Böhm extrapolation chamber: Study of its behavior in beta radiation fields at the Calibration Laboratory of IPEN

•The Böhm extrapolation chamber response was studied in two different conditions.•The extrapolation chamber was studied with two different entrance windows.•The instrument was exposed to 90Sr+90Y beams.•Different characterization tests of the chamber were performed.•All results confirmed the adequate behavior of the chamber in both situations.

The Calibration Laboratory (LCI) at the Instituto de Pesquisas Energéticas e Nucleares (IPEN) is going to establish a Böhm extrapolation chamber as a primary standard system for the dosimetry and calibration of beta radiation sources and detectors. This chamber was already tested in beta radiation beams with an aluminized Mylar entrance window, and now, it was characterized with an original Hostaphan entrance window. A comparison between the results of the extrapolation chamber with the two entrance windows was performed. The results showed that this extrapolation chamber presents the same effectiveness in beta radiation fields as a primary standard system with both entrance windows, showing that any one of them may be utilized.