Theoretical research on spiral Blumlein line

The structure of spiral Blumlein line consisting of spiral inner cylinder,spiral center cylinder and conductive outer cylinder was discussed in this paper.The formulas approximating characteristic parameters of spiral Blumlein line were obtained by thin current layer model supposing that the exterior line transmits high voltage pulse independently.The principle verifying experiment to generate long pulse on a spiral Blumlein line was proceeded preliminarily.Theoretic amplitude and width of output pulse voltage were 543 V and 24 ns respectively,while the experimental ones measured from current divider were 471 V and 30 ns respectively.The difference between theoretical and experimental values was due to the hypothesis condition that the exterior line independently transmit high voltage pulse,which was imprecise actually.One scheme combining Tesla transformer and spiral Blumlein that was presented,where single coaxial line charged by a built-in high coupling Tesla transformer formed one part of the whole exterior line.The results indicated that a pulse with 1.07 MV voltage,1.53 GW power and 93 ns pulse width could be generated by 628 mm in external radius,2.67 m long spiral Blumlein line charged to 800 kV,and the theoretical energy conversion efficiency of output line would be 50%.