Fluke Biomedical 10100AT - Manual (Page 62)

10100AT
Operators Manual
B-2
Description: vented volume, parallel-plate air ionization chamber
Overall Dimensions: 12.90 ± 0.03 cm diameter by 1.88 ± 0.01 cm thick
Nominal Volume: 150cc, 11.30 cm diameter by 1.50 cm thick active volume
Wall Material: composite graphite-filled thermoplastic
Window Material: 0.76 mm thick, graphite-coated polycarbonate (lexan). A 3.5 by 4 cm piece of
0.0025 cm thick aluminum is attached to the back of the window to improve the energy response.
Window Density: 91 mg/cm 2
Active Window Area: 100 cm 2 , centered within the chamber body
Connector: side-mounted triaxial two-lug BNC connector
Collector Plate: centrally mounted collector is a 0.8 mm thick graphite-coated acrylic plate, 10.80 cm in
diameter. Thirty-five, 6.4 mm diameter holes are drilled through the plate. A 2.16 x 2.85 cm guard
region is electrically isolated from the collector area.
Foam Supports: Two, 1.30 x 1.30 x 0.94 cm pieces of styrofoam DB are used to support the collector
plate and provide mechanical stability.
B.3 Electrical Specifications
Sheet Resistivity: All areas sprayed with graphite conductive coating measure less than 6 k /square
but greater than 3 k /square.
Leakage Current: With 300 volt bias in effect and 0.1 volt potential imposed between the guard and
collector, at 20°C and 50% relative humidity, the leakage current is < 10 fA within 60 seconds of
applying the voltage. The leakage under the above bias conditions is < 100 fA within 60 seconds of
applying the voltage over both the full operating temperature range of 8 - 38°C and for 20 - 80% relative
humidity, but only for conditions in which the absolute humidity is 20 g/m
3 (the equivalent R.H. is 75%
at 25°C, 60% at 30°C, and 50% at 35°C).
B.4 Radiological Specifications
Energy Range: 30 to 150 kVp
Nominal Sensitivity:
H60: 2.08 x 10 7 R/C (1.82 x 10 5 Gy/C) at 22°C and 1013 hPa
DV70: 2.12 x 10 7 R/C (1.86 x 10 5 Gy/C) at 20°C and 1013 hPa
DH70: 2.07 x 10 7 R/C (1.81 x 10 5 Gy/C) at 20°C and 1013 hPa
Multiply values by 0.00876 to convert from R to Gy.
Sensitivity Range: sensitivity range is ± 5% of nominal
Reference Point: The reference point of measurement for the chamber is 1.05 cm directly below the
center of the top of the entrance window. This corresponds to the center of the active region.
Incident Beam Direction: A small sticker with the word "FOCUS" is secured to the top, entrance window
of the chamber. The reference direction of incident radiation is perpendicular to this surface.
Angular Dependence: The ion chamber response to radiation incidence variations up to ± 5° of normal
is within ± 1% of the response to incident radiation striking perpendicular to the entrance window
surface.
Ion Transit Time: Maximum of 1.0 ms in the center of the chamber at STP with a bias voltage
of 300 volts.