-
#2760 by rfmwguy on 10 Feb, 2016 23:27
-
I can't make that .gif work here on NSF, but it works on Google drive for me.
Awesome aero...looks good to me. Is this the first steady-state and "churning" model you've seen?
https://drive.google.com/folderview?id=0B1XizxEfB23taGdIdGdtV3Jsdkk&usp=sharing -
#2761 by aero on 10 Feb, 2016 23:52
-
I can't make that .gif work here on NSF, but it works on Google drive for me.
Awesome aero...looks good to me. Is this the first steady-state and "churning" model you've seen?
https://drive.google.com/folderview?id=0B1XizxEfB23taGdIdGdtV3Jsdkk&usp=sharing
Its the first time I have been able to connect them together like these two. I've seen churning before and steady state before but not in the same cavity/drive freq/sequence. But this is also the first time I have understood how to and been able to take data through power cut-off.
From meep output data, comparing it from the first and second run (not really first or second, but first and second as posted). Using 12 detections in the cavity, the first posted run showed several resonant frequencies and bad quality factors, negative Q. The second posted run showed all resonant frequencies within kHz, but Q was still bad, negative in several cases.
The noise bandwidth is still to wide for a magnetron so I'm not done yet. Let myself get sidetracked by this comparison observation. But it is getting there and FYI, the resonant frequency is close to your target. -
#2762 by rfmwguy on 11 Feb, 2016 01:16
-
I noticed you ran into -Q values with shells models. Is this a meep artifact or is there something wrong with the cavity dimensions? I'm still at a point where I can tweak the dimensions. Like to know soon as I'm about to build the wooden spinning form.I can't make that .gif work here on NSF, but it works on Google drive for me.
Awesome aero...looks good to me. Is this the first steady-state and "churning" model you've seen?
https://drive.google.com/folderview?id=0B1XizxEfB23taGdIdGdtV3Jsdkk&usp=sharing
Its the first time I have been able to connect them together like these two. I've seen churning before and steady state before but not in the same cavity/drive freq/sequence. But this is also the first time I have understood how to and been able to take data through power cut-off.
From meep output data, comparing it from the first and second run (not really first or second, but first and second as posted). Using 12 detections in the cavity, the first posted run showed several resonant frequencies and bad quality factors, negative Q. The second posted run showed all resonant frequencies within kHz, but Q was still bad, negative in several cases.
The noise bandwidth is still to wide for a magnetron so I'm not done yet. Let myself get sidetracked by this comparison observation. But it is getting there and FYI, the resonant frequency is close to your target. -
#2763 by aero on 11 Feb, 2016 02:19
-
I noticed you ran into -Q values with shells models. Is this a meep artifact or is there something wrong with the cavity dimensions? I'm still at a point where I can tweak the dimensions. Like to know soon as I'm about to build the wooden spinning form.I can't make that .gif work here on NSF, but it works on Google drive for me.
Awesome aero...looks good to me. Is this the first steady-state and "churning" model you've seen?
https://drive.google.com/folderview?id=0B1XizxEfB23taGdIdGdtV3Jsdkk&usp=sharing
Its the first time I have been able to connect them together like these two. I've seen churning before and steady state before but not in the same cavity/drive freq/sequence. But this is also the first time I have understood how to and been able to take data through power cut-off.
From meep output data, comparing it from the first and second run (not really first or second, but first and second as posted). Using 12 detections in the cavity, the first posted run showed several resonant frequencies and bad quality factors, negative Q. The second posted run showed all resonant frequencies within kHz, but Q was still bad, negative in several cases.
The noise bandwidth is still to wide for a magnetron so I'm not done yet. Let myself get sidetracked by this comparison observation. But it is getting there and FYI, the resonant frequency is close to your target.
It's a meep problem. Not even that - its a meep operator problem. Or as I prefer, a problem with insufficient cpu, but I'm not even sure it is that. Harminv, the program meep uses to calculate Q, uses knowledge that the RF waves are sin waves, and so fits sin waves to the energy in the cavity. Unless one is very careful, there can be energy patterns within the cavity for which sin waves don't fit very well and the best fit includes increasing amplitudes, that is, negative Q. Or at least that's the way I understand it.
