Bragg Mirrors for Thermal Waves

We present a numerical calculation of the heat transport in a Bragg mirror configuration made of materials that do not obey Fourier’s law of heat conduction. The Bragg mirror is made of materials that are described by the Cattaneo-Vernotte equation. By analyzing the Cattaneo-Vernotte equation’s solutions, we define the thermal wave surface impedance to design highly reflective thermal Bragg mirrors. Even for mirrors with a few layers, very high reflectance is achieved (>90%). The Bragg mirror configuration is also a system that makes evident the wave-like nature of the solution of the Cattaneo-Vernotte equation by showing frequency pass-bands that are absent if the materials obey the usual Fourier’s law.

Simulating fusion alpha heating in a stellarator reactor

Gyrocenter following simulations of fusion born alpha particles in a stellarator reactor are preformed using the BEAMS3D code. The Wendelstein 7-X high mirror configuration is scaled in geometry and magnetic field to reactor relevant parameters. A 2×1020 m−3 density plasma with 20 keV core temperatures is assumed and fusion birth rates calculated for various fusion products assuming a 50/50 deuterium-tritium mixture. It is found that energetic He4 ions comprise the vast majority of the energetic particle inventory. Slowing down simulations of the He4 population suggest plasma heating consistent with scaled energy confinement times for a stellarator reactor. Losses for this configuration appear large suggesting optimization beyond the scope of the W7-X device is key to a future fusion reactor. These first simulations are designed to demonstrate the capability of the BEAMS3D code to provide fusion alpha birth and heating profiles for stellarator reactor designs.

Bragg Mirrors for Thermal Waves

We present a numerical calculation of the heat transport in a Bragg mirror configuration made of materials that do not obey Fourier's law of heat conduction. The Bragg mirror is made of materials that are described by the Cattaneo-Vernotte equation. By analyzing the Cattaneo-Vernotte equation's solutions, we define the thermal wave surface impedance to design highly reflective thermal Bragg mirrors. Even for mirrors with a few layers, very high reflectance is achieved ($>90\%$). The Bragg mirror configuration is also a system that makes evident the wave-like nature of the solution of the Cattaneo-Vernotte equation by showing frequency pass-bands that are absent if the materials obey the usual Fourier's law.

Neutron imager with micro channel plates (MCP) in electrostatic mirror configuration: Neutron beam test

A recent advancement in a new high transparency monitor device based on Micro Channel Plate (MCP) has been proposed for monitoring flux and beam spatial profiles of neutrons. It consisted of the assembly of a very thin aluminum (Al) foil with a 6Li deposit placed along the beam and a MCP equipped with a phosphor screen readout viewed by a CCD camera outside the beam line. The peculiar feature of this device is that it uses an electrostatic mirror to minimize the perturbation of the neutron beam, i.e. absorption and scattering. It can be used at existing time-of-flight facilities, in particular at the neutron Time-of-Flight (n_TOF) facility at CERN, for monitoring the flux and the spatial profile of neutron beams in the thermal and epithermal region. In this contribution, the device experimental test carried out on the n_TOF neutron beam at CERN will be presented and discussed.

The ASTRI Program

The ASTRI (Astrofisica con Specchi a Tecnologia Replicante Italiana) program was born as a collaborative international effort led by the Italian National Institute for Astrophysics (INAF) to design and realize, within the Cherenkov Telescope Array (CTA) framework, an end-to-end prototype of the Small-Sized Telescope (SST) in a dual-mirror configuration (2M). While the activities concerning the characterization of the prototype are under completion, the program entered a new phase. With the final aim of contributing at the production of the SST telescopes for the CTAO Southern site, we started the development of nine telescopes based on the evolution of the ASTRI prototype design to work as pathfinder for the CTAO. Furthermore, together with the CHEC (Compact High Energy Camera) collaboration, the ASTRI team presented a proposal, that will be evaluated with other proposals, to deliver to CTAO the complete set of SST telescopes.