Sensitive and versatile evanescent wave-sensing systems featuring polished optical fiber-based sensor designs with low-cost light sources have been developed for temperature, relative humidity, and pH measurements. The work herein contained describes the fabrication of three types of sensors based on standard silica, single-mode fibers previously subjected to a lateral polishing of the cladding. Temperature sensing through oils whose refractive index varied linearly with temperature showed applicability with up to 5 dB/ C for a 5 range. Polyvinyl alcohol films on the fibers showed almost 10-dB linear variation from 70% to 90% relative humidity. Sol-gel trapped dyes as thin films on the polished surface were capable of performing 15-dB output variation (although not linearly) for pH ranging from 2 to 11.

A Compton camera prototype for ion beam range monitoring via prompt (< 1 ns) gamma detection in hadron therapy is being developed and characterized at the Medical Physics Department of LMU Munich. Co photon sources were used for 2D irradiation scans (step size 0.5 mm) as prerequisite for studying the performance of the "k-Nearest-Neighbors" algorithm developed at TU Delft [2] (together with its variant "Categorical Average Pattern", CAP) and extending its applicability into the energy range beyond the original 511 keV. In this paper we present our most recent interaction position analysis in the absorbing scintillator, leading to a considerably improved value for the spatial resolution: systematic studies were performed as a function of the k-NN parameters and the PMT segmentation. A trend of improving spatial resolution with increasing photon energy was confirmed, resulting in the realization of the presently optimum spatial resolution of 2.9(1) mm @1.3 MeV, thus reaching the design specifications of the Compton camera absorber. The specification goal was reached also for a reduced PMT segmentation of 8x8 anode segments (each with 6x6 mm 2 active area), thus allowing to reduce the complexity of the signal processing while preserving the performance.

The availability of sensors able to determine on-line the ageing (the evolution in the condition) of oils would be of grate interest in many industries. Oil finds applications mainly in three areas: (i) food processing (mainly frying) both in industrial and home environments, (ii) engines lubrication (cars, planes, boats) and (iii) insulation in transformers (and other power devices). In all cases the oils, complex mixtures of many chemical compounds, evolve with time and use leading, eventually, to a significant loss of its properties becoming necessary its replacement. In this paper we present a novel procedure to obtain physical information on the condition of oils in situ and in a relatively simple manner. Sensing procedure clearly distinguishes between different samples of fresh oils (olive, sunflower, etc.) and their mixtures and assesses the evolution with use of a particular oil. The proposed procedure is based on the combined measurement of the transmitted optical power through a small polished zone of a single mode optical fiber immersed in the oil and its temperature.

The purpose of this study is to perform a first characterization and proof of principle investigation of a Compton camera setup composed by a scatterer component consisting of a pixelated GAGG crystal read out by a SiPM multi-pixel photon counter (MPPC) and an absorber component consisting of a monolithic LaBrc(Ce) scintillator read out by a 256-fold multianode photomultiplier (PMT). The rationale of the study is to develop a Compton camera system as a future ion beam range verification device during particle therapy, via prompt gamma imaging. The properties to be investigated are the reconstruction efficiency and accuracy achievable with this system for detecting prompt-y rays. The Compton camera system described has been tested with a laboratory radioactive Cesium-137 source, in a certain geometrical configuration. The readout system is based on individual spectroscopy (NIM+VME) electronic modules, digitizing energy and time signals. The data have been analyzed to produce an input for the image reconstruction, performed using the MEGAlib toolkit software. I. In t r o d u c t i o n P ARTICLE beam therapy is nowadays considered an advantageous option in cancer treatment, but the beneficial high dose delivery precision on the other hand demands a high accuracy of the Bragg peak placement: different approaches for the beam range monitoring are worldwide being evaluated.