The favorite answer given by the meep experts when asked how to eliminate negative Q (its a general problem) is "Increase the run time." They like that answer almost as well as they like the answer to other "How do I ..." questions, for which the answer is usually, "Write your own function."
As for increasing the run time, there are three ways to do that, that I know of.
1- Increase meep resolution which basically smooths the RF fields in the cavity at the cost of a factor of 8 in cpu resources for each doubling of resolution.
2- Reduce the noise bandwidth which reduces the spurious frequencies introduced by the source at the cost of doubling the run time for each halving of the noise bandwidth. But of course the magnetron noise bandwidth gives a hard target for reducing bandwidth, and it is an onerous one when it comes to cpu resources.
3- Increase the idle time between power cut-off and harminv initiation to allow the noise in the cavity to dissipate. This one is easy, it's linear in cpu and the only problem is that if it is to long, then all the signal will have dissipated and there won't be anything left for harminv to fit with the sin waves. That means the whole run was wasted and it is very frustrating. Of course if it is to short, I still have negative Q and the run was still wasted.
But item 3 gives me a reason to be excited about having discovered how to record the field data through power cut-off to the start of harminv calculations. I can now "theoretically" watch the fields dissipate (after the fact) and so arrive at an informed guess as to how long it takes for the noise to dissipate while there still remains some viable field energy for curve fitting. That is a major advance IMO.
Bottom line is that I am now more optimistic that I know a systematic method to eliminate negative Q. Now if I could just get Harminv to calculate realistic Q values ... But maybe it will when all the Q's are positive. -
#2764 by SeeShells on 11 Feb, 2016 02:45
-
I can't make that .gif work here on NSF, but it works on Google drive for me.
https://drive.google.com/folderview?id=0B1XizxEfB23taGdIdGdtV3Jsdkk&usp=sharing
Have been out all today (Jury Duty) and now catching up. loaded your gif again and stopped it for 1.2 sec on the last frame.
Shell
added: That's weird, it animated on my system just firm but download it and it's only one frame. I'll look into what's going on.
Added: Runs on my system in several programs. We'll try this.
Added: Think there is a problem with NSF displaying long gifs, recommend to look at areo's google drive to see the cavity actions after cutoff as it's very interesting.
-
#2765 by aero on 11 Feb, 2016 03:52
-
I can't make that .gif work here on NSF, but it works on Google drive for me.
https://drive.google.com/folderview?id=0B1XizxEfB23taGdIdGdtV3Jsdkk&usp=sharing
Have been out all today (Jury Duty) and now catching up. loaded your gif again and stopped it for 1.2 sec on the last frame.
Shell
added: That's weird, it animated on my system just firm but download it and it's only one frame. I'll look into what's going on.
Added: Runs on my system in several programs. We'll try this.
Added: Think there is a problem with NSF displaying long gifs, recommend to look at areo's google drive to see the cavity actions after cutoff as it's very interesting.
Thanks Shell. Maybe this is a problem that's not from something I did wrong. That'd be refreshing
Yes, the patterns after cut-off are very interesting and those patterns can happen 60 times a second using a magnetron source. I wonder if it is related to experiments using magnetron source claiming much more thrust than experiments without magnetrons. Of course it is caused by the drive frequency being different than the resonant frequency of the cavity (IMO) but that is likely to happen to some degree in all cases. -
#2766 by dustinthewind on 11 Feb, 2016 04:43
-
...
Complex (imaginary) fields in a waveguide would be understood as superpositions of real/propagating, sidewall reflected fields, and superluminal phase velocity would also be understood as a superposition/interference effect, likewise group velocity.
Or perhaps I just think I know and am mistaken.
It was hard for me to believe. I wanted the near field to propagate at the speed of light so I could use it for propulsion but I keep seeing these hints that for long wavelengths (cm range and longer) it appears to be super-luminal (less than a wavelength I think, err maybe further) which seems to throw a monkey wrench in the works if it's true. I'm still not sure exactly what to make of it. I know waves can superimpose to give the impression of waves that propagate faster than light but these are some links that suggest it may be more than just superposition of waves.
