  Uranium fission chambers are commonly used for neutron beam monitoring in
neutron research facilities. The challenges brought with the renewing or
commissioning of new neutron facilities encourage to minimize the interaction
between the monitor and the neutron beam. In order to characterize both their
detection efficiency and transmission factor, several fission chambers, have
been scanned on the CT1 monochromatic beam line of the ILL. Results show that
the monitor transparency, measured at the center of the monitor, varies from
90% to 96%, and that the detection efficiency varies by as much as 50% over the
active area.
