DDG Duel Detector Gamma Tool

DDG

Directional Gamma Tool

DDGThe new CBG Dual Detector MWD Gamma tool for Azimuthal Geosteering consists of two opposed, tungsten-collimated shielded Nal(TI) scintillation detectors housed within a single ruggedized assembly.  Each detector contains its own set of electronics for powering its photomultiplier tube and processing the detected gamma signals.

Two 72° “windows” are machined along the length of the Tungsten shield positioned 180° apart from one another.  The eccentric tungsten shielding has a 0.23” maximum thickness that provides the highest front to back gamma count ratio.  It is designed to maximize gamma rays entering the crystal through the window while effectively blocking them from penetrating the non-window area of the crystal.  This unique shielding design and dual detectors effectively doubles the too sensitivity while maintain the directionality.

The DDG supplies an output signal from each detector for processing in a customer supplied controller.  Power and GND are input to either MDM connector.  Output counts from each detector can be individually processed or summed together.  In addition, either tool can be turned off if a problem is detected by the controller.

DDG

Directional Gamma Tool

DDGThe new CBG Dual Detector MWD Gamma tool for Azimuthal Geosteering consists of two opposed, tungsten-collimated shielded Nal(TI) scintillation detectors housed within a single ruggedized assembly.  Each detector contains its own set of electronics for powering its photomultiplier tube and processing the detected gamma signals.

Two 72° “windows” are machined along the length of the Tungsten shield positioned 180° apart from one another.  The eccentric tungsten shielding has a 0.23” maximum thickness that provides the highest front to back gamma count ratio.  It is designed to maximize gamma rays entering the crystal through the window while effectively blocking them from penetrating the non-window area of the crystal.  This unique shielding design and dual detectors effectively doubles the too sensitivity while maintain the directionality.

The DDG supplies an output signal from each detector for processing in a customer supplied controller.  Power and GND are input to either MDM connector.  Output counts from each detector can be individually processed or summed together.  In addition, either tool can be turned off if a problem is detected by the controller.

DDG Specifications

Detector Nal(TI) Scintillator Crystal X2 0.725” Diameter  X 4.0” Length
Photomultiplier X2 R3991A (Hamamatsu)
Mechanical Diameter (OD) 1.40”
Length (make-up) 22.17”
Weight 5.5 lb
End Connectors Micro-D Subminiature, 15-Pin
Material Aluminum Alloy (chassis), Tungsten (shield)
Performance Sensitivity 0.30 CPS/API (decreased due to Tungsten shield)
Accuracy +/- 5% to 300°F
+/- 10% to 350°F
Max API @ 5% PPU error 15,000 API
Thin-Bed Resolution (8” hole Diameter) 8.8”
Environmental Operating Temperature 0°F to 350°F
Survival Temperature (reduced accuracy) -40°F to 400°F
Heat/Cool Rate, Max.  5°F per minute
Vibration (3 axis) 30-1000 Hz, Random 20G RMS
Shock (Z axis) 500 G, 0.5 mSec
Shock (X or Y axis) 1000 G, 0.5 mSec
Power Requirements DC Input Voltage 17-48 VDC, 50VDC Max.
Tool Current 18 mA – 22mA
Output Signal Negative Pulse +5V to GND, 5 uSec width

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