In this paper, we developed a photo-counting imaging detector based on the delay-line anode with induction readout, which has the advantages of high sensitivity and large detective area features. This novel detector is expected to be used in space astronomy, bioluminescence and spectral measurement applications. This detector consists of a microchannel plate (MCP), position-sensitive anode and readout. Among these key parameters, the performance of position-sensitive anode decides the performances of detectors to a large extent. As a charge induction readout delay line anode, the delay line anode decodes the position information of the incident photon by measuring the time delay between two ends of a propagation line. The detector with the anode can obtain high detection sensitivity and a large imaging area. Image charge pickup anode is placed outside the sealed vacuum tube, which not only simplifies the process difficulty of anode production but also improves the detector's reliability. Firstly, An inductive readout delay line anode was designed. We analyzed the influence of different thicknesses and mediums material of the detector on the induction charge of the position-sensitive anode. Then, a method is used to tackle the induction charge of different layers unbalance issue. After that, we designed and fabricated a 40 mmX40 mm position-sensitive anode. The experiment results indicate that the transmission attenuation of the anode output is less than 10%, and the inter-pole crosstalk is less than 3%. Finally, we implemented aphoton-counting imaging experimental system based on this anode. This experimental system provides better than 150um spatial resolution and can promote the theoretical and practical development of large-area array and highly sensitive detector for space astronomical UV spectrum measurement.

We demonstrate a photon counting three-dimensional radar system based on a micro-channel plate (MCP) detector with a position-sensitive anode. The system is mainly composed of a laser device, a photon counting imaging detector and readout electronics. The probe laser is divided into two channels. One is used to trigger the start signal, and another irradiates the sample. The reflected light enters into the MCP, and it generates the trigger stop signal. The flight time of the laser pulse is obtained through a constant fraction discriminator(CFD) and a time-to-digital converter (TDC). The time resolution can reach the nanosecond level. The distance information of targets at different distances was measured using this system. The results show that the depth resolution of the system is centimeter level. The performance of the system is demonstrated by imaging of a resolution target and a space object.

The enhanced x-ray timing and polarimetry mission (eXTP) is a flagship observatory for x-ray timing, spectroscopy and polarimetry developed by an international consortium. Thanks to its very large collecting area, good spectral resolution and unprecedented polarimetry capabilities, eXTP will explore the properties of matter and the propagation of light in the most extreme conditions found in the universe. eXTP will, in addition, be a powerful x-ray observatory. The mission will continuously monitor the x-ray sky, and will enable multi-wavelength and multi-messenger studies. The mission is currently in phase B, which will be completed in the middle of 2022.

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.

Based on the theoretical model of the interaction between X-rays and matter,the transmission characteristics of X-rays in an electromagnetic shielding environment are studied,and the feasibility of Xrays communication for information transmission in an electromagnetic shielding environment is theoretically demonstrated. After that,a numerical simulation model of X-ray communication in a shielded environment is established,and the communication parameters of X-rays in an electromagnetic shielded environment are analyzed to achieve the index constraint of the core components. Finally,based on the key technologies of X-ray modulated emission and single-photon X-ray detection,an equivalent verification experiment of X-ray passing through the shielding material is conducted to realize the experimental verification of X-ray communication with a communication rate better than 23 kbps. The results are expected to provide some theoretical basis and experimental foundation for solving the radiation data transmission in a shielded environment.

Because of the imperfect theoretical model and insufficient experimental verification technologies,the problem of information transmission in the plasma sheath has not yet been resolved. In this paper,the interaction mechanism between X-ray photons and plasma is studied firstly,and a modified theoretical model is provided through numerical calculation and theoretical modeling. Different from the conclusion that X-rays can penetrate plasma without attenuation in the traditional wave model, the modified theoretical model established in this paper points out that the transmittance of X-rays in plasma is closely related to plasma electron density and incident X-ray flux. Secondly,an experimental system was built using a grid-controlled X-ray modulation emission source,a single-photon X-ray detector,and a dynamic plasma generator. Using this system,the non- uniform plasma which electron density ranges from 10(9)/cm(3) to 10(14)/cm(3) is generated,and the X- ray communication with 1 Mbps communication rante and 10(-5) bit error rate is also verified. The experimental results indicate that the modified theoretical model can explain and predict the experimental phenomena,and the experimental system can provide the solution for solving the communication problems in the plasma sheath.

