Cathode Plasma Jet Pinching and Intense X-Ray Emission in a Moderate-Current Laser-Triggered Vacuum Discharge

Fast ion generation in the cathode plasma jet of a multipicosecond laser-triggered vacuum discharge

“…2͒ indicates the formation of pinch ͑plasma point͒ at the cathode plasma jet front. [16][17][18] However, the observation of high-energy ions could not be solely attributed to the formation of pinch in the discharge as similar TOF ion signals were recorded for laserpulse energy in the range of 2-600 mJ, whereas formation of pinch at the front of cathode plasma jet was observed only for small laser pulse energies of ϳ2 -20 mJ. Moreover, the formation of pinch occurred much later, ϳ150-160 ns, after initiation of the discharge.…”

“…1,2,[16][17][18] The process of occurrence of cathode plasma jet pinching in a vacuum discharge may be broadly understood as follows. 2 The process begins with the trigger pulse ͑electrical/laser͒ creating the cathode plasma, which starts expanding toward the anode.…”

“…This has also been confirmed by pin-hole imaging of the discharge gap. [16][17][18] Next, the TOF signals of ion were studied. Figure 3͑a͒ shows a typical TOF ion signal recorded for Al cathode for d = 13.5 mm at an anode voltage of 20 kV and laser pulse energy of 2-5 mJ.…”

“…[11][12][13][14][15] We have observed occurrence of cathode-plasma jet pinching in a moderate-current ͑few kiloamperes͒, lowenergy ͑Յ20 J͒ vacuum discharge triggered by 27 ps duration laser pulses. 16,17 Recently, we have reported the formation of single pinched plasma point in the cathode plasma jet of the discharge. 18 In this paper, we report a study on ion generation in the cathode plasma jet of the vacuum spark discharge using time of flight ͑TOF͒ technique and compare them with that observed from laser-produced plasma plume.…”

Micro-pinch formation and extreme ultraviolet emission of laser-induced discharge plasma*

“…Micro-pinch can form in a relative low current and conduce to the emission of EUV. [15] Micro-pinch develops when the radial compressive pressure of annular magnetic field P m [16] exceeds the thermal pressure P t . [17] The magnetic pressure is related to the radius of plasma column r and the current distribution I(r) as shown below: [18] P m = µ 0 8π…”