Complementary Metal Oxide Semiconductor Detector Research Articles

Comparative investigation on the performance of spot positioning sensors in point-autofocus microscopy

As products evolve towards greater precision and intelligence, their components also develop towards miniaturisation and increasing complexity. In the era of intelligence, the demand for complex small components continues to grow. The point-autofocus microscopy (PAM), with its attributes such as small measurement spots and high vertical resolution, holds a comprehensive advantage in instruments for measuring the geometry of complex small components. The performance of the spot positioning sensor directly determines the capability of the PAM to measure complex small components. This study introduces the basic measurement principles of the PAM and commonly used spot positioning sensors. The analysis explored the feasibility of applying different sensors to the PAM. An automatic segmentation and weighted localisation algorithm of the spot based on the centroid method was proposed. Using this algorithm, the spot positioning error of the complementary metal–oxide–semiconductor (CMOS) sensor can be controlled within 0.48 μm, with a measurement uncertainty of no more than ±0.19 μm. This study focuses on comparing the performance of CMOS and position-sensitive detector sensors with the performance of seven indicators. In addition, a measurement system of the PAM was constructed, and measurements of the test object were conducted using both types of sensors. The experimental results show that when the measurement system employs the CMOS sensor, it achieves higher measurement accuracy. The maximum measurement error was approximately 0.22 μm, with a measurement uncertainty of no more than ±0.10 μm.

Maximizing microcalcification detectability in low-dose dedicated cone-beam breast CT: parallel cascades-based theoretical analysis.

We aim to determine the combination of X-ray spectrum and detector scintillator thickness that maximizes the detectability of microcalcification clusters in dedicated cone-beam breast CT. A cascaded linear system analysis was implemented in the spatial frequency domain and was used to determine the detectability index using numerical observers for the imaging task of detecting a microcalcification cluster with 0.17mm diameter calcium carbonate spheres. The analysis considered a thallium-doped cesium iodide scintillator coupled to a complementary metal-oxide semiconductor detector and an analytical filtered-back-projection reconstruction algorithm. Independent system parameters considered were the scintillator thickness, applied X-ray tube voltage, and X-ray beam filtration. The combination of these parameters that maximized the detectability index was considered optimal. Prewhitening, nonprewhitening, and nonprewhitening with eye filter numerical observers indicate that the combination of 0.525 to 0.6mm thick scintillator, 70kV, and 0.25 to 0.4mm added copper filtration maximized the detectability index at a mean glandular dose (MGD) of 4.5mGy. Using parallel cascade systems' analysis, the combination of parameters that could maximize the detection of microcalcifications was identified. The analysis indicates that a harder beam than that used in current practice may be beneficial for the task of detecting microcalcifications at an MGD suitable for breast cancer screening.

New method for optimizing the detection of low-energy soft X-rays (200–300 eV) in a CMOS detector

Complementary metal-oxide semiconductor (CMOS) sensors have been widely used as soft X-ray detectors in several fields owing to their recent developments and unique advantages. The CMOS detector parameters have been extensively studied and evaluated. However, the methods for discriminating signals and dark noise have not been sufficiently studied, particularly for low-energy soft X-rays. Setting a threshold, which is widely used for discrimination, is not suitable for low-energy soft X-rays because of the crossing of the energy bands of dark noise and signals. In this study, we analyzed the charge correlation of the CMOS detector GSENSE2020BSI (G2020BSI) and proposed a new two-dimensional segmentation method to optimize the discrimination of signals according to the charge correlation. The effectiveness of the method used to discriminate low-energy soft X-rays on the G2020BSI detector was qualitatively evaluated. The optimal feature parameters used in the two-dimensional segmentation method were investigated for G2020BSI. However, the two-dimensional segmentation method is insensitive to feature parameters.

Full-aperture extended-depth oblique plane microscopy through dynamic remote focusing.

