From: John Larkin
Subject: Re: Pentupler voltage multiplier info??
Date: Tue, 17 Dec 2002 19:38:34 -0800
Organization: Posted via Supernews, http://www.supernews.com
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On Wed, 18 Dec 2002 03:29:57 GMT, Robert Baer
>"Smile, it can only get WORSE" wrote:
>> Good Day All,
>> I'm looking for pentupler info. I know very little about them, but I'm
>> hoping it can supply a 5X voltage boost at femtoamp to nanoamp current
>> levels (to power the low power stages of a photomultiplier tube).
>> I've done yahoo, askalltheweb, jeeves and ebay searches…no hits.
>> Is there really such a thing or is the pentupler voltage multiplier a
>> rumor…or is it the best kept secret around??
>> All replies appreciated.
> A voltage multiplier can be built of any number of stages: 5, 10, 20
> Every diode has a loss, low voltage silicon diodes lose about 0.7V and
>the KV types can lose 2-10 volts.
> And that is just the DC loss.
> There is the loss due to stored charge being transferred during
>switching, and that can be much larger.
> Voltage multipliers are used to get higher DC voltages from an AC
> A 5X voltage multiplier might produce near 4.5X input.
> One *CANNOT* use them to "..boost femtoamp.." _current_ levels,
Multiplier strings like this are commonly used to drive
photomultipliers. Each dynode is connected to a multiplier step, so no
resistive voltage divider string is needed. This works nicely if the
photocathode is the farthest from ground... it needs the least
current, and successive dynodes need more, so that meshes nicely with
the behavior of a C-W chain like this. The early stages of a PMT
really need very little current.
A few people make potted PMT sockets with the whole circuit inside,
powered from 5 volts DC or whatever.