First link: "ASPECTS ON THE PHASE DELAY AND PHASE VELOCITY IN THE ELECTROMAGNETIC NEAR-FIELD"
2nd link:"Nearfield Electromagnetic Effects on Einstein Special Relativity" by William D. Walker
3rd: "Near-field Analysis of Superluminally Propagating Electromagnetic and Gravitational Fields" by William D. WalkerQuoteIn the above referenced paper it has been shown that dispersion is nonlinear in the
Not sure I agree with this guy that space/time is really Galilean but I'm open to the idea that the near field might behave as such.
nearfield of a dipole and only linear in the farfield.
4th "Do Evanescent ModesViolate Relativistic Causality?" by G. NimtzQuoteThe detector receives the tunneled signal earlier than the signal, which traveled the same distance in vacuum...
And there seems to be more. It was sort of a mixed feeling for me of diasppointment and wonder. I'm still not sure what to think of it. On the other hand, phased arrays work and the antennas are within 1/4lambda.
http://forum.nasaspaceflight.com/index.php?topic=39004.msg1489915#msg1489915 -
#2767 by SeeShells on 11 Feb, 2016 09:43
-
This may help rfmwguy.Here is a really nice little article over at Space.com on the worst kept secret in physics at the moment (that happens to apply nicely to our discussions over here in the EMDrive thread).
Lack of a phase shift in the time or frequency domain?
http://www.space.com/31879-gravitational-waves-vs-gravity-waves.html
It's a lovely layman's primer on gravitational waves.Evanescent modes are characterized by an exponential attenuation and lack of a phase shift and that lack of phase shift has made me go, now that's a interesting thing to be happening in the cavity.
Shell
That. Right there. Let's talk about that.
The paper cites questions in actually measuring evanescent waves. Currently I'm looking at how a test could be designed to measure any evanescent wave actions on the outside of the copper frustum. Even though theory says it's only a <5um skin effect on the inside surface of the copper frustum. It needs to be verified that is truly the case.
We know bad construction, leaking joints in the frustum could lead to leaking of microwave energy outside the frustum. We have heard of issues in the DYI builds in measuring wave energy outside the frustum. The question remains, is this truly the case that's it's bad seams and soldered joints causing the leakage?
Shell
Superluminal Signal Velocity
G¨unter Nimtz
II.Physikalisches Institut, Universit¨at K¨oln
February 2, 2008
Abstract
It recently has been demonstrated that signals conveyed by evanescent modes can travel faster than light. In this report some special features of signals are introduced and investigated, for instance the fundamental property that signals are frequency band limited.
Evanescent modes are characterized by extraordinary properties: Their energy is negative, they are not directly measurable, and the evanescent region is not causal since the modes traverse this region instantaneously. The study demonstrates the necessity of quantum mechanical principles in order to interpret the superluminal signal velocity of classical evanescent modes.
PDF download...
http://arxiv.org/pdf/physics/9812053.pdf
Also a nice paper
University of Colorado, Boulder
CU Scholar
Undergraduate Honors Theses Honors Program
Spring 2013
Measuring and Modeling Radiation Loss in
Superconducting Microwave Re-entrant Cavities
Bradley Kenneth Mitchell
University of Colorado Boulder
http://scholar.colorado.edu/cgi/viewcontent.cgi?article=1745&context=honr_theses -
#2768 by Rodal on 11 Feb, 2016 11:49
-
...
Superluminal Signal Velocity
G¨unter Nimtz
II.Physikalisches Institut, Universit¨at K¨oln
February 2, 2008
Abstract
It recently has been demonstrated that signals conveyed by evanescent modes can travel faster than light. In this report some special features of signals are introduced and investigated, for instance the fundamental property that signals are frequency band limited.
Evanescent modes are characterized by extraordinary properties: Their energy is negative, they are not directly measurable, and the evanescent region is not causal since the modes traverse this region instantaneously. The study demonstrates the necessity of quantum mechanical principles in order to interpret the superluminal signal velocity of classical evanescent modes.
