arXiv subjects

Heinrich Schindler

Publications and source records attributed to Heinrich Schindler.

12 recordsLinked to original sources

arXiv2026

Event-by-Event Space-Charge Gain Suppression in LGADs and Its Impact on Time Resolution

Low Gain Avalanche Detectors (LGADs) achieve time resolutions below 50 ps through internal charge multiplication, yet the gain is not a fixed device property as the space-charge of the multiplied electron-hole density screens the gain layer field, which suppresses further impact ionization. While TCAD simulations reproduce the average gain suppression, their deterministic treatment of a continuous charge density cannot capture the event-by-event fluctuations that determine the timing performance. We present a Monte Carlo study of space-charge-induced gain suppression in LGADs using the Garfield++ framework, in which the dynamic field of the drifting carriers, computed from a coarse-grained system of charged rings, is superimposed on TCAD-computed static field maps of Centro Nacional de Microelectrónica (CNM) and Hamamatsu Photonics (HPK) produced sensors while preserving single carrier avalanche statistics. The simulated gain reproduces published two-photon absorption-transient current technique measurements across two orders of magnitude in injected charge, including the dependence on the injection depth. For minimum ionizing particles, the event-by-event coupling between deposited charge and gain compresses the Landau tail of the multiplied charge, narrowing the signal arrival time distribution and improving the intrinsic time resolution of the HPK-S1 sensor investigated in this work from 53.9 $\pm$ 1.0 ps to 44.5 $\pm$ 0.9 ps. Treating the primary ionization as a stochastic sequence of charge clusters, it is further shown analytically that any gain suppression that decreases with the cluster size narrows the centroid time distribution.

physics.ins-det↗

arXiv2025

The Timepix4 Beam Telescope

The spatial and temporal performance of a telescope system comprising planar silicon sensors bump-bonded to Timepix4-v2 ASICs are assessed at the CERN SPS using a $180$~GeV/$c$ mixed hadron beam. The pointing resolution at the centre of the telescope is $2.3 \pm 0.1\;\mathrm{μm}$ and $2.4 \pm 0.1\mathrm{μm}$ in x and y directions, respectively. The temporal resolution for the combined timestamps on a track using only the information from the Timepix4 planes is found to be $92 \pm 5$~ps. The telescope is extensively described including its data acquisition system and dedicated software as well as the corrections applied to the raw measurements.

hep-ex↗

arXiv2023

Studying signals in particle detectors with resistive elements such as the 2D resistive strip bulk MicroMegas

As demonstrated by the ATLAS New Small Wheel community with their MicroMegas (MM) design, resistive electrodes are now used in different detector types within the Micro Pattern Gaseous Detector family to improve their robustness or performance. The extended form of the Ramo-Shockley theorem for conductive media has been applied to a 1 M$Ω$/$\Box$ 2D resistive strip bulk MM to calculate the signal's spreading over neighbouring channels using an 80 GeV/c muon track. For this geometry, the dynamic weighting potential was obtained numerically using a finite element solver by applying a junction condition and coordinate scaling technique to accurately represent the boundary conditions of a $10\times 10$ cm$^2$ active area. Using test beam measurements, the results of this model will be used to benchmark this microscopic modelling methodology for signal induction in resistive particle detectors.

physics.ins-det↗

arXiv2022

Reconstruction of charged tracks with Timepix4 ASICs

The design of a detector system comprised of four silicon sensors bump-bonded to Timepix4 ASICs is described together with its data acquisition system, operational infrastructure, and dedicated software. The spatial and temporal performance of the system are assessed with a 180 GeV/c mixed hadron beam at the CERN SPS and reported in detail. Particle tracks are reconstructed using time-space measurements from the four detector planes. The spatial hit resolution is assessed to be $(15.5\pm 0.5)$ $μ$m and $(4.5\pm0.3)$ $μ$m for 100 and 300 $μ$m thick sensors, respectively. The timestamps from the detectors are also measured with fine precision, yielding time resolutions of $(452\pm10)$ ps, $(420\pm10)$ ps, $(639\pm10)$ ps, $(631\pm10)$ ps for the two 100 and two 300 $μ$m thick sensors respectively. These measurements are combined to a track time resolution of $(340\pm 5)$ ps.

