Low-noise and low-power pixel sensor chip for gas pixel detectors

Topmetal-M2 is a large-area pixel sensor chip fabricated using the GSMC 130 nm CMOS process in 2021.The pixel array of Topmetal-M2 consists of pixels of 400 rows×512 columns with a pixel pitch of 45μm×45μm.The array is divided into 16 subarrays,with pixels of 400 rows×32 columns per subarray.Each pixel incorporates two charge sensors:a diode sensor and a Topmetal sensor.The in-pixel circuit primarily consists of a charge-sensitive amplifier for energy measurements,a discriminator with a peak-holding circuit,and a time-to-amplitude converter for time-of-arrival measurements.The pixel of Topmetal-M2 has a charge input range of~0-3 k e-,a voltage output range of~0-180 mV,and a charge-voltage conversion gain of~59.56μV∕e-.The average equivalent noise charge of Topmetal-M2,which includes the readout electronic system noise,is~43.45 e-.In the scanning mode,the time resolution of Topmetal-M2 is 1 LSB=1.25μs,and the precision is^()7.41μs.At an operating voltage of 1.5 V,Topmetal-M2 has a power consumption of~49 mW∕cm~2.In this article,we provide a comprehensive overview of the chip architecture,pixel working principles,and functional behavior of Topmetal-M2.Furthermore,we present the results of preliminary tests conducted on Topmetal-M2,namely,alpha-particle and soft X-ray tests.

Gas microchannel plate-pixel detector for X-ray polarimetry

POLAR-2 is a gamma-ray burst(GRB)polarimeter that is designed to study the polarization in GRB radiation emissions,aiming to improve our knowledge of related mechanisms.POLAR-2 is expected to utilize an on-board polarimeter that is sensitive to soft X-rays(2-10 keV),called low-energy polarization detector.We have developed a new soft X-ray polari-zation detector prototype based on gas microchannel plates(GMCPs)and pixel chips(Topmetal).The GMCPs have bulk resistance,which prevents charging-up effects and ensures gain stability during operation.The detector is composed of low outgassing materials and is gas-sealed using a laser welding technique,ensuring long-term stability.A modulation factor of 41.28%±0.64% is obtained for a 4.5 keV polarized X-ray beam.A residual modulation of 1.96%±0.58% at 5.9 keV is observed for the entire sensitive area.

A prototype scalable readout system for micro-pattern gas detectors

A scalable readout system （SRS） is designed to provide a general solution for different micro-pattern gas detectors in various applications. The system mainly consists of three kinds of modules： the ASIC card, the adapter card and the front-end card （FEC）. The ASIC cards, mounted with particular ASIC chips, are designed for receiving detector signals. The adapter card is in charge of digitizing the output signals from several ASIC cards. The FEC, edged-mounted with the adapter, has field-programmable gate array （FPGA）-based reconfigurable logic and I/O interfaces, allowing users to choose different ASIC cards and adapters for different experiments, which expands the system to various applications. The FEC transfers data through Gigabit Ethernet protocol realized by a TCP processor （SiTCP） IP core in FPGA. By assembling a flexible number of FECs in parallel through Gigabit Ethernet, the readout system can be tailored to specific sizes to adapt to the experiment scales and readout requirements. In this paper, two kinds of multi-channel ASIC chip, VA140 and AGET, are applied to verify the scalability of this SRS architecture. Based on this VA140 or AGET SRS, one FEC covers 8 ASIC （VA140） cards handling 512 detector channels, or 4 ASIC （AGET） cards handling 256 detector channels, respectively. More FECs can be assembled in crates to handle thousands of detector channels.

A novel method of encoded multiplexing readout for micro-pattern gas detectors

The requirement of a large number of electronic channels poses a big challenge to the further applications of Micro-pattern Gas Detectors （MPGDs）. By using the redundancy that at least two neighboring strips record the signal of a particle, a novel method of encoded multiplexing readout for MPGDs is presented in this paper. The method offers a feasible and easily-extensible way of encoding and decoding, and can significantly reduce the number of readout channels. A verification test was carried out on a 5 cm×5 cm Thick Gas Electron Multiplier （THGEM） detector using a 8 keV Cu X-ray source with 100um slit, where 166 strips were read out by 21 encoded readout channels. The test results show good linearity in its position response, and the spatial resolution root-mean-square （RMS） of the test system is about 260um. This method has potential to build large area detectors and can be easily adapted to other detectors similar to MPGDs.

