Metal-Halide Perovskite Submicrometer-Thick Films for Ultra-Stable Self-Powered Direct X-Ray Detectors

Metal-halide perovskites are revolutionizing the world of X-ray detectors,due to the development of sensitive,fast,and cost-effective devices.Self-powered operation,ensuring portability and low power consumption,has also been recently demonstrated in both bulk materials and thin films.However,the signal stability and repeatability under continuous X-ray exposure has only been tested up to a few hours,often reporting degradation of the detection performance.Here it is shown that self-powered direct X-ray detectors,fabricated starting from a FAPbBr_(3)submicrometer-thick film deposition onto a mesoporous TiO_(2)scaffold,can withstand a 26-day uninterrupted X-ray exposure with negligible signal loss,demonstrating ultra-high operational stability and excellent repeatability.No structural modification is observed after irradiation with a total ionizing dose of almost 200 Gy,revealing an unexpectedly high radiation hardness for a metal-halide perovskite thin film.In addition,trap-assisted photoconductive gain enabled the device to achieve a record bulk sensitivity of 7.28 C Gy^(−1)cm^(−3)at 0 V,an unprecedented value in the field of thin-film-based photoconductors and photodiodes for“hard”X-rays.Finally,prototypal validation under the X-ray beam produced by a medical linear accelerator for cancer treatment is also introduced.

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.

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.

Design of the solar X-ray detector for the Macao Science Satellite-1B

The solar X-ray detector(SXD)onboard the Macao Science Satellite-1B was designed to monitor solar flare bursts and to study the solar activity in the 25th solar cycle.The SXD includes two parts:a soft X-ray detection unit and a hard X-ray detection unit.Both the soft X-ray detection unit and the hard X-ray detection unit include two collimators,two X-ray detectors(a silicon drift detector and a cadmium-zinc-telluride detector),and a processing circuit.Compared with similar instruments,the energy range of the SXD is wider(1–600 ke V)and the energy resolution is better(150 e V at 5.9 ke V,12%at 59.5 ke V,and 3%at 662 keV).

A characterization study on perovskite X-ray detector performance based on a digital radiography system

X-ray imaging technologies such as digital radiography(DR),is an important aspect of modern non-destructive testing and medical diagnosis.Innovative flexible X-ray detector technologies have recently been proposed and are now receiving increasing attention owing to their superior material flexibility compared with traditional flat-panel detectors.This work aims to study these innovative flexible X-ray detectors in terms of their effectiveness in DR imaging,such as detection efficiency and spatial resolution.To achieve this goal,first,a Monte Carlo model was developed and calibrated to an in-lab 150 kV DR imaging system containing a flat-panel X-ray detector.Second,the validated model was updated with various types of flexible X-ray detectors to assess their performance in nearly realistic conditions.Key parameters such as the detection efficiency pertaining to the crystal material and thickness were studied and analyzed across a broader energy range up to 662 keV.Finally,the imaging performance of the different detectors was evaluated and compared to that of the flat-panel detector in the 150 kV DR imaging system.The results show that the flexible detectors such as the CsPbBr3crystal detector deliver promising performance in X-ray imaging and can be applied to a wider range of application scenarios,especially those requiring accurate detection at challenging angles.

Two-Dimensional Perovskite Single Crystals for High-Performance X-ray Imaging and Exploring MeV X-ray Detection

