Modulated X-ray Source Research Articles

Characterization of a Modulated X-ray Source for Ion Mobility Spectrometry.

As a highly deployed field instrument for the detection of narcotics, explosives, and chemical warfare agents, drift tube ion mobility spectrometry relies heavily upon the performance of the ionization source and mechanism of ion beam modulation. For this instrumental platform, ion chemistry plays a critical role in the performance of the instrument from a sensitivity and selectivity perspective; however, a range of instrumental components also occupy pivotal roles. Most notably, the mechanism of ion modulation or ion gating is a primary contributor to peak width in a drift tube ion mobility experiment. Unfortunately, physical ion gates rarely perform perfectly, and in addition to serving as physical impediments to ion transmission, their modulation also has undesirable field effects. Using a recently developed modulated, non-radioactive X-ray source, we detail the performance of an ion mobility spectrometry (IMS) system that is free of a gating structure and utilizes the pulsed nature of the modulated X-ray source (MXS) for both ion generation and initiation of the IMS experiment. After investigating the influence of pulse duration and spatial X-ray beam width on the analytical performance of the instrument, the possibility of using multiplexing with a shutterless system is explored. By increasing ion throughput, the observed multiplexing gain compared to a signal-averaged spectrum approaches the theoretical maximum and illustrates the capability of the MXS-IMS system to realize significant signal to noise improvements.

An optimized design of grid-controlled modulated X-ray source for space communication

In this paper, by analyzing the principle of the Grid-controlled Modulated X-ray Source, the core structure parameters including half width of the cathode notch, depth of the sinking filament and target angle are systematically designed and optimized. The electron-photon conversion efficiency and the minimum cut-off voltage of the X-ray source are calculated. In addition, an experimental system is built for the optimized GMXS test and ground X-ray communication (XCOM) verification. The experimental results indicate that with the same anode voltage and filament current, the number of emitted photons increases by 16–18% after optimization, the output X-ray photons intensity stability is better than [Formula: see text]%, and the cut-off voltage is reduced to −10 V. Based on this optimized GMXS, the ground XCOM rate increased to higher than 1 Mbps.

Optimization and testing of groove-shaped grid-controlled modulated X-ray tube for X-ray communication

The current modulated X-ray source for X-ray communication (XCOM) are facing the problems of low bandwidth and weak X-ray intensity. In this paper, a groove-shaped grid-controlled modulated X-ray tube (GGMXT) with hot-cathode was proposed to improve the modulation performance. With cut-off voltage and tube current as objective function, a CST-Matlab co-simulation based on the non-dominated sorting genetic algorithm II (NSGA-II) was developed to optimize the grid structure of GGMXT. The simulation results shows that the cut-off voltage of GGMXT can be controlled between −71 and −3 V with corresponding X-ray intensity of 99.0% to 54.8% of the maximum value. Based on the optimized results, four different prototypes of GGMXT, including three optimized tubes and one non-optimized tube, were prepared, tested, and compared with the simulated version. The effectiveness of the optimization method was demonstrated through testing. Compared with the non-optimized tube, one optimized GGMXT prototype obtains a relatively low cut-off voltage of −5 V@50 kV while maintaining high X-ray emission intensity. Its modulation bandwidth is higher than 3 MHz and the X-ray pulse repetition rate is in excess of several MHz. Therefore, the optimized GGMXT shows excellent modulation signal emission performance and great application potential in the field of X-ray communication.

Single Pixel Performance of a 32 × 32 Ti/Au TES Array With Broadband X-Ray Spectra

We are developing a kilo-pixels Ti/Au TES array as a backup option for Athena X-IFU. Here we report on single-pixel performance of a 32$\times$32 array operated in a Frequency Division Multiplexing (FDM) readout system, with bias frequencies in the range 1-5 MHz. We have tested the pixels response at several photon energies, by means of a $^{55}$Fe radioactive source (emitting Mn-K$\alpha$ at 5.9 keV) and a Modulated X-ray Source (MXS, providing Cr-K$\alpha$ at 5.4 keV and Cu-K$\alpha$ at 8.0 keV). First, we report the procedure used to perform the detector energy scale calibration, usually achieving a calibration accuracy better than $\sim$ 0.5 eV in the 5.4 - 8.9 keV energy range. Then, we present the measured energy resolution at the different energies (best single pixel performance: $\Delta$E$_{FWHM}$ = 2.40 $\pm$ 0.09 eV @ 5.4 keV; 2.53 $\pm$ 0.10 eV @ 5.9 keV; 2.78 $\pm$ 0.16 eV @ 8.0 keV), investigating also the performance dependency from the pixel bias frequency and the count rate. Thanks to long background measurements ($\sim$ 1 day), we finally detected also the Al-K$\alpha$ line at 1.5 keV, generated by fluorescence inside the experimental setup. We analyzed this line to obtain a first assessment of the single-pixel performance also at low energy ($\Delta$E$_{FWHM}$ = 1.91 eV $\pm$ 0.21 eV @ 1.5 keV), and to evaluate the linearity of the detector response in a large energy band (1.5 - 8.9 keV).