Gas chromatographic method for the determination of hexaconazole residues in black tea

A highly reliable, quantitative and sensitive analytical method for determining the residues of the fungicide, hexaconazole in black tea is described. The proposed method is based on liquid-liquid extraction followed by gas chromatographic determination, using nitrogen phosphorus detector (GC-NPD) for the identification and quantitation of hexaconazole. The most appropriate solvent mixture for extracting hexaconazole residues from black tea was n-hexane:acetone at 1:1 (v/v). The extract was cleaned up by adsorption column chromatography using activated florisil. Performance of the method was assessed by evaluating quality parameters such as recovery value, repeatability, reproducibility, linearity and limits of detection and quantitation. When the method was assessed for repeatability, the percentage of recovery ranged between 86% and 96% while the relative standard deviation was between 0.30% and 2.35%. In studies on reproducibility the recovery ranged from 81% to 85% and relative standard deviation from 1.68% to 5.13%, implying that the method was reliable. A field trial was conducted to verify the application of this method with real samples. Results prove that the validated method was suitable for extracting hexaconazole residues.

Recent Achievement of Gas Electron Multiplier

Gas electron multiplier (GEM) as a novel gas detector,due to it’s simple structure,high performance,well compatibility etc.,is widely used in high-energy physics,nuclear physics and other fields.In this review,the principle,recent achievements,developments and applications of GEM are mainly described.

Gas Chromatogragh Analysis of Beaver Oil

Eight fatty acids from beaver oil were identified by GC-9A, and their contents were determinded. A simple yet effective method for separation and quantification was described. Contents of the fatty acids were related to their conditions of extraction.

Electronics system for the cosmic X-ray polarization detector

This study presents an electronics system for cosmic X-ray polarization detection(CXPD).The CXPD was designed as a high-sensitivity soft X-ray polarimeter with a measurement energy range of 2-10 keV carried by a CubeSat.A stable and functionally complete electronics system under power and space constraints is a key challenge.The complete CXPD electronics system(CXPDES)comprises hardware and firmware.CXPDES adopts a three-layer electronic board structure based on functionality and available space.Two gas pixel detectors(GPDs)were placed on the top layer board,and CXPDES provided the GPDs with voltages up to-4000 V.Each GPD signal was digitized,compressed,encoded,and stored before being transmitted to the ground.The CXPDES provided stable and high-speed communication based on a scheme that separated command and data transmission,and it supports the CXPDES in-orbit upgrade.In addition,environmental monitors,silicon photomultiplier(SiPM)triggers,power management,GPDs configuration,and mode switches were included in the overall operating logic of the CXPDES.The results obtained by testing the CXPDES showed that it satisfied all the requirements of CXPD.The CXPDES provides design experience and technological readiness for future large-area X-ray polarimetry missions.

Development of a Derivatization-free GC-FID Method for Evaluation of Free Fatty Acid Levels in Plasma of Diabetic Nephropathy Patients

Metabolism of free fatty acids（FFAs） is related to several important physiological events and therefore their quantitaion in biological samples arouses extensive interest and efforts.Existing gas chromatography with flame ionization detector（GC-FID） methods for the analysis of FFAs normally require derivatization of them in order to lower boiling points.But this extra procedure tends to induce additional error and it is laborious and time-consuming.A derivatization-free method was therefore established in the present investigation to determine FFAs in human plasma by capillary（GC-FID）.After extraction of FFAs from plasma,a highly polar FFAP（free fatty acid in plasma） column was employed to directly quantitate FFAs concentration,free from derivatization reaction.All sample pretreatments were carried out at room temperature,improving recovery of short-chain FFAs.Heptadecanoic acid（C17：0） was employed as internal standard,and the proposed method was validated for recovery,precision,sensitivity,stabi-lity,and linearity.Validation data show that it is suitable for clinical study that has been applied to the evaluation of FFAs levels in plasma of diabetic nephropathy（DN） patients during the course of treatment.Forty-seven patients diagnosed with DN were admitted to the double-blind experiment.Control group（n=17） underwent solely basic treatment and the patients did not show significant change in FFAs concentration during six months of treatment.Experiment group（n=30） was supplied with traditional Chinese medicine besides basic treatment.After six months of medication,their plasma concentration of palmitic acid（C16：0）,stearic acid（C18：0） and oleic acid（C18：1n-9） decreased while linolenic acid（C18：3n-3） increased significantly（P〈0.05）.These four compounds could be served as biomar-kers in the evaluation of drug efficacy,and their quantitation in plasma may provide additional information for disease progression in DN patients.

Determination of the volatile fraction of coal tar

The coal tar was qualitative and quantitative anMyzed by gas chromatography （GC） method. 74 components were identified exactly by gas chromatographY-mass spectrometry （GC-MS）. 31 components （37%） were quantitatively analyzed by gas chromatography-flame ionization detector （GC-FID）. The linearity, accuracy, precision, limit of detection （LOD） and limit of quantitative （LOQ） determination were inspected. The scope of quantitative analysis by CC was discussed. The experimental results of thermogravimetric analysis （TGA） proved that GC quantitative analysis of the coal tar was reliable.

