Mu-Metal Faraday Cage?

These links have some of the better explanations and keep it fairly simple.

http://en.wikipedia.org/wiki/Faraday_cage

http://en.wikipedia.org/wiki/Mu_metal

Like in nature or engineering, a 'one-solution-fits-all' is rarely possible (it's all about compromise).

There is nothing in either sited link that would forbid the use of the conductive properties of the Mu-Metal from achieving a Faraday cage effect.

That is my issue. What is the basis for the claim?

While it is clear that a simple conductive material like copper or aluminum do not have the magnetic permeability of Mu-Metal alloys and therefore could not offer effective shielding against magnetic fields, there is no equivilent reason why a Mu-Metal cage could not perform both functions at least at low frequency (below 60hz) or in static electric field environments.

Sorry, I need a more substantive explanation and case. Just because won't fly with me.

Sorry.

So as I suspected there is overlap between the two (Mu-metal and Faraday cage), but it's specific to a frequency range. In my case I'm using the Mu-Metal to significantly reduce the influence of the magnetic field of the earth on my test device. However given the fact that the device operates with High Voltage DC I cannot see how it could not shield effectively against Coloumb force influence like a standard aluminum enclosure would also.

Don't keep it simple I can more than deal with complicated and if I can't I'm sure one of my PhD friends can. Why not ask them? Because I figured this was easier especially given the time critical nature of the answer.

Doing experiments as I type this. Turbopump is running and pressure is dropping.

In my case I'm using the Mu-Metal to significantly reduce the influence of the magnetic field of the earth on my test device.

Are you shielding just the sensitive magnetic sensor or the whole electronic package. I have seen the whole enclosure of sensitive equipment used as the Faraday shield and the equipment itself operated of a self-contained battery within the shield to eliminate the 50/60Hz power supply noise problem.

Can you describe your application a little more.

However given the fact that the device operates with High Voltage DC I cannot see how it could not shield effectively against Coloumb force influence like a standard aluminum enclosure would also.

Again, if you don't have any high frequency sources you should be fine, if however you have a large switch mode power supply producing the high voltage DC and switching in the RF range (which switch mode power supplies do) then the Mu-metal cage alone may not provide adequate attenuation of this RF (KHz) field. There is no reason you cannot place an additional Faraday cage made of copper or aluminium over either the sensor or the RF-producing source (even a metal partition or EMI spray-on conductive zinc works well).

Don't keep it simple I can more than deal with complicated

The main reason is I am working at the moment.

Hi Jack, that was me giving the GA but not able to type a comment at the time.

GA because the link you posted has all the applicable information the OP needed and even the 'new needs' now revealed.

Your link (underling is mine)

What is the difference between RF and Magnetic shielding?

Radio frequency (or RF) shielding is required when it is necessary to block high frequency - 100 kilohertz and above - interference fields. These shields typically use copper, aluminum, galvanized steel, or conductive rubber, plastic or paints. These materials work at high frequencies by means of their high conductivity, and little or no magnetic permeability. Magnetic shields use their high permeability to attract magnetic fields and divert the magnetic energy through themselves. With proper construction, magnetic shielding alloys have the ability to function as broadband shields, shielding both rf and magnetic interference fields.

I.e. You covered the OP's question - to know how, on the last, he just had to read on.

Well done, and at post #4 - so I hope someone else will vote you up to the deserved Full GA.

A few minutes ago I finished doing a simple test were I used my Mu-Metal material and I rolled it around a polycarbonate tube. It's got a self adhering backing. In either case I used my FW Bell 7080 Gauss tesla meter and made sure I used the included Mu-Metal chamber to zero out the meter probe. After doing that I removed the probe from the chamber and it measured ~.40 Gauss in the environment. That is consistent with my area in Orlando FL. With the included zeroing chamber it dropped to .06 Gauss, with my basic Mu-Metal chamber that I made, it dropped the magnetic field by the same .06 Gauss.

Next I'm going to use this home made chamber to test for it's RF and Static electric shielding properties. How much you guys want to bet it does the job just like a standard aluminum Faraday shield.

Are you taking the tin foil hat design to a whole new level being newer versions of the government/alien brain implants are now no longer impeded by old aluminum foil hat design?

I think this conversation is above your level. You might want to move on to another topic.

Easy Grav01, just a bit of humor. You have to expect some on an open forum like this. I have seen tcmech provide some accurate information in the past. Just because a comment may seem flippant doesn't mean you should alienate the commenter, you might miss out on just the information you need from the correct perspective.

I believe he was just trying to get you to explain what you are working on, I too am curious. And just because your top is probably above my level doesn't mean I might not gain an insight that will help you with my questions.

