Large airborne time-domain electromagnetic transmitter coil system and apparatus
An airborne time domain electromagnetic survey system is provided. The system and apparatus of the present invention are able to address the interest in exploring base metals and uranium deposits at depths approaching 1 kilometer. It encompasses a transmitter coil having a large magnetic dipole moment, flight stability, which is light weight, compatible with small helicopters, and can be transported, setup and repaired in the field. It is of a semi-rigid modular structure that can decrease the incidence of damage or breakage during take-off or landing in rough terrain.
1. An airborne time domain electromagnetic surveying transmitter coil assembly, comprising:
(a) a transmitter section including
(ii) a transmitter coil; and
(iii) a semi-rigid modular polygonal transmitter coil frame supporting the transmitter coil, the transmitter coil frame having straight frame sections that are joined at corners of the transmitter coil frame by, joints permitting the straight frame sections to at least partially rotate about long axes thereof enabling the shape of the transmitter coil frame to adjust during landing contact with a ground surface to reduce stress on transmitter coil frame; and
(b) a suspension assembly for towing the transmitter coil frame behind an aircraft, the suspension assembly supporting the transmitter coil frame at a plurality of spaced apart locations.
2. The transmitter coil assembly of claim 1 wherein the transmitter coil frame straight frame sections are tubular sections, the transmitter coil extending inside the tubular sections.
3. The transmitter coil assembly of claim 1 including a plurality of connecting ropes that each extend outward from a common hub to a respective location on the transmitter coil frame.
4. The transmitter coil assembly of claims 1 wherein the suspension vertical height at a leading side thereof than a trailing side thereof thereby supporting the assembly has a shorter transmitter coil frame in a substantially horizontal position at a desired flight speed.
5. The transmitter coil assembly of claim 1 wherein suspension assembly comprises a tow rope for attachment to an aircraft and a plurality of suspension ropes, the suspension ropes each having an upper end attached to an end of the tow rope and a lower end connected to a respective location of the transmitter coil frame.
6. The transmitter coil assembly of claim 5 wherein the lengths of the suspension ropes attached to a trailing portion of the transmitter coil frame are longer than the suspension ropes attached to a leading portion of the transmitter coil frame.
7. The transmitter coil assembly of claim 1 wherein the joints at the corners of the transmitter coil frame are lubricated.
8. The transmitter coil assembly of claim 1 wherein the joints at the corners of the transmitter coil frame are each formed by a male portion of one transmitter frame sections received within a corresponding female portion of another transmitter frame section.