Model 9-3 Ion Chamber

Retractable Beta Shield

Features

• 5 Ranges from Background to 500 mSv/h (50 R/hr)
• 1000 mg/cm ² Retractable Beta Shield
• Temperature Compensated
• Low Battery Warning
• High Background Zero Capability
• Proportional Audio Output
• Adjustable Shoulder Strap Included

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The Ludlum 9-3 ion chamber is a rugged air ionization chamber for performing beta-gamma dose rate measurements over a five-decade span ranging from background to 500 mSv/h (50 R/hr). The chamber wall (including the instrument case) is 1000 mg/cm ² . A 1000 mg/cm ² retractable beta shield allows beta measurement with a 7 mg/cm ² window. The six-position switch selects Off, x10k, x1k, x100, x10 and x1. Each range has a front-panel mounted calibration control. Other features include an audio output, reset, and zero adjust capabilities. Means are also provided to zero the electrometer leakage current.

An adjustable shoulder strap (included) provides a convenient and comfortable mode to carry the instrument during surveys.

Detection Range 0.002 to 500 mSv/h (0.2 to 50,000 mR/hr) (typical)
Energy Response Within 20% of true value from 40 keV to 2 MeV
Linearity Reading within 10% of true value
Window 7 mg/cm2 metalized polyester; with slide open, allows gamma detection to 6 keV
Window Area 40 cm2 (6.2 in2)
31.5 cm2 (4.9 in2) open with optional 79% open screen
Chamber Volume 220 cm3 (13.4 in3)
Chamber Construction Carbon coated acrylic
Side Wall 1000 mg/cm2 aluminum and acrylic
Beta Shield

• Retractable 1000 mg/cm² phenolic slide
• BETA FACTOR with the instrument exposed to a depleted uranium slab of 234 mrad/hr:
• Reading with slide Open: 50 mR/hr
• Reading with slide Closed: 1.2 mR/hr
• Beta Factor = 234 ÷ (50 - 1.2) = 4.8

Meter Dial 0 - 5 mR/hr, BAT TEST
(Meter Faces tab lists other available meter faces)
Meter 6.4 cm (2.5 in.) arc, 1 mA, pivot-and-jewel suspension
Controls
Range Selection: x1, x10, x100, x1k, x10k, plus instrument off
Reset: The RESET circuit grounds the chamber and opens the chamber connection to the electrometer. This causes a hard upscale transient on the x1 scale. Hold the RESET down for 4 s to allow the transient to decay. When the RESET switch is opened, the chamber is reconnected to the electrometer and a hard downscale transient will occur. Allow 20 s for recovery.
Zero Adjust: Allows limited background subtract and an external one-turn potentiometer, and also used to compensate electrometer drift
Battery: Push button used to check battery capacity
Audio: On/Off
Calibration: Individual potentiometers for each range; accessible from the front cover while in operational status
Response Time Approximately 5 s for 90% of final meter deflection on the x1 and x10 scales, and 2 s on the x100, x1k, and x10k scales
Audio Built-in unimorph speaker with ON/OFF switch
Temperature Range -20 to 50 °C (-4 to 122 °F), temperature compensation maintains calibration within 15% of 25 °C reading
Power 2 each “AA” cell batteries housed in a sealed externally-accessible compartment
Battery Life
(without display light) 1050 hours with x100 and higher ranges at full scale
1500 hours at x1 and x10 in low background
Construction Cast and drawn aluminum with beige powder coating
Size (H x W x L) 23.4 x 8.9 x 21.6 cm (9.2 x 3.5 x 8.5 in.), including instrument handle
Weight 1.6 kg (3.6 lb), including batteries