physics.ins-det↗

arXiv2022

The Road Ahead for CODEX-b

In this Snowmass contribution we present a comprehensive status update on the progress and plans for the proposed CODEX-b detector, intended to search for long-lived particles beyond the Standard Model. We review the physics case for the proposal and present recent progress on optimization strategies for the detector and shielding design, as well as the development of new fast and full simulation frameworks. A summary of the technical design for a smaller demonstrator detector (CODEX-$β$) for the upcoming Run~3 of the LHC is also discussed, alongside the road towards realization of the full experiment at the High-Luminosity LHC.

hep-ex↗

arXiv2021

Microchannel cooling for the LHCb VELO Upgrade I

The LHCb VELO Upgrade I, currently being installed for the 2022 start of LHC Run 3, uses silicon microchannel coolers with internally circulating bi-phase \cotwo for thermal control of hybrid pixel modules operating in vacuum. This is the largest scale application of this technology to date. Production of the microchannel coolers was completed in July 2019 and the assembly into cooling structures was completed in September 2021. This paper describes the R\&D path supporting the microchannel production and assembly and the motivation for the design choices. The microchannel coolers have excellent thermal peformance, low and uniform mass, no thermal expansion mismatch with the ASICs and are radiation hard. The fluidic and thermal performance is presented.

physics.ins-det↗

arXiv2021

Temporal characterisation of silicon sensors on Timepix3 ASICs

The timing performance of silicon sensors bump-bonded to Timepix3 ASICs is investigated, prior to and after different types of irradiation up to $8 \times 10^{15} 1 \mathrm{\,Me\kern -0.1em V} \mathrm{ \,n_{eq}} {\mathrm{ \,cm}}^{-2}$. The sensors have been tested with a beam of charged particles in two different configurations, perpendicular to and almost parallel to the incident beam. The second approach, known as the grazing angles method, is shown to be a powerful method to investigate not only the charge collection, but also the time-to-threshold properties as a function of the depth at which the charges are liberated.

physics.ins-det↗

arXiv2021

Expression of Interest for the CODEX-b Detector

This document presents the physics case and ancillary studies for the proposed CODEX-b long-lived particle (LLP) detector, as well as for a smaller proof-of-concept demonstrator detector, CODEX-$β$, to be operated during Run 3 of the LHC. Our development of the CODEX-b physics case synthesizes `top-down' and `bottom-up' theoretical approaches, providing a detailed survey of both minimal and complete models featuring LLPs. Several of these models have not been studied previously, and for some others we amend studies from previous literature: In particular, for gluon and fermion-coupled axion-like particles. We moreover present updated simulations of expected backgrounds in CODEX-b's actively shielded environment, including the effects of shielding propagation uncertainties, high-energy tails and variation in the shielding design. Initial results are also included from a background measurement and calibration campaign. A design overview is presented for the CODEX-$β$ demonstrator detector, which will enable background calibration and detector design studies. Finally, we lay out brief studies of various design drivers of the CODEX-b experiment and potential extensions of the baseline design, including the physics case for a calorimeter element, precision timing, event tagging within LHCb, and precision low-momentum tracking.

hep-ex↗

arXiv2019

Interfacing Geant4, Garfield++ and Degrad for the Simulation of Gaseous Detectors

