Signal Charge Research Articles

Sub-GeV dark matter searches with EDELWEISS: New results and prospects

The Edelweiss collaboration performs light Dark Matter (DM) particles searches with germanium bolometer collecting charge and phonon signals. Thanks to the Neganov-Trofimov-Luke (NTL) effect, a RMS resolution of 4.46 electron-hole pairs was obtained on a massive (200g) germanium detector instrumented with a NbSi Transition Edge Sensor (TES) operated underground at the Laboratoire Souterrain de Modane (LSM). This sensitivity made possible a search for WIMP using the Migdal effect down to 32 MeV/C^{2}2 and exclude cross-sections down to 10^{-29}−29 cm^22. It is the first measurement in cryogenic germanium with such thermal sensor, proving the high relevance of this technology. Furthermore, such TES have shown sensitivity to out-of-equilibrium phonons, paving the way for EDELWEISS new experience CRYOSEL. This is an important step in the development of Ge detectors with improved performance in the context of the EDELWEISS-SubGeV program.

Experimental Study on the Charge Signal Time-Frequency Characteristics during Fracture Process of Precracked Syenogranite under Uniaxial Compression

During the process of rock deformation and failure, a significantly large number of charge signals are generated as a result of fracture appearance and crack expansion. The generation of charge signal is the comprehensive embodiment of the coal-failure behavior. The study of charge signal in the process of fractured-rock deformation and failure is of great significance to the prediction of rock dynamic disasters such as tunnel-engineering stability, slope instability and earthquake. In this work, a surveillance system utilizing charge induction is employed to extract precursory information related to the instability and failure of precracked syenogranite. The results reveal a significant influence of fractures on the strength of syenogranite specimens and the number of charge-induction signal events. The position of the charge signal generated is related to the crack dip angle. Furthermore, with the increase of the crack inclination, the number of events and the amplitude and power value of the charge-induced signal increase and reach the maximum in the instability-failure phase. The syenogranite specimen has a relatively large value, medium correlation, or even high correlation charge-induction signal in the phase of rack propagation, which can make an early warning of the deformation and failure risk of syenogranite; with the increase of the fracture degree, the charge-induction signal with large values and high correlations gradually increases.

A method to simulate Twin Frisch-grid ionization chamber response to fission fragments

In this study, the response of a Twin Frisch-grid ionization chamber (TFGIC) to fission fragments (FFs) was investigated using finite element and Monte Carlo methods. The entire process of the fission experiments, including FFs generation, gas ionization, electron drift and collection, and induced charge signal were well reproduced. Through data analysis, pulse height spectra from the anode and grid were transformed into energy and emission-angle information for the FFs. By means of double energy method, the pre-neutron emission fission fragment mass and total kinetic energy (TKE) can be finally determined. Experimental and calculated data of the mass and TKE distribution are shown in good agreement.

Triboelectric charge-separable probes for quantificationally charge investigating at the liquid-solid interface

Thoroughly researching liquid-solid contact electrification can significantly enhance our understanding of liquid energy harvesting, chemical processes, and geological mechanisms. However, this research is challenging because liquid changes dynamically, the interface chemistry is complex, and there are few rapid and simple measurement methods available. In this study, a liquid-solid triboelectric nanogenerator was developed as a probe to successfully quantify the charges with varying polarities at the liquid-solid interface. Owing to the design of two spatially arranged electrodes, this proposed probe was able to quantify the interfacial charges within a mere 50 ms propelled by the significant electrical potential difference between the liquid and the electrodes. By concomitantly analyzing the charge signal and short-circuit current signal, the probe is utilized for detecting the flow state of the liquid. Finally, the probe has been demonstrated to be applicable for liquid energy harvesting. This study presents a promising approach to address the challenges of liquid-solid contact electrification research and provides a novel perspective for enhancing our understanding of the chemical processes at liquid-solid contact electrification.

