How long do night sights last? I remember years back reading that the half life of the radioactive element used in making them was short but can't remember much more. I'm seeing some pistols popping up at stores/shows and online sites that are older and have them thats why I'm asking.
Night sights life span?
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XavierBreath
Member
Unless I'm mistaken, Trijicon guarantees theirs for ten years. I guess that means it's 3651 days.
10-Ring
Member
I have a set of Trijicons that are a tad over 10 years old & still going strong 
Jim Watson
Member
The half life of the Tritium is approximately 12 years. If the phosphors that glow under radiation from the Tritium have linear response, they would be half as bright after 12 years, a quarter as bright after 24 years. But they might not respond in a perfectly linear and proportional way. And the tube is always subject to cracking and loss of the Tritium. I think ten years is long enough to expect them to be useful, although I have seen reports of some pretty old sights still with enough glow to use.
Doc
Member
Jim:
The decay is exponential, it takes four half lives for there to be no further release of energetic particles
(neutrons if I recall correctly with tridium).
So at 12 years the tridium releases 50% of the particles that it did at time zero.
Presuming no degradation of the phosphor, this should be adequate to be seen in darkness,
probably for more than one half life. The problem is more the quality of the phosphor used.
Think of inexpensive watches with luminesent hands or numberals,
they lose there ability to remain luminescent quickly, compared to expensive watches with better phosphors.
The decay is exponential, it takes four half lives for there to be no further release of energetic particles
(neutrons if I recall correctly with tridium).
So at 12 years the tridium releases 50% of the particles that it did at time zero.
Presuming no degradation of the phosphor, this should be adequate to be seen in darkness,
probably for more than one half life. The problem is more the quality of the phosphor used.
Think of inexpensive watches with luminesent hands or numberals,
they lose there ability to remain luminescent quickly, compared to expensive watches with better phosphors.
Doc - A few corrections. Tritium, like all moderately decaying isotopes, will continue to emit particles for many halflifes. It doesn't stop at 4. At around 6 halflifes, for example, it is still emitting at about 1.5% of the rate when the sample was created. The particle emitted is a Beta particle (essentially an electron). The Tritium is transformed to Helium after the emission.
The quality and thickness of the phosphor does make a difference. Also the actual amount of Tritium at the start can affect how long a night sight is useful. IOW, if there is X amount in sight A and only X/2 in sight B, then sight B will die out much sooner as far as visibility is concerned. The lesser amount can be due to the manufacturer including a smaller amount or the sights (or Tritium supply) might have sat on the shelf for a few years before they were installed. The effect is the same.
The quality and thickness of the phosphor does make a difference. Also the actual amount of Tritium at the start can affect how long a night sight is useful. IOW, if there is X amount in sight A and only X/2 in sight B, then sight B will die out much sooner as far as visibility is concerned. The lesser amount can be due to the manufacturer including a smaller amount or the sights (or Tritium supply) might have sat on the shelf for a few years before they were installed. The effect is the same.
Doc
Member
Physics was a long time ago! thanks.
Yep, tritium (typo)
Technically radioactive elements continue to release particles until every last radioactive particle has decayed into the neutral state (ie Helium). That, while finite in actuality, is nearly infinite give 6 x 10exp23 molecules per mole. However, the length of time which radioactivity can be detected, and the presense of the radioactive isotope, is a measurable length of time. IIRC at 4 half lives the amount of remaining isotope is about 3% and the 4 half life approximation is used because 3 standard deviations of the mean of compound will have decayed, though as you say still a small (calcuable and knowable) amount will exist for many half lives to come.
You know I was thinking beta particle, but then I started thinking about Iodide and thought it was neutrons...
And I think this is the key issue for the useful length of night sight use, n'est pas?
Doc
PS: Now I know who to bother late at night when I am unable to sleep because I cannot solve a basic science conundrum.
Yep, tritium (typo)
Technically radioactive elements continue to release particles until every last radioactive particle has decayed into the neutral state (ie Helium). That, while finite in actuality, is nearly infinite give 6 x 10exp23 molecules per mole. However, the length of time which radioactivity can be detected, and the presense of the radioactive isotope, is a measurable length of time. IIRC at 4 half lives the amount of remaining isotope is about 3% and the 4 half life approximation is used because 3 standard deviations of the mean of compound will have decayed, though as you say still a small (calcuable and knowable) amount will exist for many half lives to come.
You know I was thinking beta particle, but then I started thinking about Iodide and thought it was neutrons...
