Rem counters are neutron dosemeters made of a thermal neutron detector surrounded by a shell of moderating materials, such as polythene, with metal insets


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REM counters are neutron dosemeters made of a thermal neutron detector surrounded by a shell of moderating materials, such as polythene, with metal insets. They are designed to have a spectral response that is proportional to the fluence to ambient dose equivalent H*(10) conversion coefficients.

  • REM counters are neutron dosemeters made of a thermal neutron detector surrounded by a shell of moderating materials, such as polythene, with metal insets. They are designed to have a spectral response that is proportional to the fluence to ambient dose equivalent H*(10) conversion coefficients.

  • The counts of the thermal neutron detector are proportional to H*(10)

  • REM counters designed for high energy applications usually have heavy metal insets (Lead, Tugnsten) to extend their response to high energy neutrons up to 1 -2 GeV.





α particles with energies up to 1.47 MeV are produced. Their range in the material is in the order of 7 μm. This makes etching a very delicate procedure.

  • α particles with energies up to 1.47 MeV are produced. Their range in the material is in the order of 7 μm. This makes etching a very delicate procedure.

  • The etching time has been chosen as a compromise between track radius and contrast.

  • The etching is made with NaOH 25% solution, 98°C, 40 minutes



















The detector has been tested in high energy fields both at GSI Cave A and at CERF

  • At GSI high energy neutrons are generated by 400 MeV/u C ions impinging on a carbon target.

  • Measurements have been made inside the ernty maze and out of the cave shielding, with dose rates ranging between 2-40 Sv/h.













The detector has a high uncertainty (if compared to active REM counters), because of

  • The detector has a high uncertainty (if compared to active REM counters), because of

  • Poisson uncertainty: 7 tracks/cm2μSv mean that a 10 μSv measurement is made with 70±8 tracks, that means a 12% uncertainty. This is unavoidable

  • Lot uncertainty: the tracks are formed at the very surface of the detector. Different lot of detectors may have slightly different properties in the first microns from the surface, that can cause a systematic shift of the mesurements (up to 20%). This can be avoided calibrating every lot of CR39.





The method is very sensitive, and it can provide reliable measurements even with integral doses down to 10 μSv. The LDL is in the order of 2 μSv.

  • The method is very sensitive, and it can provide reliable measurements even with integral doses down to 10 μSv. The LDL is in the order of 2 μSv.

  • It has an uncertainty significantly higher than active REM counters due to poisson uncertainty.

  • It is especially suitable for routine area environmental monitoring where a large number of measurements point are needed (es. large plants), or where a large active environmental neutron monitoring system is not justified (es. conventianal radiotherapy centres)




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