Model 44-9 with Exposure Filter - Model 44-9 EXP
Introduction

Ludlum offers its popular Model 44-9 GM pancake probe with an energy compensation filter that flattens the energy response to facilitate measuring Exposure (Roentgen). Ludlum also offers another filter for Ambient Equivalent Dose (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 33 keV to 1.2 MeV.

Energy Graph

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

Filters can be purchased separately or together with a new Model 44-9 probe. The exposure filter comes in a kit that provides the filter plus a replacement detector protective screen that can easily be changed out. 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.
 
Ludlum Measurements offers two energy compensation filters that flatten the energy response of the Model 26 to facilitate measuring either the exposure rate or the ambient dose equivalent rate. The filters flatten 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.
 

Energy Compensation Filter Products

Model 26 Integrated Frisker series
Model 26-1 DOSE: Model 26-1 with snap-on filter (PN 48-4007)
Model 26-1 EXP: Model 26-1 with snap-on Exposure Filter and replacement screen (PN 48-4006)
 
Model 44-9 GM Detector series
Model 44-9DOSE: Model 44-9 detector with snap-on Dose Filter (PN 47-3789)
Model 44-9EXP: Model 44-9 detector with snap-on Exposure Filter and replacement screen (PN 47-3788)
 
Filter Kit Modification for Model 26-1 and Model 44-9 instruments
Ambient Dose Equivalent Filter: kit includes snap-on filter (PN 2002-1050)
Model 26 Exposure Filter Kit: includes snap-on Exposure Filter and replacement screen for Model 26 series (PN 4498-334)
Model 44-9 Exposure Filter Kit: includes snap on Exposure Filter and replacement screen for Model 44-9 series (PN 4002-1066)