Author Topic: Beam currents of analog scopes  (Read 221 times)

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Offline quak

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Beam currents of analog scopes
« on: April 10, 2019, 07:58:23 pm »
I'm considering to use an analog scope as electron beam source for a physics experiment (as focusing optics and deflection are already included).

I know the question how to cut a hole in the phosphor screen without destroying the CRT is an issue... for now I'm searching for a scope which can deliver >100 uAmps beam current which can be deflected with frequencies >100 MHz.
We measured that the Tektronix 2465 only delivers 20-40 uA, as far as I found out this is due to a mesh inside the CRT. There are several older CRTs (like the T503) which can reach this current according to their datasheet. Now the scopes equipped with those CRTs usually offer rather low deflection frequencies (up to 50 MHz).

Does anyone know some scope with rather high beam current and frequency bandwidth from any manufacturer?

Thank's for your advice!
 

Offline dzseki

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Re: Beam currents of analog scopes
« Reply #1 on: April 10, 2019, 08:13:47 pm »
I think you mean the expansion mesh: that was invented in the 60's and all the high frequency oscilloscope tubes had that since then, because it ease the need of the high voltage post acceleration voltage.
What you should consider is Tektronix's MCP (Micro Channel Plate) tubes, that can be found in the 2467 or the 7104. This was really state of the art construction with built in photo multiplier to the tube, although it would be sad to see destroying such a tube...
 

Offline StillTrying

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Re: Beam currents of analog scopes
« Reply #2 on: April 10, 2019, 10:08:22 pm »
With the tube held face down you could probably pull out nearly all of the mesh, it's very delicate. But then you'd need higher deflection voltages.

https://entertaininghacks.wordpress.com/2016/03/09/rescuing-a-broken-tektronix-465-crt/#more-752
CML+  That took much longer than I thought it would.
 


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