Jump to content

I want to create a 1 meter BEC


fredreload
 Share

Recommended Posts

15 minutes ago, swansont said:

You want the light going to the atoms in a collimated beam, so what does scattering it in all directions get you?

Right that is true = =, it would turn into something messy, shouldn't they have fixed the problem for x rays by now so they all go in the same direction? My idea is a really long vacuum tube, the light going in other directions will get filtered out while only the one going straight will stay. There is probably a simple way to fix it like a mirror or something. Below is from Google @@

「mirror keeps light in the same direction」的圖片搜尋結果

Edited by fredreload
Link to comment
Share on other sites

8 minutes ago, fredreload said:

Right that is true = =, it would turn into something messy, shouldn't they have fixed the problem for x rays by now so they all go in the same direction? My idea is a really long vacuum tube, the light going in other directions will get filtered out while only the one going straight will stay. There is probably a simple way to fix it like a mirror or something

You have no clue what the myriad problem with x-rays are, even though the information has been presented. Some of it is in the blurb you posted about laser cooling.

The steps are not optional, and are fairly specific. If you don’t follow the instructions, you don’t get the result.

Link to comment
Share on other sites

2 hours ago, swansont said:

You want the light going to the atoms in a collimated beam, so what does scattering it in all directions get you?

Scattering seems fine to me. You want photons coming from different directions, because the atoms are moving in all different directions. As long as the wavelength is right, it can slow an atom moving in the opposite direction of the photon. Is that wrong? Why do you want it collimated?

Scattering would be less efficient if the photons aren't going through enough of the cloud. You'd use lasers for the single wavelength, focus, and high output. The light being collimated is actually a problem---you need the light coming from different directions---which is solved by using 6 lasers.

Link to comment
Share on other sites

1 hour ago, md65536 said:

Scattering seems fine to me. You want photons coming from different directions,

Yes

Quote

because the atoms are moving in all different directions. As long as the wavelength is right, it can slow an atom moving in the opposite direction of the photon. Is that wrong? Why do you want it collimated?

If you shine light toward a cloud of atoms, and scatter the light with a filter, how does the scattered light get to the atoms?

You have a collimated source, aimed at a target. If it scatters, it’s no longer directed at the target.

Quote

Scattering would be less efficient if the photons aren't going through enough of the cloud.

That what lenses are for. You can expand and re-collimate the beam. 

Quote

You'd use lasers for the single wavelength, focus, and high output. The light being collimated is actually a problem---you need the light coming from different directions---which is solved by using 6 lasers.

Or one laser and beamsplitters, or one laser and a bunch of mirrors to redirect and retro-reflect the beam, or three lasers and retro-reflection. I’ve done all of these options.

4 hours ago, fredreload said:

Right that is true = =, it would turn into something messy, shouldn't they have fixed the problem for x rays by now so they all go in the same direction?

X-rays won’t work. If you understood the atomic physics you’d see this, or be able to ask a pertinent question, rather than just tossing out random ideas and/or repeating the same flawed suggestions.

It’s not a matter of them going in the same direction, but good luck with that; x-ray optics are notoriously difficult to work with, and inefficient.

 

Quote

My idea is a really long vacuum tube, the light going in other directions will get filtered out while only the one going straight will stay. There is probably a simple way to fix it like a mirror or something. Below is from Google @@

「mirror keeps light in the same direction」的圖片搜尋結果

Or just use mirrors to expand the beam. That’s not the sticking point here.

1 hour ago, studiot said:

How do you address my point about two of these being irrelevant ?

md65536 was not the one spouting nonsense about spin. You can technically cool the atoms with 4 beams (I’ve done that, too) but it’s not very forgiving, and is “leaky” so you don’t get as many atoms. 6 beams is overconstrained so any small misalignment doesn’t hurt you - it’s fairly robust. 

Link to comment
Share on other sites

1 hour ago, studiot said:

How do you address my point about two of these being irrelevant ?

Which two are irrelevant?

Do you mean when you wrote, "Do you not realise the basic mechanics that momentum directed along 2 of those 6 directions cannot affect spin?" I'm not talking about affecting spin, I'm talking about slowing of atoms that are moving toward the laser, ie. laser cooling. If you have 4 lasers aimed at +x, -x, +y, and -y, then atoms with movement in the z direction will not be cooled effectively.

I think you don't need lasers aimed in opposite directions, but merely a symmetric distribution of photon directions, to avoid propelling the cloud. 4 lasers arranged like a triangular pyramid might work, but probably not as well. Maybe it's better to use more than 6 lasers, surely with diminishing return. 6 is not "magic", but probably the simplest arrangement needed to get good results.

48 minutes ago, swansont said:

That what lenses are for. You can expand and re-collimate the beam.

Sorry, I (and fredreload it seems) thought you meant the photons had to have parallel directions, not just that they're lined up with the target.

Link to comment
Share on other sites

30 minutes ago, md65536 said:

I think you don't need lasers aimed in opposite directions, but merely a symmetric distribution of photon directions, to avoid propelling the cloud. 4 lasers arranged like a triangular pyramid might work, but probably not as well.

That’s exactly the arrangement we used.

30 minutes ago, md65536 said:

Maybe it's better to use more than 6 lasers, surely with diminishing return. 6 is not "magic", but probably the simplest arrangement needed to get good results.

The larger picture is you need space on your vacuum chamber for windows, and need ports to look in and to get atoms into (and possibly out of) the chamber. More windows means a larger chamber, which might be a luxury (you might have space constraints, and it costs more money)

 

Link to comment
Share on other sites

13 hours ago, md65536 said:

o you mean when you wrote, "Do you not realise the basic mechanics that momentum directed along 2 of those 6 directions cannot affect spin?" I'm not talking about affecting spin, I'm talking about slowing of atoms that are moving toward the laser, ie. laser cooling. If you have 4 lasers aimed at +x, -x, +y, and -y, then atoms with movement in the z direction will not be cooled effectively.

Fair enough if you are only considering linear momentum.

I'm sorry if I misunderstood,  as Fred keeps reintroducing angular motion even after repeated telling that this is irrelevent.

 

13 hours ago, md65536 said:

I think you don't need lasers aimed in opposite directions, but merely a symmetric distribution of photon directions, to avoid propelling the cloud. 4 lasers arranged like a triangular pyramid might work, but probably not as well. Maybe it's better to use more than 6 lasers, surely with diminishing return. 6 is not "magic", but probably the simplest arrangement needed to get good results.

Certainly my thoughts are that if you allow scattering before the impact of the photons ther is no point in using a laser

You seemed to imply this when you wrote, perhaps I misunderstood again.

16 hours ago, md65536 said:

Scattering seems fine to me. You want photons coming from different directions, because the atoms are moving in all different directions. As long as the wavelength is right, it can slow an atom moving in the opposite direction of the photon. Is that wrong? Why do you want it collimated?

Further I don't see that scattering after the impact is relevent since any change to the target's momentum will already have occurred.

 

So why is scattering not a red herring ?

Link to comment
Share on other sites

2 hours ago, studiot said:

Fair enough if you are only considering linear momentum.

I'm sorry if I misunderstood,  as Fred keeps reintroducing angular motion even after repeated telling that this is irrelevent.

 

Certainly my thoughts are that if you allow scattering before the impact of the photons ther is no point in using a laser

You seemed to imply this when you wrote, perhaps I misunderstood again.

Further I don't see that scattering after the impact is relevent since any change to the target's momentum will already have occurred.

 

So why is scattering not a red herring ?

Hmm, perhaps you are hacking the sodium atoms with more than enough photons then it could handle(getting into a stimulated emission state). The more photons they get, the colder then get. Because the whole getting hotter as it moves faster does not make sense, cuz imagine moving at the speed of light. The light scattering is because you want to keep the atoms at the same spot acting as a magneto-optic cage. If the light scatters around the atoms would bounce around in this cage, I dunno if it would absorb enough photons to turn into BEC in this case.

20 hours ago, swansont said:

You have no clue what the myriad problem with x-rays are, even though the information has been presented. Some of it is in the blurb you posted about laser cooling.

The steps are not optional, and are fairly specific. If you don’t follow the instructions, you don’t get the result.

Well, x ray requires a different refraction index then visible light waves, so a mirror would not reflect x rays.

Edited by fredreload
Link to comment
Share on other sites

P.S. Thanks for helping me arrive at the truth, I would have been content with the magnetic field idea, because you know, the fastest way to stop/slow an atom is to confine it at a magnetic field. But since Swanson kept pushing it just sort of leads on to the final conclusion.

P.S. Anyway, now I would confine the atoms in a place with a magnetic field so that it does not touch glass/plastic barrier to reheat itself, then bombard it with x ray/gamma ray, I think scattering wouldn't matter as long as you hack enough photons into the atoms.

P.S. And I apologize if I seem slow/stubborn at getting things

Edited by fredreload
Link to comment
Share on other sites

1 hour ago, fredreload said:

Hmm, perhaps you are hacking the sodium atoms with more than enough photons then it could handle(getting into a stimulated emission state).

This is something you could estimate.

1 hour ago, fredreload said:

The more photons they get, the colder then get.

This does not follow. The photons have to be the right photons (correct frequency, direction, etc.) in order to cool.

Quote

Because the whole getting hotter as it moves faster does not make sense, cuz imagine moving at the speed of light

This would seem to be yet another non-sequitur

1 hour ago, fredreload said:

Well, x ray requires a different refraction index then visible light waves, so a mirror would not reflect x rays.

That's one of many. X-rays tend to be absorbed. Even dealing with UV light is problematic.

5 minutes ago, fredreload said:

P.S. Thanks for helping me arrive at the truth, I would have been content with the magnetic field idea, because you know, the fastest way to stop/slow an atom is to confine it at a magnetic field.

Magnetic fields do not slow the atoms. And "fastest" is a dubious claim if you can't actually confine them because they aren't cold.

5 minutes ago, fredreload said:

But since Swanson kept pushing it just sort of leads on to the final conclusion.

I'm not aware you've arrived at a valid conclusion.

5 minutes ago, fredreload said:

P.S. Anyway, now I would confine the atoms in a place with a magnetic field so that it does not touch glass/plastic barrier to reheat itself, then bombard it with x ray/gamma ray, I think scattering wouldn't matter as long as you hack enough photons into the atoms.

Despite being told that this will not work.

5 minutes ago, fredreload said:

P.S. And I apologize if I seem slow/stubborn at getting things

The problem is you never stop to question why things won't work, when you are told your ideas won't work. You just toss out a new idea to get shot down, and ignore the feedback.

Have you ever considered learning physics?

Link to comment
Share on other sites

20 minutes ago, swansont said:

Have you ever considered learning physics?

LOL, I am looking at things more from an engineering perspective, I will learn more Physics from you guys when I have time :D 

Link to comment
Share on other sites

13 minutes ago, fredreload said:

LOL, I am looking at things more from an engineering perspective, I will learn more Physics from you guys when I have time :D 

The attitude from some engineers that they don't need to understand physics has always scared me.

Link to comment
Share on other sites

21 minutes ago, fredreload said:

LOL, I am looking at things more from an engineering perspective, I will learn more Physics from you guys when I have time :D 

I can't see how you can learn much engineering without learning and understanding a good deal of Physics.

Simple things like the difference between a Force and a Pressure.
Simple things like a fluid going round a corner or bend in a pipeline exerts a force that can be sufficient to need thrustblocks.
Failure to understand this and use these can have spectacular results as the engineers who flooded Harrow Hill in London with bentonite found out.

Edited by studiot
Link to comment
Share on other sites

2 hours ago, swansont said:

This does not follow. The photons have to be the right photons (correct frequency, direction, etc.) in order to cool.

Hmm, it says here. https://en.wikipedia.org/wiki/Absorption_(electromagnetic_radiation)

 "Although the absorption of waves does not usually depend on their intensity (linear absorption), in certain conditions (optics) the medium's transparency changes by a factor that varies as a function of wave intensity, and saturable absorption (or nonlinear absorption) occurs."

Also, let's say a light wave hits a sodium atom and it goes into stimulated emission. I do not see the sodium atoms bounce around as that happens because of stimulated emission's velocity.

Perhaps you guys are hacking the atoms with a higher intensity waves coming from different directions.

1 hour ago, studiot said:

I can't see how you can learn much engineering without learning and understanding a good deal of Physics.

Simple things like the difference between a Force and a Pressure.
Simple things like a fluid going round a corner or bend in a pipeline exerts a force that can be sufficient to need thrustblocks.
Failure to understand this and use these can have spectacular results as the engineers who flooded Harrow Hill in London with bentonite found out.

Pressure is something exerted on an area

Link to comment
Share on other sites

Just now, fredreload said:

Hmm, it says here. https://en.wikipedia.org/wiki/Absorption_(electromagnetic_radiation)

 "Although the absorption of waves does not usually depend on their intensity (linear absorption), in certain conditions (optics) the medium's transparency changes by a factor that varies as a function of wave intensity, and saturable absorption (or nonlinear absorption) occurs."

What’s the connection to your claim that “The more photons they get, the colder then get.”?

Fact of the matter is that when we do the final cooling stage in our fountains, we turn the intensity down to get colder temperatures.

 

Just now, fredreload said:

Also, let's say a light wave hits a sodium atom and it goes into stimulated emission. I do not see the sodium atoms bounce around as that happens because of stimulated emission's velocity.

“goes into stimulated emission”? Stimulated emission has a velocity?

WTH are you talking about?

 

 

Link to comment
Share on other sites

55 minutes ago, swansont said:

Fact of the matter is that when we do the final cooling stage in our fountains, we turn the intensity down to get colder temperatures.

That is interesting, perhaps the atoms are saturated with photons.
 

Quote

 

“goes into stimulated emission”? Stimulated emission has a velocity?

WTH are you talking about?

 

You need a frequency wave(light wave) that has enough intensity to hack in enough photons into the sodium atoms without damaging the structure(somewhere from x rays to gamma rays). Coincidentally, having more directions of the light source helps the atoms absorb the light better. But it does not matter which direction the light is coming from, it does not make atoms absorb the photons better so as long as it is coming from 2 or three different angles it should be alright(does not need to be orthogonal).

I was worried that the atoms would move around when they are hit by the laser, but it seems that would not happen. If it is an electron laser it might be different, but we are using photons. Clearly a gas hit by visible sun light does not move around.

2 hours ago, studiot said:

I can't see how you can learn much engineering without learning and understanding a good deal of Physics.

Simple things like the difference between a Force and a Pressure.
Simple things like a fluid going round a corner or bend in a pipeline exerts a force that can be sufficient to need thrustblocks.
Failure to understand this and use these can have spectacular results as the engineers who flooded Harrow Hill in London with bentonite found out.

Well, failing is the mother of success :D

Edited by fredreload
Link to comment
Share on other sites

9 minutes ago, fredreload said:

That is interesting, perhaps the atoms are saturated with photons.

You have no idea what saturated means in this context, do you?

 

9 minutes ago, fredreload said:

You need a frequency wave(light wave) that has enough intensity to hack in enough photons into the sodium atoms without damaging the structure(somewhere from x rays to gamma rays).

Energy and intensity are not the same thing.

9 minutes ago, fredreload said:

Coincidentally, having more directions of the light source helps the atoms absorb the light better.

Absorbing from multiple directions destroys the cooling effect. You want an atom to absorb a photon that opposes its motion.

9 minutes ago, fredreload said:

But it does not matter which direction the light is coming from, it does not make atoms absorb the photons better so as long as it is coming from 2 or three different angles it should be alright(does not need to be orthogonal).

As I said above, it does matter what direction the light comes from

9 minutes ago, fredreload said:

I was worried that the atoms would move around when they are hit by the laser, but it seems that would not happen.

Of course it happens. 

9 minutes ago, fredreload said:

If it is an electron laser it might be different, but we are using photons.

A free-electron laser emits photons.

 

9 minutes ago, fredreload said:

Clearly a gas hit by visible sun light does not move around.

Of course it does.

9 minutes ago, fredreload said:

Well, failing is the mother of success :D

Failing without learning from your failure is pointless.

Link to comment
Share on other sites

43 minutes ago, swansont said:

You have no idea what saturated means in this context, do you?

Coming from two different definitions I found on  Google. The atoms acquired enough wave energy, changed its state, and stays.

1801417390_.png.e9cc31884bbff6f354f79d133501f051.png

Quote

Energy and intensity are not the same thing.

Light with a higher frequency generally has more energy when interacting with matters.

Quote

Absorbing from multiple directions destroys the cooling effect. You want an atom to absorb a photon that opposes its motion.

Right, you are trying to force the atoms to absorb the wave energy, although I am skeptical about how you keep the atoms stationary. You see the cloud(water vapor), it is stationary, it does not move around from sun light.

P.S. Where do you get the material that generates gamma radiation? Perhaps from radioactive materials

Edited by fredreload
Link to comment
Share on other sites

57 minutes ago, fredreload said:

Coming from two different definitions I found on  Google. The atoms acquired enough wave energy, changed its state, and stays.

1801417390_.png.e9cc31884bbff6f354f79d133501f051.png

No mention of “saturated” here. And I was asking if you knew what it meant, not if you could google, and you’ve confirmed that you don’t.

 

Quote

Light with a higher frequency generally has more energy when interacting with matters.

Light with a higher frequency has more energy regardless of whether it’s interacting

Quote

Right, you are trying to force the atoms to absorb the wave energy, although I am skeptical about how you keep the atoms stationary.

You don’t keep them stationary. You’re trying to slow them down, so they are moving.

Quote

You see the cloud(water vapor), it is stationary, it does not move around from sun light.

Vapor is invisible, so how could you tell?

Quote

P.S. Where do you get the material that generates gamma radiation? Perhaps from radioactive materials

Gamma radiation has nothing to do with our discussion, save for your irrelevant tangents.

Link to comment
Share on other sites

1 hour ago, swansont said:

No mention of “saturated” here. And I was asking if you knew what it meant, not if you could google, and you’ve confirmed that you don’t.

Must have learned it from an English class = =

Quote

Vapor is invisible, so how could you tell?

Because it absorbs sunlight

Quote

Gamma radiation has nothing to do with our discussion, save for your irrelevant tangents.

You use infrared in this case, sort of like infrared vision(heat vision). You hack in the infrared light to make the objects having more energy as oppose to it dissipating infrared energy as heat.

P.S. It would naturally dissipates infrared as heat, do you inhibit infrared dissipation?

P.S. But since it emits infrared, you might be able to reverse hack it, or use something with more energy than infrared that the material absorbs

On 2/8/2021 at 1:04 PM, md65536 said:

You could also try a microwave oven, to bombard it with microwaves. You could add a toaster, and let it absorb infrared. But will that cause spontaneous emission like in what you quoted? And how do you get the atoms moving toward these heat sources to preferentially absorb the light? Why does resonance matter, in what gets absorbed and what is emitted, if the atoms can simply absorb light of many different wavelengths?

Haven't tried microwaving water vapor in vacuum, did it work? You beat me to this one

P.S. This is beyond fusion temperature, you might form a black hole

Edited by fredreload
Link to comment
Share on other sites

8 hours ago, studiot said:

Certainly my thoughts are that if you allow scattering before the impact of the photons ther is no point in using a laser

A laser is practical for other reasons, like being single wavelength, high intensity, easy to direct, and needing a small window into the vacuum chamber. If you had some other setup and a single-wavelength light source that directed photons into the atom cloud, but the photons came from different directions, that would work too. I think all that's needed is enough photons with a) right wavelength b) aimed at the atoms c) symmetric or balanced distribution of directions.

