- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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Non-linear soft x-ray methods on solids with MUSIX—the multi-dimensional spectroscopy and inelastic x-ray scattering endstation
摘要： With the intense and coherent x-ray pulses available from free-electron lasers, the possibility to transfer non-linear spectroscopic methods from the laser lab to the x-ray world arises. Advantages especially regarding selectivity and thus information content as well as an improvement of signal levels are expected. The use of coherences is especially fruitful and the example of coherent x-ray/optical sum-frequency generation is discussed. However, many non-linear x-ray methods still await discovery, partially due to the necessity for extremely adaptable and versatile instrumentation that can be brought to free-electron lasers for the analysis of the spectral content emitted from the sample into a continuous range of emission angles. Such an instrument (called MUSIX) is being developed and employed at FLASH, the free-electron laser in Hamburg and is described in this contribution together with first results.
关键词： free-electron lasers,x-ray instrumentation,x-ray spectroscopy,ultrafast dynamics
更新于2025-09-09 09:28:46
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A synchronization and data acquisition system for silicon detectors
摘要： A dedicated synchronization bus has been developed and integrated into the FITPix COMBO device. It can be used as Timepix read-out (involving back-side-pulse acquisition) or as a simple spectrometer device — Spectrig (when an external single pad sensor is connected, e.g. ?E detector). The synchronization bus permits the implementation of a system of up to 32 distinct devices running in clock locked mode while the absolute value of the timestamp is distributed to all devices in the system. Any combination of Timepix or spectrometer devices (up to 32) can be connected-up to create a ?nal measurement set-up. The synchronization bus has also been designed to control a trigger signal and busy signal to allow an e?ective ?ltration of unpaired events when coincidence measurement is performed. The system has been tested with a ?E?E telescope consisting of a thin detector and Timepix. The thin detector has been used for ?E and the Timepix detector for E measurements. The ?E detector has an area of 10 × 10 mm2 and a thickness of 12 μm with non-uniformity of 8%. The area and thickness of Timepix are 14 × 14 mm2 and 300 μm, respectively. The detection system can provide simultaneous information about position, energy, time and type of registered particles with high synchronization accuracy. Test measurements have been carried out with an alpha particle source (Ra-226) in a vacuum and the results of these measurements are presented in this paper.
关键词： Trigger concepts and systems (hardware and software),Instrumentation and methods for heavy-ion reactions and ?ssion studies,Ion identi?cation systems,Data acquisition concepts
更新于2025-09-09 09:28:46
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A new calibration strategy for adaptive telescopes with pyramid WFS
摘要： Several telescopes include large deformable mirrors (DM) located directly inside the telescope. These adaptive telescopes trigger new constraints for the calibration of the adaptive optics (AO) systems as they usually offer no access to an artificial calibration source for the interaction matrix measurement. Moreover, the optical propagation between the DM and the wavefront sensor (WFS) may evolve during the operation, resulting in misregistrations that highly affect the AO performance and thus the scientific observation. They have to be measured and compensated, for instance by updating the calibration. A new strategy consists of estimating the misregistrations and injecting them into synthetic models to generate noise-free interaction matrices. This pseudo-synthetic approach is the baseline for the adaptive optics facility working with a Shack–Hartmann WFS and seems particularly suited for the future Extremely Large Telescope as the calibration will have to be regularly updated, for a large numbers of actuators. In this paper, the feasibility of a pseudo-synthetic calibration with pyramid WFS at the Large Binocular Telescope (LBT) is investigated. A synthetic model of the LBT AO systems is developed, and the procedure to adjust the misregistrations parameters is introduced, extracting them from an experimental interaction matrix. We successfully tested an interaction matrix generated from the model on the real system in high-order AO mode. We recorded a slightly better performance with respect to the experimental one. This work demonstrates that a high-accuracy calibration can be obtained using the pseudo-synthetic approach with pyramid WFS.