Scintillation semiconductors play increasingly important medical diagnosis and industrial inspection roles.Recently,two-dimensional(2D)perovskites have been shown to be promising materials for medical X-ray imaging,but they are mostly used in low-energy(≤130 keV)regions.Direct detection of MeV X-rays,which ensure thorough penetration of the thick shell walls of containers,trucks,and aircraft,is also highly desired in practical industrial applications.Unfortunately,scintillation semiconductors for high-energy X-ray detection are currently scarce.Here,This paper reports a 2D(C_(4)H_(9)NH_(3))_(2)PbBr_(4)single crystal with outstanding sensitivity and stability toward X-ray radiation that provides an ultra-wide detectable X-ray range of between 8.20 nGy_(air)s^(-1)(50 keV)and 15.24 mGy_(air)s^(-1)(9 MeV).The(C_(4)H_(9)NH_(3))_(2)PbBr_(4)single-crystal detector with a vertical structure is used for high-performance X-ray imaging,delivering a good spatial resolution of 4.3 Ip mm^(-1)in a plane-scan imaging system.Low ionic migration in the 2D perovskite enables the vertical device to be operated with hundreds of keV to MeV X-ray radiation at high bias voltages,leading to a sensitivity of 46.90μC Gy_(air)-1 cm^(-2)(-1.16 Vμm^(-1))with 9 MeV X-ray radiation,demonstrating that 2D perovskites have enormous potential for high-energy industrial applications.

Study of Secondary Cosmic Rays and Astronomical X-Ray Sources using Small Stratospheric Balloons

The X-ray sources of the universe are extraterrestrial in nature which emit X-ray photons.The closest strong X-ray source is the Sun,which is followed by various compact sources such as neutron stars,black holes,the Crab pulsar,etc.In this paper,we analyze the data received from several low-cost lightweight meteorological balloon-borne missions launched by the Indian Centre for Space Physics.Our main interest is to study the variation of the vertical intensity of secondary cosmic rays,the detection of strong X-ray sources,and their spectra in the energy band of^(1)0–80 keV during the complete flights.Due to the lack of an onboard pointing system,low exposure time,achieving a maximum altitude of only~42 km,and freely rotating the payload about its axis,we modeled the background radiation flux for the X-ray detector using physical assumptions.We also present the source detection method,observation of the pulsation of the Crab(^(3)3 Hz),and spectra of some sources such as the quiet Sun and the Crab pulsar.

A rapid and convenient experimental method of absolutely calibrating transmission of x-ray flat-response filter

We develop a rapid and convenient experimental method of absolutely calibrating the transmission of an x-ray flatresponse filter. The calibration experiment is performed on a small laser-target facility, and a set of high resolution holographic flat-field grating spectrometers is used as a discrimination system of the laser-produced x-ray source. Given that the holographic flat-field grating has a relatively large width, the grating is divided into two regions for use in that direction,where one region has the filter added and the other region does not. The filter transmission is determined by dividing the x-ray signal counts detected when the filter is in the line of sight by those detected when the filter is out of the line of sight.We find that the calibration results of this experiment agree with the calibration results using a synchrotron radiation source,as well as simulation results. Our method is not only highly reliable but also rapid and convenient.

Self Consistent Calibration of Detectors and Sources for Hard and Soft X-Ray Diagnostics

X-Ray sources, detectors and optical components are now used in a wide range of applications. What is crucial is the absolute calibration of such devices to permit a quantitative assessment of the system under study. A new X-ray laboratory has been built in Frascati (ENEA) to develop diagnostics for nuclear fusion experiments and study applications of these X-ray techniques in other domains, like new material science, non destructive tests and so on. An in-house developed selfconsistent calibration procedure is described that permits the absolute calibration of sources (X-ray emitted fluxes) and detectors (detection efficiencies) as function of the X-ray photon energy, in the range 2 - 120 keV. The calibration procedure involves the use of an in-house developed code that also predicts the spectral response of any detector in any experimental condition that can be setup in the laboratory. The procedure has been then applied for the calibration and characterisation of gas and solid state imaging detectors, such as Medipix-2, GEM gas detector, CCD camera, Cd-Te C-MOS imager, demonstrating the versatility of the method developed here.

