bwhite@oucsace.cs.ohiou.edu (Bill White ) (07/29/90)
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. So, any idea? If worse comes to worse, I can crack open the latter one for the sodium-potassium alloy and drop it in the Hocking River, but I'd prefer to know what these are actually _for_. | Bill White Internet: bwhite@oucsace.cs.ohiou.edu | | MURPHY'S EIGHTH COROLLARY: | | It is impossible to make anything foolproof because | | fools are so ingenious. |
dbell@cup.portal.com (David J Bell) (07/31/90)
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
larry@kitty.UUCP (Larry Lippman) (07/31/90)
In article <1624@oucsace.cs.OHIOU.EDU>, bwhite@oucsace.cs.ohiou.edu (Bill White ) writes: > I happened to end up with two tubes that had originally been for > some sort of X-ray experiment, I think .. Not x-ray. Both of these items are most likely from a Jarrell-Ash AA (Atomic Absorption) spectrophometer. AA is a sensitive method used in analytical chemistry for quantitative elemental determinations. A sample of an unknown is atomized into a flame (typically acetylene-nitrous oxide), with the flame being inserted in the optical path between a single-element light source and a photomultiplier tube with a monochromator in front of it. The monochromator is set to a particular absorbance wavelength for the element being determined. A good AA has sensitivity into the ppb range. Jarrell-Ash is an old line company which manufactured spectrographs for many years. During the 1970's they were bought by Fisher Scientific, which was in turn bought by Allied Chemical. Several years ago, Allied sold Jarrell-Ash to Instrumentation Laboratory, Inc. > 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. This is a very common photomultiplier tube, originally made by RCA, but now made by Hamamatsu and other vendors. The 1P28 has a UV glass window and is usable from below 200 nm to probably 650 nm. The photocathode material is antimony-cesium. Of the 11 pins, 9 are dynodes, 1 is a plate, and 1 is a cathode. Dynodes are typically connected in series with resistors. Operating voltage (anode to cathode) is typically 1,000 VDC. > 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. This lamp is used as a light source for an AA, and appears to contain a two-element cathode impregnated with sodium and potassium. When suitably excited, this lamp will provide emission lines of sodium, potassium and neon. Hollow cathode lamps are available with other elements, usually one element per lamp, but multi-element lamps such as you have also exist. The hollow cathode lamp does not produce great light intensity, but it does have very narrow resonance lines - which makes it usedful for AA. A hollow cathode lamp typically operates from 200 to 300 volts DC at less than 30 mA, and develops a cathode temperature of between 300 and 400 deg C (which is colder than it may look). > So, any idea? If worse comes to worse, I can crack open the latter one for > the sodium-potassium alloy and drop it in the Hocking River, but I'd prefer > to know what these are actually _for_. You won't get any meaningful quantity of sodium or potassium. Why not save it for a rainy day, or to calibrate a spectrographic instrument some day? Or, you can build your own AA. :-) Larry Lippman @ Recognition Research Corp. "Have you hugged your cat today?" VOICE: 716/688-1231 {boulder, rutgers, watmath}!ub!kitty!larry FAX: 716/741-9635 {utzoo, uunet}!/ \aerion!larry
tomb@hplsla.HP.COM (Tom Bruhns) (08/01/90)
Considering that Jarrell-Ash made it, and the "hollow cathode" description, the second tube is probably one that emits spectral lines of those elements, for calibration of an optical spectrometer. J-A makes (made) spectrometers and associated equipment. And that would say that the first one is indeed probably a PMT or a photodiode (not solid state ;-). (My PMT book is at home; can't look it up.)