The reprojection setup typical of oblique plane microscopy (OPM) limits the effective aperture of the imaging system, and therefore its efficiency and resolution. Large aperture system is only possible through the use of custom specialized optics. A full-aperture OPM made with off the shelf components would both improve the performance of the method and encourage its widespread adoption. To prove the feasibility of an OPM without a conventional reprojection setup, retaining the full aperture of the primary objective employed. A deformable lens based remote focusing setup synchronized with the rolling shutter of a complementary metal-oxide semiconductor detector is used instead of a traditional reprojection system. The system was tested on microbeads, prepared slides, and zebrafish embryos. Resolution and pixel throughput were superior to conventional OPM with cropped apertures, and comparable with OPM implementations with custom made optical components. An easily reproducible approach to OPM imaging is presented, eliminating the conventional reprojection setup and exploiting the full aperture of the employed objective.

Comprehensive characterisation of the IBA myQA SRS for SRS and SBRT patient specific quality assurance.

The myQA SRS (IBA) is a new to market 2D complementary metal oxide semiconductor detector array with an active area 140 × 120mm2 and 0.4mm resolution, making it a potential real-time dosimetry alternative to radiochromic film for stereotactic plan verification. Characterisation of the device was completed to assess performance. The dosimetric properties of the device were assessed for 6FF and 6FFF beams from a Varian TrueBeam STx with high definition multileaf collimator. Clinical suitability of the device for Patient Specific Quality Assurance was verified using ten SRS/SBRT plans, compared against other detectors, as well as multi leaf collimator (MLC) tests including picket fence and chair. Gamma analysis was performed using myQA software with criteria of 4%/1mm. The device demonstrated compliance with recommended specifications for basic tests. After the required warm-up period, the maximum deviation in detector signal from initial readings was 0.2%. Short-term and long-term reproducibility was 0.1% (6FF) and 1.0% (6FFF), respectively. Dose linearity was within 0.3% (6FF) and 0.7% (6FFF) and dose-rate dependence within 1.7% (6FF) and 2.9% (6FFF) and were verified with a Farmer type ionization chamber (PTW 30013). Angular dependence was quantified for coplanar and non-coplanar situations. Output factors and beam profiles measured on the device showed agreement within 1% of baseline RAZOR diode (IBA) and CC04 ionisation chamber (IBA) measurements for field sizes 1 × 1 to 10 × 10cm2. The minimum gamma (4%/1mm) pass rates for MLC-pattern tests were 96.5% and 98.1% for the myQA SRS and film, respectively. The average gamma (4%/1mm) pass rates for SBRT and SRS plans were 98.8% and 99.8% respectively. This work represents one of the first studies performed on the commissioning and performance characterisation of this novel device, demonstrating its accuracy and reliability, making it highly useful as a film alternative in stereotactic treatment plan verification.

Star Image Registration Modeling and Parameter Calibration for a 3CMOS Star Sensor.

This paper presents an image registration method specifically designed for a star sensor equipped with three complementary metal oxide semiconductor (CMOS) detectors. Its purpose is to register the red-, green-, and blue-channel star images acquired from three CMOS detectors, assuring the precision of star image fusion and centroid extraction in subsequent stages. This study starts with a theoretical analysis aimed at investigating the effect of inconsistent three-channel imaging parameters on the position of feature points. Based on this analysis, this paper establishes a registration model for transforming the red- and blue-channel star images into the green channel's coordinate system. Subsequently, the method estimates model parameters by finding a nonlinear least-squares solution. The experimental results demonstrate the correctness of the theoretical analysis and the proposed registration method. This method can achieve subpixel alignment accuracy in both the x and y directions, thus effectively ensuring the performance of subsequent operation steps in the 3CMOS star sensor.

Angular correction methodology and characterization of a high-resolution CMOS array for patient specific quality assurance on a robotic arm linac.

