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Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
Nah wrote ...
I'm asuming that this was used in pulsed low power radar, correct?
Well, as you can see in the ML-6442 datasheet, the manufacturers target the market in 'telegraphy' and 'telephony' applications. By 'telegraphy,' I think they mean the different sorts of pulse modulation - rather than just simple on/off keying of Morse Code - so I'd expect to see the 6442 in transponders, aeronautical beacons, remote control and guidance, data telemetry applications, and perhaps things like RTTY links too.
'Telephony' is less ambiguous, so we are left to wonder who might fancy a chat on 5GHz - microwave telephone relay links and aeronautical communications, I'd guess, but there are surely many other applications that are happy with the line-of-sight propagation limitation of centimetric waves.
Registered Member #2941
Joined: Fri Jun 25 2010, 08:08AM
Location:
Posts: 143
a lot of reaction ,it's nice ... one of the reason they might be no documentation about recovery time of vacuum tube might be that they where no scope fast enough in this time, For the rest ,it must be some recovery time because of the free-flying of the electron in between the anode and the cathode ,and this should depend of the potential vs distance (I guess).
now would it be possible to use some vacuum tube as high voltage srd diode?
I will probably try with a magnetron with out magnet when I have some time...
Registered Member #2901
Joined: Thu Jun 03 2010, 01:25PM
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Posts: 837
Dunno if you're already aware, but the name for this kind of switch is Plasma Opening Switch, I don't think they are generally done with electron plasmas in vacuum though.
PS. the peak current you can generate per cm2 of a thermionic cathode seems pretty poor. The reverse current will be on the same order of magnitude of the forward current, since it's space charge limited, so for a kA switch you're going to need a huge amount of cm2 of cathode AFAICS. Using normal diodes in DSRD regime seems cheaper (even though they can't block too much current a piece either).
Registered Member #2901
Joined: Thu Jun 03 2010, 01:25PM
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Posts: 837
On a complete different note ... I wonder if you could make a POS (wonderful acronym) out of a xenon tube? Put some foil on both sides length wise and excite the gas with an HV AC source to ionize it before use.
PS. oops nm, it couldn't hold off any significant voltage of course.
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
Pinky's Brain wrote ...
On a complete different note ... I wonder if you could make a POS (wonderful acronym) out of a xenon tube? Put some foil on both sides length wise and excite the gas with an HV AC source to ionize it before use.
PS. oops nm, it couldn't hold off any significant voltage of course.
A coil around the tube (inductively coupled plasma) could be the answer, Pinky.
Registered Member #2901
Joined: Thu Jun 03 2010, 01:25PM
Location:
Posts: 837
The problem isn't inducing the plasma, the problem is that though an applied voltage can erode a pre-existing plasma ... it won't block anything more than the sustaining voltage of the xenon tube (which is pretty low).
Registered Member #2941
Joined: Fri Jun 25 2010, 08:08AM
Location:
Posts: 143
Pinky's Brain wrote ...
Dunno if you're already aware, but the name for this kind of switch is Plasma Opening Switch, I don't think they are generally done with electron plasmas in vacuum though.
PS. the peak current you can generate per cm2 of a thermionic cathode seems pretty poor. The reverse current will be on the same order of magnitude of the forward current, since it's space charge limited, so for a kA switch you're going to need a huge amount of cm2 of cathode AFAICS. Using normal diodes in DSRD regime seems cheaper (even though they can't block too much current a piece either).
I didn't knew about plasma opening switch. I had the idea that in reverse mode ,the current was not really limited before depletion of the "floating charge"and only depend of the acceleration potential ,the space charge is what limit the density of electron in vacuum ? using normal diode in dsrd mode look like a good way to go but the lay out does not look simple.
Registered Member #2941
Joined: Fri Jun 25 2010, 08:08AM
Location:
Posts: 143
Pinky's Brain wrote ...
cedric wrote ...
using normal diode in dsrd mode look like a good way to go but the lay out does not look simple.
How do you mean? The last DSRD circuit they designed was pretty elegant, 1 switch, 2 inductors, a capacitor and the diode(-array).
nice dock, thank ,I have to dig in to it ,I get similar result with commercial diode (negative pulse)with a circuit a bit similar ,I have to see what is the difference,I get 400 volt on a coax with 3 ns rise time. in there system ,I don't understand why L2 is having a negative current flow when L1 is positive,pass this point the current flow through the diode in my circuit is the same ,only I didn't know it was dsrd ,I just south I get lucky with diodes exhibiting a very strong step recovery ,the diode I use is a 6A8 dc ,I also get some result with fast recovery diodes like :stth6012w and the u1560.
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vacuum diode
