B-Dot Probe Applet

## Calculate Machine Attributes:              top

### Special Values

#### Inputs:

ZS (Source Line Impedance) [Ω]
VS (Source Voltage) [MV]
ZVac (MITL Vacuum Impedance) [Ω]
ZD (Diode Impedance) [Ω]  Optional Input for "With Radiographic Diode" outputs, only affects output when less than self-limited ZB

#### Outputs:

Running Self Limited

VL (Load Voltage) [MV]
IA (Anode Current) [kA]
Zop (MITL Operating Impedance) [Ω]
ZB (Bound Impedance) [Ω]
IB (Bound Current) [kA]
IS (Sheath Current) [kA]
gm (Gamma Minimum)

With Radiographic Diode: "Retrapping" Solution

VL (Load Voltage) [MV]
IA (Anode Current) [kA]
Zop (MITL Operating Impedance) [Ω]
ZB (Bound Impedance) [Ω]
IB (Bound Current) [kA]
IS (Sheath Current) [kA]
gm (Gamma Sheath)

VL (Load Voltage) [MV]
IA (Anode Current) [kA]
Zop (MITL Operating Impedance) [Ω]
ZB (Bound Impedance) [Ω]
IB (Bound Current) [kA]
IS (Sheath Current) [kA]
gm (Gamma Sheath)

## Output Format:top

 Select Format: Scientific Engineering Fixed

## Notes:top

• Upon further reflection, there are two solutions of interest...  These are the "re-trapping" solution and the steady state solution.  The "re-trapping" solution is the result when the forward wave first hits the load but before the retrapping wave goes back to the machine.  In a sense, this is the result before the generator is aware of the actual load.  Because the retrapping wave velocity is often very slow, this result may be the most useful for actual generators.  This result does not lie on the load line.  Eventually, after waves propagate back and forth between the generator and the load, the "steady state" solution will be reached.  This result does lie on the load line.  27Aug07

•  Fixed a bug regarding "With Radiographic Diode" results where answer did not lie on the load line 11May07

• It is assumed that the source transmission line transit time is much longer than the electrical pulse.

•  Solver assumes no reflection from self-limited load and MITL has same effective impedance as load.  (I think this is usually a pretty good assumption, although not 100% accurate). Undermatched solver assumes a forward going wave in MITL with same voltage as in self-limited case and an MITL impedance equal to the vacuum impedance.  (This is probably only a good assumption when very undermatched.)

• Sources:

•  Private communications with Dave L. Johnson and Vern Bailey of Titan, PSD.

•  Vern Bailey's Beams2004 paper.

•  J. M. Creedon,  Appl. Phys. 48, 1070 (1977).

•  Creedon JM. J Appl Phys 1975; 46: 2946-2955.