I observe to learn.

Drew

Thanks. Humor it was.

I am actually learning more about Mu-metal and its real practical applications from people mentioning it and explaining what its for and can do just as is being done here.

As has been stated before most metallic materials when properly designed have good EM and RF blocking abilities but unfortunately being the electromagnetic spectrum encompasses such an incredible wide range of energy forms and relative ways that it interacts with every substance to have a single material that covers everything and at all reasonable energy levels is a very big order to expect something to fill.

To me its like saying I need a thermal insulation that covers all levels of heat from absolute zero to nuclear reaction and works in conductive, convective, and radiated heat applications as well.

But I am rather surprised the foil hat guys don't have more to say about Mu-metal though. Just think of all the new levels of crazy it could work with!

Sorry I took your answer the wrong way.

Sorry guys. My research deals with Advanced Electric Space Propulsion. I have a propulsion system that operates at much higher voltages than other Electric Propulsion systems like XIPS or Hall Thrusters. This presents a unique set of challenges when operating in vacuum. For example as I type this I'm pumping down my chamber again with a new test device. I covered it with a layer of Ultraperm 80. Given my high voltage, but very low current and the fact that it's all DC in nature I think I can succesfully use the Ultraperm 80 as both an effective magnetic field shield and Faraday cage.

The issue is mirror charges and or Coulomb forces on the wall of the chamber as a result of the high voltages being used. These forces could give false positive thrust results, which could account for the high efficiency that the test device keeps showing.

I looked into the material and I don't think that the high permeability of the Ultraperm 80 has affected the Permittivity of the metal sufficiently to prevent it from acting as an effective Faraday cage at the applied DC voltages.

Sorry if I was out of line earlier, but I really needed a real opinion.

Wow...this is intense science. I look forward to reading more about it. Would you be interested in starting a blog about your work? I don't want to pry into any classified research, but really enjoy this aspect of propulsion.

My area of expertise is more mechanical, I had an idea about how to use the g-force of acceleration to provide electricity for zero gravity systems.

I hope you feel at ease here and continue participating in this online forum, I am still fairly new here but have encountered various personalities that ranged from familial to caustic. I apologize of my criticism of your comment seemed brusque.

Drew

My work is not classified, but in the circle I travel you don't bite the hand the feeds you. However I made sure I retained publishing rights on the work and they actually want me to go public with the work in the near future. That would serve their purpose. We have about 5 seperate teams wanting to confirm the results of the work 3 government 2 private that work with the government people involved.

I won't lie the work is considered new physics and a real breakthrough if confirmed. Recently filed for an SBIR with DoD that shows the general scope of the work and expands on it if approved.

I tried the Ultraperm 80 in hard vacuum and it's a nasty outgassing source. I recently solved a similar kind of problem with a previous device so I'm going to have to seal the entire Ultraperm 80 material so that it's not directly exposed to vacuum.

Common problem with my research is adapting the devices to operate in both air and vacuum. Has not been easy, but I've pulled it off several times now. Replication is the only way this work can be confirmed. Have strong data and getting more every day. Made the entire tests stand and process stupid simple so that alternative force mechanisms could be easily isolated and eliminated.

Thanks for the comments, very useful and actually gives me a different perspective on the issue. Based on this, I have a better understanding why you would not use one as a solution for both, even if you could. So in my case I would make two distinct tests, one using aluminum as a Faraday cage, the other Mu-metal to only deal with magnetic effects if they exist at all.

Thank you, this was very helpful.

mu-metal works by "absorbing" the energy in the field? Aluminum and copper work by "reflecting" the field?

You're kidding, right?

I don't know which is most disheartening; this crock of you-know-what by Guest and the fact that Mr. Space Propulsion bought it outright, or the number of accolades it garnered from some in this community.

Question for Mr. Space Propulsion: these PhDs you know, are their degrees in Voodoo Physics? You certainly had no use for the excellent links provided by others here.

Mystery Guess,

Being a skeptic is easy, all you have to do is nothing. If you have something constructive to say please do so. Feel free to contribute to the conversation in a productive constructive matter and share your knowledge with us.

Put it another way, I can't fix it if I don't know what's broke. So help us all out here.

"If you have something constructive to say please do so."

Read

the

links.

By the way you are correct Mu-Metal does not absorb the energy of the magnetic field, it simply channels the magnetic field around and away from the object you are trying to shield from exposure. That is why geometry is very important in achieving a good shielding effect.

In my case there is enough overlap between this property and the polarization rate of the Ultraperm 80 to allow me to use it as both a Faraday cage and for magnetic shielding, but I've decided that it's better to just put a Mu-metal shield inside an aluminum Faraday cage.

