Once in a great while, we have a series of events where our machines
with beam scanning functions in them will all be steered out of place
enough to trigger alarms and shut the units down.
It does take a lot of magnetic disturbance to force these out of
alignment, but there is no other equipment adjacent, on the roof nor in
the ground. This area of operations are on ground level cement slab and
the roof is tin with nothing but static vents. Power feed transformers
are far away.. There was no near by strikes which has never cause this
in the passed.
The strange thing is, we had to wait ~ 20 mins for a restart because
we kept on getting an error in steering, on all the machines, then it
finally cleared up..
All these machines are independent of each other..
Is there any geological events that can take place to cause this in the
ground or maybe solar charge of some kind? It's almost like some one was
hanging a large magnet over our plant.
Jamie
solar flares cause massive disturbances to the earth's magnetic field.
Take a look at the Noise Floor of the Earth's Field:
<
http://www.vlf.it/naturalnoisefloor/naturalnoisefloor.htm>
the field noise data cmoes ffrom actual meaurments of sites
From paper, here is its bibliography:
1. E.L. Maxwell and D.L. Stone, "Natural Noise Fields 1cps to 100kc",
IEEE Transactions on Antennas an Propagation, Volume AP-11, Number 3,
pp 339-43, May 1963.
2_ D.A. Chrissan, A.C. Fraser-Smith, Seasonal Variations of Globally
Measured ELF/VLF Radio Noise, Technical Report D177-1, Stanford
University Dept of Electrical Engineering, STAR Lab, December 1996.
3_ R. Barr, D. Llanwyn Jones, C.J. Rodger, "ELF and VLF radio waves",
Journal of Atmospheric and Solar-Terrestrial Physics, Volume 62, Issue
18, pp 1689-1718, November 2000.
4_ Kenneth Davies, Chapter 9, Propagation of Low and Very Low
Frequency Waves, Ionospheric Radio Propagation, New York, N.Y., Dover
Publications, Inc., 1966.
5_ M. Balser and C.A. Wagner, "Observations of Earth-ionosphere cavity
resonances", Nature, Volume 188, pp 638-41, 1960
Magnetic fields are insidious, once created you can't destroy them,
simply redirect them. And, low frequency are the worst, because they
penetrate EVERYTHING! Using mumetal can get expensive, and if not done
properly can easily exacerbate the problem by 'sucking' in magnetic
fields and actually intensifying them locally, so even that type of
shielding must be done carefully.
from those charts:
at 1 Hz the noise spectral density is 'normally' 1pT/rtHz, and it has
a 1/f distribution [I think]
at 0.01Hz it has climbed to over 1nT/rtHz.
If your e-beams are low speed, circa 10-20kV and the run path is long,
it doesn't take much field to deflect the beam over 100nm down at the
target, which in today's geometries is HUGE!
Has anybody produced the calculations for you? It should be part of
your equipment's performance spec - specifying the operating ambient
fields that are allowed. Then it'sup to you to prove your fields are
less than that.
Anyway, the number in those charts is 'average' which means during
solar storms it can easily go above 10X that value - for days! and
even into the 100X for short periods.
Do you have ambient magnetic field instrumentation monitoring the
fields? They are purchaseable items.