Very-High Energy (VHE) gamma-ray astroparticle physics is a relatively young field, and observations over the past decade have surprisingly revealed almost two hundred VHE emitters which appear to act as cosmic particle accelerators. These sources are an important component of the Universe, influencing the evolution of stars and galaxies. At the same time, they also act as a probe of physics in the most extreme environments known -such as in supernova explosions, and around or after the merging of black holes and neutron stars. However, the existing experiments have provided exciting glimpses, but often falling short of supplying the full answer. A deeper understanding of the TeV sky requires a significant improvement in sensitivity at TeV energies, a wider energy coverage from tens of GeV to hundreds of TeV and a much better angular and energy resolution with respect to the currently running facilities. The next generation gamma-ray observatory, the Cherenkov Telescope Array Observatory (CTAO), is the answer to this need. In this talk I will present this upcoming observatory from its design to the construction, and its potential science exploitation. CTAO will allow the entire astronomical community to explore a new discovery space that will likely lead to paradigm-changing breakthroughs. In particular, CTA has an unprecedented sensitivity to short (sub-minute) timescale phenomena, placing it as a key instrument in the future of multi-messenger and multi-wavelength time domain astronomy. I will conclude the talk presenting the first scientific results obtained by the LST-1, the prototype of one CTA telescope type -the Large Sized Telescope, that is currently under commission.

There is a need for new conductive, scalable sensors with piezoresistive and thermoresistive properties for applications in bioengineering. For example, the demand for real-time sensory feedback in upper-limb prosthetics requires sensors that are low-cost, scalable, and sensitive to temperature, pressure, and movement. It is possible to manufacture low-cost conductive sensors by directly mixing a low-cost filler such as graphite into fillers such as polyorganosiloxane, although they can have poor electrical and mechanical homogeneity. In this paper, an alternative approach is outlined to form these sensors: ethylene was polymerized using a nickel catalyst to form a polymer with up to 93 branches per 1000 carbon atoms. This branched polyethylene was fibrous and had a greater volume than high-density polyethylene. After hot pressing with a graphite filler to form a conductive, flexible sensor, the polyethylene samples had electrical resistivity down to ≈0.067 𝛀m, a thermal coefficient of resistance ≈−7.5 𝛀 • C −1 at 27 • C, and a electrical resistance sensitive to forces down to 0.1 N. The process is scalable, and provides a route to homogeneous, low-cost sensors for future prosthetics applications.

The Gamma-ray Cherenkov Telescope (GCT) is one of the telescopes proposed for the Small Sized Telescope (SST) section of CTA. Based on a dual-mirror Schwarzschild-Couder design, which allows for more compact telescopes and cameras than the usual single-mirror designs, it will be equipped with a Compact High-Energy Camera (CHEC) based on silicon photomultipliers (SiPM). In 2015, the GCT prototype was the first dual-mirror telescope constructed in the prospect of CTA to record Cherenkov light on the night sky. Further tests and observations have been performed since then. This report describes the current status of the GCT, the results of tests performed to demonstrate its compliance with CTA requirements, and the optimisation of the design for mass production. The GCT collaboration, including teams from Australia, France, Germany, Japan, the Netherlands and the United Kingdom, plans to install the first telescopes on site in Chile for 2019-2020 as part of the CTA pre-production phase.

Bilayer graphene has many unique optoelectronic properties [1], including a tuneable band gap, that make it possible to develop new and more efficient optical and nanoelectronic devices. We have developed a Monte Carlo simulation for a single photon counting photodetector incorporating bilayer graphene. Our results show that, conceptually it would be feasible to manufacture a single photon counting photodetector (with colour sensitivity) from bilayer graphene for use across both optical and infrared wavelengths. Our concept exploits the high carrier mobility and tuneable band gap associated with a bilayer graphene approach. This allows for low noise operation over a range of cryogenic temperatures, thereby reducing the cost of cryogens with a trade off between resolution and operating temperature. The results from this theoretical study now enable us to progress onto the manufacture of prototype photon counters at optical and IR wavelengths that may have the potential to be groundbreaking in some scientific research applications.

Optical crosstalk (OCT) in silicon photomultipliers (SiPM) occurs when photon detection in a microcell leads to the production of further photons that are also detected. Various models have been considered to predict experimental data with varying degrees of success. In this paper, we introduce the Normally-Distributed Crosstalk Model (NDCM), where the probability of triggering additional microcells is given by a 2-d normal distribution with a standard deviation of σ: a device-specific parameter representing OCT photon propagation path length in terms of microcell pitch. Monte Carlo (MC) simulations of NDCM are compared to existing models and experimental data from the CHEC-S camera developed for the Cherenkov Telescope Array, which suggests that OCT occurs with a σ ≈ 5 microcells in this device.