1324 THE BELL SYSTEM TECHNICAL JOURNAL, NOVEMBER 1957 



III. ANALYSIS OF THE SWITCHING PROPERTIES OF THE TWISTOR 



Section 3.1 will deal with the basic properties of magnetic wire as they 

 pertain to the twistor memory cell. Section 3.2 will be concerned with a 

 composite magnetic wire. The theoretical conclusions will be supported 

 by expermiental results wherever possible. 



3.1 Solid Magnetic Wire 



It has been stated above that there is a voltage gain inherent in the 

 operation of the twistor. This voltage gain makes it possible to obtain 

 millivolt signals from wires several mils in diameter. An expression will 

 now be derived relating the axial flux of an untwisted wire to the circular 

 flux component of that wire when twisted. Assume that the magnetic 

 wire has been twisted so that the flux spirals at an angle 6 (normally 

 6 = 45°) with respect to the axis of the wire. If d and I are the diameter 

 and length of the magnetized region respectively, then, for a com- 

 plete flux reversal the change in the circular flux component is ^circ = 

 l(d/2){2Bs sin 6). 



Here, ^circ is the flux change that would be observed on a hypothetical 

 pickup wire which passed down the axis of the magnetic wire. The flux 

 change which would be observed by a single pickup loop around the wire, 

 if the magnetic wire were not twisted, is ^longituudinai = tt d~Bs/2. 

 Therefore, ^circ/v'iong = 2 Z sin d/rd, and for 6 = 45°, this expression 

 reduces to 



^ciro 



l/d 



9 99- ^^^ 



Thus, for example, if the storage length on a 3-mil wire is 100 mils, 

 then a 15:1 gain in flux change (or voltage) is obtained. 



V, 



OBS 



R(r) 



(a) 



(b) 



v(r)- 



V(0) 



Fig. 7 — (a) Calculation of the observable voltage Fobs for a solid magnetic 

 wire, (b) Diagram of induced voltage V{r) and resistance RO'). 



