534 A1

(12)

(43) Date of publication: 09.04.1986 Bulletin 1986/15 (21) Application number: 85901475.0 (22) Date of filing: 05.03.1985

(51) International Patent Classification (IPC):  G01N 27/ 62( . ) H01J 49/ 04( . ) (86) International application number: PCT/GB1985/000091 (87) International publication number: WO 1985/004281 (26.09.1985 Gazette 1985/21)

(84) Designated Contracting States: AT BE CH DE FR GB LI LU NL SE (30) Priority: 15.03.1984 GB 19840006774 (71) Applicant: PRUTEC LIMITED London EC1N 2NH (GB)	(72) Inventor: OTTLEY, Thomas William Horizon Scientific Services High Street Rotherfield East Sussex TN6 (GB) (74) Representative: Messulam, Alec Moses  A. Messulam & Co. 24 Broadway Leigh on Sea Essex SS9 1BN Leigh on Sea Essex SS9 1BN (GB)