Development of neutron detection systems at the NDPS of RAON

The Nuclear Data Production System (NDPS) at RAON has been built to produce nuclear data generated by the reactions induced by neutrons of tens of MeV. For the neutron Time-Of-Flight (TOF) measurement, neutron monitoring detectors based on a gas-filled Parallel Plate Avalanche Counter (PPAC) and a MICRO-MEsh-GASeous (MICROMEGAS) detector have been developed by the Rare Isotope Science Project (RISP) and Sungkyunkwan University (SKKU). These detectors have a neutron converter with a thin 232Th layer, which produces fission products due to fast neutrons. The PPAC achieved a 1 ns FWHM time resolution in a test with an 241Am α source and also showed good performance when tested with fast neutrons generated by a 45 MeV proton beam through the 9Be(p, n)9B reaction. Additionally, EJ-301, liquid scintillation detectors are assembled for the measurement of neutron flux with pulse shape discrimination capability. Slow charge signals as well as fast timing signals from the detectors will be processed for particle identification by a data acquisition (DAQ) system, located at a separate control room through 30 m long cables. Development of the detection system and the test results will be reported together with the on-site assembly status.

Noise reduction by using wavelet transform in charge signal acquired from an electrostatic inductive sensor

Noise reduction by using wavelet transform in charge signal acquired from an electrostatic inductive sensor

Experimental Verification and Analysis of Vibration Damping Structure of Piezoelectric Ceramic Grain Loss Sensor

In this study, in order to achieve accurate detection of grain loss during the process of combine harvester harvesting, a piezoelectric-based grain loss sensor has been developed. The sensor utilizes a double-layer circular piezoelectric ceramic sheet as its sensitive element. When different grains come into contact with the sensitive element, the piezoelectric effect of the ceramic sheet generates corresponding charges. These charges are then converted into knock charge signals through a charge amplification signal processing circuit that has been specially designed for this purpose. The harsh operating conditions of the sensor, including the presence of significant vibration and noise interference, necessitate the incorporation of a double-layer vibration-damping structure in both the top and bottom layers of the sensor. This paper seeks to analyze the vibration-damping effect of various shock-absorbing materials and structures incorporated into the sensor. This is accomplished by creating a dynamic analysis model that accounts for vibration interference. Furthermore, an experimental bench is established for the purpose of verifying the vibration-damping test results. These tests demonstrate that the utilization of a properly selected vibration-damping structure and materials can effectively eliminate mechanical vibration and noise interference. This, in turn, leads to improved detection accuracy of charge signals after knocking and enhances the overall anti-interference ability of the sensor.

Analysis of Space Charge Signal Spatial Resolution Determined with PEA Method in Flat Samples including Attenuation Effects

The constant development of the electrical engineering sector, especially in the transmission of electrical energy under high-voltage direct current (HVDC), requires research on new insulation materials and investigations of physical phenomena under ultrahigh electrical fields in solid dielectrics. One of the current problematic issues is the formation of space charge in HV insulation systems, which affects the operational electrical field distribution and can lead to faster insulation degradation. There are several problems that have to be considered before every space charge measurement, such as the attenuation and dispersion of sound waves in tested dielectric materials, reflections at the interfaces, and the spatial resolution of the measured charge profile. The spatial resolution is one of the most important technical factors of the PEA measurement stand. The spatial resolution, as it is assumed, depends on several factors, such as the width of the pulser and the pulse rise time, the thickness of the piezoelectric sensor, and the dispersion of the tested material. The article presents the laboratory measurement results of the impact of pulser parameters, such as pulse width and rise time, and sensor thickness on the equivalent thickness of the measured net charge layer corresponding to the resolution of the method. The dispersion in the tested LDPE material is also presented and analysed. The results show that with an increase in the pulser rise time, a higher resolution of the pea method can be achieved.

Development of multichannel readout electronics prototype system for TPC detector of CSR External-Target Experiment

We present a multichannel readout electronics prototype system developed for the Time Projection Chamber (TPC) detector of CSR External-Target Experiment (CEE). The whole system consists of two Front-End readout Electronics (FEE) boards, fiber converters, host computers and a trigger fan-out board. A single FEE board is mainly equipped with four SAMPA chips and a Field Programmable Logic Array (FPGA), processing 128 channels of signals from the TPC detector. The SAMPA chips convert the charge signals into digital signals and send them to FPGA for data processing, and then transmit the data to the host computer through a fiber converter. The control commands from the host computer software realize the control of SAMPA and monitor temperature and current. In the dynamic range of input charge from 2 fC to 100 fC, the readout electronics output amplitude linearity is better than 1%. The relative energy resolution of electronics is about 23% at a minimum input charge of 1.4 fC. The test results with TPC illustrate that with a 55Fe source, an energy resolution of 28.5% was acquired, and with cosmic rays, the track resolution on the pad plane is less than 390μm.