Ti/Au TES 32 × 32 Pixel Array: Uniformity, Thermal Crosstalk and Performance at Different X-Ray Energies

Large format arrays of transition edge sensor (TES) are crucial for the next generation of X-ray space observatories. Such arrays are required to achieve an energy resolution of ΔE <; 3 eV full-width-half-maximum (FWHM) in the soft X-ray energy range. We are currently developing X-ray microcalorimeter arrays as a backup option for the X-IFU instrument on board of ATHENA space telescope, led by ESA and foreseen to be launched in 2031. In this contribution, we report on the development and the characterization of a uniform 32 × 32 pixel array with (length × width) 140 × 30 μm$^2$ TiAu TESs, which have a 2.3 μm thick Au absorber for X-ray photons. The pixels have a typical normal resistance R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</sub> = 121 mΩ and a critical temperature T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> ~ 90 mK. We performed extensive measurements on 60 pixels out of the array in order to show the uniformity of the array. We obtained an energy resolutions between 2.4 and 2.6 eV (FWHM) at 5.9 keV, measured in a single-pixel mode at AC bias frequencies ranging from 1 to 5 MHz, with a frequency domain multiplexing (FDM) readout system, which is developed at SRON/VTT. We also present the detector energy resolution at X-ray with different photon energies generated by a modulated external X-ray source from 1.45 keV up to 8.9 keV. Multiplexing readout across several pixels has also been performed to evaluate the impact of the thermal crosstalk to the instrument's energy resolution budget requirement. This value results in a derived requirement, for the first neighbour, that is less than 1 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> when considering the ratio between the amplitude of the crosstalk signal to an X-ray pulse (for example at 5.9 keV).

Detectability of Modulated X-Rays from LISA’s Supermassive Black Hole Mergers

Abstract One of the central goals of the Laser Interferometer Space Antenna (LISA) is the detection of gravitational waves from the merger of supermassive black holes. Contrary to stellar-mass black hole mergers, such events are expected to be rich X-ray sources due to the accretion of material from the circumbinary disks onto the black holes. The orbital dynamics before merger is also expected to modulate the resulting X-ray emission via Doppler boosting in a quasiperiodic way and in a simple phase relation with the gravitational wave from the inspiral of the black holes. Detecting the X-ray source would enable a precise and early localization of the binary, thus allowing many telescopes to observe the very moment of the merger. Although identifying the correct X-ray source in the relatively large LISA sky localization will be challenging due to the presence of many confounding point sources, the quasiperiodic modulation may aid in the identification. We explore the practical feasibility of such idea. We simulate populations of merging supermassive black holes, their detection with LISA, and their X-ray light curves using a simple model. Taking the parameters of the X-ray telescope on the proposed NASA Transient Astrophysics Probe, we then design and simulate an observation campaign that searches for the modulated X-ray source while LISA is still observing the inspiral of the black holes. Assuming a fiducial LISA detection rate of 10 mergers per year at redshift closer than 3.5, we expect a few detections of modulated X-ray counterparts over the nominal duration of the LISA mission.

Re-entry blackout elimination and communication performance analysis based on laser-plasma-induced X-ray emission

X-ray communication (XCOM) offers important advantages to both civilian and military space projects. Rapid advance in high-intensity laser interaction with plasma has become a driving force for providing a new X-ray carrier generation based on the laser wakefield acceleration scheme. XCOM has the potential to eliminate RF shielding on the ground and communicate with the re-entry supersonic spacecraft during blackout occurrence. In this process, the plasma sheath is formed around the surface due to air compression and ablation, which blocks the traditional communication signals. In this paper, the hazardous substance was proactively exploited and coupled with the modulated laser. Particle-In-Cell simulation results indicate the ultra-bright controllable X-ray emission with a small angular divergence (0.04 rad×0.03 rad), a tunable X-ray energy range (4.60 keV to 321.48 keV), and high photon yields. Additionally, the data rate of the communication via the X-ray carrier during re-entry was estimated up to ∼20.7 Mbps by considering the transmission model, encoding schemes and photon information efficiency. Combined with an existing or developing X-ray detection technique, this regime can eliminate re-entry blackout and also provide a novel modulated X-ray source to acquire high-rate, low transmit power, and highly secure space-based data links.

