- #1
cragar
- 2,552
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can i use ni-chrome wire , for my heated cathode on my electron gun ,
using Thermionic emission , or what would be a better filament to use.
using Thermionic emission , or what would be a better filament to use.
Using Ni-Chrome Wire for Heated Cathode in Electron Gun
- Thread starter cragar
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- Cathode Electron Electron gun Gun Wire
In summary: ., in summary, you could use a flashlight bulb or an automotive electric lamp bulb as an inexpensive, plentiful thermionic-emission electron source.
- #2
Rajini
- 621
- 4
Hi,
seems like there are quite amount of materials available for thermionic emission.
look this:
http://en.wikipedia.org/wiki/Hot_cathode
seems like there are quite amount of materials available for thermionic emission.
look this:
http://en.wikipedia.org/wiki/Hot_cathode
- #3
cragar
- 2,552
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sweet thanks for the answer .
- #4
sophiecentaur
Science Advisor
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You could possibly get the filament from a defunct radio valve / TV tube. Goggles, face mask, gloves and protective clothes are needed and be careful when imploding it - knock the tube neck off rather than breaking the screen end? That would give you a convenient source of the best material for electron emission.
- #5
captn
- 36
- 0
sophiecentaur said:
Just breaking a neck could be bad--- a 'slug' of air can be injected towards the screen---large and fast enough could shatter the tube--and stir up the phosphor into the air that you will be breathing. It's probably better to break off the tip that was used to seal in the vacuum. At least, that is how I have released the vacuum (not implying that I let the vacuum out!
)If you do this to a color TV tube, please recycle the glass face--it contains several pounds of lead.
Neil
- #6
sophiecentaur
Science Advisor
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I thoroughly agree with that - I forgot about the details of the process but did mention the facemask!
At one time, CRTs were re-gunned by 'letting the vacuum out' with your method then sawing off the neck.
At one time, CRTs were re-gunned by 'letting the vacuum out' with your method then sawing off the neck.
- #7
Bob S
- 4,662
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The electron emission current from a hot filament is called thermionic emission, and is discussed in
http://en.wikipedia.org/wiki/Thermionic_emission
See also
http://www.avs.org/pdf/vossenwinner01.pdf
It is important to get a filament that has a very high melting point (and low vapor pressure), because the thermionic emission coefficient varies as temperature (kelvin) squared (Richardson's equation). If I were looking for a cheap plentiful thermionic-emission electron source, I would use a 3 to 6-volt flashlight bulb or a 6 volt automotive electric lamp bulb.
Bob S
http://en.wikipedia.org/wiki/Thermionic_emission
See also
http://www.avs.org/pdf/vossenwinner01.pdf
It is important to get a filament that has a very high melting point (and low vapor pressure), because the thermionic emission coefficient varies as temperature (kelvin) squared (Richardson's equation). If I were looking for a cheap plentiful thermionic-emission electron source, I would use a 3 to 6-volt flashlight bulb or a 6 volt automotive electric lamp bulb.
Bob S
Related to Using Ni-Chrome Wire for Heated Cathode in Electron Gun
1. What is Ni-Chrome wire and why is it used in heated cathodes?
Ni-Chrome wire is a type of resistance wire made from a combination of nickel and chromium. It is commonly used in heated cathodes because it has a high melting point and can withstand high temperatures without breaking or degrading, making it ideal for applications that require a steady and consistent source of heat.
2. How does Ni-Chrome wire produce heat in an electron gun?
Ni-Chrome wire is made of a material with high electrical resistance. When an electric current is passed through it, the wire heats up due to the resistance, and this heat is then transferred to the cathode. The heated cathode then emits electrons, which are accelerated by the electric field to create a beam of electrons.
3. What are the advantages of using Ni-Chrome wire in an electron gun?
Ni-Chrome wire has several advantages in electron gun applications. It has a high melting point, can reach high temperatures quickly, and has good thermal conductivity, allowing for efficient heat transfer. It is also relatively inexpensive and readily available.
4. Are there any potential drawbacks of using Ni-Chrome wire in heated cathodes?
One potential drawback of using Ni-Chrome wire is that it can become brittle and break over time due to repeated heating and cooling cycles. It is also not suitable for use in high-voltage applications as it may experience electrical breakdown. Additionally, care must be taken to ensure the wire is properly insulated to avoid electrical shocks.
5. How should Ni-Chrome wire be maintained in heated cathodes?
To ensure the longevity of Ni-Chrome wire in heated cathodes, it is important to avoid overheating and overstressing the wire. It should be operated within its recommended temperature range and not subjected to frequent on-off cycles. Regular cleaning and maintenance of the cathode can also help prevent buildup and prolong the lifespan of the wire.
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