PDF download...
http://arxiv.org/pdf/physics/9812053.pdf
...
http://arstechnica.com/uncategorized/2007/08/faster-than-the-speed-of-light-no-i-dont-think-so/
http://spie.org/newsroom/technical-articles-archive/09-1000/0927-new-paradigm-resolves-old-paradox-of-faster-than-light-tunneling?ArticleID=x18001
http://www.eurekalert.org/pub_releases/2007-08/ns-lst081607.php
http://arxiv.org/abs/0709.2736
http://www.sciencedirect.com/science/article/pii/S0370157306003292
https://en.wikipedia.org/wiki/G%C3%BCnter_Nimtz#Scientific_opponents_and_their_interpretationsQuoteChris Lee has stated that there is no new physics involved here, and that the apparent faster-than-c transmission can be explained by carefully considering how the time of arrival is measured (whether the group velocity or some other measure).[8] Actually, these questions are well defined in the papers[2] and.[9]
Furthermore, recent papers by Herbert Winful were written in order to point out errors in Nimtz' interpretation.[4][10] According to these articles, far from contradicting special relativity, in reality Nimtz has rather provided a trivial experimental confirmation for it. Winful says that there is nothing specifically quantum-mechanical about Nimtz's experiment, that in fact the results agree with the predictions of classical electromagnetism (Maxwell's equations), and that in one of his papers on tunneling through undersized waveguides Nimtz himself had written "Therefore microwave tunneling, i.e. the propagation of guided evanescent modes, can be described to an extremely high degree of accuracy by a theory based on Maxwell's equations and on phase time approach."[10] (Elsewhere Nimtz has argued that since evanescent modes have an imaginary wave number, they represent a "mathematical analogy" to quantum tunnelling,[4] and that "evanescent modes are not fully describable by the Maxwell equations and quantum mechanics have to be taken into consideration." Since Maxwell's laws respect special relativity, Winful argues that an experiment which is describable using these laws cannot involve a relativistic causality violation (which would be implied by transmitting information faster than light). He also argues that "Nothing was observed to be traveling faster than light. The measured delay is the lifetime of stored energy leaking out of both sides of the barrier. The equality of transmission and reflection delays is what one expects for energy leaking out of both sides of a symmetric barrier."
Aephraim M. Steinberg of the University of Toronto has also stated that Nimtz has not demonstrated causality violation (which would be implied by transmitting information faster than light). Steinberg also uses a classical argument.[3] In a New Scientist article, he uses the analogy of a train traveling from Chicago to New York, but dropping off train cars at each station along the way, so that the center of the train moves forward at each stop; in this way, the speed of the center of the train exceeds the speed of any of the individual cars.[11] Herbert Winful argues that the train analogy is a variant of the "reshaping argument" for superluminal tunneling velocities, but he goes on to say that this argument is not actually supported by experiment or simulations, which actually show that the transmitted pulse has the same length and shape as the incident pulse.[10] Instead, Winful argues that the group delay in tunneling is not actually the transit time for the pulse (whose spatial length must be greater than the barrier length in order for its spectrum to be narrow enough to allow tunneling), but is instead the lifetime of the energy stored in a standing wave which forms inside the barrier. Since the stored energy in the barrier is less than the energy stored in a barrier-free region of the same length due to destructive interference, the group delay for the energy to escape the barrier region is shorter than it would be in free space, which according to Winful is the explanation for apparently superluminal tunneling.[12][13]
Apart from these interpretations further authors have published papers arguing that quantum tunneling does not violate the relativistic notion of causality, and that Nimtz's experiments (which are argued to be purely classical in nature) don't violate it either.[14] Oppositional theoretical interpretations are not cited in this reference, some of them are cited in. -
#2769 by Rodal on 11 Feb, 2016 13:01
-
....The paper cites questions in actually measuring evanescent waves. Currently I'm looking at how a test could be designed to measure any evanescent wave actions on the outside of the copper frustum. Even though theory says it's only a <5um skin effect on the inside surface of the copper frustum. It needs to be verified that is truly the case. ...
