Photocathode color difference between two XX1080 image intensifier tubes ? - Page 1
Forum section: electronics / general

author: Lambda
author_rank: Regular Contributor
timestamp: December 06, 2022, 05:02:11 pm
content: Hello.First of all, sorry to bring perhaps a thread a bit off topic...I did not know where to put it, and i know only you in this vast community....But it concerns items able to detect NIR part of the spectrum.... So, it may be at least slightly related to the " (very) high temperature" thermal domain...;DI just received two gen 1 tubes XX1080 from Philips, for a DIY project.Apparently, depending the batch of available tubes which may appear time to time on second hand market, the photocathode's color from one tube to another can differ.Some tubes may have a blue photocathode, some others a redish photocathode, or a silver/brownish one, for instance....In my case, one of my tube has a blue photocathode, the other a silver one.I guess the composition of the photocathode may differ (basically it should be a S25 type), but for which reasons? Were some XX1080 tubes dedicated to a specific application, more related to Vis spectrum part, or NIR spectrum part, or UV partWhat is the reason of such disparity?In advance, thank you for your lights about this matter.Here are photos of my tubes.

author: sephalix
author_rank: Newbie
timestamp: December 06, 2022, 06:45:57 pm
content: Do you know if both tubes work? A grey or silver PC color _can_ be a sign of an oxidized PC, if the tube last lost vacuum aka "gone to air".Perhaps it's a different variant of the PC, looking at those tube specs it appears they use S25 which has at least two variants. Or perhaps one was used far more than the other, and the PC material has thinned.Those are my guesses, hopefully someone knows for certain!

author: Lambda
author_rank: Regular Contributor
timestamp: December 06, 2022, 07:31:58 pm
content: Hi Sephalix.It may be the case for the silver one.I bought them from a german militaria shop as "old stock from Bundeswehr"... untested, therefore, with the "totto-lotto" effect.I have to settle a HT power supply (14-15 kV PC-screen voltage, 350-450 V focusing electrode) for testing them.I was hearing that oxydation would result in a more dull greyish color. Here it is more like a mirror finishing, like christmas tree silver ball.But the truth will be known when tubes will be properly tested.Thank you for your feedback!Stéphane

author: sephalix
author_rank: Newbie
timestamp: December 06, 2022, 08:29:10 pm
content: The silver one does look more uniform than I would expect, almost like a layer of getter.These won't answer the question, but I figured I'd show these photos from an old arfcom thread.This photo apparently shows four MX-9916s, the top two have a grey colored PC and work fine, the bottom two have gone to air.This photo shows an array of PC colors found in MX-9916 tubes:

author: Lambda
author_rank: Regular Contributor
timestamp: December 07, 2022, 08:30:10 am
content: Hi Sephalix,Thank you a lot for your input. greatly appreciated!I keep some hope for the silverish tube...wait and see.I am right know checking carefully this tube. when looking through it in ambient light, i can say also that the silverish photocathode has also a very light brownish nuance and is translucid (i can see the internal (i guess) focusing electrode).The silverish tube has also an internal serial number carved on the body of an electrode (the focusing one, big chance): 042229The blueish tube has also an internal serial number carved on the body of the electrode (the focusing one, big chance): 5080960I may suppose from that the silverish tube is older than the blueish one.Wait and see.Regards.Lambda

author: Lambda
author_rank: Regular Contributor
timestamp: December 07, 2022, 08:51:04 am
content: Here is one example of a binocular unit (supposed being in function (photos from the ebay)) with two tubes having different photocathode color.

author: Fraser
author_rank: Super Contributor
timestamp: December 07, 2022, 12:13:04 pm
content: Lambda,If you decide to get into more high end image intensifier based imaging at a later stage, I have a very nice Electrophysics Astroscope camera adapter that is fitted with a superb Gen 3(UK) image intensifier. My unit is the higher specification UK version (Higher Figure of Merit) that is not normally available in EuropePerfect condition with C mounts at both ends for easy integration into a camera system or experimentation. This is a serious level of image intensificationhttps://www.thomasjacks.co.uk/pdf/11-56_07_tj_iss2_electrophysics_web.pdfhttps://www.bhphotovideo.com/c/product/484679-REG/AstroScope_914952_Night_Vision_Adapter_9350_30_3LPRO.htmlhttps://www.bhphotovideo.com/c/product/484666-REG/AstroScope_914886_Night_Vision_Adapter_9350BRAC_37_3PRO.htmlLet me know if you are interested but it is quite an expensive bit of kit as it originally cost around $7K. We might be able to do a deal though. My unit comes with the complete Astroscope casing, Gen 3 (UK spec) IIT module, C male and C female mounts and battery power supply module.Fraser

author: Fraser
author_rank: Super Contributor
timestamp: December 07, 2022, 12:29:36 pm
content: I almost forgot, I have a box of image intensifier tubes languishing in my spare room somewhere. I believe they will all be Gen 1 though. If you need some different IIT modules to play with, I might be able to assist. I have some Mullard/Philips XX1332 Gen2 modules as well but they did not light up when power was applied so likely have dead HV inverters.Fraser

author: sephalix
author_rank: Newbie
timestamp: December 08, 2022, 12:16:25 am
content: lawdy, and I thought TNVC was perhaps charging a little much for theirafocal adapter!

author: Lambda
author_rank: Regular Contributor
timestamp: December 08, 2022, 07:31:30 am
content: Hi!Fraser, just to be safe, i sent yesterday to you a PM, but i am not sure it was properly emitted.Hoping you received it. if it is the case, no hurry!Best regards.Stéphane