To develop an angular correction methodology and characterize a high-resolution complementary metal-oxide-semiconductor (CMOS) array for patient specific quality assurance on a robotic arm linear accelerator. Beam path files from the treatment planning software (TPS) were used to calculate the angle of radiation beam with respect to the detector plane. Beams from multiple discrete angles were delivered to the CMOS detector array and an angular dependency look up table (LUT) was created. The LUT was then used to correct for the angular dependency of the detector. An iso-centric 5mm fixed cone, non iso-centric multi-target fixed cone, 10mm Iris and a multi-leaf collimator (MLC) based collimated plan were delivered to the phantom and compared to the TPS with and without angular correction applied. Additionally, the CMOS array was compared to gafchromic film and a diode array. Large errors of up to 30% were observed for oblique angles. When angular correction was applied, the gamma passing rate increased from 99.2% to 100% (average gamma value decreased from 0.29 to 0.14) for the 5-mm iso-centric cone plan. Similarly, the passing rate increased from 84.0% to 100% for the Iris plan and from 49.98% to 98.4% for the MLC plan when angular correction was applied. For the multi-target plan, applying angular correction improved the gamma passing rate from 94% to 99.6%. The 5mm iso-centric fixed cone plan was also delivered to film, and the gamma passing rate was 91.3% when using gafchromic film as the reference dataset, whereas the diode array provided insufficient sampling for this plan. A methodology of calculating the beam angle based on the beam path files was developed and validated. The array was demonstrated to be superior to other quality assurance tools because of its sub-millimeter spatial resolution and immediate read out of the results.

Development of CMOS dosimetry in proton minibeams for enhanced QA and primary standard absorbed dose calorimetry

Performing accurate and reliable dosimetry in spatially fractionated beams remains a significant challenge due to the steep dose gradients and microscopic scale of features. This results in many conventional detectors and instrumentation being unsuitable for online dosimetry, necessitating frequent offline validation using radiochromic film.In this study, the use of a Complementary Metal-Oxide-Semiconductor (CMOS) detector for evaluation of relative real-time dosimetry of proton minibeam radiation therapy (pMBRT) was investigated. The linearity of the CMOS detector was investigated by varying the proton beam current, with a comparison to a PTW 34001 Roos ionisation chamber used to carry out an independent check. It was found that the relative peaks and valleys of the pMBRT beam could be measured, with results comparable to EBT3XD film. The high sensitivity of the CMOS detector meant it was able to measure dose profiles from peak to valley regions, something not possible with the EBT3XD. The CMOS detector was compared to the treatment delivery log files, with correlation in beam position seen as the beam is scanned along each slit, but not across; and agreement in beam intensity, with the CMOS detector able to observe beam interruptions.Lastly, the CMOS detector was used in conjunction with the NPL primary-standard proton calorimeter (NPL PSPC) for a preliminary study on combining the NPL PSPC with high resolution temporal information about the incident pMBRT beam. The ultimate aim of this approach is to facilitate detailed thermal modelling to reduce the overall uncertainty in the absolute dose measured from the calorimeter. In these experiments, saturation in the CMOS pixels prevented further thermal modelling of the radiation induced heat flow, however the instantaneous dose rate was observed to be comparable with the predicted NPL PSPC response obtained by masking the CMOS detector.

Evaluation of a complementary metal oxide semiconductor detector as a tool for stereotactic body radiotherapy plan quality assurance.

A sub-mm resolution Complementary Metal Oxide Semiconductor sensor has been developed for stereotactic radiotherapy quality assurance. Herein we evaluate its basic dosimetric performance and its application for linac C-arm stereotactic body radiotherapy (SBRT) plan quality assurance. The detector was integrated into its accompanying phantom or in Water Equivalent Plastic (WEP). The measurement reproducibility, stability, dose linearity and dependence on angularity, dose rate and field size were investigated. Clinical plan measurements were compared to our radiotherapy treatment planning system and radiochromic film. Sensitivity to introduced Multi Leaf Collimator (MLC) offsets was evaluated by simulating single MLC offsets in SBRT plans and comparing measurements to expected doses. Signal reproducibility was within±0.1% and output calibration was stable over a 6month period. Detector showed good linearity with dose (r2=1). Signal decreased by 5% when dose rate was decreased from 1300 MU/min to 300 MU/min. Output factors agreed within 0.5% of chamber measurements for 1x1 cm field sizes or greater. Angularity measurements showed good agreement with reference. For measurement of planned clinical doses, gamma pass-rates were 98.5%±2.3% (treatment planning system reference, 2%/2mm) and 99.2%±1.0% (film reference, 2%,2mm). The detector also showed sensitivity to errors of 1mm offsets in MLC positioning. The detector performed well when used for pre-treatment SBRT plan quality assurance, offering a good alternative to radiochromic film.

