DGA Focused Gamma Tool

DGA

Directional Gamma Tool

DGAThe DGA, Directional Gamma Tool, is a Tungsten-collimated version of the NGT-T gamma tool.  These tools are sometimes referred to as “focused” or “shielded” gamma tools.  In this design a 67° “window” is machined along the length of the Tungsten shield that surrounds the crystal/phototube detector.  Only gamma ray entering from the formation through this window can be detected and counted.  When aligned with the tool face or other physical reference, the DGA indicates the direction from which gamma ray energies originate.

The DGA is interchangeable with the standard NGT-T gamma tool.  It is same overall length and diameter.  Because of the required thickness of the Tungsten shield, the Nal(TI) scintillator crystal is of a smaller diameter.  The length is increased to 6.0” however, to deliver an equivalent volume of crystal material as in the NGT-T to provide maximum sensitivity.

DGA

Directional Gamma Tool

DGAThe DGA, Directional Gamma Tool, is a Tungsten-collimated version of the NGT-T gamma tool.  These tools are sometimes referred to as “focused” or “shielded” gamma tools.  In this design a 67° “window” is machined along the length of the Tungsten shield that surrounds the crystal/phototube detector.  Only gamma ray entering from the formation through this window can be detected and counted.  When aligned with the tool face or other physical reference, the DGA indicates the direction from which gamma ray energies originate.

The DGA is interchangeable with the standard NGT-T gamma tool.  It is same overall length and diameter.  Because of the required thickness of the Tungsten shield, the Nal(TI) scintillator crystal is of a smaller diameter.  The length is increased to 6.0” however, to deliver an equivalent volume of crystal material as in the NGT-T to provide maximum sensitivity.

DGA Specifications

Detector  Nal(TI) Scintillator Crystal 0.625” Diameter  X 6.0” Length  
Photomultiplier R3991A (Hamamatsu)  
Mechanical Diameter (OD) 1.36”  
Length (make-up) 13.7”  
Weight 3.0 lb  
End Connectors Micro-D Subminiature, 15-Pin  
Material Aluminum Alloy (chassis), Tungsten (shield)  
Performance Sensitivity 0.35* CPS/API (decreased due to Tungsten shield)  
Accuracy +/- 5% to 300°F
+/- 10% to 350°F
 
Thin-Bed Resolution (8” hole Diameter) 8.8”  
Operating Temperature 0°F to 350°F  
Survival Temperature -40°F to 400°F  
Vibration (3 axis) 50-1000Hz, Random 20G RMS  
Environmental Heat/Cool Rate, Max.  5°F per minute  
Shock (3 axis) 1000G, 0.5ms, half-sine  
Power Requirements DC Input Voltage 17-48 VDC, 50VDC Max.  
Tool Current 8-11 mA  
Output Signal Negative Pulse +5V to GND, 5 uSec width  

* Counts are collected with gamma tool mounted within standard BeCu pressure barrel, (OD 1.875″, ID 1.500″).  API Calibration performed with AEA Technology, QSA Inc., KUTh Field Verifier #188074, S/N 255 Radionuclides: K-40(11.7%), U-238(90 ppm), Th-232(40 ppm).

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