And I think this is the key issue for the useful length of night sight use, n'est pas?
Doc
PS: Now I know who to bother late at night when I am unable to sleep because I cannot solve a basic science conundrum.
faustulus
Member
Ok I missed something, if Tritium decays into Helium where does the extra proton come from?
Doc
Member
ah another contact for late night science...
"And I think this is the key issue for the useful length of night sight use, n'est pas?" Oui, je conviens.
faustulus - The "extra" proton in the He comes from the extra neutron in the Tritium. When the ß ray is emitted (along with a neutrino, but who cares), abracadabra, the neutron becomes a proton.
But we digress.
faustulus - The "extra" proton in the He comes from the extra neutron in the Tritium. When the ß ray is emitted (along with a neutrino, but who cares), abracadabra, the neutron becomes a proton.
But we digress.
Mike Irwin
Member
I LOVE it when Moderator Mal talks physics...
Gets me electrons all excited, it does!
Gets me electrons all excited, it does!
Aww, I'll bet it was the magical 'abracadabra' part, wasn't it?"Gets me electrons all excited, it does!" Now you're getting into the mechanics of how the phosphor works.
benEzra
Moderator Emeritus
Actually, with tritium (beta-minus decay), it's an antineutrino.
A neutrino is emitted in beta-plus decay (along with a positron) when a proton becomes a neutron, yes?BTW, my wife's Trijicons on her Glock 26 are still quite bright after six years, as would be expected.
Doc
Member
OK, there are alot of RINGERS lurking here. Come on, all you closest physicists sound off so we can reference you directly with these tidbits.
benEzra - "Actually, with tritium (beta-minus decay), it's an antineutrino."
Prove it!
You're right, it is an antineutrino.
I was thinking a little more on this today (a dangerous concept). Since two particles are emitted at a constant sum of energy, the energy of the beta particle can vary from very little to about the total energy of the reaction in accordance with the uncertainty principle. I think it is a little less than half of the beta particles will have enough energy to activate the phosphor (going on memory alone here). So this is where it affects the night sights, you won't get the benefit of all the beta decays lighting up the sights, only a little less than half. So we ought to insist on paying only half of what the sights cost since we are only getting to use half of the Tritium. Damn that Herr Heisenberg! He's so unpredictable!
Prove it!
You're right, it is an antineutrino.I was thinking a little more on this today (a dangerous concept). Since two particles are emitted at a constant sum of energy, the energy of the beta particle can vary from very little to about the total energy of the reaction in accordance with the uncertainty principle. I think it is a little less than half of the beta particles will have enough energy to activate the phosphor (going on memory alone here). So this is where it affects the night sights, you won't get the benefit of all the beta decays lighting up the sights, only a little less than half. So we ought to insist on paying only half of what the sights cost since we are only getting to use half of the Tritium. Damn that Herr Heisenberg! He's so unpredictable!
faustulus
Member
thanks for the lesson one more question are neurtinos quarks or leptons?
faustulus - A neutrino is in the lepton family and has no charge and practically no mass. It is exceptionally hard to detect, which is why I told benEzra to "prove it".
faustulus
Member
Thanks for the info Mal. I guess I better hit the books, my quantum theory is a bit rusty
harrydog - I hear ya. I was thinking several days ago that we may be going too far from the original reason for this thread. Then I started thinking that there is nothing off topic about the discussion. I view it the same as someone asking about the internal ballistics of a round or the chemical composition of nitrocellulose or some subject like those. Subjects which are completely on-topic here on THR. Nothing wrong with wanting to know the minute details of how things gunnery work.
Now about that string theory. There are several different theories floating around, open strings, closed loops, ......
Now about that string theory. There are several different theories floating around, open strings, closed loops, ......
Symantics...
The sights last indefinitely. The tritium decays. I say this because Trijicon will replace the tritium inserts for significantly less than a set of new sights would cost (on their sights anyway). A quote from Trijicon's web site: "Tritium can not be 'recharged', however, we can replace the lamps for a nominal fee. Please contact our Customer Service Department for return and payment instructions."
When looking at a used gun, this can be factored into the cost/benefit analysis.
The sights last indefinitely. The tritium decays. I say this because Trijicon will replace the tritium inserts for significantly less than a set of new sights would cost (on their sights anyway). A quote from Trijicon's web site: "Tritium can not be 'recharged', however, we can replace the lamps for a nominal fee. Please contact our Customer Service Department for return and payment instructions."
When looking at a used gun, this can be factored into the cost/benefit analysis.
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