Performance improvement of space-resolved extreme ultraviolet spectrometer by use of complementary metal-oxide semiconductor detectors at the Experimental Advanced Superconducting Tokamak.

Two pairs of space-resolved extreme ultraviolet (EUV) spectrometers working at 5-138 Å with different vertical observation ranges of -7 ≤ Z ≤ 19 and -18 ≤ Z ≤ 8cm have been newly developed to observe the radial profile of impurity line emissions and to study the transport of high-Z impurity ions intrinsically existing in EAST tokamak plasmas. Both spectrometers are equipped with a complementary metal-oxide semiconductor (CMOS) detector (Andor Marana-X 4.2B-6, Oxford Instruments) with sensitive area of 13.3 × 13.3mm2 and number of pixels equal to 2048 × 2048 (6.5 × 6.5 µm2/pixels). Compared to the currently operating space-resolved EUV spectrometers with a charge-coupled detector (CCD: 1024 × 255 pixels, 26 × 26 µm2) working at 30-520 Å, this spectrometer's performance was substantially improved by using the CMOS detector. First, the spectral resolution measured at full width at half maximum was improved in the whole wavelength range, e.g., Δλ1/2_CMOS = 0.092 Å and Δλ1/2_CCD = 0.124 Å at C VI 33.73 Å and Δλ1/2_CMOS = 0.104 Å and Δλ1/2_CCD = 0.228 Å at Mo XXXI 115.999 Å, thus enabling a more accurate analysis of spectra with complicated structure such as tungsten unresolved transition array in the range 45-65 Å. Second, the temporal resolution was largely improved due to the high-speed data acquisition system of the CMOS detector, e.g., Δt_CMOS = 15 ms/frame and Δt_CCD = 200 ms/frame at routine operation in the radial profile measurement. Third, signal saturation issues that occurred when using the old CCD sensor during impurity accumulation now disappeared entirely using the CMOS detector due to lower exposure time at high readout rates, which largely improved the observation performance in similar impurity burst events. The above-mentioned performance improvements of the space-resolved EUV spectrometer led to a rapid change in the W XXXIII (52.22 Å) radial profile during a single cycle of low-frequency sawtooth oscillation with fst = 5-6Hz at a sufficient detector count rate.

Quantum Dots‐Functionalized Encryption Camera for Text Image Security Protection

With the wide utilization of mobile devices with a camera as online communication tools, there is a great need to develop image encryption technology for protecting confidential and sensitive information. Herein, quantum dots‐functionalized encryption (QDE) camera is proposed by integrating the fluorescence emission of quantum dots (QDs) with charge coupled device or complementary metal oxide semiconductor detector arrays during the imaging process. The variation of the photoluminescence emission from QDs controlled by UV365 nm illumination provides a convenient way to scramble the spatial distribution of RGB values in the captured image, which expands the information entropy of the captured image to realize in situ image encryption. The encrypted text images can be decrypted by a convolutional neural network‐based algorithm, resulting in high‐quality decrypted images with peak signal‐to‐noise ratio up to 45 dB. Compared with the previous reported image encryption techniques of chaotic cryptosystem, fluorescent material‐based encryption, and optical encryption, the proposed QDE camera shows advantages of high execution speed and easy miniaturization. It provides a promising in situ image encryption technique to guarantee information security in digitization process.

Development of a Lensless Radiomicroscope for Cellular-Resolution Radionuclide Imaging.

