AeroTEM (Figure 1) Helicopter time-domain avionics system was developed by Aeroquest Company, which is a geophysical exploration method system based on the principle of central loop time-domain aero-electromagnetic method, with a single engine and multiple receivers, and the theoretical exploration depth can reach 500m m. In 2000, Aeroquest Company improved the system, mainly increasing the dipole moment of the transmitter, reducing the lowest fundamental frequency (to 30Hz) and introducing data flow. In mid-2004, Aeroquest Company began to develop a new generation of AeroTEM time-domain avionics system for helicopters. By 2007, the fourth generation AeroTEM time domain digital helicopter avionics system has been developed. See table 1 for the latest three generations of parameters. The new AeroTEM system has a detection depth of more than 600 meters, which can even be compared with the fixed-wing aircraft system.
Figure 1 AeroTEM time domain helicopter avionics electromagnetic system
(According to Laurie Industries)
The transmitting coil of AeroTEM system loaded by helicopter is 5m in diameter and consists of 8 turns of copper wire. The maximum emission current is 250A, and the peak emission torque of 40000Am2 can be generated. There are two receiving coils, one along the Z axis and the other along the X axis.
Table 1 aero tem performance parameters comparison of the last three generations.
The triangular current pulse (primary field) emitted by the transmitting coil propagates underground and produces a secondary field when it meets the detection target of the conductor. The primary field and the secondary field are received by the receiving coil and stored in the removable hard disk for post-processing. The transmitting coil, the receiving coil and the transmitting driving circuit are installed on a circular frame, and the transmitting coil and the receiving coil are 30m away from the ground and 40m away from the helicopter during flight. Cesium optically pumped magnetometer is installed in the cabin, and the receiving and transmitting coil is 10m. Data acquisition system and positioning system, such as GPS and radio altimeter, are installed inside the helicopter.
The symmetry of the system relative to the vertical axis makes the target sensitive to the heading of the pod, thus eliminating the interference response of other systems when climbing in rough terrain; Highly focused electromagnetic radiation surface, protruding underground electrical conductors, portable rapid measurement system, suitable for almost all geographical locations, even rugged terrain, rigid platform can provide good results; High-precision positioning and two-component recording are beneficial to direct sitting drilling; The superior early turn-off time is conducive to detecting weak conductive targets, and collecting data on time can understand shallow information; At present, the penetration depth of AeroTEM IV system is more than 500 meters, which is twice that of traditional frequency domain helicopter electromagnetic system. The highly concentrated coverage of EM system provides excellent description and characterization for underground conductors, which is superior to the more expensive large coil ground electromagnetic method. The system is highly portable, and can be easily disassembled and reassembled at any geographical location to realize economic transportation. It has the dual characteristics of frequency domain and time domain electromagnetic system.
Second, the scope of application and application examples
Mineral survey and structural survey of copper mine, polymetallic sulfide mine, gold mine, nickel-copper-platinum aggregate, diamond, iron ore, skarn ore body, oil and natural gas with a depth of 400 meters or more.
Three. sources of information
Air Canada Exploration Company. /netshow/sh100788/c152241.htm (website of Laurie industries)
www.aeroquestairborne.com