X-ray spectroscopy is an important method in exploring the material composition and elemental properties. Traditional spectrometers in X-ray spectroscopy include wavelength-dispersive type and semiconductors-based energy-dispersive type. The former possesses high energy resolution but low collecting efficiency and narrow spectral band coverage, while the latter is more efficient and wider in spectral range but give relatively low energy resolution. Spectrometers based on microcalorimeters serve as a new class of energy-dispersive type spectrometers which balance the performance in energy resolution, detection efficiency, and spectral coverage, making them promising in many spectroscopy applications. The superconducting transition-edge sensor (TES) is a representative class of maturely developed microcalorimeters success in array fabrication and readout. We are developing TESs-based X-ray spectrometer at ShanghaiTech University aiming at the application in advanced X-ray light source, like synchrotron radiation or free electron laser facilities. Recently, a prototype has been set up and started running in the lab. This paper introduces a systematic work on data processing with this prototype, focusing on both data acquisition and analysis. With optimization on both hardware and analysis, we have achieved resolution better than 7 eV in the range from 2 keV to 9 keV on the prototype.
In order to meet the demand of X-ray spectroscopy measurement for SHINE and other X-ray light source projects, a multi-pixel TES X-ray spectrometer with high counting rate is currently being developed by the joint team of ShanghaiTech University and Shanghai Institute of Microsystem and Information Technology, etc. Recently, a 16-pixel prototype chip has been completed. With the long-term goal to build a set of X-ray spectrometer with more than 100 channels, which can be applied for the energy band of 0.3 -20 keV. In the mean time, a calibration system constructed, TES based X-ray detector of SBP tested on this system, energy resolution of 5.2 eV@5.9 keV has been obtained.
In the case of no synchrotron radiation source or free electron X-ray laser, it is difficult to obtain narrow energy-band X-rays in energy range lower than the 1 keV, which mainly owing to that soft X-rays are easily absorbed, and the low fluorescence efficiency of this energy range, thus the fluorescence photons are often submerged under a strong scattering background.1 In order to complete the calibration of TES chips in this energy range, our team built up a set of intrinsic energy resolution calibration system for TESs by the 405 nm laser.2-4 Its working principle, structure and preliminary test results will be briefly introduced in this paper.
Hot Universe Baryon Surveyor (HUBS) is being conceptualized in China as a high throughput and high-resolution spectroscopic X-ray mission dedicated to studying cosmic "missing" baryons, which are thought to exist in the gas of very low density and temperature roughly one million degrees in the halo of galaxies or in large-scale structures. To detect weak emission from the "missing" baryons, HUBS will employ a TES-based X-ray microcalorimeter array that operates at very low temperatures. The key characteristics of the detector technology are excellent energy resolution and high quantum efficiency, which makes it an ideal choice for constructing a non-dispersive X-ray imaging spectrometer. We are developing X-ray microcalorimeters for HUBS, based on superconducting Mo/Cu bilayer films. In this work, we present results on the characterization of the Mo/Cu films and TES devices at temperatures below 100 mK, including their R-T curves, I-V characteristics, energy resolutions, etc. We have also studied correlations between the superconducting transition temperature and other properties of the films (including residual resistivity ratio, stress, crystalline structure, interface properties, and so on), and looked into factors that might affect the energy resolution of the detectors. Preliminary results will be presented.
The Hot Universe Baryon Surveyor (HUBS) mission is proposed to study “missing” baryons in the universe. Unlike dark matter, baryonic matter is made of elements in the periodic table, and can be directly observed through the electromagnetic signals that it produces. Stars contain only a tiny fraction of the baryonic matter known to be present in the universe. Additional baryons are found to be in diffuse (gaseous) form, in or between galaxies, but a significant fraction has not yet been seen. The latter (“missing” baryons) are thought to be hiding in low-density warm-hot ionized medium (WHIM), based on results from theoretical studies and recent observations, and be distributed in the vicinity of galaxies (i.e., circumgalactic medium) and between galaxies (i.e., intergalactic medium). Such gas would radiate mainly in the soft X-ray band and the emission would be very weak, due to its very low density. HUBS is optimized to detect the X-ray emission from the hot baryons in the circumgalactic medium, and thus fill a void in observational astronomy. The goal is not only to detect the “missing” baryons, but to characterize their physical and chemical properties, as well as to measure their spatial distribution. The results would establish the boundary conditions for understanding galaxy evolution. Though highly challenging, detecting “missing” baryons in the intergalactic medium could be attempted, perhaps in the outskirts of galaxy clusters, and could shed significant light on the large-scale structures of the universe. The current design of HUBS will be presented, along with the status of technology development.
Hot Universe Baryon Surveyor (HUBS)1 is being conceptualized in China as a high throughput and highresolution spectroscopic X-ray mission dedicated to studying cosmic “missing” baryons, which are thought to exist in the gas of very low density and temperature of roughly one million degrees in the halo of galaxies or in large-scale structures. To detect weak emission from the “missing” baryons, HUBS will employ an X-ray microcalorimeter based on transition-edge sensors (TES) array that operates at very low temperatures. The key characteristics of the detector technology are excellent energy resolution and high quantum efficiency, which makes it an ideal choice for constructing a non-dispersive X-ray imaging spectrometer. We are developing X-ray microcalorimeters for HUBS, based on superconducting Mo/Cu bilayer films. In this work, we present results on characterization of the Mo/Cu films and TES devices at temperatures below 200 mK, including their I − V characteristics, pulse signals and energy resolutions. We have also studied correlations between the superconductivity and other properties of the films (including residual resistivity ratio, stress, crystalline structure, interface properties, etc.). Preliminary results are presented in this work.
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