The action of radiopharmaceuticals takes place at the level of cells. However, existing radionuclide assays can only measure uptake in bulk or in small populations of single cells. This potentially hinders the development of effective radiopharmaceuticals for disease detection, staging, and treatment. Methods: We have developed a new imaging modality, the lensless radiomicroscope (LRM), for invitro, cellular-resolution imaging of β- and α-emitting radionuclides. The palm-sized instrument is constructed from off-the-shelf parts for a total cost of less than $100, about 500 times less than the radioluminescence microscope, its closest equivalent. The instrument images radiopharmaceuticals by direct detection of ionizing charged particles via a consumer-grade complementary metal-oxide semiconductor detector. Results: The LRM can simultaneously image more than 5,000 cells within its 1 cm2 field of view, a 100-times increase over state-of-the-art technology. It has spatial resolution of 5 μm for brightfield imaging and 30 μm for 18F positron imaging. We used the LRM to quantify 18F-FDG uptake in MDA-MB-231 breast cancer cells 72 h after radiation treatment. Cells receiving 3 Gy were 3 times larger (mean = 3,116 μm2) than their untreated counterparts (mean = 940 μm2) but had 2 times less 18F-FDG per area (mean = 217 Bq/mm2), a finding in agreement with the clinical use of this tracer to monitor response. Additionally, the LRM was used to dynamically image the uptake of 18F-FDG by live cancer cells, and thus measure their avidity for glucose. Conclusion: The LRM is a high-resolution, large-field-of-view, and cost-effective approach to image radiotracer uptake with single-cell resolution invitro.

Compact laboratory-based X-ray microscope enabling nondestructive 3D structure acquisition of mouse nephron with high speed and better user accessibility.

X-ray microscopes adopting computed tomography enable nondestructive 3D visualization of biological specimens at micron-level resolution without conventional 2D serial sectioning that is a destructive/laborious method and is routinely used for analyzing renal biopsy in clinical diagnosis of kidney diseases. Here we applied a compact commercial system of laboratory-based X-ray microscope to observe a resin-embedded osmium-stained 1-mm strip of a mouse kidney piece as a model of renal biopsy, toward a more efficient diagnosis of kidney diseases. A reconstructed computed tomography image from several hours of data collection using CCD detector allowed us to unambiguously segment a single nephron connected to a renal corpuscle, which was consistent with previous reports using serial sectioning. Histogram analysis on the segmented nephron confirmed that the proximal and distal tubules were distinguishable on the basis of their X-ray opacities. A 3D rendering model of the segmented nephron visualized a convoluted structure of renal tubules neighboring the renal corpuscle and a branched structure of efferent arterioles. Furthermore, another data collection using scientific complementary metal-oxide semiconductor detector with a much shorter data acquisition time of 15 min provided similar results from the same samples. These results suggest a potential application of the compact laboratory-based X-ray microscope to analyze mouse renal biopsy.

Two-component compensators of field aberrations of optical systems

Subject of study. Two-component optical schemes of compensators of field aberrations of optical systems calculated based on the third-order aberration theory and modular method of optical system design [Izv. Vyssh. Uchebn. Zaved., Priborostr.57, 57 (2014)] are proposed. These compensators enable correction of two aberrations: Petzval field curvature and astigmatism or longitudinal chromatic aberration and lateral color or transverse chromatic aberration. Method. A modular method for the design of optical systems based on the third-order aberration theory was used in the calculation. This method consists of synthesis of the systems using optical elements (modules) with known correcting properties [Izv. Vyssh. Uchebn. Zaved., Priborostr.57, 57 (2014)]. Aplanatic menisci with different linear magnifications and a hyperchromatic lens were used as optical modules. The aplanatic menisci were used to calculate the compensator of Petzval field curvature and astigmatism, whereas the hyperchromatic lens was used to calculate the compensator of longitudinal and transverse chromatic aberrations. Main results. The use of two-component compensators of field aberrations enables significant enhancements in the aberrational properties of the objectives, improves the image quality of optical systems, and increases their optical parameters, particularly the angular field of doublet objectives (fivefold) using the correcting properties of optical modules (menisci and hyperchromatic lens). Practical significance. The introduction of a compensator composed of two aplanatic menisci positioned at a significant distance from each other into the optical system makes it possible to correct such aberrations as field curvature and astigmatism regardless of the number of lenses in the objective and increase the angular field. The introduction of a compensator of chromatic aberrations into an optical scheme of a high-aperture microscope objective with 100×1.25 oil immersion corrects the longitudinal and transverse chromatic aberrations. This makes it possible to cease the use of compensating eyepieces with a complex optical scheme and replace them with standard eyepieces as well as to use a microscope where the optical radiation is detected by a charge-coupled device array or complementary metal oxide semiconductor detector instead of the human eye.

