Pressurised drift tube response to photons of energies from 6 keV to 1 MeV

The response of the aluminium drift tubes to the photons of different energies in the 0.6 T magnetic field has been studied. A Monte Carlo model for the simulation of the photon detection in the drift tube has been developed. The results of the model calculation are compared with the measured amplitude spectra from radioactive sources. For photon energies above 100 keV a significant reduction of the measured response with respect to the calculated value is observed. This effect can originate from the avalanche saturation for very large proportional signals. The tube response was found to be equal to the photon gamma energy softer than 30 keV and to vary between 35 and 40 keV for the photon energy between 50 and 1000 keV