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Ordering Info


The FWT EIC-1 is a tissue equivalent parallel plate ionization chamber specifically designed for skin sparing measurements. The electrode spacing is continuously adjustable, making it a true extrapolation chamber.

The detecting volume (which includes one-half of the insulator thickness on each side) is a right circular cylinder whose height is adjusted by turning an aluminum ring on which the entrance window is mounted. This ring turns on a brass sleeve, and a reference mark permits repeatable settings.

The entrance window is conductive polyethylene. An optional thin dag-coated polypropylene window is also available. The collecting electrode and the guard ring are made of conducting tissue equivalent plastic, and the signal insulator is polyethylene. The inner wall of the adjustable ring carrying the entrance window has a 0.150-inch-thick polyethylene liner to prevent electron contamination from the aluminum wall . No metal is exposed to the chamber interior.

Chamber voltage should be 50V or less at the nominal 0 turn spacing and 250 V at greater spacing. Both positive and negative polarities may be used on the high voltage. The window and support ring are at this high voltage and caution must be used. At 20 rads per minute, saturation is achieved with a chamber voltage of 20 V or greater at the 2-turn (2-3 mm) spacing.

The optional gas provision flow will allow tissue equivalent (TE) gas to be used in a flow mode. (A flow rate of 5 cc per minute or less is recommended; higher rates may cause window bulging or modulation.) Typical chambers have a sensitivity of 0.16 esu/rad with TE gas and a spacing of 2.3 mm.


Skin sparing measurements, gamma rays, and neutrons
Soft x-ray dosimetry
Beta source dosimetry
Depth dose data with a thin (0-3 mm) ionization chamber (either beta, gamma, or neutron).
Electron beam dosimetry

Type: Ionization Chamber Parallel plate, guarded three terminal design, tissue equivalent conducting plastic; one cm diameter sensitive volume; plate spacing continuously variable from 0.3 mm to 4.5 mm.
Window: Conductive polyethylene is standard, 6.9 mg/cm2; graphite coated polypropylene is available at 0.2 mg/cm2.
Signal Connector: BNC, mates with UG 260 B/U or equivalent.
Signal Output: 0.16 esu/rad with methane based T.E. gas and a plate spacing of 2.3 mm.
Signal Cable Recommended: RG-59/U or equivalent.
Signal Connector: Low noise coax, e.g. MALCO 250-3834-000.
High Voltage Requirements: Positive or negative polarity, 20 to 500V. MHV mates with UG 932 A/U or equal; optional SHV, mates with Star-Tronics 5135 or equal.
Overall Size and Weight: Length including connectors 13.75 inches (35.0 cm); stem is 11.5 inches (29.2 cm) long; weight 150 grams; wooden storage box weight 1540 grams.
Calibrations Furnished: Nominal esu/rad at one plate spacing; plate spacing at zero turns.
Ordering Information

EIC-1: Extrapolation Chamber with storage box and calibration
EIC-1-GF: Extrapolation Chamber with Gas flow provision, storage box, and calibration
EIC-1-BD: 8 plastic buildup discs, 2 ea. 30, 2 ea. 60, 1 ea. 120, 240 , 600 and 1200 mg/cm2
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Specifications subject to change without notice.
Far West Technology, Inc. © 2003 Fax: +1.805.964.3162 Tel: +1.805.964.3615 Email: info@fwt.com