MAGNETIC EFFECTS ON NOISE IN A GERMANIUM FILAMENT 651 



handle computationally. It is therefore desirable to simplify the experi- 

 mental conditions to a point where the problem becomes almost one- 

 dimensional. A solution for w can then be found in closed form. 



Consider a very long uniform rectangular filament with one pair of 

 sides very much wider than the other pair. Suppose that the y and z 

 directions are respectively parallel to the wide sides and to the length 

 of the filament (Fig. 1). 



Consider sources located anywhere on a plane x = |, which is parallel 

 to the wide sides of the filament. If the recombination properties of the 

 filament are uniform in the y — z directions, the Hfetime due to a unit 

 source anywhere in that plane is independent of the location of the 

 source on that plane, and depends only on ^. Hence the conductivity 

 modulation due to sources of strength 



Ji^, Vr , Zr) 



(r = 1,2...) 



in that plane is simply 



T(?)EA?,2/r,2r) 



I 



^2 

 (REAR PLANE) 



(FRONT PLANE) 



Fig. 1 — Geometry of the filament, and disposition of the fields. 



