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From: dbell@cup.portal.com (David J Bell)
Newsgroups: sci.electronics
Subject: Re: Can anyone identify these tubes?
Message-ID: <32253@cup.portal.com>
Date: 30 Jul 90 19:11:55 GMT
References: <1624@oucsace.cs.OHIOU.EDU>
Distribution: na
Organization: The Portal System (TM)
Lines: 36

Bill White asks:

>	I happened to end up with two tubes that had originally been for
>some sort of X-ray experiment, I think; I doubt if they are actually
>X-ray tubes, but I think they might be detectors or some such.  In any case,
>I want to know what they are:

>1.	1P28 (or IP28, I'm not sure).  This has 11 pins, and the glass part
>	is covered with some kind of black paint, save for a window in which
>	I can see either a filament or a grid of some kind.

>2.	Jarrell Ash Hollow Cathode Type 45439.  It also says "Cathode Na-K",
>	"Max Current 25 ma", and "Gas NE".  And indeed, it is filled with
>	neon, as a little experimentation shows.  Looking down into it,
>	I see a squat cylinder open at both top and bottom, surrounded by
>	what looks like metal deposition on the side of the tube (or maybe
>	it's just from a getter).  Below the cylinder is a a long cylinder
>	of metal (looks like sodium/potassium alloy, so I guess it's the
>	cathode) with a hole stretching down the center.
>	The entire tube looks a lot like a straight-necked "chimney" from
>	an oil lamp, and the top is very flat.  The whole tube (glass, by
>	the way) fits into a metal shield of some sort that has four holes
>	about mid-way up the tube, plus is open at the front end.  There
>	are two electrodes for this tube, the anode and cathode.

1) The 1P28 sounds familiar, but I can't recall for sure. The physical
description sounds like a photomultiplier tube - very sensitive photon
detector.

2) DONT PURSUE THE "LITTLE EXPERIMENTATION"!  This sounds very much like
a gas-filled X-Ray tube. The cold cathode and ionic medium provide a current
in the tube. The radiation exits from the top of the "chimney", from ions
splashing into the cathode...


Dave       dbell@cup.portal.com