Reduction of the source size of gas-puff z-pinch plasmas using an inductive pulsed power system

Abstract

A small scale inductive pulsed power (IPP) generator with copper wire fuses as an opening switch has been applied to an argon gas-puff z-pinch plasma which can be used as a point source for x-ray lithography. The IPP generator with fuses supplies a driving current of 60 kA in 400 ns to the z-pinch plasma. Without fuses, the generator serves as a conventional fast bank (FB) system which supplies z-pinch current of 60 kA in 4.5 μs. Characteristics of the z-pinch implosions in IPP and FB systems are investigated and compared. The result obtained shows that the intensity of soft x rays emitted from hot spots in both systems is decreased gradually with longer delay time, which is the time difference between energizing a gas-puff actuator and a primary current trigger. Dual axis pinhole imagery shows that the hot spot size is 0.8 mm in diameter in both systems. However, the average radial displacement of hot spots is 0.9 mm in the FB system and it is reduced to 0.4 mm in the IPP system. Optical framing camera images have confirmed that the radial distribution of hot spots is due to kink instability. The framing images also show that the imploding plasma in the FB system which has a pinch size of 2.2 mm in diameter can be further compressed to 1.3 mm. The IPP system can suppress the kink instability of pinch plasma and increases plasma column uniformity along the z axis. This suggests that the IPP system can improve the stability of the pinched plasma so as to minimize the end-on source size for x-ray lithography applications.