X-ray photon counting detectors for preclinical and clinical applications

Photon counting detectors(PCDs) have attained w ide use in X-ray imaging for various preclinical and clinical applications in the past decade. This paper briefly review s the preclinical and clinical applications of PCDs based X-ray imaging systems.Starting with an introduction of X-ray single photon detection mechanism,the brief review first describes tw o major advantages of utilizing PCDs: photon energy resolving capability and electronic noise elimination. Compared to energy integrating detectors(EIDs),the aforementioned advantages make PCDs more favorable in X-ray imaging with profound benefits such as enhanced tissue contrast,decreased image noise,increased signal to noise ratio,decreased radiation dose to the small animals and patients,and more accurate material decomposition. The utilizations of PCDs in X-ray projection radiography and computed tomography(CT)including micro-CT,dedicated breast CT,K-edge CT,and clinical CT are then review ed for the imaging applications ranging from phantoms to small animals and humans. In addition,optimization methods aiming to improve the imaging performance using PCDs are briefly review ed. PCDs are not flaw less though,and their limitations are also discussed in this review. Nevertheless,PCDs may continuously contribute to the advancement of X-ray imaging techniques in future preclinical and clinical applications.

Readout electronics for a high-resolution soft X-ray spectrometer based on silicon drift detector

The readout electronics for a prototype soft X-ray spectrometer based on silicon drift detector(SDD),for precisely measuring the energy and arrival time of X-ray photons is presented in this paper.The system mainly consists of two parts,i.e.,an analog electronics section(including a pre-amplifier,a signal shaper and filter,a constant fraction timing circuit,and a peak hold circuit)and a digital electronics section(including an ADC and a TDC).Test results with X-ray sources show that an energy dynamic range of 1-10 keV with an integral nonlinearity of less than 0.1%can be achieved,and the energy resolution is better than 160 eV @ 5.9 keV FWHM.Using a waveform generator,test results also indicate that time resolution of the electronics system is about 3.7 ns,which is much less than the transit time spread of SDD(<100 ns)and satisfies the requirements of future applications.

Transition edge sensor-based detector:from X-ray to γ-ray

A transition edge sensor(TES)is extremely sensitive to changes in temperature,and combined with a high-Z metal of a certain thickness,it can realize high-energy resolution measurements of particles such as X-rays.X-rays with energies below 10 keV have a weak penetrating ability,hence,only gold or bismuth of a few micrometers in thickness can guarantee a quantum efficiency higher than 70%.Therefore,the entire structure of the TES X-ray detector in this energy range can be realized using a microfabrication process.However,for X-rays or γ-rays from 10 keV to 200 keV,submillimeter absorber layers are required,which cannot be realized using the microfabrication process.This paper first briefly introduces a set of TES X-ray detectors and their auxiliary systems,and then focuses on the introduction of the TES γ-ray detector with an absorber based on a submillimeter lead-tin alloy sphere.The detector achieved a quantum efficiency above 70% near 100 keV and an energy resolution of approximately 161.5 eV at 59.5 keV.

A large-grain-size thick-film polycrystalline diamond detector for x-ray detection

A diamond film with a size of 6×6×0.5 mm^3 is fabricated by electron-assisted chemical vapor deposition. Raman spectrum analysis, x-ray diffraction and scanning electron microscope images confirm the high purity and large grain size, which is larger than 300 μm. Its resistivity is higher than 10^12 W· cm. Interlaced-finger electrodes are imprinted onto the diamond film to develop an x-ray detector. Ohmic contact is confirmed by checking the linearity of its current–voltage curve. The dark current is lower than 0.1 n A under an electric field of 30 k V cm^-1. The time response is 220 ps. The sensitivity is about 125 m A W^-1 under a biasing voltage of 100 V.A good linear radiation dose rate is also confirmed. This diamond detector is used to measure x-ray on a Z-pinch, which has a double-layer 'nested tungsten wire array'. The pronounced peaks in the measured waveform clearly characterize the x-ray bursts, which proves the performance of this diamond detector.

