LEFAC (low energy free air chamber)
The LEFAC is a smaller version of the MEFAC. The size of the chamber is optimised for measurements in the range 10 – 70 kVp. In all other respects, the chamber operation is the same as the MEFAC. The smaller dimensions mean that attenuation and scatter corrections are reduced, at the expense of the electron loss correction.
LEFAC with cover removed, revealing the guard electrodes and the gap which allows the beam to pass out of the chamber. The X-ray source is behind the Pb sheet in front of the chamber.