关键词： telescopes,instrumentation: adaptive optics
更新于2025-09-09 09:28:46
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67P/Churyumov-Gerasimenko active areas before perihelion identified by GIADA and VIRTIS data fusion
摘要： We characterised 67P/Churyumov-Gerasimenko?s cometary activity during its inbound arc before perihelion (August 2014-January 2015). We focused on the geomorphological regions of the Northern hemisphere observed by the ESA/Rosetta space probe during this time period. The GIADA dust detector characterised the physical properties of the fluffy and compact particles ejected from the nucleus; the VIRTIS imaging spectrometer detected exposed water ice. We identified specific cometary active areas by adopting the following GIADA and VIRTIS indicators: a) The decrease with increasing temperature of the centre of the 3.2-?m absorption band and of the spectral slope between 1.1 and 1.9??m, as measured by VIRTIS, which are both possible effects of water ice exposition. b) The number of fluffy and compact particles ejected from a specific region, which we determined by tracing dust particles in the coma, as detected by GIADA, back down to the nucleus. The correlation between GIADA and VIRTIS indicators led us to conclude that dust emission causes exposition of water ice on the surface of the nucleus, and fluffy and compact particles have common ejection regions; their lack of correlation in the coma is due to spread induced by their different velocities. We find that the most active regions are located in the neck (Hapi and Seth) and in the body (Ash, Babi and Aten) of the comet. These regions are also the ones most illuminated during the considered observation period, indicating that insolation is the main, if not only, driver of cometary activity.
关键词： Methods: data analysis,Instrumentation: detectors,Comets: Churyumov-Gerasimenko,Techniques: imaging spectroscopy
更新于2025-09-09 09:28:46
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Review of Measured Photon Detection Efficiencies of Microchannel Plates
摘要： In this work, we examine the history of detection efficiency measurements of photons (soft to hard X-rays and beyond) with microchannel plates (MCPs). We investigate the detection efficiency as a function of photon energy over a wide energy range, from a few hundred eV up to 20 MeV. We also investigate detection efficiency as a function of incident angle onto the MCP. We interpreted the published efficiency data measured with a variety of MCPs, the use of MCP coatings for enhancement of X-ray quantum detection efficiency, and discuss theoretical expectations based on the main photon interactions with matter: the photoelectric effect, Compton scattering, and pair production. Contributing to the published literature at the highest end of the energy range, we also discuss our photon detection efficiency experiments from 2.5 to 20 MeV and theoretical implications.
关键词： Radiation environment,Space radiation environments,Radiation effects,Space instrumentation,Detectors,Space radiation
更新于2025-09-09 09:28:46
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NELIOTA: The wide-field, high-cadence, lunar monitoring system at the prime focus of the Kryoneri telescope
摘要： We present the technical specifications and first results of the ESA-funded, lunar monitoring project "NELIOTA" (NEO Lunar Impacts and Optical TrAnsients) at the National Observatory of Athens, which aims to determine the size-frequency distribution of small near-Earth objects (NEOs) via detection of impact flashes on the surface of the Moon. For the purposes of this project a twin camera instrument was specially designed and installed at the 1.2 m Kryoneri telescope utilizing the fast-frame capabilities of scientific Complementary Metal-Oxide Semiconductor detectors (sCMOS). The system provides a wide field-of-view (17.0'×14.4') and simultaneous observations in two photometric bands (R and I), reaching limiting magnitudes of 18.7 mag in 10 s in both bands at a 2.5 signal-to-noise ratio (S/N) level. This makes it a unique instrument that can be used for the detection of NEO impacts on the Moon, as well as for any astronomy projects that demand high-cadence multicolor observations. The wide field-of-view ensures that a large portion of the Moon is observed, while the simultaneous, high-cadence, monitoring in two photometric bands makes possible the determination of the temperatures of the impacts on the Moon’s surface and the validation of the impact flashes from a single site. Considering the varying background level on the Moon’s surface we demonstrate that the NELIOTA system can detect NEO impact flashes at a 2.5 S/N level of ～12.4 mag in the I-band and R-band for observations made at low lunar phases (～0.1). We report 31 NEO impact flashes detected during the first year of the NELIOTA campaign. The faintest flash was at 11.24 mag in the R-band (about two magnitudes fainter than ever observed before) at lunar phase 0.32. Our observations suggest a detection rate of 1.96 × 10?7 events km?2 h?1.