Study of Chemical Etching and Chemo-Mechanical Polishing on CdZnTe Nuclear Detectors

Cadmium zinc telluride (CdZnTe) semiconductor has applications in the detection of X-rays and gamma-rays at room temperature without having to use a cooling system. Chemical etching and chemo-mechanical polishing are processes used to smoothen CdZnTe wafer during detector device fabrication. These processes reduce surface damages left after polishing the wafers. In this paper, we compare the effects of etching and chemo-mechanical polishing on CdZnTe nuclear detectors, using a solution of hydrogen bromide in hydrogen peroxide and ethylene glycol mixture. X-ray photoelectron spectroscopy (XPS) was used to monitor TeO2 on the wafer surfaces. Current-voltage and detector-response measurements were made to study the electrical properties and energy resolution. XPS results showed that the chemical etching process resulted in the formation of more TeO2 on the detector surfaces compared to chemo-mechanical polishing. The electrical resistivity of the detector is of the order of 1010 &#937;-cm. The chemo-mechanical polishing process increased the leakage current more that chemical etching. For freshly treated surfaces, the etching process is more detrimental to the energy resolution compared to chemo-mechanically polishing.

High-Throughput Powder Diffraction Using White X-Ray Beam and a Simulated Energy-Dispersive Array Detector

High-throughput powder X-ray diffraction(XRD)with white X-ray beam and an energy-dispersive detector array is demonstrated in this work on a CeO;powder sample on a bending magnet synchrotron beamline at the Shanghai Synchrotron Radiation Facility(SSRF),using a simulated energy-dispersive array detector consisting of a spatially scanning silicon-drift detector(SDD).Careful analysis and corrections are applied to account for various experimental hardware-related and diffraction angle-related factors.The resulting diffraction patterns show that the relative strength between different diffraction peaks from energy-dispersive XRD(EDXRD)spectra is consistent with that from angle-resolved XRD(ARXRD),which is necessary for analyzing crystal structures for unknown samples.The X-ray fluorescence(XRF)signal is collected simultaneously.XRF counts from all pixels are integrated directly by energy,while the diffraction spectra are integrated by d-spacing,resulting in a much improved peak strength and signal-to-noise(S/N)ratio for the array detector.In comparison with ARXRD,the diffraction signal generated by a white X-ray beam over monochromic light under the experimental conditions is about 104 times higher.The full width at half maximum(FWHM)of the peaks in q-space is found to be dependent on the energy resolution of the detector,the angle span of the detector,and the diffraction angle.It is possible for EDXRD to achieve the same or even smaller FWHM as ARXRD under the energy resolution of the current detector if the experimental parameters are properly chosen.

Detailed characterization of polycapillary focusing x-ray lenses by a charge-coupled device detector and a pinhole

A method to measure the detailed performance of polycapillary x-ray optics by a pinhole and charge coupled device(CCD)detector was proposed in this study.The pinhole was located between the x-ray source and the polycapillary x-ray optics to determine the illuminating region of the incident x-ray beam on the input side of the optics.The CCD detector placed downstream of the polycapillary x-ray optics ensured that the incident x-ray beam controlled by the pinhole irradiated a specific region of the input surface of the optics.The intensity of the output beam of the polycapillary x-ray optics was obtained from the far-field image of the output beam of the optics captured by CCD detector.As an application example,the focal spot size,gain in power density,transmission efficiency,and beam divergence of different parts of a polycapillary focusing x-ray lenses(PFXRL)were measured by a pinhole and CCD detector.Three pinholes with diameters of 500,1000,and 2000μm were used to adjust the diameter of the incident x-ray beam illuminating the PFXRL from 500μm to the entire surface of the input side of the PFXRL.The focal spot size of the PFXRL,gain in power density,transmission efficiency,and beam divergence ranged from 27.1μm to 34.6μm,400 to 3460,26.70%to 5.38%,and 16.8 mrad to 84.86 mrad,respectively.

