Shikma Bressler Lab

The Thick Gas Electron Multiplier (THGEM) is a robust high-gain gas-avalanche electron multiplier a building block of a variety of radiation detectors. It can be manufactured economically by standard printed-circuit drilling and etching technology. We present a detailed review of the THGEM and its derivatives. We focus on the physics phenomena that govern their operation and performances under different operation conditions. Technological aspects associated with the production of these detectors and their current and potential applications are discussed.

Thousands of person years have been invested in searches for new physics (NP), the majority of them motivated by theoretical considerations. Yet, no evidence of beyond the Standard Model physics has been found. This suggests that model-agnostic searches might be an important key to explore NP, and help discover unexpected phenomena which can inspire future theoretical developments. A possible strategy for such searches is identifying asymmetries between data samples that are expected to be symmetric within the Standard Model. We propose exploiting neural networks (NNs) to quickly fit and statistically test the differences between two samples. Our method is based on an earlier work, originally designed for inferring the deviations of an observed dataset from that of a much larger reference dataset. We present a symmetric formalism, generalizing the original one, avoiding fine-tuning of the NN parameters and any constraints on the relative sizes of the samples. Our formalism could be used to detect small symmetry violations, extending the discovery potential of current and future particle physics experiments.

Resistive electrodes are used in gaseous detectors to quench electrical discharges. This helps to protect delicate electrodes and readout electronics and to improve the stability of the detector operation. An RPWELL is a THGEM-based WELL detector with a resistive plate coupled to a conductive anode. Till now, the choice of the resistive plate was limited to a few materials, like LRS Glass and Semitron. These materials have fixed resistivities and, sometimes, thickness and area limitations. This restricts the potential usage of the detector to a rather small range of applications, as well as the possibility of studying in depth the physics processes governing the discharge quenching mechanism. In our present study, we used a new plastic material doped with carbon nanotubes to produce resistive plates with a commercial 3D printer. This method has the flexibility to produce samples of different thicknesses and different resistivity values. We describe here the sample production and characterize the RPWELL performance with different resistive plates. In particular we show the dependence of discharge quenching on the thickness and resistivity of the plate. The dynamics of the charge carriers in the material is proposed as an explanation for the long gain recovery time after a discharge.