"By the way" the proper order is read and digest then if justified, eruct.

You're wasting a lot of time by doing it backwards.

And no - you haven't quite grasped the difference especially the structural side.

Though many have tried to tell you: read the links.

Upon reading this thread in its entirety, one's impression is that the OP is merely impervious to good advice. In persisting to offer the OP guidance, one gets the uneasy feeling that one is essentially 'throwing pearls before swine.' The OP evidently prefers wandering about in the dark to taking the collective hand of his experienced guides.

Mystery Guest

I've read the links and my current design is consistent with their advice.

As I stated I'm now using two separate shielding, Aluminum as a Faraday cage and Ultraperm 80 for magnetic shielding. If I missed something feel free to point it out.

I did, but you obviously know something that I'm missing. Want to share? Specifics would be nice.

"Want to share? Specifics would be nice." <sigh> - you're a hopeless case.

Nevertheless

Most advice above has been from the point of view of keeping a field out of a space or the effects of a field contained. Not the forces between shield and field normally dealt with by fasteners

If your high d.c. voltage is creating a field, that field will be attracted to the shield.

If that shield is constructed in a manner than allows it to polarize, that shield is attracted to external objects just as the unshielded field was - though the vector may change. I.e. the wrapping around a polycarbonate rod might produce a horseshoe magnet (at the joint) or a bar magnet (ends of tube). (see; spikes at edges - above)

Another thing with Mu-metal is if you form it to a significant extent - you must re anneal it to restore permeability. See Lyn's link for methods.

But overall - test design wise - I'd say what you want to look at is not so much 'shielding' but magnetic symmetry in your test environment. As asymmetry will give an asymmetrical attraction (thrust)

I think I need to clarify something about my device. While it does operate at high voltages, the current never rises above 2 microAmps. So all I'm trying to shield it from is the influence (if any) that the magnetic field of the earth could contribute to the observed effect.

I've tested the geometry of the Mu-metal shield which is cylindrical, for it's ability to reduce the strength of the magnetic field of the earth and is equal to the zeroing out chamber included with my F.W. Bell 7030 Tesla/Gauss meter I have. I'm not sure how much better I can get.

I'm simply not worried about the magnetic field that is produced by 2 micro-Amps of current.

RF is not an issue for me, neither is A/C of any kind. Strong magnetic fields are not present. There is only a relatively static magnetic field that never rises above 1.22 Gauss in the chamber and the ambient magnetic field is ~.48 Gauss.

Signed,

Hopeless. :)

A force usually has both magnitude and direction

You appear to have a change in magnitude - where are they pointing?

Is it 'worst case' significant, depends largely on the magnitude of the force you are measuring - no I don't need to know, it's just a thought for you to explore.

(much improved )

By the way, though I have never done it, but the guys above may have, or know why not to, I don't see why you couldn't copper plate the shield and have a broad band result.

The force is also small, but I'm measuring the difference between what I see with and without the Mu-metal and Faraday shielding. Up to this moment there has been no change in force, but I will take what you said into consideration.

The force is axially through the device in the horizontal plane and the device is setup in a level pendulum configuration at the center of the chamber.

Thanks for the advice.

As someone above said the bigger chamber may make things easier - but it may also demonstrate a new set of variables.

A thought is to go the other way, by introducing a known large effect in each spectrum (RF, Gauss, and combo).

If you can make these variable and reversible - if there is a change then you know what to look for - and you have a benchmark to test/develop/evaluate your shielding against

If there is something external acting - you would see a peak or null with a reversal.

Happy thinking.

Hi,

Ultra-perm is not outgassing more or less than typical similar alloys except you have dirty surfaces or not vacuum-grade material.

Vacuum-grade is equivalent to zero porosity!

There is more than one problem with any of the high permeability alloys:

1. Annealing below hydrogen is needed to convert any iron oxide to iron and water. If not done long enough some of the water will remain inside, slowly diffusing out at UHV conditions.

2. Cleanliness and bakeout is a major issue in UHV applications. You have to clean with high purity fluids and still will leave a lot of contaminations on the surface. So you have to bake any material at 450°C for 3 to 6 hours to get rid of the surface water and other contaminants. (Any material!)

3. Mu-Metal has a low saturation flux density of only 0.7T, compared to soft iron at 2T. Soft iron is not more expensive if compared to Mu-Metal and similar alloys but will need a protecting (vacuum deposited) coating as it is very susceptible to corrosion, especially if very clean.