A method for correcting characteristic X-ray net peak count from drifted shadow peak

To correct spectral peak drift and obtain more reliable net counts,this study proposes a long short-term memory(LSTM)model fused with a convolutional neural network(CNN)to accurately estimate the relevant parameters of a nuclear pulse signal by learning of samples.A predefined mathematical model was used to train the CNN-LSTM model and generate a dataset composed of distorted pulse sequences.The trained model was validated using simulated pulses.The relative errors in the amplitude estimation of pulse sequences with different degrees of distortion were obtained using triangular shaping,CNN-LSTM,and LSTM models.As a result,for severely distorted pulses,the relative error of the CNN-LSTM model in estimating the pulse parameters was reduced by 14.35%compared with that of the triangular shaping algorithm.For slightly distorted pulses,the relative error of the CNN-LSTM model was reduced by 0.33%compared with that of the triangular shaping algorithm.The model was then evaluated considering two performance indicators,the correction ratio and the efficiency ratio,which represent the proportion of the increase in peak area of the two characteristic peak regions of interest(ROIs)to the peak area of the corrected characteristic peak ROI and the proportion of the increase in peak area of the two characteristic peak ROIs to the peak areas of the two shadow peak ROI,respectively.Ten measurement results of the iron ore samples indicate that approximately 86.27%of the decreased peak area of the shadow peak ROI was corrected to the characteristic peak ROI,and the proportion of the corrected peak area to the peak area of the characteristic peak ROI was approximately 1.72%.The proposed CNN-LSTM model can be applied to X-ray energy spectrum correction,which is of great significance for X-ray spectroscopy and elemental content analyses.

Performance of Large Area Thin-Film CdTe Detector in Diagnostic X-Ray Imaging

Significant advancement in thin-film cadmium telluride (CdTe) deposition techniques in recent years has made this material attractive for the development of low-cost large area detector. Here we evaluate the intrinsic performance of the detector for a range of energies relevant to diagnostic imaging applications, such as fluoroscopy. The input x-ray spectra for a set of tube potentials ranging from 70 to 140 kVp were computed with the tungsten anode spectral model using interpolating polynomials (TASMIP) based on the measured output of our diagnostic x-ray simulator. Frequency-dependent detector performance analysis was conducted through Monte Carlo simulations of energy deposition within the detector. Intrinsic modulation transfer functions (MTF), noise power spectra (NPS), and detective quantum efficiencies (DQE) were computed for a set of CdTe detectors of varying thickness, from 100 to 1000 μm. MTF behavior at higher frequencies was affected by thickness and input energy, NPS increased with film thickness and energy, and the resultant DQE(f) decreased with increasing the input energy, but increased with the thickness of the detector. We found that the optimal thickness of CdTe under diagnostic x-ray beam is in the range of 300 to 600 μm. Physical properties of CdTe, such as the high atomic number and density, used in direct detection configuration, together with the recently established thin-film manufacturing techniques makes this technology a promising photoconductor for large area diagnostic flat panel imaging.

Dual-Energy X-Ray Computed Tomography Scanner Using Two Different Energy-Selection Electronics and a Lutetium-Oxyorthosilicate Photomultiplier Detector

To obtain two kinds of tomograms at two different X-ray energy ranges simultaneously, we have constructed a dual-energy X-ray photon counter with a lutetium-oxyorthosilicate photomultiplier detector system, three comparators, two microcomputers, and two frequency-voltage converters. X-ray photons are detected using the detector system, and the event pulses are input to three comparators simultaneously to determine threshold energies. At a tube voltage of 100 kV, the three threshold energies are 16, 35 and 52 keV, and two energy ranges are 16 - 35 and 52 - 100 keV. X-ray photons in the two ranges are counted using microcomputers, and the logical pulses from the two microcomputers are input to two frequency-voltage converters. In dual-energy computed tomography (CT), the tube voltage and current were 100 kV and 0.29 mA, respectively. Two tomograms were obtained simultaneously at two energy ranges. The energy ranges for gadolinium-L-edge and K-edge CT were 16 - 35 and 52 - 100 keV, respectively. The maximum count rate of dual-energy CT was 105 kilocounts per second with energies ranging from 16 to 100 keV, and the exposure time for tomography was 19.6 min.