Comparison and Analysis of Fabric Deodorization Test Methods

The test methods of deodorization fabric are studied in daily life. In view of different deodorization fabrics and source gases,the detector tube method and gas chromatography-flame ionization detector ( GC-FID ) method were chosen to test the deodorizing rates of fabric and the influencing factors on deodorization test were discussed. Through the two methods,the residual concentration of odorous substance after adsorption can be measured,and the deodorizing rates of deodorization fabric can be got by calculation. The results show that the two test methods are both appropriate for deodorization test of fabric.

Parameters optimization of π-phase-shifted long-period fiber grating for gas sensing

The gas-sensitive film coated π-phase-shifted long-period fiber grating(LPFG),consisting of two same long-period fiber gratings cascaded by a regular fiber with length of half of the grating period,is proposed for gas sensing.The sensitivity of the sensor is defined by the change rate of the transmission at specific wavelength with respect to the film refractive index.The qualitative and numerical analyses show that to get a high sensitivity,the optimal coupling strength of each long-period fiber grating is √2 π/4.With this coupling strength,the longer the grating is,the higher sensitivity the sensor has.By choosing appropriate grating period,a high sensitivity for the film with a certain refractive index and thickness can be attained.

An optical fiber methane gas sensing film sensor based on core diameter mismatch

An optical fiber evanescent wave methane gas sensor based on core diameter mismatch is reported.The sensor consists of a multimode fiber in which a short section of standard single-mode fiber,coated with the inclusion of cryptophane molecules E in a transparent polysiloxane film,is inserted.The sensing principle is analyzed by optical waveguide theory.For different sensing film thicknesses and interaction lengths,the sensor signal is investigated within the methane concentration range of 0-14.5%（v/v）.It is shown that the sensor signal with the thickness of 5μm and the interaction length of 3 mm strengthens linearly with the increasing concentration of methane,with a slope of 0.0186.The best detection limit of the sensor for methane is 2.2%（v/v） with a response time of 90 s.This sensor is suitable for the detection of methane concentration below the critical value of 5%.

Formaldehyde gas sensor based on TiO_2 thin membrane integrated with nano silicon structure

An innovative formaldehyde gas sensor based on thin membrane type metal oxide of Ti O2 layer was designed and fabricated. This sensor under ultraviolet(UV) light emitting diode(LED) illumination exhibits a higher response to formaldehyde than that without UV illumination at low temperature. The sensitivities of the sensor under steady working condition were calculated for different gas concentrations. The sensitivity to formaldehyde of 7.14 mg/m^3 is about 15.91 under UV illumination with response time of 580 s and recovery time of 500 s. The device was fabricated through micro-electro-mechanical system(MEMS) processing technology. First, plasma immersion ion implantation(PIII) was adopted to form black polysilicon, then a nanoscale TiO_2 membrane with thickness of 53 nm was deposited by DC reactive magnetron sputtering to obtain the sensing layer. By such fabrication approaches, the nanoscale polysilicon presents continuous rough surface with thickness of 50 nm, which could improve the porosity of the sensing membrane. The fabrication process can be mass-produced for the MEMS process compatibility.

A new solid-conversion gas detector for high energy X-ray industrial computed tomography

A new type of solid-conversion gas detector is investigated for high energy X-ray industrial computed tomography (HECT). The conversion efficiency is calculated by using the EGSnrc Monte Carlo code on the Linux platform to simulate the transport process of photons and electrons in the detector. The simulation results show that the conversion efficiency could be more than 65%, if the X-ray beam width is less than about 0.2 mm, and a tungsten slab with 0.2 mm thickness and 30 mm length is employed as a radiation conversion medium. Meanwhile the results indicate that this new detector has higher conversion efficiency as well as less volume. Theoretically this new kind of detector could take place of the traditional scintillation detector for HECT.

Sulfonic acid-based metal organic framework functionalized magnetic nanocomposite combined with gas chromatography-electron capture detector for extraction and determination of organochlorine

The metal organic framework functionalized with sulfonic acid was combined with magnetic nanoparticles to fabricate a new nanocomposite(denoted as Fe3O4@PDA@Zr-SO3H).By combining with gas chromatography-electron capture detector,the resulting Fe3O4@PDA@Zr-SO3H nanocomposite was successfully used as a high-efficiency adsorbent for pre-concentrating eight organochlorine pesticides from water sample in environment.Apart from the ability of fast separation,the as-prepared Fe3O4@PDA@Zr-SO3H nanocomposite also exhibited high adsorption capacity for organochlorine pesticides.With the use of optimal experimental conditions,the linear relationship can be obtained in the range of 0.05~300μg/L,the correlation coefficient was over 0.9978,and the relative standard deviation was located in 2.5%-7.7%.Moreover,the limit of detection and quantification was between0.005-0.016μg/L and 0.017~0.050μg/L.Finally,the nanocomposite was used for the determination of organochlorine pesticides from environmental water samples,and displayed the recovery of 82%-118%.

