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Exradin Ion Chambers









External Beam Quality Assurance Equipment

Implementation of TG 51in the USA, requiring absorbed dose to water calibration factors, presents the need for a new set of water phantoms and ion chamber calibrations. SeeDOS has a variety of calibration systems available for these new applications equally applicable in Europe and the rest of the world.

As new protocols come along, SeeDOS is meeting the challenge of providing the proper tools, at reasonable cost, to make the transition smooth and accurate. We offer a complete TG-51 Water Calibration System or any of the separate components needed to follow the new guidelines.

Remote Computer Controlled TG51 Worksheet Calculator and Chamber Positioning Device

MD Anderson Cancer Center, Research / TG51 ( link to MD Anderson Centre website TG51 information)

Manual and remote Motor Drive TG51 Calibration System

Everything needed for the new TG51 Protocol

Complete Calibration System
Close up of motor drive and Exradin A12 Farmer Chamber

Water Tank

  •  0.1mm precision depth positioning
  •  Convenient drain valve
  •  25cm depth positioning assembly
  •  Sturdy Acrylic handles, portable and easy to use

Exradin A12 Waterproof Farmer Chamber

  •  Fully Waterproof, Fully Guarded
  •  Collector, guard, outer electrode made of Shonka™ conductive plastic
  •  Calibrations available from University of Wisconsin ADCL for both Water and Air

Remote Motor Drive

  •  Control detector depth of your water tank from outside the  room saving you time and effort
  •  6 digit Digital Readout and Zero Re-Set button
  •  0.1mm positioning accuracy also allows continuous run and intermittent jog to establish reference position
  •  Easy Installation

FREE TG51 Lead Foil with purchase of Exradin A12 or CDX 2000B.

CDX 2000B Electrometer

  •  Versatile Primary Electrometer excellent for use with all standard farmer chamber and parallel plate chambers used in absolute dosimetry as well as all radiation therapy and brachytherapy measurements
  •  2 row x 20 column LCD display
  •  Amp and Coulomb scale with unique timing feature
  •  Battery operated, lightweight & portable
  •  Automatic zeroing
  •  Isolated RS-232 interface

EXCALIBUR CDX 2000B, The lowest priced general purpose electrometer to include an Amp scale, a Coulomb scale, and a unique timing feature.


1mm Lead Foil

  •  Used for absorbing Electrons
  •  Easily slides inside wedge tray or tape to collimator
  •  20cm x 20cm x 1mm; 10cm x 10cm grid
  •  Protective coating provides strength so lead is rigid

1mm Lead Foil


CDX 2000B Electrometer Specifications
Exradin A12 Farmer Chamber Specifications
Sensitivity 0.01nC count
Charge Range - 0.01 to 999,999 nC
Rate Range - 0.01 to 200.00 nA
Deviation from Linearity

0 to 100 nA
101 to 150 nA



Precision 0.02% reproducibility
Leakage <1x10-15 A
Voltage Nominal ±300 V bais, dual polarity and half voltage
Display Alpha Numeric 2 Row by 20 Column LCD
Input BNC triaxial connector
Output RS232 port
Power Rechargeable battery with UL listed battery charger
Colleting Volume 0.651 cm3
Centroid of Collecting Volume 12.9mm from tip of chamber
Collector Diameter 1.0mm
Outside Diameter Sensitive Region 7.1mm
Wall Thickness 0.5mm
Wall, Collector, and Guard Material Shonka™ air-equivalent plastic C552
Maximum Polarizing Potential Greater than 1000V
Inherent Leakage Currents Less than 10-15 Amperes

Water Phantom for TG51 with Depth Positioning Assembly

The Model WP-3840 is a water Phantom with a convenient manual ion chamber depth positioning assembly. The water tank is constructed of 3/8" acrylic and provided with side mounted handles, a drain and a ball valve. The outstanding feature is the depth positioning assembly that is unique in construction and operation. The ion chamber holder Teflon block slides on two stainless steel rods and is driven by a brass lead screw. One turn of the hand crank quickly and accurately moves the chamber holder block 1mm. A mechanical counter with push-button reset capability indicates depth to the nearest 0.1mm.

The horizontal off-centre positioning is achieved by sliding the depth positioning assembly along the edge of the water tank to the desired position as indicated on the horizontal scale mounted on the side of the tank. The depth positioning assembly may be easily retro-fitted with an the Model RMD-100-5 Remote Motor Drive that allows chamber depth positioning from a remote location. The depth is indicated by a digital LCD display with push-button zeroing, adding convenience and significant time saving to your monthly routine.

Specification Model WP-3840
  •  Tank Dimensions: 38 cm wide x 40 cm long x 38 cm high
  •  Materials: sides-3/8" clear acrylic, Bottom-3/8" white acrylic
  •  Drain Valve: ball type, PVC with Teflon seats and 1/2" PVC barbed nipple
  •  Weight : 7.5 kg(16.5 lbs) empty, Approx. 65 kg(142lbs) filled
Depth Positioning Assembly
  •  Travel: 25 cm vertical
  •  Counter: mechanical, 5-digit, 0.1 mm precision
  •  Chamber holder: cylindrical chamber holder accommodates Diameters from 3 mm to 20 mm
  •  Parallel plate ion chamber holders are available as an option
  •  Materials: clear acrylic, stainless steel, brass, Teflon
  •  Weight: 1.8 kg (4 lbs)

Model RMD-100-5 Remote Motor Drive

With the Model RMD-100-5 Remote Motor Drive it is now possible to convert the manual crank mechanism of the WP-3840 depth positioning assembly to allow ion chamber positioning from outside of the treatment room, adding convenience and significant time saving to your monthly routine.

Installation is easy, since it makes use of existing threaded holes for mounting the motor drive assembly to the depth positioning assembly. Although the installation includes adding two drive sprockets, the hand crank is reinstalled on the motor shaft, thereby retaining the original manual positioning and mechanical counter readout functions.

The control/display module is connected to the drive motor by a 15-meter cable for complete control of chamber depth from the accelerator console. Its six-digit liquid crystal display indicates the depth position in units of centimetres to 0.001cm. The RUN switch operates the motor drive in a continuous mode, while the JOG switch provides intermittent operation. Both switches control the motor drive in up/down directions, indicated on display as + and – respectively.

Specifications Model RMD-100-5
  •  Display: 6-digit liquid crystal display with +/- indicators corresponding to up/down, and decimal point
  •  Accuracy: depth displayed to 0.001cm (depth measured to 0.005cm)
  •  Controls: bi-directional continuous (RUN) and intermittent (JOG), display reset switch to establish reference position, on/off switch
  •  Cable: controller to motor: 15m (50ft), PVC-jacketed, multi-conductor cable
  •  Power: 120/240 VAC, 50/60Hz
  •  Dimensions: 19.7 cm x 15.2 cm x 7m, (7.75 in x 6 in x 2.75 in)
  •  Weight: 3 kg(6.6 kg) including controller, motor & mounting assembly, and cable
  •  Motor: 12VDC, reversible, variable speed, 160 rpm @ 12VDC

If you are interested in any of the products mentioned here, please complete a Quotation Request Form  or an

Enquiry Form so that we may promptly respond to your detailed request.



Please contact Colin Walters at cwalters@seedos.com if you would like further  information or you have questions

or comments about this web site.
SeeDOS Ltd, 26, The Maltings, Leighton Buzzard, Bedfordshire LU7 4BS, United Kingdom
Tel: +44 1525 850 670  • Fax: +44 1525 850 685