. Electronic apparatus for biological research . (a) (b) Figure deflecting current the screen ought to lie wholly on the surface of an imagi- nary sphere with centre to centre of the coil assembly. Such a curved screen would be unsatisfactory, and practical screens are flatter than this, and in consequence the length of the beam increases with deflection angle, to produce greater sensitivity at the screen periphery, giving the grid of Figure The effect may be allowed for by designing the deflector coils so that the fields are not uniform {Figure ) but are stronger near the t
. Electronic apparatus for biological research . (a) (b) Figure deflecting current the screen ought to lie wholly on the surface of an imagi- nary sphere with centre to centre of the coil assembly. Such a curved screen would be unsatisfactory, and practical screens are flatter than this, and in consequence the length of the beam increases with deflection angle, to produce greater sensitivity at the screen periphery, giving the grid of Figure The effect may be allowed for by designing the deflector coils so that the fields are not uniform {Figure ) but are stronger near the tube axis {Figure ). Deflection defocusing—This is a loss of sharpness of the spot as it is deflected away from the tube axis. It is attributable partly to the change in beam length due to the flat screen and partly to poor deflector coil design. The fringes of the deflecting field contain components which act along the axis of the tube to modify the focusing conditions {Figure ). The remedy is to have deflector coils which are long along the tube axis, so that fringe effects are rendered as far as possible relatively insignificant; also to bend the ends of the deflector coils away from the tube {Figure ). Lack of similarity between the two Y deflector coils can produce a grid of the type shown in Figure , and between the X coils. Figure Insufficient perpendicularity between the X and Y fields can produce orthogonality errors {Figure ) though this is unlikely to occur if the coils are accurately located by fitting tightly the slots in the moulded core. 463
Size: 3251px × 1537px
Photo credit: © The Bookworm Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookcollectionameri, bookcollectionbiodiversity
