Experimental research on time-resolved evolution of cathode plasma expansion velocity in a long pulsed magnetically insulated coaxial diode

2018 ◽  
Vol 123 (7) ◽  
pp. 073301 ◽  
Keyword(s):  
Experimental Research ◽  
Expansion Velocity ◽  
Plasma Expansion ◽  
Cathode Plasma ◽  
Time Resolved

scholarly journals Time evolution of the two-dimensional expansion velocity distributions of the cathode plasma in pulsed high-power diodes

2013 ◽  
Vol 31 (1) ◽  
pp. 129-134 ◽  
Author(s):  
Jie Yang ◽  
Ting Shu ◽  
Yuwei Fan
Keyword(s):  
High Power ◽  
Cathode Surface ◽  
Transverse Velocity ◽  
Longitudinal Velocity ◽  
Expansion Velocity ◽  
Two Dimensional ◽  
Plasma Expansion ◽  
Cathode Plasma ◽  
Power Diodes ◽  
Diode Current

AbstractA combination of electrical and optical diagnostics has been used to investigate the time evolution of the two-dimensional expansion velocity distributions of the cathode plasma in pulsed high-power diodes. The perveance model based on the Child-Langmuir law was used to calculate the expansion velocity of the diode plasmas from voltage and current profiles. Additionally, a four-channel high speed framing camera was used to observe the formation and subsequent movement of the cathode plasma. More accurate and valuable information about the dynamics of the cathode plasma was also acquired by utilizing the digital image processing methods. Results from the experiments and theoretical analysis were compared. In this paper, the experiments have been performed using a high-voltage pulse generator with 200 kV output voltage and 110 ns pulse duration. Current densities up to 440 A/cm2were produced. The observation of the cathode plasma expansion in transverse direction indicated that the diode current was cathode-limited in the current rising stage (the first 60 ns of the current pulse). The perveance model should be modified taking in account the time dependent expanding plasma surface (i.e., not the whole cathode surface) for this period. The velocity in the direction parallel to the cathode surface (transverse velocity) was much larger than that in the direction perpendicular to the cathode surface (longitudinal velocity), and further, it dropped from 90 cm/μs to nearly 20 cm/μs rapidly. It was shown that, during the current flattop stage, the plasma filled out all the surface of cathode and the diode current was space-charge-limited. The values of the transverse velocity and longitudinal velocity were nearly the same and decreased relatively slowly. The satisfactory coincidence of experimental and calculated (both were in the range of 6–8 cm/μs) values of the cathode plasma expansion velocities was obtained.

scholarly journals Features of 200 kV, 300 ns reflex triode vircator operation for different explosive emission cathodes

2012 ◽  
Vol 31 (1) ◽  
pp. 45-54 ◽  
Author(s):  
Amitava Roy ◽  
R. Menon ◽  
Vishnu Sharma ◽  
Ankur Patel ◽  
Archana Sharma ◽  
...  
Keyword(s):  
Carbon Fiber ◽  
Pulse Duration ◽  
High Power ◽  
Virtual Cathode ◽  
Expansion Velocity ◽  
Marx Generator ◽  
Plasma Expansion ◽  
Cathode Plasma ◽  
High Power Microwave ◽  
Power Microwave

AbstractTo study the effect of explosive field emission cathodes on high power microwave generation, experiments were conducted on a reflex triode virtual cathode oscillator. Experimental results with cathodes made of graphite, stainless steel nails, and carbon fiber (needle type) are presented. The experiments have been performed at the 1 kJ Marx generator (200 kV, 300 ns, and 9 kA). The experimentally obtained electron beam diode perveance has been compared with the one-dimensional Child-Langmuir law. The cathode plasma expansion velocity has been calculated from the perveance data. It was found that the carbon fiber cathode has the lowest cathode plasma expansion velocity of 1.7 cm/μs. The radiated high power microwave has maximum field strength and pulse duration for the graphite cathode. It was found that the reflex triode virtual cathode oscillator radiates a single microwave frequency with the multiple needle cathodes for a shorter (<200 ns full width at half maximum) voltage pulse duration.

Time-resolved investigation of the plasma expansion during picosecond laser material processing

1997 ◽  
Author(s):  
G. Urbasch ◽  
F. Billmann ◽  
Juergen Jandeleit ◽  
P. Russbueldt ◽  
Hans-Georg Treusch ◽  
...  
Keyword(s):  
Material Processing ◽  
Picosecond Laser ◽  
Plasma Expansion ◽  
Laser Material Processing ◽  
Time Resolved ◽  
Laser Material

Cathode plasma expansion in diode with explosive emission

2012 ◽  
Vol 24 (6) ◽  
pp. 1471-1474
Author(s):  
左应红 Zuo Yinghong ◽  
王建国 Wang Jianguo ◽  
朱金辉 Zhu Jinhui ◽  
范如玉 Fan Ruyu
Keyword(s):  
Plasma Expansion ◽  
Cathode Plasma ◽  
Explosive Emission
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