Monitoring pencil beam scanned proton radiotherapy using a large format CMOS detector

Pencil beam scanning is an effective form of proton radiotherapy for cancer treatment. Small beams of protons are magnetically deflected in order to conform to a tumour shape, and exploiting the Bragg peak in order to minimise dose deposited in healthy tissues. Compared to other therapy modalities, it presents many dosimetric challenges requiring new methods of quality-assurance to ensure the best patient outcome possible. Position Sensitive Detectors (PSD) made from Complementary Metal–Oxide–Semiconductor (CMOS) technology offer one such solution for in-situ and in-vivo dosimetry, with ongoing developments towards high resolution imaging panels that are tolerant to high levels of ionising radiation. After confirming the linearity of the detector using a pulsed laser system, the suitability of CMOS technology, the vM2428 detector, a large-format CMOS device with 50μm pixel pitch, was investigated at the University College Hospitals London NHS Foundation Trust (UCLH) proton beam centre using a 220 MeV proton beam at clinical beam currents. The shape of the proton beam was intentionally distorted, enabling the comparison of the vM2428 detector and EBT3 film spot shapes in a fault-finding scenario for QA purposes. For stationary beams, it was found that the vM2428 detector was capable of acquiring 1D and 2D beam profiles comparable to EBT3 film within a single frame (≈4 ms). The detector was then exposed to laterally displaced beams of the same spot size (”spot scanning”) that emulates a clinical beam delivery and was found able to record the beam displacement in real time. The spot-to-spot separation was measured to be 5.35 ± 0.03 mm, in agreement with the planned 5.356 mm. These results highlight the versatility and potential of large-format CMOS detectors to proton beam therapy.

Single-shot experiments at the soft X-FEL FERMI using a back-side-illuminated scientific CMOS detector.

The latest Complementary Metal Oxide Semiconductor (CMOS) 2D sensors now rival the performance of state-of-the-art photon detectors for optical application, combining a high-frame-rate speed with a wide dynamic range. While the advent of high-repetition-rate hard X-ray free-electron lasers (FELs) has boosted the development of complex large-area fast CCD detectors in the extreme ultraviolet (EUV) and soft X-ray domains, scientists lacked such high-performance 2D detectors, principally due to the very poor efficiency limited by the sensor processing. Recently, a new generation of large back-side-illuminated scientific CMOS sensors (CMOS-BSI) has been developed and commercialized. One of these cost-efficient and competitive sensors, the GSENSE400BSI, has been implemented and characterized, and the proof of concept has been carried out at a synchrotron or laser-based X-ray source. In this article, we explore the feasibility of single-shot ultra-fast experiments at FEL sources operating in theEUV/soft X-ray regime with an AXIS-SXR camera equipped with the GSENSE400BSI-TVISB sensor. We illustrate the detector capabilities by performing a soft X-ray magnetic scattering experiment at the DiProi end-station of the FERMI FEL. These measurements show the possibility of integrating this camera for collecting single-shot images at the 50 Hz operation mode of FERMI with a cropped image size of 700× 700 pixels. The efficiency of the sensor at a working photon energy of 58 eV and the linearity over the large FEL intensity have been verified. Moreover, on-the-fly time-resolved single-shot X-ray resonant magnetic scattering imaging from prototype Co/Pt multilayer films has been carried out with a time collection gain of 30 compared to the classical start-and-stop acquisition method performed with the conventional CCD-BSI detector available at the end-station.

Automated Crystal Orientation Mapping by Precession Electron Diffraction-Assisted Four-Dimensional Scanning Transmission Electron Microscopy Using a Scintillator-Based CMOS Detector

The recent development of electron-sensitive and pixelated detectors has attracted the use of four-dimensional scanning transmission electron microscopy (4D-STEM). Here, we present a precession electron diffraction-assisted 4D-STEM technique for automated orientation mapping using diffraction spot patterns directly captured by an in-column scintillator-based complementary metal-oxide-semiconductor (CMOS) detector. We compare the results to a conventional approach, which utilizes a fluorescent screen filmed by an external charge charge-coupled device camera. The high-dynamic range and signal-to-noise characteristics of the detector greatly improve the image quality of the diffraction patterns, especially the visibility of diffraction spots at high scattering angles. In the orientation maps reconstructed via the template matching process, the CMOS data yield a significant reduction of false indexing and higher reliability compared to the conventional approach. The angular resolution of misorientation measurement could also be improved by masking reflections close to the direct beam. This is because the orientation sensitive, weak, and small diffraction spots at high scattering angles are more significant. The results show that fine details, such as nanograins, nanotwins, and sub-grain boundaries, can be resolved with a sub-degree angular resolution which is comparable to orientation mapping using Kikuchi diffraction patterns.

