Fluke Biomedical 10100AT - Manual (Page 70)

10100AT
Operators Manual
C-2
Description: vented volume, parallel-plate air ionization chamber. This is a dual entrance window ion
chamber. Diagnostic measurements are made using one side of the chamber as the entrance window
and mammographic measurements are made using the other side as the entrance window.
Dimensions: 6.35 ± 0.04 cm diameter by 1.30 ± 0.01 cm thick
Nominal Volume: 15cc, 3.96 cm diameter by 1.22 cm thick active volume
Wall Material: graphite-coated acrylic (methyl-methacrylate)
Window Material: Both entrance windows are made of 0.25 mm graphite-coated polycarbonate (lexan).
A 1.5 by 1.6 cm piece of 0.0025 cm thick aluminum is attached to the back of the window with the
“DIAGNOSTIC FOCUS” sticker to improve the energy response for diagnostic measurements.
Window Density: 32 mg/cm 2
Active Window Area: Each side of the chamber has a circular active window region centered 7.1 mm
further from the BNC connector than the center of the chamber body. These regions are centered in
the other direction (see Figure C-1). The active window regions have an area of 12.32 cm
2 .
Connector: side-mounted triaxial two-lug BNC connector
Collector Plate: The collector is a 0.25 mm thick, centrally mounted, graphite-coated, polycarbonate
(lexan) plate. The diameter is 3.18 ± 0.01 cm. A 1.27 x 0.89 cm guard region is electrically isolated
from the collector area.
C.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/m3 (the equivalent R.H. is
75% at 25°C, 60% at 30°C, and 50% at 35°C).
C.4 Radiological Specifications
Energy Range: 30 to 150 kVp for diagnostic measurements; 20 to 50 kVp for mammographic
measurements.
Nominal Sensitivity:
L100: 2.00 x 10 8 R/C (1.75 x 10 6 Gy/C) at 22°C and 1013 hPa
MV30: 2.21 x 10 8 R/C (1.94 x 10 6 Gy/C) at 22°C and 1013 hPa
DV70: 2.01 x 10 8 R/C (1.76 x 10 6 Gy/C) at 20°C and 1013 hPa
DH70: 1.89 x 10 8 R/C (1.66 x 10 6 Gy/C) at 20°C and 1013 hPa
MH30: 2.16 x 10 8 R/C (1.89 x 10 6 Gy/C) at 20°C and 1013 hPa
L100, DV70, and DN70 nominal sensitivities apply to the diagnostic side of the chamber, while MV30
and MH30 apply to the mammographic side. Multiply values by 0.00876 to convert from R to Gy.
Sensitivity Range: sensitivity range is ± 8% of nominal
Reference Point: The reference point is located 6.5 cm directly below the center of the either active
window region. This corresponds to the center of the active volume.