High Temperature Telemetry Gamma Ray Cartridge (HTGC*)
Description
The HTGC had a gamma-ray detector that was made of a NaI crystal, a photo multiplier tube, a high-voltage generation circuit, and a preamplifier of the gamma-ray pulse, all built in one package. The number of output pulses from the detector was counted at a rate of 8 Hz, and the count sent uphole. Housed in a heatsink and dewar flask that allowed operations in high-temperature environments (260°C), this tool also had a 31-pin upper and lower head asset and was combinable with any standard 3.375-in tool without additional adaptors. The data acquisition software could not distinguish between the tools, but the HTGC had the correct length and measure point and gamma-ray response for the flasked tool.
The HTGC was deployed at the top of the triple combo tool string on two sites during ODP Leg 193.
Tool Specifications
| Temperature rating | 500° F (260° C) |
| Pressure rating: | 25 kpsi (172 MPa) |
| Length: | 10.7 ft (3.26 m) |
| Weight: | 265 lbs (120 kg) |
| Diameter: | 4.75 in (12.1 cm) |
Measurement Specifications
| Range: | 0-2,000 GAPI |
| Accuracy: | 5% |
| Vertical resolution: | 12 in (30.48 cm) |
| Depth of investigation: | 2 4in (60.96 cm) |
| Logging speed: | 1,800 ft/hr (549 m/hr) |