Evanescent waves decay exponentially (for angles to the normal greater than the total reflection angle), in the direction normal to the surface, proportional to the wavelength. Hence it makes sense that papers dealing with optical frequencies will mention the difficulty of measuring evanescent waves at optical frequencies. However, one has to make a big difference between the issue of measuring evanescent waves in the optical region, at wavelengths of hundreds of nanometers compared with measuring evanescent waves in the microwave region with wavelengths of 0.1 meter, (inches) in the ~2 GHz range.
c=299792458 m/s
f = 2.45 *10^9 1/s
free space wavelength = 0.122 m = 4.82 inches
1/2 wavelength = 2.41 inches
1/4 wavelength = 1.20 inches
At microwave frequencies evanescent waves can and have been measured using for example antennas that are subwavelength in length, at subwavelength distances from the surface.
It is difficult to measure an evanescent wave that is hugging a surface nanometers away from the surface at optical frequencies, it is much easier to measure an evanescent wave at microwave frequencies, at an inch from the surface.
Actually measurement of evanescent wavelength is done in non-destructive evaluation of surfaces by evanescent microwaves and also routine in microwave microscopy.
I'm interested in this issue of measuring exterior evanescent surface waves, so please let me know if you find any specific information regarding difficulty in measuring evanescent surface waves at microwave frequencies, as opposed to optical frequencies
Actually at the exact total angle of reflection, the evanescent wave theoretically still exists at an infinite distance from the surface, however, the field quickly diminishes for different angles, since this effect goes like
1/((ω n2/c)Sqrt[(n1/n2)(Sin theta)2 -1])
(at the angle of total reflection this becomes 1/0 = ∞, but at just 1 degree different from it the field decays in a few wavelenghts).
Also, attention must be paid to what surface materials and wall thicknesses are being used in these papers. Evanescent exterior surface waves will be present for electromagnetic waves propagating inside dielectrics, at the interface with air, or vacuum, for angles greater than the total reflection angle. However, for microwave frequencies, copper walls mm thick are way too thick compared to the skin depth of micrometers and hence there are no evanescent waves unless there are holes or gaps in the copper. -
#2770 by rfmwguy on 11 Feb, 2016 13:33
-
Since I'm still evanescent wave-lite, am I wrong in assuming this theory is roughly based on a paper where evW propagation extended beyond the cutoff in a conical waveguide or did this theory originate elsewhere? Sorry for not following this too closely, but maybe others could use a brief summary of this theory as well. Tried searching NSF but the info is fragmented across several weeks.
Thanks
-
#2771 by Rodal on 11 Feb, 2016 13:42
-
Since I'm still evanescent wave-lite, am I wrong in assuming this theory is roughly based on a paper where evW propagation extended beyond the cutoff in a conical waveguide or did this theory originate elsewhere? Sorry for not following this too closely, but maybe others could use a brief summary of this theory as well. Tried searching NSF but the info is fragmented across several weeks.
The paper by Günter Nimtz claiming superluminal travel refers to exterior evanescent surface waves due to internal angles of incidence greater than the total internal reflectance angle for inner waves.
Thanks
<< Their preferred experimental setup involved microwaves either being sent across two space-separated prisms or through frequency-filtered waveguides>>
It does not deal with mm thick copper walls for micrometer skin depth.
<<could use a brief summary of this theory as well. Tried searching NSF>> See: https://en.wikipedia.org/wiki/G%C3%BCnter_Nimtz#Experiments_related_to_superluminal_quantum_tunneling -
#2772 by rfmwguy on 11 Feb, 2016 13:55
-
I probably need to PM shell, thought for sure she was "tunneling" into an evW theory and I read it here. There was also some discussion on her using thicker metal for frustums and thought it might be related.Since I'm still evanescent wave-lite, am I wrong in assuming this theory is roughly based on a paper where evW propagation extended beyond the cutoff in a conical waveguide or did this theory originate elsewhere? Sorry for not following this too closely, but maybe others could use a brief summary of this theory as well. Tried searching NSF but the info is fragmented across several weeks.
The paper by Günter Nimtz claiming superluminal travel refers to exterior evanescent surface waves due to internal angles of incidence greater than the total internal reflectance angle for inner waves , and not to inner waves related to a cut-off.
Thanks
It deals with light, optical frequencies and not with microwave frequencies.
It does not deal with mm thick copper walls for micrometer skin depth.
