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 Crystal0.625” Diameter  X 6.0” Length 
PhotomultiplierR3991A (Hamamatsu) 
MechanicalDiameter (OD)1.36” 
Length (make-up)13.7” 
Weight3.0 lb 
End ConnectorsMicro-D Subminiature, 15-Pin 
MaterialAluminum Alloy (chassis), Tungsten (shield) 
PerformanceSensitivity0.35* 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 Temperature0°F to 350°F 
Survival Temperature-40°F to 400°F 
Vibration (3 axis) 50-1000Hz, Random20G RMS 
EnvironmentalHeat/Cool Rate, Max. 5°F per minute 
Shock (3 axis)1000G, 0.5ms, half-sine 
Power RequirementsDC Input Voltage17-48 VDC, 50VDC Max. 
Tool Current8-11 mA 
Output SignalNegative 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).