Dynamical spin-orbit-based spin transistor

Spin-orbit interaction (SOI) has been a key tool to steer and manipulate spin-dependent transport properties in two-dimensional electron gases. Here we demonstrate how spin currents can be created and efficiently read out in nano- or mesoscale conductors with time-dependent and spatially inhomogeneous Rashba SOI. Invoking an underlying non-Abelian SU(2) gauge structure we show how time-periodic spin-orbit fields give rise to spin electric forces and enable the generation of pure spin currents of the order of several hundred nano-Amperes. In a complementary way, by combining gauge transformations with “hidden” Onsager relations, we exploit spatially inhomogeneous Rashba SOI to convert spin currents (back) into charge currents. In combining both concepts, we devise a spin transistor that integrates efficient spin current generation, by employing dynamical SOI, with its experimentally feasible detection via conversion into charge signals. We derive general expressions for the respective spin- and charge conductance, covering large parameter regimes of SOI strength and driving frequencies, far beyond usual adiabatic approaches such as the frozen scattering matrix approximation. We check our analytical expressions and approximations with full numerical spin-dependent transport simulations and demonstrate that the predictions hold true in a wide range from low to high driving frequencies.

Baseline Tracking in Bipolar Charge Signal Process by Dynamic Time Warping Algorithm

Electrostatic charge of solid particles can cause problems in many handling processes and need to be evaluated in terms of charge levels and charge polarity. An inductive charge sensor is suitable for the evaluation of both levels and distributions of particle charges at the same time. However, the performance of charge sensing is critically subject to its signal process, which can result in huge errors. One of error sources is drifting of the baseline tracked, which leads raw signals generated by the sensor to be distorted. Especially in determining polarity and quantity of bipolar charges, the distorted signal leads to significant biases and errors in charge measurements, when the number of particles measured is big. Currently, the existing correction algorithms cannot produce a satisfied result in baseline tracking. In this paper, the baseline drifting problem for the charge signals has been explored according to the types of charge polarity. For unipolar charge signals, charge polarity and quantity are determined directly by a poles-pairing method without any further baseline correction. For bipolar charge signals, a new method in baseline tracking and correction has been developed based on dynamic time warping algorithm. Further optimization by a double-check process is used to remove the ‘small hump’ errors in the signal. With the results of the charge measurements, this new method shows significant advantages on accuracy and efficiency of charge detection compared to the other existing methods.

Conceptual Design and Preliminary Verification of Distributed Wireless System of Weigh-in-Motion

In this paper, the concept of a distributed wireless system of weigh-in-motion is proposed. A wireless sensor for weigh-in-motion (WIM) based on piezoelectric materials is designed. The corresponding prototype for indoor testing is made according to the design. It aims to realize the main functions of dynamic pressure sensing, charge signal amplification and conversion, wireless signal transmission and reception, etc. The material properties of the mechanical properties and the piezoelectric properties in the analyses are provided in detail. Through the indoor test platform, the feasibility of the wireless sensor for WIM designed in this paper is preliminarily verified, which provides a basic tool for the realization of the distributed self-powered wireless system of WIM in the next step.

An automated testing system for the RD51 VMM hybrid and yield measurement of the first production batches

We present the development of an automated testing system for the VMM hybrid of the RD51 collaboration. The VMM hybrid is a new front-end board for the RD51 common readout system, the Scalable Readout System, and will become the workhorse for the next decade to read out Micro-Pattern Gaseous Detectors. It uses the VMM chip developed for the ATLAS New Small Wheel to convert charge signals from detectors to digital data. Our testing system automatically characterises the quality of the VMM chips on the hybrid after production during multiple tests. Results are evaluated to classify the chips and hybrids and uploaded to a database. We evaluated those results for the first two production batches to measure the production yield. The yield is better than the threshold below which chip testing on a wafer level offers financial benefits. Observations on prominent chip failures were propagated back to the hybrid production process to further increase the yield for future productions.

