Clea Sunny (AstroCent/CAMK PAN, Warsaw)
The Global Argon Dark Matter Collaboration is currently developing its flagship detector, DarkSide-20k (DS-20k), a multi-tonne-scale experiment designed for the direct detection of the weakly interacting massive particles using a double-phase Liquid Argon Time Projection Chamber (LAr TPC) with 20.2 tonnes of fiducial mass. The shift from its predecessor, DarkSide-50, with 46.4 kg of active mass, to a significantly larger detector relies on intermediate prototypes for technical design validation. The DS-20k TPC Mockup is one such prototype detector intended to replicate the critical aspects of the functionality of DS-20k in a tonne-scale setup. The Mockup detector was assembled in a clean room of the Nuova Officina Assergi (NOA) facility at the Laboratori Nazionali del Gran Sasso (LNGS) above ground in early 2025, and was later transported to Hall C of the LNGS underground laboratory to be put inside a cryostat. The main tests focused on the long-term exposure of the Clevios coatings, an innovative conductive polymer, to LAr, analyzing gas-pocket formation, and conducting tests of the high voltage delivery. The detector is now decommissioned and transported back to the NOA facility for visual inspection for any possible damage or degradation. This talk presents the assembly, operation, ongoing analysis, findings, and future prospects of the Mockup project.
Anabella Araudo (Institute of Physics, Czech Academy of Sciences)
Fast Radio Bursts (FRBs) are transient episodes of intense, coherent radio emission lasting from microseconds to milliseconds. While the origin of FRBs remains uncertain, most are detected at extragalactic distances. Notably, the repeating FRB 200428 has been associated with the Galactic magnetar SGR 1935+2154. We propose a new model for FRB emission from SGR 1935+2154, where streaming instabilities in a baryon-loaded expanding fireball with different electron and ion temperatures forms density cavities filled with electrostatic fields. Using one-dimensional particle-in-cell kinetic simulations, we constrain the size of these plasma cavities and characterize the electrostatic fields. The resulting FRB emission originates from the coherent Bremsstrahlung of relativistic particle bunches accelerated within the cavities. Our model reproduces the observed radio fluxes of FRBs from SGR 1935+2154 with a small coherence parameter. The relationship between the wave coherence scale and the electric field amplitudes indicates that harmonic emission is several orders of magnitude weaker than the fundamental emission. Moreover, unlike previous models that attribute cavity formation to Langmuir collapse in pair plasmas, our results show that these structures can continue to generate ion acoustic waves after Langmuir saturation. Detecting harmonics in FRB observations, or placing upper limits on their luminosity, can help discriminate among emission mechanisms and constrain the electron–ion or electron–positron composition of magnetar environments during such events.
