E. Giovenale

A.Doria1 , E. Giovenale1 , G. Galatola Teka1 , G.P. Gallerano1 , M. Greco2 , L. Senni1, A. Taschin1, M. Zerbini1 1ENEA, Fusion and Nuclear Safety Department, 00044 Frascati, Italy 2SMFN De a e , U e La Sa e a , 00185 R a, I a

Abstract—In recent years THz radiation has been widely used in different research and application fields, ranging from security, to cultural heritage conservation, from medicine to biological applications. The THz research group at ENEA has a long term experience with sources and systems operating in this spectral range, which is useful to develop applications in several fields, including biology and medicine. The main THz sources and systems operating at the ENEA center of Frascati are described, together with their actual and potential applications.

I. INTRODUCTION

IN he 90 he TH ec a eg , a a Fa Infrared (FIR) was practically unexplored, due to the lack of sources and applications. Sources were lacking due to the fact that the spectral region was in between the region of microwaves, where the electronic generation of radiation is easy to obtain, and the infrared region, where optical generation is possible. A he beg g f he 90 he ENEA center of Frascati three useful sources were available in this spectral region: a FIR gas laser, providing narrow fixed frequency laser emission, a compact Free Electron Laser (FEL) providing powerful tunable emission in the region between 0.1 and 0.15 THz [1], and a Cherenkov FEL operating between 0.18 and 0.33 THz [2].

The peculiar characteristics of THz radiation and the flexibility of the FEL sources made it possible to design several experiments. The first comprehensive review about the effects of THz radiation on biological cells was carried out in the framework of the THz-BRIDGE EU project [3], utilizing he FEL a ad a ce, d e dea cha ac e ics for biological applications: high peak power, high local electric field, with a low average power, thus excluding heating effects. Over the next years more efforts were devoted to the development of THz imaging systems in the field of cultural heritage and for biological applications. In more recent years the complex and expensive FEL sources were replaced by cheaper and small solid state sources, aimed at developing portable devices, specifically designed for a single application [4]. Meanwhile, in light of the growing interest in tokamak plasma diagnostics applications of THz-TDS techniques, a new testing setup has been developed in Frascati [5]. The system, based on THz generation from ultrashort laser pulses and detection via optical rectification or photoconductive antennas, has a great potential to study fusion applications in Frascati and worldwide. The spectral windows covered by the THz-TDS spans from 0.1 THz to 4 THz.

II. RESULTS

The increasing interest of the scientific community regarding THz radiation produced a quick growth in the available sources and detectors, in the spectral range from 0.1 THz to 0.4 THz, and such sources, together with more conventional ones in the 20-40 GHz range, were utilized to build up systems in this spectral range, to perform optical measurements and imaging experiments.

One of our most interesting devices was originally developed to perform in depth analysis on frescoes, to monitor degradation, with particular focus on detachments and humidity damages.

The same device is now being utilized to perform analysis on the degradation of mosaics [6], where biological weeds can produce the detachment of the stone tiles. The ability of the THz imaging system to detect the presence of water under the mosaic tiles has been demonstrated and more experiments are scheduled to check the limits of such a technique to identify biological material. A similar activity was started to provide results about the degradation of rich decorated leather wallpapers (Fig. 1), utilized in 16th and the 17th century, in most of the noble residences [6].

Fig. 1. ENEA portable THz imaging system, performing measurements on leather wallpapers. Courtesy of Baroque Museum at Ariccia (RM) [6]

REFERENCES

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