关键词： Moon,telescopes,techniques: miscellaneous,instrumentation: detectors,surveys
更新于2025-09-09 09:28:46
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Interstellar communication: The colors of optical SETI
摘要： It has recently been argued from a laser engineering point of view that there are only a few magic colors for optical SETI. These are primarily the Nd:YAG line at 1,064 nm and its second harmonic (532.1 nm). Next best choices would be the sum frequency and/or second harmonic generation of Nd:YAG and Nd:YLF laser lines, 393.8 nm (near Fraunhofer CaK), 656.5 nm (Hα) and 589.1 nm (NaD2). In this paper, we examine the interstellar extinction, atmospheric transparency and scintillation, as well as noise conditions for these laser lines. For strong signals, we ?nd that optical wavelengths are optimal for distances d (cid:2) kpc. Nd:YAG at λ = 1,064 nm is a similarly good choice, within a factor of two, under most conditions and out to d (cid:2) 3 kpc. For weaker transmitters, where the signal-to-noise ratio with respect to the blended host star is relevant, the optimal wavelength depends on the background source, such as the stellar type. Fraunhofer spectral lines, while providing lower stellar background noise, are irrelevant in most use cases, as they are overpowered by other factors. Laser-pushed space?ight concepts, such as “Breakthrough Starshot”, would produce brighter and tighter beams than ever assumed for OSETI. Such beamers would appear as naked eye stars out to kpc distances. If laser physics has already matured and converged on the most ef?cient technology, the laser line of choice for a given scenario (e.g., Nd:YAG for strong signals) can be observed with a narrow ?lter to dramatically reduce background noise, allowing for large ?eld-of-view observations in fast surveys.
关键词： Techniques: photometric,Instrumentation: spectrometers,Optical SETI,lasers,interstellar communication
更新于2025-09-09 09:28:46
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Flame : A flexible data reduction pipeline for near-infrared and optical spectroscopy
摘要： We present flame, a pipeline for reducing spectroscopic observations obtained with multislit near-infrared and optical instruments. Because of its ?exible design, flame can be easily applied to data obtained with a wide variety of spectrographs. The ?exibility is due to a modular architecture, which allows changes and customizations to the pipeline, and relegates the instrument-speci?c parts to a single module. At the core of the data reduction is the transformation from observed pixel coordinates (x, y) to recti?ed coordinates (λ, γ ). This transformation consists in the polynomial functions λ(x, y) and γ (x, y) that are derived from arc or sky emission lines and slit edge tracing, respectively. The use of 2D transformations allows one to wavelength calibrate and rectify the data using just one interpolation step. Furthermore, the γ (x, y) transformation includes also the spatial misalignment between frames, which can be measured from a reference star observed simultaneously with the science targets. The misalignment can then be fully corrected during the recti?cation, without having to further resample the data. Sky subtraction can be performed via nodding and/or modelling of the sky spectrum; the combination of the two methods typically yields the best results. We illustrate the pipeline by showing examples of data reduction for a near-infrared instrument (LUCI at the Large Binocular Telescope) and an optical one (LRIS at the Keck telescope).
关键词： techniques: spectroscopic,methods: observational,methods: data analysis,instrumentation: spectrographs
更新于2025-09-09 09:28:46
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Design and Bolometer Characterization of the SPT-3G First-Year Focal Plane
摘要： During the austral summer of 2016–2017, the third-generation camera, SPT-3G, was installed on the South Pole Telescope, increasing the detector count in the focal plane by an order of magnitude relative to the previous generation. Designed to map the polarization of the cosmic microwave background, SPT-3G contains ten 6(cid:2)(cid:2)-hexagonal modules of detectors, each with 269 trichroic and dual-polarization pixels, read out using 68× frequency-domain multiplexing. Here we discuss design, assembly, and layout of the modules, as well as early performance characterization of the ?rst-year array, including yield and detector properties.
关键词： CMB,Instrumentation,TES,Bolometer,SPT-3G
更新于2025-09-09 09:28:46
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OIFITS 2: the 2nd version of the data exchange standard for optical interferometry
摘要： This paper describes version 2 of the Optical Interferometry exchange Format (OIFITS), the standard for exchanging calibrated data from optical (visible or infrared) interferometers. This IAU-endorsed standard has been in use for 10 years at most of the past and current optical interferometer projects, including COAST, NPOI, IOTA, CHARA, VLTI, PTI and the Keck interferometer. Software is available for reading, writing and merging OIFITS files. This version 2 provides definitions of additional data tables (for example for polarisation measurements), addressing the needs of future interferometric instruments. Also included are data columns for a more rigorous description of measurement errors and their correlations. In that, this document is a step towards the design of a common data model for optical interferometry. Finally, the main OIFITS header is expanded with several new keywords summarising the content to allow doing data base searches.
关键词： standards,virtual observatory tools,techniques: interferometric,instrumentation: interferometers,methods: data analysis,techniques: image processing
更新于2025-09-09 09:28:46