In order to solve the easy-broken structure, low energy efficiency and heat dissipation of the traditional X-ray tube with filament based on thermionic cathode, a novel light-controlled pulsed X-ray tube device is deostrated in this paper. By matching the parameters of photocathode and light source, S20 cathode with high quantum efficiency and LED with 460 nm wavelength were selected. At the same time, the overall structure design of the X-ray tube is determined by the simulation. Finally, the maximum tube current of 2.37 mA is realized, the electron emission efficiency of photocathode is 0.288 mA/lm, and the output X-ray energy is adjustable from 0 to 25 keV. In addition, based on the characteristics of easy-access to be modulated of the light-controlled pulsed X-ray tube, different frequencies input signal restoration experiment and arbitrary contor X-ray restoration experiment was carried out.

X-rays have the characteristics of high single photon energy, high frequency, and strong penetrating ability, are widely used in space communication, radiation imaging, medical diagnosis, non-destructive testing, and other fields. The development of X-rays has had a positive impact on broadening the use of the electromagnetic spectrum. As the core component of the X-ray application, high modulation rate, low power consumption, and excellent performance X-ray generators have been a hot research topic for decades. In this paper, a light-controlled pulsed X- ray source is modeled by simulation software. We perform simulation calculations and summary analysis on the effects of cathode structure, focus structure height, and metal anode voltage on the focal spot size, electron transit-time, and transit-time spread. At an operating voltage of 30KV, if the photocathode is 42mm in diameter, the focal spot diameter is about 1.5mm, the electron transit-time is 3.75ns, and the transit- time spread is 895ps when the focusing structure height is 6mm. And if the diameter of the photocathode is 12mm, the focal spot diameter is the smallest when the focusing pole height is 9mm, which is about 0.7mm, as for the time characteristics, the electron transit-time is 4.1ns, and the transit-time spread is 242ps. The results suggest that the light-controlled pulsed X-ray source is expected to be the next-generation source with easy modulation and short X-ray pulse properties.

Photon-counting imaging detectors based on microchannel plate (MCP) and position-sensitive anode are characterized by extremely high sensitivity, as well as the ability to detect single photons. In this study, a visible light photon-counting imaging detector based on induction readout was developed for the detection of weak light intensities, such as photon counting radar and biofluorescence lifetime imaging. The design is based on a 25 mm diameter multi-alkali S20 photocathode followed by a MCP stack, and read out by a high-resistance Ge layer anode. The position-sensitive anode was located at the atmosphere side of the Ge substrate. Such a detector was advantageous in terms of reconfigurability and detachability. The imaging performance of the detector was tested by using the wedge and strip anode to decode the photon event position information. The experimental results showed a detector gain reaching about 3×106 , pulse height resolution (PHR) of about 105%, and spatial resolution better than 100μm.

Unstable mechanical structure, low energy efficiency, and cooling requirements limit the application of conventional x-ray tubes based on filament as cathode in several academic areas. In this paper, we demonstrate a light-controlled pulsed x-ray tube using multialkali cathode as electron generator. The photocathode active area of the light controlled x-ray tube is 13.2 cm2 (41 mm in diameter), which provides high photoelectron-emitting efficiency up to 0.288 mA/lm in 460-nm LED and 2.37-mA maximum tube current. Furthermore, the modulation ability from 1 kHz to 100 kHz of the x-ray tube is tested. The results suggest that the light-controlled pulsed x-ray tube has easy modulation and short x-ray pulse properties and is promising to be the next generation x-ray tube with wide applications in medical radiationtherapy as well as the calibration for detectors and scintillators.

In this study, a visible light photon-counting imaging detector was developed for weak light intensities, such as biofluorescence and photon-counting 3D imaging radars. The proposed visible light photon-counting imaging detector was based on a semitransparent S25 photocathode able of responding to visible light or even near-infrared wavelengths. The detector adopted image charge readout mode through high-resistance Ge layer receiver of electron cloud from the microchannel plate. The performance of the as-obtained visible light photon-counting imaging detector was tested in existing readout electronics and newly designed position-sensitive anodes. The quantum efficiency of the as-prepared detector reached 13.4% (@532 nm) with spatial resolution better than 100 μm. Preliminary imaging results of real objects with commercial lens and detector were also obtained and applied to ultra-weak light detection. In sum, these results look promising for future applications in photon-counting radars and biofluorescence imaging.

