## 4 UV-VIS-IR Radiation Detectors  
### Luminescence Induced by Electrons, Ions and X-rays  
The emission of photons in the UV-VIS-IR range can be induced by different probes (e.g., electrons, ions, X-rays), and it is not uncommon to find the acquisition of the luminescence signal coupled with the simultaneous acquisition of signals of other type of radiation. The properties of the constitutive materials in the CH field can be investigated also by means of their induced luminescence. At present, many experimental configurations for luminescence measurements can be used, depending on many parameters, such as the desired wavelength or wavelength range, kind of result provided (map, spectrum, etc. ), efficiency, time required for a measurement, dimensions and weight of the instrumentation, portability, need to darken the room, ease of use and costs. In the following discussion we will focus only on the setups used in the CH field. Cathodoluminescence (CL) is the emission of a luminous signal from a target hit by an electron beam. This technique finds frequent application in the geological field but can be as well used in the art market for the authentication of gems, such as yellow diamonds [184], or in provenance studies for gems and stones [185; 186; 187]. As luminescence can be a fingerprint of the compound and its structural state, CL has also been employed in the characterization of mineral crusts developed on cave painting [188] or for distinguishing original and restoration material in marble facades. The electron beam is accelerated in vacuum, in a dedicated cold cathode stage [189] or directly in the chamber of a Scanning Electron Microscope (SEM), where microprobe elemental analysis can also be performed [190]. Imaging is the most common output for CL analysis, as the different wavelengths of the emitted light may allow for a rapid identification of minerals. For the acquisition of CL images, a digital camera is usually coupled with an optical microscope (in some cases equipped with a polarizer). In some studies, CL is collected both as photograph and spectrum, arranging on the same SEM a CCD camera and a spectrometer that can range from 200 to 900 nm. Differently from CL, ionoluminescence (IL) exploits MeV ion beams to induce light emission. It offers two important advantages over CL: a deeper region of analysis and a higher sensitivity [191]. This allows, for example, the use of features such as trace element which act as light emission activators for provenance purposes [192; 193]. In addition, taking advantage of the sensitivity of IL to small changes in the material structure, IL is a good monitor of radiation damage for pigments and varnish in paintings [194; 195] (no IL spectrum change \(\rightarrow\) no or negligible damage). IL can be applied for authentication studies of gemstones [196], characterization and correct assignment of ceramic productions [197]. Moreover, external beam IL enables non-invasive measurements in air or in controlled atmosphere (usually He), that better meet the needs for archaeological and artistic samples. IL imaging is not particularly common: when applied, the setup is similar to the one for CL, combining a microscope and a CCD camera. Definitely more frequent is the acquisition of the IL spectrum [198]: an example is shown in Figure 12.  
The basic setup consists of an optical fiber (or a bundle of them) which leads the signal to a spectrometer; the fiber has a diameter that varies between 400 \(\upmu\)m and 1 mm. In some cases, a collimating lens can be added at the entrance of the fiber, to maximize the captured luminescence. In most studies, IL and PIXE are used simultaneously. In the application of IL, there is a wide use of cooled spectrometers (thermoelectrically or nitrogen cooled): this option enables obtaining a better signal-to-noise ratio, with sharp peaks that facilitate their attribution. The use of a CCD detector enables collecting the full spectrum at once, decreasing the acquisition time.