Ambient Dose Equivalent Filter - Model L-2002-1050
Introduction

Ludlum offers an energy compensation filter that flattens the energy response of its popular Model 44-9 GM pancake detector to facilitate measuring Ambient Equivalent Dose (Sieverts). Ludlum also offers another filter for Exposure...see below 

As most know, the venerable GM pancake has a significant over-response at lower energies between approximately 20 to 160 keV (see red line on graph below). Any exposure or dose measurements taken with an unfiltered GM pancake detector would thus have unacceptable errors at these lower energies. This  filter developed by Ludlum flattens the response to within  ± 20% referenced to 137Cs (662 keV) over an energy range of 20 keV to 1.2 MeV .

Energy Graph

This filter simply snaps on across the face of a Ludlum Model 44-9 and Ludlum Model 26-series GM pancake probe whenever this type of measurements is desired. The filter is then easily removed to continue on with measuring contamination (cpm or Bq).

Filters can be purchased separately or together with a new Model 44-9 probe.  Note: The Model 2002-1050 Dose Filters and Model 4002-1066 Exposure Filters are designed to fit Model 44-9 Series of Radiation Detectors with serial number 97000 and higher. Neither filter will fit the Model 44-9-13 or older units unless modified.

Energy Compensation Filter Products

Ludlum Measurements offers two energy compensation filters that flatten the energy response of the Model 26-series and Model 44-9, to facilitate measuring either the exposure rate or the ambient dose equivalent rate. The filters evens the response to within ±20% referenced to 137Cs (662 keV) over an energy range of 33 keV to 1.2 MeV for exposure and down to 20 keV for ambient dose equivalent.
 
Model 26 Integrated Frisker series
Model 26-1 DOSE: Model 26-1 with snap-on filter (PN 48-4007)