<<could use a brief summary of this theory as well. Tried searching NSF>> See: https://en.wikipedia.org/wiki/G%C3%BCnter_Nimtz#Experiments_related_to_superluminal_quantum_tunneling , I'm not clear as to why you think that this may be related to NSF content, so that it would be in NSF
-
#2773 by Rodal on 11 Feb, 2016 13:59
-
I probably need to PM shell, thought for sure she was "tunneling" into an evW theory and I read it here. There was also some discussion on her using thicker metal for frustums and thought it might be related.
I was not familiar with his experiments either, the linked paper did not detail them. I was wrong saying that Nimtz used optical frequencies. The wiki link https://en.wikipedia.org/wiki/G%C3%BCnter_Nimtz#Experiments_related_to_superluminal_quantum_tunneling says they performed microwave experiments in the 1990's with prisms as their preferred arrangement.
The fact that Nimtz used microwave frequencies in his 1990's experiment makes eminent sense to me, because, as I said, it is very feasible to measure evanescent waves in the microwave range as opposed to the optical range.
Here is a sketch of the experiments conducted in the 1990's"
QuoteDiagram of the Nimtz and Stahlhofen double prism experiment. Photons can be detected behind the right-hand prism until the gap exceeds up to about one meter. Wavelength was 33 mm
This is 1.30 inches wavelength, which if referring to the free space wavelength, means a frequency of 9 GHz
notice the total internal reflection inside the prism at the left, and the evanescent wave on the surfaces of the prisms, as a horizontal line connecting the prisms, where it says "tunnel". I agree with the critics that this is a well-known effect in textbooks, explainable by Maxwell's equations, and I'm perplexed by his claim of superluminal speeds. I'm perplexed by his calling this effect "tunneling".
Surface waves (like evanescent waves) also occurs in solids as elastic waves (Lamb waves, etc.) and liquids. Nobody calls that "tunneling". Also as I explained, if the electromagnetic wave hits the surface exactly at the angle of total reflectance the extent of the evanescent wave is huge: near infinity (but it quickly diminishes for small angle deviations from this angle of total reflection). So, the fact that they were able to detect this at distances between the prisms of 1 meter = 30 times the wavelength, is due to the fact that their experiment was conducted at an angle very close to the angle of total reflectance.
I have a 1955-1962 book by the famous Stanford scientist Panofsky (that worked with Nobel Prize winner Luis Alvarez in the 40 ft long resonating cavity he made for his proton accelerator), "Classical Electricity and Magnetism" where this experiment, using prisms to measure evanescent waves is -very briefly- discussed.
EDIT: My initial wording of the Goos-Hänchen effect was terrible!.
Notice the fact that the total internal reflection in the left prism appears to go out of the prism if you follow the thick line. It really does not follow the thin line, the physical wave shifts inside the prism at the left, this is known as the https://en.wikipedia.org/wiki/Goos%E2%80%93H%C3%A4nchen_effect which is also well understood in textbooks (since 1947: F. Goos and H. Hänchen, Ein neuer und fundamentaler Versuch zur Totalreflexion, Ann. Phys. (436) 7–8, 333–346 (1947) ).
Is he claiming superluminal speed because of the Goos-Hanchen-Shift ?
Also I don't see a relationship of this to an EM Drive, (which has mm thick copper walls instead of prisms). -
#2774 by RERT on 11 Feb, 2016 14:12
-
Dr.Rodal reminded us a few pages back that unexpected gravitation/EM interactions haven't been entirely ruled out as explanations of any real EMdrive effect.
One related experiment which might be in-budget for DIY testers is to strap a (range of) inert/non-conducting weight(s) to the outside of the frustrum, and see if any thrust signal changes. The hypothesis being checked would be of some non-zero gravitational effect which the weights could 'feel' and add to/take away from the apparent thrust.
I don't think a negative result would eliminate GM/EM interaction, but any kind of positive result would be extremely interesting, even if not GM related. The test doesn't seem so hard.
No, I don't know which end of the frustrum, other than guessing the end with the highest fields!
R.
[Edited to remove square bracketed text destroying the formatting.] -
#2775 by rfmwguy on 11 Feb, 2016 14:17
-
Yes, this is where I was getting lost. evW propagation thru a metallic frustum I thought was a no-no...I'll PM shell, she's enlightened me before...I probably need to PM shell, thought for sure she was "tunneling" into an evW theory and I read it here. There was also some discussion on her using thicker metal for frustums and thought it might be related.