The importance of the interface for picosecond spin pumping in antiferromagnet-heavy metal heterostructures

Interfaces in heavy metal (HM) - antiferromagnetic insulator (AFI) heterostructures have recently become highly investigated and debated systems in the effort to create spintronic devices that function at terahertz frequencies. Such heterostructures have great technological potential because AFIs can generate sub-picosecond spin currents which the HMs can convert into charge signals. In this work we demonstrate an optically induced picosecond spin transfer at the interface between AFIs and Pt using time-domain THz emission spectroscopy. We select two antiferromagnets in the same family of fluoride cubic perovskites, KCoF3 and KNiF3, whose magnon frequencies at the centre of the Brillouin zone differ by an order of magnitude. By studying their behaviour with temperature, we correlate changes in the spin transfer efficiency across the interface to the opening of a gap in the magnon density of states below the Néel temperature. Our observations are reproduced in a model based on the spin exchange between the localized electrons in the antiferromagnet and the free electrons in Pt. Through this comparative study of selected materials, we are able to shine light on the microscopy of spin transfer at picosecond timescales between antiferromagnets and heavy metals and identify a key figure of merit for its efficiency: the magnon gap. Our results are important for progressing in the fundamental understanding of the highly discussed physics of the HM/AFI interfaces, which is the necessary cornerstone for the designing of femtosecond antiferromagnetic spintronics devices with optimized characteristics.

Reconstruction algorithm for a novel Cherenkov scintillation detector

For future MeV-scale neutrino experiments, a Cherenkov scintillation detector, CSD, is of particular interest for its capability to reconstruct both energy and direction for charged particles. A type of new target material, slow liquid scintillator, SlowLS, which can be used to separate Cherenkov and scintillation lights, is one of the options for the neutrino detectors. A multi-hundred ton spherical CSD is simulated using a Geant4-based Monte Carlo software, which handles the detailed the micro processes of MeV particles and optical photons and the functions for photomultiplier, PMT, and readout electronics. Twelve SlowLS samples are simulated and studied to cover a wide range of scintillation light yields and scintillation emission time constants. Based on the detailed knowledge of the signal processes, simplified functions are constructed to predict the charge and time signals on the PMTs to fulfill an efficient reconstruction for the energy, direction, and position of charged particles. The performance of the SlowLS reconstruction, including the resulting energy, angular, and position resolution, and particle identification capability, is presented for these samples. The dependence of the performance on the scintillation light yield and emission time constants is understood. This study will be a guideline for future MeV-scale neutrino CSD design and SlowLS development for the interested physics goals.

A novel flexible substrate-free NH3 sensing membrane based on PANI covered rGO functionalized fiber

To alleviate the lack of sensors on the Internet of Things (IoT), a novel flexible substrate-free sensing membrane has been put forward, of which the fabrication is simple, low-cost and has potential of large-scale production via a vacuum filtration method. After alkaline hydrolysis, paper fibers were covered with reduced graphene oxide (rGO) and further functionalized with a layer of polyaniline (PANI) by in-situ polymerization. The rGO functionalized fiber (GF) played a competent role as the embedded conductive network, efficiently transferring the charge signal from the surface sensing layer. Eventually, the functionalized fibers were re-filmed under a 0.1 MPa negative pressure by vacuum filtration method. The surface area of the film was about 23.76 cm2 and 1 × 1 cm2 square was cut for the following test. The sensing membrane based on PANI covered rGO functionalized fiber (PGF) has shown superb sensing performance to NH3, with excellent stability, selectivity and sensitivity at room temperature. The linear response range of sensor based on PGF was 25 ppm, the correlation coefficient was 0.9908 and the limit of detection (LOD) was 34 ppb. The response to NH3 was ∼14% while the responses of other testified interfering gases were all below 0.5%. Most importantly, the sensing membrane has exhibited an excellent capability of resisting bending, and maintained the response to 10 ppm NH3 (13.55–14.3%) even after 1200 bends, indicating that the sensor has a bright prospect of future wearable applications.

Position linearity analysis of circular arc terminated resistive anode using finite element method for photon-counting imaging detectors.

This study proposes a comprehensive model of the circular arc terminated (CAT) resistive anode based on the finite element method to explore the dynamic process of charge diffusion on this anode and its position linearity performance. The waveforms of charges of the electrodes on the anode are calculated for different electrical parameters and their influence on positional linearity is investigated. The influence of the signal development time and the non-uniformity of the resistance per square of the anode on positional linearity is also analyzed. The results of simulations show that the non-linearity of the image varies monotonically with the termination resistance and the non-uniformity of the resistance per square of the anode, but has a non-linear relationship with the signal development time and the ratio of the resistance per square. A CAT resistive anode with capacitance c and a resistance per square of the sensitive area of R▱ can be used to recover an image with a root mean-squared non-linearity of 2%, when the charge signals of the electrode are collected for at least 0.6R▱c s. The reliability of the results of the simulations was verified with experimental measurements.

