GB674729A - Mass spectrographs and like apparatus - Google Patents

Abstract

674,729. Positive ion tubes. MULLARD RADIO VALVE CO., Ltd., MILLS, V. R., POPPER, P., and TYRELL, A. J. July 4, 1950 [April 13, 1949], No. 9845/49. Class 39 (i). [Also in Group XXXV] A permanent magnet system having an adjustable magnetic shunt is employed in a mass spectrograph or the like for deflecting the beam of ions. Permanent bar magnets 1-4, (Fig. 2), are arranged side by side between end cheeks 5 of the magnetic system having pole-pieces 7, the arrangement being arcuate to correspond with the beam path. The end cheeks have extensions on the opposite sides of the magnets from the pole-pieces, connected by a non-magnetic cylinder 9 having non- rotatably mounted in it by longitudinal keys and guideways 15, a cylindrical block 11 which is caused to partially or wholly bridge the end cheeks by a hand-driven leadscrew 12 passing through the block. In the minimum shunt position the block is contained in an annular extension cap of one cheek. A rack-and-pinion mechanism may adjust the magnet system along rails 21 in the plane of the magnetic gap. Two shunts in parallel may be employed, one for fine control. In a modification the cylindrical block has an external thread engaging in a threaded hole in one cheek and is adjustably screwed into an annular extension of the other cheek, which is slotted or castellated or has varying thickness to give a more open or linear scale of adjustment near the maximum shunt position. Specification 522,731, [Group II], is referred to.