Abstract
The NEXT experiment aims to observe the neutrinoless double beta decay of 136Xe
in a high-pressure xenon gas TPC using electroluminescence (EL) to amplify the signal from ionization.
Understanding the response of the detector is imperative in achieving a consistent and well
understood energy measurement. The abundance of xenon K-shell X-ray emission during data taking
has been identified as a multitool for the characterisation of the fundamental parameters of the
gas as well as the equalisation of the response of the detector.
The NEXT-DEMO prototype is a 1.5 kg volume TPC filled with natural xenon. It employs
an array of 19 PMTs as an energy plane and of 256 SiPMs as a tracking plane with the TPC light
tube and SiPM surfaces being coated with tetraphenyl butadiene (TPB) which acts as a wavelength
shifter for the VUV scintillation light produced by xenon. This paper presents the measurement
of the properties of the drift of electrons in the TPC, the effects of the EL production region, and
the extraction of position dependent correction constants using Ka X-ray deposits. These constants
were used to equalise the response of the detector to deposits left by gammas from 22Na.
