Microchannel plate x-ray image intensifier / Electromagnetic Radiation / Forums

Forums

4hv.org :: Forums :: Electromagnetic Radiation

« Previous topic | Next topic »

Microchannel plate x-ray image intensifier

Move Thread

LAN_403

zrg

Tue Jun 05 2012, 12:08AM

Registered Member #4762 Joined: Sun May 06 2012, 05:59PM
Location: Russia
Posts: 93

Got this thing today. One of the coolest (if it's not dead, of course) and most weird devices I've ever seen, and I've seen quite a few. Seems to be a subject. In short, this vacuum tube thing receives x-rays in a really small quantity, much lower than dangerous levels, and intensifies them so image is seen real-time on the giant fluorescent screen, which is not a small 1-inch window like on classic x-ray image intensifiers, but of size similar to receiving window - something about 9 inches. An x-ray live show.
The bad point is - it doesn't work out of box. The high voltage circuit seems to be in working order, as it generates some small HV sparks if shorted. Surely there is quite a chance that the tube itself is dead, but I would prefer to try all I can before making such a diagnosis.
Although this is an USSR production (and I'm too), found absolutely no info on this device on the Internet. The only related page is

which describes modern devices from this class.
The question is, maybe someone has seen or worked with such tubes, or would just have some nice ideas, and could be able to give any advice on getting this to work or making sure it is completely dead...

Wolfram

Tue Jun 05 2012, 05:52AM

Registered Member #33 Joined: Sat Feb 04 2006, 01:31PM
Location: Norway
Posts: 971

That certainly is unusual, I've never seen MCP x-ray intensifiers before. As you probably know, ommon medical x-ray intensifiers are based on the same principles as first generation night vision image intensifiers. Maybe you could get some idea of the voltages needed by looking for info on 2nd geneation night vision image intensifiers. The voltages will be higher for this since it's bigger, but it should give you an idea of what the different voltages should be relative to each other.

I know MCP intensifiers need a few different voltages, I think they at least need two voltages for the MCP itself to set up the voltage gradient, and an anode voltage for the acceleration. Do you know if the HV supply block generates all the voltages, or if the HV block only generates one voltage that is fed into a resistive divider to provide all of the voltages? If it's the first one, then I would try to disassemble the HV supply block to figure out the voltage it generates. If the HV supply block only provides a single voltage then I think it would be easier to just try it out with a weak x-ray source and an adjustable HV supply to see if you can get it to work.

The tube in the link seems to have an open side where the photocathode should be, so it's probably made for sealing into a vacuum system. On the bottom of the page it says that they also have a sealed version available. Do you have a picture of the input window of your device?

There's some info on MCP image intensifiers in this link

It would be an extremely nice toy if you could get it to work. How big is it? Where did you manage to get it, and do you think there's a chance of getting more of them?

plazmatron

Tue Jun 05 2012, 03:07PM

Registered Member #1134 Joined: Tue Nov 20 2007, 04:39PM
Location: Bonnie Scotland
Posts: 351

Your anode should be at or more than +5kv, but probably not more than 10kv (or depending on the design the anode may be grounded and the photocathode is at -5kV)

You should be getting 5-10mm sparks off of your HT power supply, so you may have a good tube.

The MCP should be somewhere between 200v and 2kV

A simple low current eht supply can be built for these, with a voltage divider network for the MCP.

Never ever seen one that big though! Amazing find!

Les

zrg

Tue Jun 05 2012, 08:35PM

Registered Member #4762 Joined: Sun May 06 2012, 05:59PM
Location: Russia
Posts: 93

The HV voltage multipier seems to be working: it gives just about 1 cm spark, which is ~10 kV. The multiplier looks like as if there were some attempts to repair it, and sometimes there are sparks inside the compound.
I contacted the seller and he told me that this items was dispatched from the working fluoroscopic lab because of instability of power supply (the screen flashed and occasionaly darkened), which means that it wasn't due to tube destruction.
The front window is covered with some kind of plastic, I don't want to remove it yet, as that would require detaching all wires and tube from it's mounting.
I think that the best idea would be to build a weak x-ray source from a vacuum rectifier (for testing) and to try powering this from a custom HV supply, but I'm concerned about the sounds of sparking: seems that they are happening _inside_ the tube, which is quite adversely.

Conundrum

Tue Jun 05 2012, 08:36PM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4059

Yeah, they are essentially the same as a microchannel plate night vision tube but a different photocathode.

I have it on reasonable authority that they also respond to UV light as well, if that helps.
Its not supposed to spark internally, this indicates overvoltage or internal movement of the plates..

-A

plazmatron

Wed Jun 06 2012, 12:45AM

Registered Member #1134 Joined: Tue Nov 20 2007, 04:39PM
Location: Bonnie Scotland
Posts: 351

OK well, if you have EHT, enough to generate a wee crackle, you may be ok here.

My tubes, like yours have a covered photocathode, ie, they aren't going to respond to any light at all, only radiation.

However, if you wait till night time, turn off the lights so it is pitch black, and wait in the dark for at least 5 minutes, for your eyes to become accustomed to the dark, then power on the tube, you will see tiny pinpricks of light on the screen (assuming all is well). Some of these scintillations are caused by quantum noise, and the brighter ones are caused by background radiation, including cosmic rays.

Les

radhoo

Sat Feb 16 2013, 11:48AM

Registered Member #1938 Joined: Sun Jan 25 2009, 12:44PM
Location: Romania
Posts: 699

zrg, do you have any news on this?

Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob