B Has a Double Slit Experiment Been Conducted in a Vacuum Tube?

[dave1223]

i.e a vacuum tube. using the gate in a triode to adjust the amplification of the electrons. i guess you would have to have a photographic plate attached to the anode but this shouldnt effect the operation of the valve. just a thought... not sure where you would put the detector, maybe it would work outside the glass... you would put the slit between the gate and the anode or the gate and the cathode...

 

[Drakkith]

Even if you could, why would you? You wouldn't get any difference in results than a normal experiment.

 

[dave1223]

well, considering the amount of variations on the double slit experiments that have been tried and the number of times it has been repeated, i would say its probably worth a try

 

[DennisN]

i.e a vacuum tube.

The double slit experiment has been made with other objects than photons (i.e light), e.g. electrons and C₆₀ molecules.

At the moment I don't remember if the electron version of the experiment is done in vacuum, but I wouldn't be surprised... I think it is... I'll look around for it.

But it is my understanding that the C₆₀ version of the experiment has been done in vacuum, quote:

A significant advantage of the thermionic mechanism is that it does not detect any of the residual gases
present in the vacuum chamber. We could thus achieve dark count rates of less than one per second even under moderately high vacuum conditions (5 x 10^-7 mbar).

[...]

The vacuum chamber is rigidly mounted on an optical table together with the ionizing laser, in order to minimize spatial drifts.

Source: Wave–particle duality of C60 molecules (by Arndt et al, Letters to Nature)

Edit, note: Above I assumed that you were interested in whether the experiment has the same result in vacuum as in air at normal pressure.

 

[vanhees71]

The electron version is usually done in a vacuum. See, e.g.,

https://pubs.aip.org/aapt/ajp/article-abstract/42/1/4/1049574/Electron-Diffraction-at-Multiple-Slits

 

[dave1223]

the electronic valve (vacuum tube) acts as an amplifier/suppressor, so it is not just about having a vacuum.

 

[Drakkith]

There's nothing fundamentally different about doing the double slit experiment inside a vacuum tube than anywhere else. This is analogous to rolling a ball down the aisle of a bus vs a train vs a plane. Sure the carpet might be different, but you're still just rolling a ball on a surface. The electrons don't care where they are at. They'll still react to fields, barriers, and detectors just the same no matter where you put them.

 

[Vanadium 50]

If this thread turns into us giving you examples you adding new criteria as we do so to explain why the examples don't "count", this will get very old very fast.

Why don't you tell us where you are going with this (assuming it is in line with the PF rules, of course)?

 

[vanhees71]

Hm, I don't know, whether the double-slit experiment with electrons is feasible just at normal air pressure. I don't know, what's the mean free path of electrons in air under normal conditions. For sure it's also dependent on the electrons' energy.

 

[kered rettop]

From a quick Google, it's reasonable to suppose a mfp of several microns. So the apparatus would have to be much smaller than this. You might be able to fabricate something on a silicon chip. :)

 

[mwodzinski]

If photons are being transmitted through a fluid (air) then why would one not expect the same results as one sees in double slits with waves in water? Also, the photons are going through slits made in a substance such as metal. Would there not be interactions between the photons and the slit material? Matter and energy are the same thing, just another form. If you can bend light, then why wouldn’t passing by some substance (a lattice of atoms) not have some effect? This all seems a bit silly to me. I would like to see the results of the double slit experiment in a pure vacuum. Good luck creating a pure vacuum.

 

[weirdoguy]

Matter and energy are the same thing

No they are not. Matter is a "thing", energy is a property of that thing. One of many properties.

 

[sophiecentaur]

There's nothing fundamentally different about doing the double slit experiment inside a vacuum tube than anywhere else.

True but the devil is in the detail. The convenient method for showing diffraction effecs on an electron beam is with an 'elecgtron diffraction tube' which is available for a lot of money (£900).A beam is fired through a thin layer of graphite and a set of concentric ring fringes in a phosphor screen. This doesn't use two slits but a crystalline array of Carbon atoms (the tube has a deep vacuum). A similar pattern of ring fringes can be obtained with a light beam fired through a tiny pinhole. No vacuum his time.

Now I could well be wrong but I have a feeling that the 'analogous' two slit electron pattern is too hard to demonstrate conveniently. The sites that I have found seem to 'imply' the Young's pattern for electrons rather than showing how it's done. The graphite screen tube pattern actually puts its money where its mouth is - and in the context of school budget limitations.

 

[Nugatory]

I would like to see the results of the double slit experiment in a pure vacuum. Good luck creating a pure vacuum.

All experiments that use free electrons are done in a vacuum hard enough that each electron has negligible probability of encountering even a single air molecule on its path through the apparatus.
This is a rather tedious and expensive process, so experimentalists generally prefer to use photons for experiments involving general quantum principles that are common to all particles because then we can do them in normal lab air. We choose wavelengths that have negligible interaction with air, and we have enough experience studying light under various conditions (from truly hard vacuum, less than one gas atom per cubic meter, to pressures many times atmospheric) to know if the presence or absence of air will affect our results.

 

[PeterDonis]

If photons are being transmitted through a fluid (air) then why would one not expect the same results as one sees in double slits with waves in water?

Because light is not water. And no, you do not get the same results in both cases. If you turn down the intensity of the wave source in a double slit experiment with water, you get a gradually fainter interference pattern, but it's still all there at once. If you turn down the intensity of the light source in a double slit experiment with light, you get individual dots on the detector screen, that build up the interference pattern over time. That can't be explained with classical wave theory; you need quantum mechanics.

Also, the photons are going through slits made in a substance such as metal. Would there not be interactions between the photons and the slit material?

Yes, of course there are. That's why you can get light on the detector screen at places other than right behind the slits. Why is this an issue?

 

[gentzen]

... vacuum hard enough that each electron has negligible probability of encountering even a single air molecule on its path through the apparatus. This is a rather tedious and expensive process ...

Sounds like the conditions in a TEM (transmission electron microscope), which indeed are quite expensive. (However, "encountering even a single air molecule" might be misleading in this context.)

But the conditions in a SEM (scanning electron microscope) are much less extreme, SEMs are often much cheaper, and you still can provoke various diffraction interference effects: sometimes desired and beneficial, sometimes undesired and a nuissance. It is true that there is often an incoherent background intensity, and that you might be forced to use many electrons to get a sufficiently good diffraction contrast.

But I guess you had something completely different in mind, when you wrote that.

 

[berkeman]

Thread is closed for Moderation...

 

[PeterDonis]

After some cleanup, the thread has been reopened.

 

[sophiecentaur]

But the conditions in a SEM (scanning electron microscope) are much less extreme

The conditions in an SEM are not ideal for precise diffraction measurements because that isn't needed. Good Engineering only demands excellence where it is needed. If you really wanted to see measurable detailed diffraction effects then, for a start, the timescale involved would be extreme because objects to be scanned would be out-gassing for hours (?) - a long time.