Info about the MEG core's hysteresis curve
Recently I had a phone conversation with a serious MEG experimenter who shared with me some information about the MEG core that apparently comes from a source close to the Bearden team and so with his permission, I am sharing this information with you. The source ... the MEG experimenter who I have great respect for ... wishes to remain anonymous. Below is the info:
A while ago, it was brought to my attention that the standard core needs to be processed so that the hysteresis curve is "square". This is why Tom Bearden says that any lab with $100k of equipment can replicate the MEG. That $100k of equipment performs the necessary processing for the core. A square hysteresis curve means that the magnetization of the core requires a strong coercive force (the external field trying to reverse the polarity of the magnetic domains in the core) before the core magnetic field reverses direction.
I believe it is this sudden reversal of the core's magnetic direction in essentially an avalanche that provides the large output of the MEG. Because the reversal requires a finite time, the switching frequency of the drive flux is adjusted so that it occurs just as the core completes its reversal. The output voltage then is a square wave because V = dB/dt ( V is the voltage, dB is the change in the core's magnetic field, dt is the time of the change of the magnetic field) and the driver keeps the external B changing as quickly as the core can change direction.
Metglas may be willing to provide information about annealing or they may even be willing to perform custom annealing for a standard core to provide different hysteresis performance. I have not made this inquiry since I do not have knowledge of materials processing nor the equipment required to do so. To me, the processing of the off-the-shelf core is one of the secrets of the MEG. Clearly it is not simple because Dr. Bearden says that the development team has very few working prototypes.
- This is not necessarily new news to some people. If you really think the critical factor is the B/H curve then get a bunch of small strip wound toroidal cores and look for a resonance ring coming from the core. For this you will want to use a small number of turns because you could otherwise get ringing from the inter-winding capacitance.
You don't need a lot of expensive equipment. Just a scope, signal generator, and MOSFET driver setup. My lab has about 10 different strip wound materials for testing and I paid about $10 each for the cores.
However, at this point in my research I think we are dealing with a standing wave condition that will work with any magnetic material. For producing the effect at lower frequencies you need a lot of turns and careful tuning.
--- In MEG_builders@yahoogroups.com, "mayerstan" <StanMayer@...> wrote:
> Recently I had a phone conversation with a serious MEG
> experimenter who shared with me some information about the MEG core ..... <remainder of this snipped by moderator for brevity>