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Model 90100
Operators Manual
1-4
Recommended Operation Conditions
Source Distance: 100 cm
Collimated Field Size: 25 × 25 cm
Source Dose Rate Range: 50 to 500 rads/min
Nominal Ion Chamber Characteristics
Wall and Window Material: Continental Polymers ACRYCAL-CP or equivalent
Window Area Density: 600 mg/sq cm (0.51 cm acrylic plastic)
Window Transmission: 95% for 662 keV photons; for electrons, transmission through window occurs
above 1.5 MeV.
Sensitivity: 3.52 R/nC at 22°C and 760 mm Hg
Active Volume: 0.93 cc ±5%
Active Diameter: 1.162 cm
Active Cross-Sectional Area: 1.06 sq cm
Collector-to-Bias Separation: 0.44 cm
Ion Transit Time: 0.418 ms @ bias voltage of 300V
Collection Efficiency: >99% at 500 rads/min pulsed; >99.9% at 500 rads/min continuous
Leakage: Less than 0.5 pA over the full operating temperature range
Ion Chamber Factory Calibration
Method: Each of the 5 ion chambers within the detector array is calibrated by comparison with a
reference standard ion chamber in a Co
60
beam. The comparison is performed in free air and results
in an R/nC Calibration Factor for each of the five ion chambers.
Comparison Standard: 0.6 cc NE Farmer Probe with 3 MeV buildup cap.
Uncertainty: 2.5% using IEC/NIST guidelines.
Mechanical Specifications
Detector Configuration: The detector array consists of four orthogonally placed ion chambers on 10 cm
radii from a fifth centrally located ion chamber.
Dimensions: 33.7 cm wide x 43.8 cm deep x 2.2 cm high (13.25 in. x 17.25 in. x 0.875 in.). Depth
dimension assumes handle is fully extended; height dimension assumes no accessory pegs or build-up
added.
Weight: 4 kg (8.8 lbs)