Performance of improved RPCs demonstrator for the CMS at the HL-LHC

With the increase of the LHC luminosity foreseen in the coming years, components of detectors currently used in the LHC need to be replaced or new ones should be added. The new ones should be capable not only to support the high particle rate, but also to provide time information to reduce the data ambiguity due to the expected high pileup. The CMS collaboration have shown that the RPCs, using smaller gas gap (1.4 mm) and low-resistivity High Pressure Laminate, can stand rates of few kHz/cm2. They are equipped with new electronics sensitive to low signal charges. The electronics was developed to read out the RPC detectors from both sides of a strip and, using timing information, to identify the position along it. The excellent relative resolution of 160 ps leads to a space resolution of 1.5 cm. The absolute time measurement, determined by RPC signal around 500 ps, will also reduce the data ambiguity due to the expected high pileup at the Level 1 trigger. An engineering prototype of the final chamber was qualified in test beams at the Gamma Irradiation Facility (GIF++), located on one of the SPS beam lines at CERN. In addition, 4 demonstrator chambers have just been installed in the CMS cavern. This paper will present the results of the tests done in GIF++, as well as brand new results from the demonstrator chambers.

Design and characterisation of the JadePix-3 CMOS pixel sensor

The JadePix-3 CMOS pixel sensors have been developed and studied with a design optimised for a high position resolution of 3μm, which is one of the key requirements for the physics programmes at the Circular Electron-Positron Collider (CEPC) experiments. The sensors are orientated to the vertex detector for the experiments at the proposed future CEPC. The sensors with high-resistance substrates were produced using Tower Semiconductor’s 180 nm CMOS Imaging Sensor (CIS) process, which feature small sensing diodes, low power analogue front-ends with an in-pixel discriminator, and a rolling shutter readout scheme to minimise the pixel pitch. In the sensors, the pixel matrix of 512 rows × 192 columns is divided into four sectors with varied pixel size (16μm×26μm and 16μm×23.11μm) and circuit design. Electrical pulse tests reveal that for various sectors, the minimum thresholds range from 90 to 140 e, with a noise hit rate below an upper limit of 1 × 10−10/frame/pixel. An infra-red laser beam and a radioactive source of 90Sr have been used to characterise the sensors. The tests show that with the equivalent threshold charge fixed to 220 e−, a position resolution between pitch/212 and pitch/12 can be achieved by tuning the laser power for a signal charge between 440 e− and 880 e−. The measured power consumption is 127 mW for the JadePix-3 sensor and 87 mW/cm 2 when extrapolated to a large sensor of 1 cm × 2.5 cm.

Novel Experimental Setup for Coulometric Signal Transduction of Ion-Selective Electrodes.

In this work, a novel and versatile experimental setup for coulometric signal transduction of ion-selective electrodes (ISEs) is introduced and studied. It is based on a constant potential coulometric measurement carried out using a one-compartment three-electrode electrochemical cell. In the setup, a potassium ion-selective electrode (K+- ISE) is connected as the reference electrode (RE). A poly(3,4-ethylenedioxythiophene) doped with polystyrene sulfonate (PEDOT:PSS)-based electrode with a dummy membrane (DM) and a glassy carbon (GC) rod are connected as the working electrode (WE) and counter electrode (CE), respectively. Adding a non-selective dummy membrane to the structure of the WE facilitates the regulation of the measured signal and response time. The results from electrochemical impedance spectroscopy measurements carried out on the WE showed that the time constant is profoundly influenced by the dummy membrane thickness. In addition, the redox capacitance of the PEDOT:PSS film shows a better correlation with the electrode area than the film thickness. Sequential addition/dilution experiments showed the improvement of current and cumulated charge signals in the new setup studied in this work compared to the setup used in the original coulometric signal transduction method. Both conventional ISEs and solid-contact ISEs (SCISEs) were used in this work. The results showed that the coulometric response was independent of the type of ISE used as RE, confirming the versatility of the novel set-up.