(snip)
Also I don't see a relationship of this to an EM Drive, (which has mm thick copper walls instead of prisms).
-
#2776 by Rodal on 11 Feb, 2016 14:23
-
Yes, this is where I was getting lost. evW propagation thru a metallic frustum I thought was a no-no...I'll PM shell, she's enlightened me before...I probably need to PM shell, thought for sure she was "tunneling" into an evW theory and I read it here. There was also some discussion on her using thicker metal for frustums and thought it might be related.
(snip)
Also I don't see a relationship of this to an EM Drive, (which has mm thick copper walls instead of prisms).
For copper walls, you would need either:
1) Copper thickness of 1 micrometer or less than 1 micrometer thin
or
2) Small holes or gaps in the frustum constuction.
Important for DIY experimenters to measure the field outside for safety considerations anyway and never assume that your frustum is free of holes and gaps: your health could be at stake -
#2777 by SeeShells on 11 Feb, 2016 15:16
-
Dr. Rodal,I probably need to PM shell, thought for sure she was "tunneling" into an evW theory and I read it here. There was also some discussion on her using thicker metal for frustums and thought it might be related.
I was not familiar with his experiments either, the linked paper did not detail them. I was wrong saying that Nimtz used optical frequencies. The wiki link I give says they performed microwave experiments in the 1990's with prisms as their preferred arrangement.
The fact that Nimtz used microwave frequencies in his 1990's experiment makes eminent sense to me, because, as I said, it is very feasible to measure evanescent waves in the microwave range as opposed to the optical range.
Here is a sketch of the experiments conducted in the 1990's"QuoteDiagram of the Nimtz and Stahlhofen double prism experiment. Photons can be detected behind the right-hand prism until the gap exceeds up to about one meter. Wavelength was 33 mm
notice the total internal reflection inside the prism at the left, and the evanescent wave on the surfaces of the prisms, as a horizontal line connecting the prisms, where it says "tunnel". I agree with the critics that this is a well-known effect in textbooks, explainable by Maxwell's equations, and I'm perplexed by his claim of superluminal speeds.
I have a 1955-1962 book by the famous Stanford scientist Panofsky (that worked with Nobel Prize winner Luis Alvarez in the 40 ft long resonating cavity he made for his proton accelerator), "Classical Electricity and Magnetism" where this experiment, using prisms to measure evanescent waves is discussed
Notice the fact that the total internal reflection in the left prism appears to go out of the prism if you follow the thick line. It really does not as the physical wave follows the thin line inside the prism at the left, this is known as the https://en.wikipedia.org/wiki/Goos%E2%80%93H%C3%A4nchen_effect which is also well understood in textbooks.
Is he claiming superluminal speed because of the Goos-Hanchen-Shift ?
Also I don't see a relationship of this to an EM Drive, (which has mm thick copper walls instead of prisms).
There is a relationship to the drive. It is occurring in the drive, also it is another piece of testing to gain data. I wrote this down in my lab book 6 months ago as you posted it to me when you and I were first talking about this effect. (same pic)
The question you stated.QuoteAlso I don't see a relationship of this to an EM Drive, (which has mm thick copper walls instead of prisms).
It will happen at microwave energies with conducting walls like in the cavity.
The observed effect of thrust or a pressure gradient with the drive hasn't been open to classical theories as to why it is happening. We thought we had some answers with invoking the Lorentz actions but that hasn't explained all the thrusts, we thought we had it in thermal heating and thermal deformation of the metals but that doesn't stand up to deeper scrutiny either because of the variety of different test beds.
I've stated that I intend to take this apart bit by bit piece by piece to test including our current theories of evanescent wave actions and to see if for some reason they don't follow our understanding of classical physics. I'm not trying to tear down but re-enforce our understanding of what is happening using physics as they stand. Paul March said (paraphrase here) "the anomalous thrust remains." NASA's EagleWorks is simply doing the same thing as I am.
I don't think I'm going to be in for any surprises but.....
-
#2778 by Rodal on 11 Feb, 2016 15:48
-
...