4. Mu-Metal and most other high permeability materials are very very susceptible to stress and strain: they loose a considerable part of the high µ!. So it is much simpler and much more cost effective to switch to a low-carbon grade steel. As low carbon in steels is equivalent to strength you have an easy indicator. There is steel sheet for deep drawing purpose with ultimate tensile strength of 120 down to 80 N/mm², these are beautifully matching your needs and not very sensitive to stress and strain.

If you cover the steel with a thin Al-film it may do best. Think about explosive cladding too.

I doubt if you really need UHV testing (10exp-9 mbar and below) as this atmosphere is not existing near Earth or satellites: too much outgassing!

Have success

RHABE

UltraPerm can be supplied with an adhesive backing, if that is being used it will be the adhesive outgassing causing problems.

I suspect that you are correct and that when I removed it I simply did not do a good enough job.

Thanks for the information. Assuming you're correct than there is a second outgassing source that is much more likely and I will address in the next test.

Thanks

If you're interested in zeroing out the earth's field see this:

http://en.wikipedia.org/wiki/Helmholtz_coil

It could be used in addition to a copper faraday cage.

Good idea and in my case I could do this kind of testing in atmosphere just as an extra test.

Are you familiar with the work (Now moved to China because of financing) of a Microwave Engineer who built a high gain SWR microwave cavity and demonstrated a net thrust from a closed cavity system?

I think the gentleman coined the term EM Drive.

http://www.emdrive.com/IAC-08-C4-4-7.pdf

08 – C4.4.7 MICROWAVE PROPULSION – PROGRESS IN THE EMDRIVE PROGRAMME Roger Shawyer C.Eng. MIET. FRAeS

SPR Ltd, United Kingdom sprltd@emdrive.com

Yes I know about the EM Drive and so do the people who are confirming my work. The only reason there is interest in my approach is because it shows efficiencies in excess of 24mN/W. The EM Drive concept can't reach that degree of efficiency, yet.

Also my system is very small, has no moving parts, no need for cooling or complex subsystems. Still this is all just unsupported claims until I publish and others confirm it.

The Faraday cage is just another attempt by me to show that the effect is not conventional in nature as is the Mu-metal shielding. I technically don't need the Mu-metal test, since I have run test with the device under a very strong magnetic field in the 1000 plus Gauss range and above and it has not diminished or increase the performance of the test device. The Mu-metal test is just so I can say I did it and to make sure nothing new or unexpected happens.

The Faraday cage test is just a repeat of air test and should not change the results, but again I like to make sure of that.

Well the best of luck and science to you grav01, please know that TPTB have a unique power to sequester your work behind closed doors via the National Secrecy Act and I hope you have a redundant backup on a HD somewhere.

I had a good friend who worked at LLL and Sandia for some years, he told me of a similar line of work for a time. He worked on one project where he described an effect he called 'discrete mass variance using electrical current' along the lines of reverse engineering an unknown source sample that was made of layered composite of aluminum/bismuth and diamond as the dielectric.

There was a security detail that followed "the sample" through each and every test collecting copies of the data and documents as they were done over the 12 weeks of testing at LLL.

Anyway, keep your work in the open as much as possible with a good way to disseminate in case someone wants your work to go 'black'.

Keep us informed and thanks for your work and efforts.

Thanks for the advice. We are doing everything possible to keep the work from going black. Even some in government are helping keep it public.

Still there are many test still ahead and hopefully publication in a few months,then anyone can take a shot at the work.

Grav, considering what you are testing for (removing repulsion forces) your best bet might be simply space. Basically the larger the chamber that you put your device into, the less repulsion can be felt/measured from the electromagnetic fields. Since the field that you are worried about decays with the square of the distance from the source (Coulombs law), even a little extra space can make a difference.

Another note that you might already realize, mu-metal works by moving the field from the center of the plate, to the edge of the plate. This means that if you have a seam in the middle of the chamber, or edge in the plate that is turned inward, you will have a massive spike in the magnetic field at that line. This site has some good tips for working with mu-metal and sells some other similar materials: http://www.lessemf.com/mag-shld.html

Good luck with your testing.

Good points. As for the space, in 2003 I did a tests in a 5 foot diameter nasa vacuum chamber. It worked then also. After my own testing is done, one of the parties that is going to run confirmation tests is going to use an 8 foot diameter chamber. It should work, but you never know until you do it.

As for the Mu-metal advice, thanks.

Just wanted to let everyone know that the outgassing was being caused by glue some left over glue on the back of the Ultraperm 80. At the end it took MEK and a spatula to remove it all off. After it was all removed I used Alcohol to clean the Ultraperm from any remaining contaminants.

Thanks for the tip.

Are you a Federal Contractor? Yeh, I thought so. So was I until I finished my Doctorate. Now I actually understand what these fine gentlemen have been trying to tell you.