This paper describes an approach to develop and deploy low-cost plastic optical fiber sensors suitable for measuring low concentrations of pollutants in the atmosphere. The sensors are designed by depositing onto the exposed core of a plastic fiber thin films of sensitive compounds via either plasma sputtering or via plasma-enhanced chemical vapor deposition (PECVD). The interaction between the deposited layer and the gas alters the fiber's capability to transmit the light, so that the sensor can simply be realized with a few centimeters of fiber, an LED and a photodiode. Sensors arranged in this way exhibit several advantages in comparison to electrochemical and optical conventional sensors; in particular, they have an extremely low cost and can be easily designed to have an integral, i.e., cumulative, response. The paper describes the sensor design, the preparation procedure and two examples of sensor prototypes that exploit a cumulative response. One sensor is designed for monitoring indoor atmospheres for cultural heritage applications and the other for detecting the presence of particular gas species inside the RPC (resistive plate chamber) muon detector of the Compact Muon Solenoid (CMS) experiment at CERN in Geneva.
The bone surgery often makes use of implants to sustain and fix the bones during the healing phase. Commonly used implants require a surgical procedure to be removed after bone healing, so there is a strong demand for a new typology of bio-absorbable implants. Magnesium and its alloys are promising materials for orthopedic self-degrading implants, mainly if they are protected by a thin coating. The design of Mg-based implants cannot disregard the adoption of a simple measurement procedure for assessing and monitoring the corrosion evolution in environments simulating the body fluids. This paper describes a measuring approach for the corrosion behavior assessment of different Mg-based alloys uncoated and coated with innovative surface treatments, based on Electrochemical Impedance Spectroscopy measurements.
Resistive Plate Counters (RPC) are employed as muon detectors in many high-rate high-energy physics experiments, such as the Compact Muon Solenoid (CMS) experiment currently under way in the Large Hadron Collider (LHC) accelerator at the European Center for Nuclear Research (CERN). A gas mixture containing C 2 H 2 F 4 , i− C 4 H 10 and SF 6 is recirculated inside the RPCs during their use and subjected to degradation due to the production of fluoride ions which limits the sensitivity of the RPCs. This paper describes a new sensor that is able to detect low concentrations of fluoride ions in gas mixtures. The sensor is made of a plastic optic fiber (POF) which is made sensitive to F − gaseous ions by means of a thin layer of a glass-like material, deposited via plasma onto the fiber core. The F − ions attack the glass-like film and alter the transmission capability of the fiber so that the detection simply requires a LED and a photodiode. The sensor exploits a cumulative response which makes it suitable for direct estimation of the total exposure to the F − ions, thus providing a tool that can be used to tune the maintenance of the gas filters. The glass-like film is deposited by means of plasma enhanced chemical vapor deposition (PECVD) of organosilicons monomers, which allows the deposition to be performed a low temperature in order to avoid damaging the fiber core.
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