8 hours ago, studiot said:

Further I don't see that scattering after the impact is relevent since any change to the target's momentum will already have occurred.

So why is scattering not a red herring ?

If you're talking about fredreload's ideas, I don't agree that any of them improve on what's already been done. If you had a way to scatter light into the cloud to get a distribution of directions, that's great, but using mirrors and multiple laser beams seems much easier.

Scattering after the impact is basically how the atoms are cooled. As per the quote provided earlier by fredreload, from https://www.sciencedirect.com/topics/chemical-engineering/laser-cooling

Quote

The absorbed radiation is quickly emitted by the atom, either through stimulated emission or spontaneous emission. Stimulated emission occurs in the same direction as the absorption, and the recoil effect accelerates the atom back to its original velocity so that the absorption and emission effects cancel. Spontaneous emission, on the other hand, results in a random emission of a photon (and hence recoil of the atom) in any direction, with the net effect that, on average, the atom slows down in the direction of the absorption.

So to recap, "in the direction of absorption" is why you need photons coming from multiple directions, and you need a wavelength slightly longer than the atom's resonant frequency so that the photons are only absorbed by atoms moving toward the light source (blue-shifted to the resonant frequency). Contrary to what fredreload seems to suggest (I may be misinterpreting), you need the atoms to release that energy to get them to a lower quantum state. If they only absorb, I suppose you could still cool them, but they won't form a BEC by being in their lowest quantum state.

Edited by md65536
Link to comment
Share on other sites

31 minutes ago, md65536 said:

So to recap, "in the direction of absorption" is why you need photons coming from multiple directions, and you need a wavelength slightly longer than the atom's resonant frequency so that the photons are only absorbed by atoms moving toward the light source (blue-shifted to the resonant frequency). Contrary to what fredreload seems to suggest (I may be misinterpreting), you need the atoms to release that energy to get them to a lower quantum state. If they only absorb, I suppose you could still cool them, but they won't form a BEC by being in their lowest quantum state.

Hmm, is there a way to inhibit infrared dissipation/heat dissipation? With infrared laser perhaps? Just curious

P.S. I think you use infrared lasers to inhibit the infrared dissipation of the material, at the same time you apply another wavelength of light for the material to absorb.

P.S. I dunno about the microwave method though, it might release enough infrared to compensate for the heat, or it might build up

Edited by fredreload
Link to comment
Share on other sites

2 hours ago, fredreload said:

Must have learned it from an English class = =

Scientific terminology is sometimes different from lay usage

2 hours ago, fredreload said:

Because it absorbs sunlight

And?

2 hours ago, fredreload said:

You use infrared in this case, sort of like infrared vision(heat vision). You hack in the infrared light to make the objects having more energy as oppose to it dissipating infrared energy as heat.

You mentioned gamma radiation, for some reason. 

 

2 hours ago, fredreload said:

P.S. It would naturally dissipates infrared as heat, do you inhibit infrared dissipation?

P.S. But since it emits infrared, you might be able to reverse hack it, or use something with more energy than infrared that the material absorbs

What is “it”? This was a comment on gamma radiation?

 

 

Link to comment
Share on other sites

52 minutes ago, swansont said:

Scientific terminology is sometimes different from lay usage

Google helps from time to time

Quote

And?

And emits light of wavelength particularly of that of the blue color

Quote

You mentioned gamma radiation, for some reason. 

Cuz I thought you guys are hacking in photons with high frequency light. But the important part here is more on blocking the infrared heat dissipation on 6 directions.

Would something like this work(infrared lamp)? https://en.wikipedia.org/wiki/Infrared_lamp

Or should I put it through a converging lens? What is the intensity of the laser you use to work on an atomic scale? I am not sure about the unit for laser/light measurement(Lumen? Photons per area?Might be proportional to heat dissipation).

P.S. Thanks for sharing your knowledge

Edited by fredreload
Link to comment
Share on other sites

Guest
This topic is now closed to further replies.
 Share

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.