A system consisted of flame ionization detector and sulfur chemiluminescence detector for interference free determination of total sulfur in natural gas

A new detection system consisted of a flame ionization detector（FID） and a sulfur chemiluminescence detector（SCD） was developed for sensitive and interference free determination of total sulfur in natural gas by non-separation gas chromatography. In this system, sulfur containing compounds and hydrocarbons were firstly burned in the FID using oxygen rich flame and converted to SO_2, CO_2 and H_2O, respectively. The products from FID were transported into the SCD with hydrogen rich atmosphere wherein only SO_2 could be reduced to SO and reacted with O_3 to produce characteristic chemiluminescence. Therefore, the chemiluminescence of CO found in conventional SCD were eliminated because CO_2 could not be reduced to CO under these conditions. The experimental parameters were systematically investigated. Limit of detection obtained by the proposed system is better than 0.5 mmol/mol for total sulfur and superior to those previously reported. The proposed method not only retains the advantages of the conventional SCD but also provides several unique advantages including no hydrocarbon interference, better stability, and easier calculation. The utility of this technique was demonstrated by the determination of total sulfur in real samples and two certified reference materials（GBW 06332 and GBW（E） 061320）.

A Novel Analytical Method of 1‑(3‑Trifluoromethylphenyl)piperazine and 1‑(3‑Chlorophenyl)piperazine in Fluids of Drug Addicts Using Liquid‑liquid Extraction–gas Chromatographic/Nitrogen–phosphorous Detection

In accordance with the research specifications and guidelines in China,we developed a novel experimental method to detect new piperazine‑type drugs,such as 1‑(3‑trifluoromethylphenyl)piperazine and 1‑(3‑chlorophenyl)piperazine.In this study,a new pretreatment method and gas chromatography(GC)/nitrogen–phosphorus detector detection technique were used to characterize these two kinds of drugs in urine and blood samples.For the purpose of isolation of these trace drugs from the samples,liquid‑liquid extraction/solid‑phase extraction was modified and validated for this specific study.The pretreatment method presented in this paper has many advantages,such as high recovery rate,high extraction efficiency,high detection sensitivity,low limit of detection,and simple operation.The GC/NPD instrument is popular in most laboratories because it can meet the routine requirements of forensic science.All these aspects make this combination of sample pretreatment and GC/NPD technique the most suitable choice for drug detection in biological samples.

Studies of the linearity of the readout module assembling using the eXTP-GPD chips

Background The Gas Pixel Detector(GPD)is a key part of the Polarimetry Focusing Array(PFA)sub-system onboard the enhance X-ray Timing and Polarimetry mission(eXTP).The GPD can accurately provide the polarized angle and degree for incoming soft X-rays(requirements of minimum detectable polarization<1%(10^(6) s,1 mCrab))from celestial objects under extreme conditions of density,gravity and magnetism.Purpose Paste the GPD chips on a matched ceramic package is one of the most important procedures for the GPD assembly,and the parallelism between the top surface of an ASIC chip and the bottom surface of a Gas Electron Multiplier(GEM)foil can have impact on the distribution of electric field within transfer region and reconstruction of photoelectric trajectories,resulting in deterioration of the GPD sensitivity.This study quantifies the influence and gives a reasonable expectation of the parallelism.Methods A simulation framework of the GPD is constructed to quantify the influence on the GPD performance and values of the parallelism are measured by a gauge with a position resolution of o.1μm.Results:The difference of degree of modulation is less than 1% comparing the parallelism with a value of 20μm to a value of 0μm in response to both polarized and unpolarized X-rays.Meanwhile,the value of parallelism can reach 6.9±3.4μm(0.0176°±0.0087°)by testing and verifying.Conclusions The impact on the GPD performance can be less than 1%as the parallelism with an order of 20μm,and we also give a reasonable measuring method and verify the controllability and feasibility of the parallelism with an order of 20μm for pasting the ASIC chip on the surface of a ceramic package.

Cavity enhanced absorption spectroscopy for N_2O detection at 2.86 μm using a continuous tunable color center laser

The cavity enhanced absorption technique is applied to N2O detection around 2.86 μm using a continuous-wave color center laser. A high-finesse triangular ring cavity is used in this technology. Transmission through the cavity is obtained by jittering the cavity-length with a piezo on one of the cavity mirrors. A minimum detectable absorption coefficient of 2 × 10-6 cm-1 is achieved with a mirror reflectivity of 99.24%, corresponding to a N2O detection limit of 600 parts per billion.