Obtain Cathode Ray Tubes Without X-rays

[Albertgauss]

TL;DR Summary

Trying to obtain a beam of electrons to deflect with a magnet but don't want X-rays

Good Day,

I would like to obtain cathode-ray tubes for deflecting electrons with a magnet. However, I don't want to deal with X-rays, and would prefer to obtain cathode tubes that cannot produce X-rays at all. I haven't had much luck on the internet finding such cathode ray tubes or I don't know what I am looking at when I scan the internet through all the different cathode-ray tubes that exist. It seems that non-X-ray cathode ray tubes should exist, since TVs and Oscilloscopes were built using them for decades and I seriously doubt the manufacturers would sell TV's and oscilloscopes that would produce X-rays in the family living room housing the TV. Can someone help me to find a website where I can buy non-X-ray cathode ray tubes where the electron beam is visible, if such a tube is even possible? If such a cathode ray tube does exist, would the glass be transparent so that someone could see the electron beam? I couldn't tell from my internet searches if cathode ray tubes in TVs and oscilloscopes had transparent casings or not.

 

[davenn]

Summary: Trying to obtain a beam of electrons to deflect with a magnet but don't want X-rays

It seems that non-X-ray cathode ray tubes should exist, since TVs and Oscilloscopes were built using them for decades and I seriously doubt the manufacturers would sell TV's and oscilloscopes that would produce X-rays in the family living room housing the TV.

they did produce X-rays

I suspect you don't understand how X-rays are produced ?

Before I state it, let's see if you know ?



Dave

 

[Klystron]

In my experience the Aquadag coating on the glass obscures the interior of the CRT. AFAIK cathode rays are invisible to the human eye. We see light on the screen from the excited phosphor coating reacting to the electron beam.

I see @davenn has addressed X-rays. Hazards from CRT's also include electrocution from the power supply and nasty shocks from touching the collector attached to the aquadag.

 

[davenn]

AFAIK cathode rays are invisible to the human eye.

yes, they can be made visible along the length of the tube by having a tube that is not fully evacuated.
This was common with the Crooke's Tube where the green electron beam was easily visible and is still
used in high school or university physics classes to demonstrate the magnetic field effect on the electron
beam.

The OP @Albertgauss needs to get a Crooke's Tube, it's is what he has been searching for without
knowing the name of it.

The only concern I have is if he has the skill and experience to work with the very high voltages required to
operate the tube.

I would still like him to do some research and see why CRT tubes produced X-rays and what was done to
lessen their emission out of the tube.


Dave

 

[Albertgauss]

X-rays are produced when electrons are accelerated to high speeds and smash into target metal. If the electrons have high enough energy, they will produce X-rays. I know, at least, conceptual, how the X-rays are produced and can add more if needed.

But I don't need (or want) the electrons to have a high energy to produce the X-rays, I just want the beam of electrons. It seems that a beam of electrons with energy less than X-rays should be possible to make---just lessen the accelerating voltage low enough that the electrons cannot make X-rays when they hit their target.

I admit that I did not know that TVs and O-scopes did produce X-rays the whole time. They apparently covered TV cathode ray tubes were covered in lead glass.

Remember that I am NOT looking for a tube to make X-rays. I want a tube with no X-rays. The Crooke's Tube seems to be the thing I want. It looks like it has an operating voltage of max at 5000 volts but there are versions that operate at less than 300 volts. This is what I have found so far. I have a 300 volt power supply already and have not encountered any problems using it. The level of demonstration of high school or university class is all that I am interested in for using the Crooke's Tube.

 

[Rive]

Oscilloscope tubes will also work, and that way you can get a focused beam and a ready-to-use electronics in one go.

 

[davenn]

X-rays are produced when electrons are accelerated to high speeds and smash into target metal.

Yes, that is the main way X-rays are purposely produced for, say, a medical X-ray machine
the Anode voltage can be up around 40kV or so

In a TV tube (CRT) they are inadvertently produced in 2 places
1) when the electron beam fires through the anode and some of the electrons hitting the anode
produce X-rays
2) when the electron beam hits the phosphor screen at the front ( viewing end)
remember phosphor is a metal, tho in powder form on the screen, there are low levels of
X-rays produced

Ohh and just thinking, there is a third place. In a colour TV, there is a metallic "shadow mask"
just behind the screen. Electrons hitting that will also produce X-rays.
the old colour TV's had an anode voltage of ~ 20 - 26kV depending on the size of the screen

But I don't need (or want) the electrons to have a high energy to produce the X-rays, I just want the beam of electrons.

The trick there is to keep the anode voltage below ~ 2kV

Remember that I am NOT looking for a tube to make X-rays. I want a tube with no X-rays. The Crooke's Tube seems to be the thing I want

yup, which is why I aimed you in that direction. There's a zillion videos on youtube showing teachers etc using Crooke's tubes and magnets to deflect the beam

tis good to see I got you on the right path


cheers
Dave

 

[Albertgauss]

Excellent! I think what I need I have here. The proactive step is now to figure out the Crooke Tube to use with all the considerations of this post in mind. I'll let you know if I have any more questions and I thank everyone for their help.

 

[tech99]

Various types of educational tubes are available from equipment suppliers, usually made by Teltron.

 

[Albertgauss]

That's exactly what I was looking for, a supplier with the kind of tube I want to use for demos. I realize it took some time to be more clear about what i needed, but a supplier just like listed above is the end goal.