In this paper, a novel X-ray tube, which uses a photocathode as an electron emission source, is first introduced. The X-ray tube with photocathode can use an external light source to control the output of photoelectrons, thereby controlling the characteristics of the emitted X-rays. Compared with the traditional X-ray tube with hot cathode, the X-ray emitted by the photocathode X-ray tube is completely modulated by the external light source. Therefore, X-rays can achieve instant on-off and arbitrary pulse waveform emission, and have extremely high time resolution. The basic characteristics of the photocathode X-ray tube was tested. By using the developed X-ray tube and LED light source, preliminary X-ray communication experiments have been carried out. The results show that the digital signal restoration with a frequency of up to 1MHz can be achieved. Except for X-ray communication, the developed photocathode X-ray tube can also have important applications in many fields such as radiation calibration and scintillator afterglow measurement.

In this paper, the relationship between direct measurement of X-ray pulsar angular position and second-order correlation is analyzed by classical statistical optics. On this basis, a scheme for measuring pulsar angle position is put forward on account of X-ray band intensity correlation, which is expected to achieve a positioning accuracy of 10 Mas. Finally, the connection between positioning accuracy and complex correlation in the intensity correlation measurement is studied. Also, main factors that affected the measurement are analyzed.

After the concept of X-ray communication was proposed, its application in complex electromagnetic environment has received more attention, such as data transmission in re-enter special electromagnetic condition. In this article, a new type of X-ray source was introduced firstly, which was expected to generate multiple characteristic lines and achieve wavelength division multiplexing technology in X-ray band. Then an experimental platform was built for analyzing transmission characteristics of X-ray photon in various plasma media. Finally, the calculation model for a link power equation was given. Experiment results show that transmittance of 8–18 keV X-ray signal is relatively stable, atomic numbers from 29 to 42 are the most suitable materials for wavelength division multiplexing, the X-ray communication system is expected to realize about 200 kbps data transmission rate in adjacent space.

Compared with the other wireless communication band, X-ray carrier has the merits of lower wavelength, higher frequency and photon energy, which could provide a novel method to solve the communication problems of re-entry blackout region. In this paper, transmission characteristics of X-ray carrier in the re-entry dusty plasma medium were analyzed first, simulation results indicate that dusty particles were more likely to impede the microwave signal than X-ray carrier. Then an alkali metal plasma source was designed to simulate the re-entry dusty plasma sheath for simplification. Transmission co-efficiency under different X-ray energy were tested, which pointed out that X-ray signal would obtain more than 79.4% transmission co-efficiency on condition of dynamic and dusty plasma medium. Finally, we give our proposal and potential capability of X-ray communication in the re-entry plasma condition.

A micro-channel plate detector with wedge and strip anode can be used for visible and ultraviolet light imaging. In this paper, the imager electronics are designed in order to process specific output charge characteristics. The original signal output from the detector is shaped into a Gaussian pulse signal, and a digital Constant Fraction Discriminator is used to judge the arrival time of the pulse. The resolution of the electronic output image is 1024 x 1024, and the position decoding accuracy is 1 pixel. The experimental imaging resolving power of the detector is as high as 70 mu m.

In this paper, a focused detection system for X-ray pulsar-based Navigation (XNAV) is designed based on Silicon Drift Detector (SDD). The detector electronics mainly adopts the digital trapezoidal shaping method to measure the Times-Of-Arrival (TOAs) and energy of photons. The time measurement accuracy is better than 500ns. The energy resolution is 191eV at 8.05keV, and the maximum count rate is 500kcps between 1 and 12keV. In the semi-physical simulation experiment, the filtering of noise photons by energy discrimination significantly improves the correlation degree between the cumulative pulse profile and the standard profile.