Temporal characteristic analysis of laser-modulated pulsed X-ray source for space X-ray communication

X-ray communication (XCOM) is a new communication type and is expected to realize high-speed data transmission in some special communication scenarios, such as deep space communication and blackout communication. This study proposes a high-speed modulated X-ray source scheme based on the laser-to-X-ray conversion. The temporal characteristics of the essential components of the proposed laser-modulated pulsed X-ray source (LMPXS) were analyzed to evaluate its pulse emission performance. Results show that the LMPXS can provide a maximum modulation rate up to 100 Mbps which is expected to significantly improve the data rate of XCOM.

Transmission properties and physical mechanisms of X-ray communication for blackout mitigation during spacecraft reentry

Recent advances in X-ray science have witnessed the X-ray communication (XCOM), a new revolutionary technology first proposed by NASA since 2007. In combination with the advanced modulated X-ray source, XCOM shows a promising prospect for helping to alleviate the occurrence of inevitable blackout communication by using the regular radio frequency (RF) signal, paving the way towards realizing real-time communication during spacecraft reentry into atmosphere. Here, we acquired the detailed information of electron density distribution of plasma sheath encountered during vehicle reentry through Computational Fluid Dynamics simulation. Based on these derived parameters, Finite-difference Time-domain method was employed to investigate the transmission properties of X-rays through the plasma sheath, and the results indicated that X-ray transmission was not influenced by the reentry plasma sheath at different reentry altitudes and spacecraft surface positions compared with RF signal. In addition, 2D Particle-In-Cell simulation was also adopted to provide deeper insight into the transmission properties and physical mechanisms of X-ray carrier propagating through the plasma sheath, and results showed that the transmission coefficient was over 0.994 and the observation of plasma channel effect was also an important signature, which was of great importance to X-ray propagating through the plasma sheath.

Transmission-type miniature micro-beam modulated X-ray source based on space application

X-ray sources have been extensively penetrated into all aspects in daily life, such as pharmaceutical analysis, X-ray diagnostics, and radioactive static elimination. Along with the burgeoning field of deep exploration, all kinds of X-ray sources are fabricated to meet the needs of space applications. Therefore a design proposal of a transmission-type miniature micro-beam modulated X-ray source, in allusion to the space application of X-ray sources, is proposed and its theoretical model is constructed. In contrast with the traditional X-ray sources, a grid electrode is added and three focusing electrodes are chosen and used. Amplitude modulation and pulse modulation of X-rays, by controlling the voltage value of the grid electrode, are realized. Electrons are restrained to pass when the grid electrode is loaded with a negative voltage and no X-ray photons are produced. When loaded with a positive voltage, the grid electrode lets electrons get through and finally reaches up to the anode electrode. Three focusing electrodes, meanwhile, are used to make the electron beam converge and finally focus on the anode target. The thickness of the transmission-type target material is considerable, considering it to be a key parameter influencing the conversion efficiency of X-rays. If the target thickness is too thin, only a part of electrons can convert into X-ray. On the contrary, when the target thickness is too thick, the produced X-ray intensity is low too. That is because some X-ray photons are absorbed by the anode target material even though all of the electrons convert into X-ray. And the optimum target thickness, in different anode voltage values and different target materials, is simulated using charged particle optical simulation software, and the results are presented in a table. In addition, the influence of grid voltage value on electron beam trajectory is also taken into account and finally a 150-m-diameter focusing spot is obtained. The prototype model is fabricated via coating film on the anode and the single-step brazing process in a vacuum furnace. After the test platform is set up, the spectrum feature of tungsten target is attained. And it is analyzed that the X-ray intensity is related to the grid electrode voltage value. The feasibility of grid amplitude modulation and grid pulse modulation are verified in the end. As a multifunctional modulated X-ray source, it will have more important scientific significance and space application prospects, and be used in inter-satellite X-ray communication, ionization blackout area communication, planetary science, pulsar simulation and single event effect simulation of space radiation environment.