For several years, attempts have been made to interface Geant4 and other software packages with the aim of simulating the complete response of a gaseous particle detector. In such a simulation, Geant4 is always responsible for the primary particle generation and the interactions that occur in the non-gaseous detector material. Garfield++ on the other hand always deals with the drift of ions and electrons, amplification via electron avalanches and finally signal generation. For the ionizing interaction of particles with the gas, different options and physics models exist. The present paper focuses on how to use Geant4, Garfield++ (including its Heed and SRIM interfaces) and Degrad to create the ionization electron-ion pairs in the gas. Software-wise, the proposed idea is to use the Geant4 physics parameterization feature, and to implement a Garfield++ or Degrad based detector simulation as an external model. With a Degrad model, detailed simulations of the X-ray interaction in gaseous detectors, including shell absorption by photoelectric effect, subsequent Auger cascade, shake-off and fluorescence emission, become possible. A simple Garfield++ model can be used for photons (Heed), heavy ions (SRIM) and relativistic charged particles or MIPs (Heed). For non-relativistic charged particles, more effort is required, and a combined Geant4/Garfield++ model must be used. This model, the Geant4/Heed PAI model interface, uses the Geant4 PAI model in conjunction with the Heed PAI model. Parameters, such as the lower production cut of the Geant4 PAI model and the lowest electron energy limit have to be set correctly. The paper demonstrates how to determine these parameters for certain values of the W parameter and Fano factor of the gas mixture. The simulation results of this Geant4/Heed PAI model interface are then verified against the results obtained with the stand-alone software packages.

physics.ins-det↗

arXiv2019

LHCb VELO Timepix3 Telescope

The LHCb VELO Timepix3 telescope is a silicon pixel tracking system constructed initially to evaluate the performance of LHCb VELO Upgrade prototypes. The telesope consists of eight hybrid pixel silicon sensor planes equipped with the Timepix3 ASIC. The planes provide excellent charge measurement, timestamping and spatial resolution and the system can function at high track rates. This paper describes the construction of the telescope and its data acquisition system and offline reconstruction software. A timing resolution of 350~ps was obtained for reconstructed tracks. A pointing resolution of better than 2~\mum was determined for the 180~GeV/c %\gevc mixed hadron beam at the CERN SPS. The telescope has been shown to operate at a rate of 5 million particles~\unit{s^{-1}\cdot cm^{-2}} without a loss in efficiency.

physics.ins-det↗

arXiv2017

Signal coupling to embedded pitch adapters in silicon sensors

We have examined the effects of embedded pitch adapters on signal formation in n-substrate silicon microstrip sensors with data from beam tests and simulation. According to simulation, the presence of the pitch adapter metal layer changes the electric field inside the sensor, resulting in slowed signal formation on the nearby strips and a pick-up effect on the pitch adapter. This can result in an inefficiency to detect particles passing through the pitch adapter region. All these effects have been observed in the beam test data.

physics.ins-det↗

arXiv2013

The Timepix Telescope for High Performance Particle Tracking

The Timepix particle tracking telescope has been developed as part of the LHCb VELO Upgrade project, supported by the Medipix Collaboration and the AIDA framework. It is a primary piece of infrastructure for the VELO Upgrade project and is being used for the development of new sensors and front end technologies for several upcoming LHC trackers and vertexing systems. The telescope is designed around the dual capability of the Timepix ASICs to provide information about either the deposited charge or the timing information from tracks traversing the 14 x 14mm matrix of 55 x 55 um pixels. The rate of reconstructed tracks available is optimised by taking advantage of the shutter driven readout architecture of the Timepix chip, operated with existing readout systems. Results of tests conducted in the SPS North Area beam facility at CERN show that the telescope typically provides reconstructed track rates during the beam spills of between 3.5 and 7.5 kHz, depending on beam conditions. The tracks are time stamped with 1 ns resolution with an efficiency of above 98% and provide a pointing resolution at the centre of the telescope of 1.6 um . By dropping the time stamping requirement the rate can be increased to 15 kHz, at the expense of a small increase in background. The telescope infrastructure provides CO2 cooling and a flexible mechanical interface to the device under test, and has been used for a wide range of measurements during the 2011-2012 data taking campaigns.

physics.ins-det↗