Micro-channel Plates(MCPs) are an important part of ultraviolet photon counting imaging detectors. They can intensify single particles or photons by the multiplication of electrons via secondary emission. Thus, the MCP gain has an very important influence on the performance of ultraviolet photon counting imaging detectors. In this article, influence of MCP gain on decoding accuracy is studied by using Monte Carlo method. Simulation results show that decoding error is large when MCP gain is low,and MCPs shoud have at least 10(6) gain to ensure accurate decoding. At the same time, influence of MCP gain on decoding error was tested by using ultraviolet photon counting imaging system based on TWA(Tetra Wedge Anode,TWA). Experimental results are consistent with the theoretical analysis and simulation.

When a supersonic spacecraft enters into the atmosphere of earth, part of the spacecraft's kinetic energy changes into thermal energy, thus causing the air surrounding the craft to be heated and compressed. As a result, the temperature near the surface may reach several thousands of kelvins, which leads the surface materials to be ionized and form a plasma sheath around the vehicle. This plasma layer has an electron density ranging from 1015m-3 to 1020m-3, and may interrupt the radio communication signal between the re-entry vehicle and ground-based stations, which is known as ‘communication blackout’. According to the radio attenuation measurement (RAM) experiments carried out by NASA(National Aeronautics and Space Administration) in the 1970s, the duration time of communication blackout ranges from 4 to 10 minutes in an altitude range from 40 km to 100 km. Communication blackout has puzzled aerospace industry for several decades, and has not yet been completely resolved. Due to this, it becomes necessary to understand the causes of communication blackout and the methods for its mitigation. Compared with other communication methods, x-ray communication(XCOM) has the advantages of short carrier wavelength and high photon energy, as well as strong ability to resist anti-interference, thus being able to open a novel way to solve this long-lasting unresolved problem. In this paper, to begin with, we analyze the transmission coefficiencies under different plasma electron densities and collision frequencies based on Wentzel Kramers Brillouin (WKB) approximation method. The simulation results indicate that the x-ray carrier is not influenced by the reentry plasma sheath. After that, a plasma source based on glow discharge is used to verify the mathematical model. The non-magnetized unobstructed plasma region is \begin{document}$\varPhi $\end{document}200 mm × 180 mm, which can be used for simulating plasma sheath near the reenter spacecraft. Then the transmission coefficiency, energy spectrum similarity and energy spectrum peak offset under different x-ray energy, x-ray flow and plasma electron density are firstly analyzed. Experimental results indicate that plasma can lead the x-ray signal to be attenuated to a certain extent, the increase of plasma electron density will cause higher attenuation. However, with a higher signal x-ray energy and x-ray flow, the XCOM could achieve less attenuation in the re-enter plasma layer. When the plasma electron density ranges from 6 × 1016/m3 to 1.2 × 1017/m3, 1.34 Mcps signal x-ray photons’ flow with 20 kV anode voltage would achieve more than a 95% transmission efficiency. Also, the spectrum of x-ray signal can obtain more than 95.5% similarity and the peak offset is less than 1.3% after passing the plasma sheath. Subsequently, based on the original mathematic model and experimental results, considering the free-free absorption, free-bound absorption, bound-bound absorption and scattering effect of x-ray photons in plasma, the x-ray transmission characteristics are optimized to make simulation results well consistent with the experiment results. Finally, an MCNP (Monte Carlo N Particle) transport simulation is used to analyze the feasibility of XCOM in blackout region, which indicates that the energy range 15—25 keV is the suitable to achieve the XCOM in adjacent space, and the relation of potential transmitting speed with bit error is calculated. Theoretically, the XCOM can achieve about 1.3 Mbps communication speed in blackout region. In summary, these theoretical and experimental results indicate that the XCOM is a potential and novel method to solve the blackout communication problems.

In this study, a geometric model of Wolter-I X-ray focusing mirror was established, and a set of equations were derived for determining the parameters of glass substrate focusing mirror. In order to study the focal spot diffusion at the theoretical focal point under the condition of point light source. A formula for calculating the focal spot size of the single-layer focusing mirror at the theoretical focal length under point-source incident light was derived through theoretical analysis. A set of Wolter-I X-ray focusing mirror were fabricated through a slumping process using Schott D263 T glass,which is designed based on the derived equations. Ray tracing software was used to simulate the size variations of focal spot under parallel incident light and point-source incident light. A test system was constructed, and experiments were conducted to verify the validity of the calculation formula and the results of the simulation analysis. The test results showed that the theoretical results are in good agreement with the experimental results.