Vacuum-sealed miniature modulated x-ray source and the influence factors of x-ray intensity

The vacuum-sealed miniature modulated x-ray source (VMMXS) with a hot cathode is fabricated via the single-step brazing process in a vacuum furnace. An experiment following the VMMXS is implemented to present its performances, including the influence of grid electrode potential on x-ray intensities. The modulation type of the grid electrode as a switch is proposed, and its feasibility is successfully demonstrated. It is noteworthy to discover a phenomenon for the first time, to the best of our knowledge, that the high repetition frequency grid pulse of the VMMXS has a significant effect on the x-ray intensity. The probable cause for this new finding is analyzed.

Validation of Pulsar Phase Tracking for Spacecraft Navigation

Previous theoretical work has shown that pulsars have fascinating potential as aids for autonomous, deep space navigation. In this paper, phase tracking is investigated as a technique to measure the distance traveled by a spacecraft over an observation interval. Phase tracking was experimentally validated using photons emitted by a modulated x-ray source and detected by a silicon-drift detector using the NASA Goddard X-Ray Navigation Laboratory Testbed. Models of the Crab pulsar and PSR B1821-24 were used. Three simulated, one-dimensional trajectories were considered: one stationary, one with constant velocity, and one with constant acceleration. For constant signal frequency, a maximum-likelihood phase estimator was used. Otherwise, the observation window was broken into smaller blocks over which maximum-likelihood phase estimates were looped through a digital phase-locked loop to reduce errors and estimate the Doppler frequency. The maximum-likelihood phase estimator tracked the initial phase within 0.15% for the simulations and 2.5% in the experiments. The maximum-likelihood phase estimator–digital phase-locked loop cascade tracked the phase and frequency in both the simulations and experiments. The phase error and Doppler frequency error tended toward zero in under 250 and 100 s, respectively, with the Crab pulsar.

The discovery of the 2 hour modulated X-ray source EXO 033319-2554.2, an AM Herculis system

view Abstract Citations (43) References (25) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Discovery of the 2 Hour Modulated X-Ray Source EXO 033319-2554.2, an AM Herculis System Osborne, J. P. ; Giommi, P. ; Angelini, L. ; Tagliaferri, G. ; Stella, L. Abstract The authors report the discovery of EXO 033319-2554.2, a soft X-ray source with 100% modulation of its soft X-ray flux, found during a systematic analysis of all of the EXOSAT soft X-ray data. The soft X-ray light curve, which has an on-off behavior, shows a period of 127.7±3.0 minutes. The bright part of the cycle lasts 0.55 in phase and is cut by an eclipse-like feature lasting 8 minutes. The optical counterpart has a magnitude of mv≈ 18.5. The characteristics of EXO 033319-2554.2 imply that it is an AM Her system. The companion star is probably responsible for the eclipse. Using the lengths of the bright phase and of the eclipse, the authors derive limits to the system geometry. Publication: The Astrophysical Journal Pub Date: May 1988 DOI: 10.1086/185157 Bibcode: 1988ApJ...328L..45O Keywords: Magnetic Stars; Stellar Mass Accretion; White Dwarf Stars; X Ray Binaries; X Ray Sources; Exosat Satellite; Modulation; Stellar Luminosity; Astrophysics; STARS: ACCRETION; STARS: INDIVIDUAL ALPHANUMERIC: EXO 033319-2554.2; STARS: MAGNETIC; STARS: WHITE DWARFS; X-RAYS: BINARIES; X-RAYS: SOURCES full text sources ADS | data products SIMBAD (5)

Soft x-ray imaging instrument for the Alcator A tokamak

We describe an instrument that images the Alcator A tokamak plasma in the soft x-ray energy range with high temporal resolution. Radiation from a cross section of the plasma column is detected by an array of seventeen surface barrier detectors which provides 1 cm poloidal spatial resolution over a 16 cm field of view. The instrument’s nominal sensitivity lies in the spectral range from 0.27 to 25 keV; this range includes much of the radiation emitted by the Alcator A plasma, whose core temperature is typically in the 0.6 to 1.1 keV range. The frequency response of the detector-electronics system extends from dc to 170 kHz. We discuss: (1) some design considerations and instrument calibrations, including the instrument’s measured response to 0.28, 1.5, 8.0, and 17.5 keV x-rays and its theoretical response to a bremsstrahlung spectrum; (2) the detector-electronics noise levels under various conditions; (3) the instrument’s response to an electrically modulated x-ray source; (4) the detector x-ray response as a function of bias voltage and temperature; (5) the detector linearity of response to 1.5 keV x-rays; and (6) the stability of the detector x-ray response despite numerous and prolonged vacuum breaks. Sample data, obtained from Alcator A discharges, are presented.