arXiv subjects

S. Peters

Publications and source records attributed to S. Peters.

4 recordsLinked to original sources

arXiv2026

Measurement of the free ion yield and estimate of the electron mobility of Trimethyl-Bismuth (TMBi)

This paper investigates the physical characteristics of the liquid Trimethyl-Bismuth (TMBi) relevant for charge readout in potential TMBi filled detectors for Positron-Emission-Tomography (PET) instruments. The high photo-efficiency and the possibility of fast timing by detection of Cherenkov light created in the liquid are both favorable for use of TMBi in a PET system. However, to obtain a high position and energy resolution also a readout of the charge signal created due to the absorption of a 511 keV photon is required. For this purpose the liquid has to be clean of electro-negative and ionic impurities. A distillation technique was developed within this study as one of the possible methods to remove such impurities and a measurement on the efficiency of this cleaning method is provided. The relevant quantities for an efficient charge readout are the free ion yield and the electron mobility of the liquid. We report on a new measurement of the zero-field free ion yield in TMBi and, using that result, produce an estimate of the electron mobility. The rather low zero-field free ion yield and its much lower expected electron mobility compared to tetramethyl-n compounds like TMSi question the use of the trimethyl molecule TMBi for a PET detector liquid. But we are also giving arguments that the tetramethyl molecule TMPb could be an interesting alternative.

physics.ins-det↗

arXiv2022

Electro-purification studies and first measurement of relative permittivity of TMBi

A new type of detector for positron-emission tomography (PET) has been proposed recently, using a heavy organo-metallic liquid - TriMethyl Bismuth (TMBi) - as target material. TMBi is a transparent liquid with the high Z element Bismuth contributing 82% of its mass. 511keV annihilation photons are converted efficiently into photo-electrons within the detector material producing both Cherenkov light and free charge carriers in the liquid. While the optical component enables a fast timing, a charge readout using a segmented anode can provide an accurate position reconstruction and energy determination. The charge measurement requires a high level of purification, as any electronegative contaminants cause signal degradation. In addition to the purity requirements, the reactive nature of TMBi poses many challenges that need to be met until a fully functioning detector for PET applications can be realized. The paper presents an experimental setup that aims to remove electronegative impurities by electrostatic filtering and to characterise the properties of TMBi, e.g. the relative permittivity, for its application as a detector medium for charge read out.

physics.ins-det↗

arXiv2021

Room temperature Mott metal-insulator transition in V2O3 compounds induced via strain-engineering

Vanadium sesquioxide (V2O3) is an archetypal Mott insulator in which the atomic positions and electron correlations change as temperature, pressure or doping are varied giving rise to different structural, magnetic or electronic phase transitions. Remarkably, the isostructural Mott transition in Cr-doped V2O3 between paramagnetic metallic and insulating phase observed in bulk has been elusive in thin film compounds so far. Here, via continuous lattice deformations induced by heteroepitaxy we demonstrate a room temperature Mott metal-insulator transition in 1.5% Cr-doped and pure V2O3 thin films. By means of a controlled epitaxial strain, not only the structure but also the intrinsic electronic and optical properties of the thin films are stabilized at different intermediate states between the metallic and insulating phases, inaccessible in bulk materials. This leads to films with unique features such as a colossal change in room temperature resistivity (DR/R up to 100,000 %) and a broad range of optical constant values, as consequence of a strain-modulated bandgap. We propose a new phase diagram for pure and Cr-doped V2O3 thin films with the engineered in-plane lattice constant as a tuneable parameter. Our results demonstrate that controlling phase transitions in correlated systems by epitaxial strain offers a radical new approach to create the next generation of Mott devices.

cond-mat.str-el↗

arXiv2000

The Parameterized Simulation of Electromagnetic Showers in Homogeneous and Sampling Calorimeters

A general approach to a fast simulation of electromagnetic showers using parameterizations of the longitudinal and radial profiles in homogeneous and sampling calorimeters is described. The dependence of the shower development on the materials used and the sampling geometry is taken into account explicitly. Comparisons with detailed simulations of various calorimeters and with data from the liquid argon calorimeter of the H1 experiment are made.

hep-ex↗