The original experimental scheme required the electrical field to
be planar to within 10
nanoradians to achieve the goal sensitivity of 10-24 e-cm.
Newer schemes, using, for example, a central electric field structure with
the beam circulating in both directions, relax the planarity requirement appreciably. However, it is still
necessary to monitor the direction of the E field to the order of microradians
or less, and to establish the effect of known changes
generated in the tilt of the E field.
The Jones differential capacitor device was suggested by
Farley who knew of the work of his fellow Fellow of the Royal
Society. (See, e.g., Journal of Physics E: Scientific Instruments 1973, Vol 6, p 589.) The intrinsic
sensitivity of this instrument appears to
be limited only by quantum mechanical considerations; sensitivity
better than 10-10 radians was demonstrated decades ago.
The differential capacitor approach offers extreme simplicity,
great sensitivity, and modest cost. The first development phase
is to incorporate modern electronics, and to demonstrate
sensitivity of 100 nanoradians, sufficient to observe earth tides
at BNL. The second development phase will explore the use of
modern materials unavailable when the device was first developed almost a half
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