The Radiological Detection System (RDS) Field Instrument for the Detection of Low Energy Radiation (FIDLER) Probe is used for low-energy X-ray and gamma radiation detection. The FIDLER Probe detects and distinguishes between low-energy X-rays and gammas. It simultaneously records data over four separate energy windows, by use of a multichannel discriminator. Analysis of this information can enable the detection of materials commonly used in weapons of mass destruction. The FIDLER Probe monitors all four of the following energy windows simultaneously. The Base Unit Home screen has the ability to display one or two energy channels at a time.

  • Energy Window 1: 13 – 18 keV
  • Energy Window 2: 59 – 60 keV
  • Energy Window 3: 143 – 220 keV
  • Energy Window 4: 13 – 220 keV


Mission Survey for low-energy X-ray and gamma radiation
Detector Type Scintillator
Dose Rate Units Count Rate – cpm, cps.
Simultaneous Detection · 13-18 keV (L x-rays) · 59-60 keV (Am-241) · 147-220 keV (U-235) · 13-220 keV (gamma)
Scintillation Crystal Nal (TI), 127 dia. x 1.66 mm thick (5 x 0.063”)
Radiation Entrance Window Beryllium, 127 dia. x 0.254 mm (5 x 0.010”)
Photomultiplier Tube 127 mm (5 in.) diameter
Count Rate Range 0 – 1.5 Mcpm
Alarms Saved in Base Unit memory, ability to set thresholds for various energy channels
Display RDS Base Unit
Power Supplied by RDS Base Unit
Voltage +1600 maximum volts Internal, integrally-wired voltage divider
Dimensions 8.5″ x 7.6″ x 17.2-26.7″
Weight 7.9 lb. (3.60 kg)

Additional information

FIDLER Probe Features:

Large gamma NaI(Tl) scintillator

Part of the Rad-Defender radiation detecting probe family

Adjustable handle

Multi-channel discrimination

Simultaneous detection of 4 channels + display of 2 selectable channels

Calibration and firmware upgrades via Rad Defender Data Exchange Console

Common probe connector cable can be used with any Rad Defender probe

Durable, easy-to-use ergonomic design with optional shoulder strap

Robust cable connections

Smart Capability as a smart probe

Designed and tested for military ruggedness to meet both military/defense requirements and industrial applications

As a smart probe, the FIDLER Probe contains a microprocessor and High Voltage circuitry for creating it’s own high voltage. No high voltage is transferred across the interface cable. When connected to the Base Unit, the display will show the probe’s image and radiation measurement—the probe’s onboard memory stores the probe type and calibration information.