• AXIOMA
• axion
• cooling system
• erbium
• fluorescence measurements
• holmium
• infrared fluorescence
• IRQC
• rare earths
• RE-doped crystals
• thulium
• X-ray induced fluorescence

This thesis work is part of AXIOMA project, a research's collaboration of several Italian groups aimed at the development of a new class of particle detectors, characterized by both low energy threshold, ranging from µeV to meV , and an active volume of the order of a few cm^3, in order to detect axionic dark matter.
In particular, one of the two research lines of this project investigates the feasibility of using a rare earth (RE) doped solid state crystal as the active material in a detection scheme based on the infrared quantum counter (IRQC) one.
A first step in this research is to study X-ray induced fluorescence emission of a RE doped crystal as a function of temperature ranging from 3 K to 300 K. The energy of X-ray is high enough to excite all optical transitions of activator ions and of the host crystal from UV to IR, and thus it offers a convenient and powerful tool for a general survey of the luminescence of the sample.
In order to fulfil this objective, the work done firstly concerned with the planning and realization of an experimental apparatus to cool a RE doped crystal, paying close attention to built such system in order to be able to irradiate the crystal with X-ray beam emitted from a X-tube and collect its induced fluorescence prependicularly to the excitation beam.
Then we realized two optical systems to measure X-ray induced fluorescence in the visibile and infrared regions, until almost 2.5 um. A QE-PRO spectrometer let us measure the fluorescence spectrum from 350 nm to 1050 nm, with a spectral resolution of the order of 1 nm, enough to distinguish emission lines due to the radiative transitions between RE dopant ions' multiplets. Whereas, an InSb detector, equipped with some bandpass and lonpass filters, let us measure total IR signal from 1.05 um to 1.65 um and around 2 um. Optical setup let us measure also the integrated X-ray induced fluorescence signal from 300 nm to 850 nm by using a PMT.
As a resulting conclusion of the thesis, we collected the first preliminary data on seven RE-doped crystals of four different host matrices (YLF, BYF, GLF, KYF) and doped with three different rare earths (thulium, holmium and erbium), cooled at a temperature in the interval 3-300 K. These measurements proved that apparatus realized fulfills its task, but at the same time they let us understand how to improve it in the next future.
Additionally, a first qualitative analysis of them allow a preliminary characterization of X-ray induced fluorescence emission from the studied crystals as a function of temperature from 3 K to 300 K.