Transit Search for Exoplanets around Alpha Centauri A and B with ASTERIA

Abstract Alpha Centauri is a triple star system with two Sun-like stars, α Cen A (V = 0.01) and B (V = 1.33), and a third fainter red dwarf star, Proxima Centauri. Most current transit missions cannot produce precision photometry of α Cen A and B as their detectors saturate for these very bright stars. The Arcsecond Space Telescope Enabling Research in Astrophysics (ASTERIA) was a technology demonstration mission that successfully demonstrated two key technologies necessary for precision photometry achieving line-of-sight fine-pointing stability of 0.5″ rms and focal plane temperature control of ±0.01 K over a period of 20 minutes. The payload consisted of a 6.7 cm aperture diameter refractive camera and used a scientific complementary metal-oxide semiconductor detector that enabled monitoring of the brightest stars without saturating. We obtained spatially unresolved (blended) observations of α Cen A and B during opportunistic science campaigns as part of ASTERIA’s extended mission. The resulting 1σ photometric precision for the blended α Cen A and B data is 250 ppm (parts per million) per 9 s exposure. We do not find evidence of transits in the blended data. We establish limits for transiting exoplanets around both α Cen A and B using transit signal injection and recovery tests. We find that ASTERIA is sensitive to planets with radii as small as 3.0 R ⊕ around α Cen A and 3.7 R ⊕ around α Cen B, corresponding to signals of ∼500 ppm (signal-to-noise ratio = 5.0) in the blended data, with periods ranging from 0.5 to 6 days.

Towards soft x-ray fluorescence measurements in the laboratory using a laser-produced plasma source and a complementary metal-oxide semiconductor detector

With the advent of commercially available CMOS technology suitable for direct detection of photons in the soft X-ray range, new possibilities are opening up for the improvement and optimization of experiments requiring energy discrimination capabilities in this energy range. SDDs are widely used as energy-dispersive detectors, but they cannot be used with pulsed sources due to the overwhelming temporal photon density. Wavelength-dispersive solutions offer unmatched energy resolution, but suffer from low detection efficiency and a limited energy bandwidth which can be monitored. The use of common CCDs as energy-dispersive detectors in this energy range is limited by their energy resolution and especially their readout speed, which can result in significant experimental dead time and limits the usable frequency of pulsed sources. Therewhile, CMOS detectors with high energy resolution and high frame rates are an efficient, versatile and cost-effective alternative as detectors for pulsed sources. In this work we present the characterization of a commercially available, backside-illuminated CMOS detector regarding its energy resolution and quantum efficiency at the BESSY II synchrotron radiation facility with a well-known soft X-ray radiation source. Furthermore it is used in a proof of principle XRF measurement with a laboratory-based laser-plasma source.

Overview of CMOS Sensors for Future Tracking Detectors

Depleted Complementary Metal-Oxide-Semiconductor (CMOS) sensors are emerging as one of the main candidate technologies for future tracking detectors in high luminosity colliders. Their capability of integrating the sensing diode into the CMOS wafer hosting the front-end electronics allows for reduced noise and higher signal sensitivity, due to the direct collection of the sensor signal by the readout electronics. They are suitable for high radiation environments due to the possibility of applying high depletion voltage and the availability of relatively high resistivity substrates. The use of a CMOS commercial fabrication process leads to their cost reduction and allows faster construction of large area detectors. In this contribution, a general perspective of the state of the art of CMOS detectors for High Energy Physics experiments is given. The main developments carried out with regard to these devices in the framework of the CERN RD50 collaboration are summarized.