QUESTION: Shell, are you planning to measure surface evanescent wave fields on the exterior surface of the EM Drive? and if so how are you planning to measure them ? have you conducted such measurements already?
I've stated that I intend to take this apart bit by bit piece by piece to test including our current theories of evanescent wave actions and to see if for some reason they don't follow our understanding of classical physics. I'm not trying to tear down but re-enforce our understanding of what is happening using physics as they stand. Paul March said (paraphrase here) "the anomalous thrust remains." NASA's EagleWorks is simply doing the same thing as I am.
I don't think I'm going to be in for any surprises but.....
I do think that it is a good idea to measure them because I suspect that the EM Drive constructions (particularly DIY constructions) have gaps and holes through which the electromagnetic field can escape, and if they do so escape, they are a safety problem for those near the EM Drive experiments. -
#2779 by Rodal on 11 Feb, 2016 16:32
-
I confirm that the experiment by G. Nimtz and A. A. Stahlhofen was conducted at frequency of 9 GHz as I calculated based on the wavelength:Quote from: G. Nimtz and A. A. Stahlhofen
The experimental set-up is illustrated in Fig.1. We have investigated double prisms of Perspex with a refractive index n = 1.6 with microwaves at a frequency of 9.15 GHz, i.e. at a wavelength of 32.8 mm. The sides of the right triangle prisms are 0.4 x 0.4 m^2, which is of a macroscopic dimension for a quantum mechanical experiment. The experiment was carried out with a symmetrical beam path as sketched in Fig. 1. The beam has a perpendicular incidence at the first prism and is reflected at the Perspex/ air boundary under an angle of 45°, which is above the critical angle of total reflection. (The critical angle for the Perspex prism is 38.7°.) The dish antennas had diameters of 350 mm; the receiver antenna was movable parallel to the prism's surfaces. The microwave polarization was TM, with the electric field in the plane of incidence. The measured Goos-Hänchen shift in this experiment is of the order of a wavelength.
Also, as I correctly supposed, they measured the well-known Goos-Hänchen shift.
The prisms they used were made of Poly(methyl methacrylate) (PMMA), also known as acrylic or acrylic glass as well as by the trade names Plexiglas, Acrylite, Lucite, and Perspex, a transparent thermoplastic often used in sheet form as a lightweight or shatter-resistant alternative to glass.
Thus, Nimtz experiment consisted of the well known surface evanescent wave that takes place at angles greater than the total reflectance angle, inside acrylic thermoplastic.
They used an angle of 45°, which is above the critical angle of total reflection. (The critical angle for the Perspex prism is quoted as 38.7°).
Also notice that they used dish antennas with diameters of 350 mm (13.78 inches); the receiver antenna was movable parallel to the prism's surfaces. The microwave polarization was TM, with the electric field in the plane of incidence.
This experiment is similar to the one briefly discussed in the textbook by Panofsky, dating to 1955.
Also, as I expected, there is nothing "unusual" in this effect, or needing Quantum Mechanics, since such surface waves also take place in solid and liquid interfaces due to elastic waves (instead of electromagnetic waves), and they can be explained by wave theory:
the authors themselves confirm my expectation:QuoteThis universal tunneling time seems to hold even for sound waves (i.e. phonons) as measured by Yang et al. at 1 MHz and by Robertson et al. at 1 kHz in a sound tunneling experimental set-up
I find the claims of the authors about superluminal travel very perplexing since this effect is well known, it is discussed in most textbooks, and it can be simply explained.
There was NO copper sheet involved, the evanescent waves occur at the surface due to the difference in electric permittivity between the acrylic and air.
The fact that there are evanescent waves in the surface of the acrylic at angles equal or greater than the total reflectance angle is fully expected (this is discussed in most books in electromagnetism: Jackson, Collin, etc.). I don't see any possibility that this can occur with a fully sealed EM Drive with copper walls mm thick at ~2.45 GHz, since the skin depth is only ~ micrometer.
Even if one would have an EM Drive with a very thin wall of less than 1 micrometer I don't see how these surface evanescent waves even if they would occur would be able to explain the claims of EM Drive researchers of force/Power exceeding a perfect photon rocket.
