Title :
Analysis of rod-pinch-like radiography sources on a compact pulsed power generator
Author :
Young, Frederic ; Cooperstein, G. ; Allen, R.J. ; Hinshelwood, D.D. ; Schumer, J.W.
Author_Institution :
Div. of Plasma Phys., Naval Res. Lab., Washington, DC, USA
Abstract :
Summary form only given. Radiography sources driven by a compact 800-kV, 7-kV pulsed power generator (the Hybrid Radiation Source) are analyzed with a rod-pinch diode model. The diode consists of a small diameter tungsten rod anode (1 to 4 mm diam) protruding through an annular stainless steel cathode. The rod-pinch model is applied to these diodes to understand the diode physics and to optimize radiographic performance. The measured diode voltage is used in the rod-pinch model to calculate the diode current. The formation and expansion of both cathode and anode plasma is included in the model. These diodes operate in the space-charge-limited (SCL) regime and do not achieve critical current. For a 4-mm diam anode, the model current fits the measured diode current for reasonable values of the cathode and anode plasma turn-on times, development times, and expansion velocities. The cathode plasma formation and ions from plasma drive the diode into a bipolar SCL mode at low impedance (<50 /spl Omega/) loading down the generator and leading to low voltage late in the pulse. For a 1-mm diam anode, the current approaches critical current near peak current, but not transition into the magnetically-limited regime. In the model. larger anode velocities (1.8-3.0 cm//spl mu/s) are required to fit the measured current late in time. However, heating the anode to 370/spl deg/C prior to the shot leads to smaller anode expansion velocities (/spl les/1 cm//spl mu/s) and increase the impedance lifetime.
Keywords :
limited space charge accumulation; pinch effect; plasma X-ray sources; plasma diodes; plasma sources; pulsed power technology; radiography; tungsten; 1 to 4 mm; 370 degC; 7 kV; 800 kV; W; anode expansion velocity; anode plasma; bipolar SCL mode; cathode plasma; compact pulsed power generator; diode current; diode voltage; hybrid radiation source; magnetically-limited regime; plasma drive; rod pinch like radiography sources; rod-pinch diode model; space-charge-limited regime; stainless steel cathode; tungsten rod anode; Anodes; Cathodes; Critical current; Current measurement; Diodes; Plasma measurements; Power generation; Pulse generation; Radiography; Velocity measurement;
Conference_Titel :
Plasma Science, 2004. ICOPS 2004. IEEE Conference Record - Abstracts. The 31st IEEE International Conference on
Conference_Location :
Baltimore, MD, USA
Print_ISBN :
0-7803-8334-6
DOI :
10.1109/PLASMA.2004.1339740