http://webcache.googleusercontent.com/search?q=cache:http://aip.org/tip/INPHFA/vol-7/iss-5/p24.pdf
*How does magnetic shielding work?* All EMI shielding materials are manufac- tured from high-permeability alloys that con- tain about 80% nickel; the alloys vary in the composition of their remaining metals. They are usually fabricated as foils or sheets and are baked at 2,000 °F in a dry hydrogen-rich atmosphere to anneal them. Annealing sig- nificantly improves a material’s attenuation, that is, its ability to absorb and redirect mag- netic fields. A shielding alloy works by diverting a magnetic flux into itself. The alloy redirects the magnetic flux away from the sensitive object and returns it to the north–south field. Although the field from a magnet is greatly reduced by a shield plate, the protec- tive alloy itself is attracted to the magnet, but with no ill effects. Closed shapes are the most efficient for magnetic shielding—cylin- ders with caps, boxes with covers, and simi- lar enclosed shapes are the most effective (see figure). Magnetic shielding materials offer a very- high-permeability path for magnetic field lines to travel through, directing them through the thickness of the shielding alloy and keeping them from going where they are not wanted. It is important that the shield should offer a complete path for the field lines, so that they do not exit the mate- rial in a place where they will cause unin- tended interference. *What is the difference between RF shield -* *ing and magnetic shielding?* Ra d i o-frequency (RF) shielding is required when it is necessary to block high- frequency (100 kHz and above) interference fields. RF shields typically use copper, alu- minum, galvanized steel, or conductive rub- b e r, plastic, or paints. These materials work at high frequencies by means of their high c o n d u c t i v i t y. Unlike magnetic shields that use their high permeability to attract mag- netic fields, RF shielding has little or no magnetic permeability. However, when they are properly engineered and constructed, magnetic-shield alloys become broadband shields that protect against both EMI and RF interference. On Fri, Oct 3, 2014 at 9:53 AM, Bob Higgins <[email protected]> wrote: > For an EM field to propagate, the electric and magnetic fields must be > coupled. Once you stop the electric field, the magnetic field will also be > stopped. At low enough frequencies, the penetration depth of the field > will allow some EM field to escape, attenuated by the propagation through > the metal. > > Even if SiC was used for the tubes, it would block most RF as SiC ceramic > is a conductor, but a poor one. SiC is an expensive ceramic to make in the > size of the hotCat and if Rossi were using this, it would probably price > his hotCat out of the market for home devices. I don't believe he is using > SiC in his hotCat - I believe the reactor core is stainless steel (as the > Penon report describes) welded closed at the ends of the coaxial tubes. > That doesn't mean he hasn't experimented with SiC. SiC is very hard to > machine and it would be challenging and expensive to produce a coaxial > reactor vessel (as shown in the Penon report) and seal its ends. > > Bob Higgins > > On Thu, Oct 2, 2014 at 8:05 PM, Axil Axil <[email protected]> wrote: > >> NMR is caused by the vibration of the non-zero spin vector of a nucleus. >> This vibrating nuclear spin produces a vibrating magnetic field. >> >> The point of a Faraday cage is that it's made of a conductor, which >> responds to electric fields. Both a strong magnetostatic (DC) and Ac fields >> are different, and will barely be affected by the Faraday cage. (The cage >> may have some magnetic properties, but that's not what makes it a Faraday >> cage, and it's unlikely to have a significant impact on magnetic fields.) >> >> On Thu, Oct 2, 2014 at 8:29 PM, Bob Higgins <[email protected]> >> wrote: >> >>> I have posted the cross-section of the hotCat as I have surmised it to >>> be constructed. The active medium is entirely in a hermetically sealed >>> stainless coaxial tube arrangement. The reactor vessel itself IS the >>> Faraday cage. It is not a part of the test, it is a part of the hotCat. >>> >>> Bob Higgins >>> >>> On Thu, Oct 2, 2014 at 6:21 PM, Axil Axil <[email protected]> wrote: >>> >>>> How do you know that a faraday cage is part of the test? >>>> >>>> On Thu, Oct 2, 2014 at 5:25 PM, Bob Higgins <[email protected]> >>>> wrote: >>>> >>>>> The 3.6 keV x-ray photons are easily detected with an x-ray >>>>> spectrometer such as the Amptek X-123SDD at >>>>> http://www.amptek.com/products/x-123sdd-complete-x-ray-spectrometer-with-silicon-drift-detector-sdd/ >>>>> . See their chart at this URL for the different window options that will >>>>> easily allow detection down to 1 keV: >>>>> http://www.amptek.com/products/c-series-low-energy-x-ray-windows/ . >>>>> I am hoping to get one of these some day. >>>>> >>>>> The bigger issue is that not much will make it out of the hotCat even >>>>> if that is the primary channel for conveying the heat. >>>>> >>>>> In the case of RF, I would expect almost none to escape the hotCat >>>>> because the reaction is in a Faraday cage. The RF that could penetrate >>>>> would have to be below 1 kHz. >>>>> >>>>> >> >
