Development of a seven-cell S-band standing-wave RF-deflecting cavity for Tsinghua Thomson scattering X-ray source

A 2856-MHz,π-mode,seven-cell standingwave deflecting cavity was designed and fabricated for bunch length measurement in Tsinghua Thomson scattering X-ray source(TTX)facility.This cavity was installed in the TTX and provided a deflecting voltage of 4.2 MV with an input power of 2.5 MW.Bunch length diagnoses of electron beams with energies up to 39 MeV have been performed.In this article,the RF design of the cavity using HFSS,fabrication,and RF test processes are reviewed.High-power operation with accelerated beams and calibration of the deflecting voltage are also presented.

Laser-produced plasma helium-like titanium Kα x-ray source and its application to Rayleigh-Taylor instability study

Several experiments are performed on the ShenGuang-Ⅱ laser facility to investigate an x-ray source and test radiography concepts. X-ray lines emitted from laser-produced plasmas are the most practical means of generating these high intensity sources. By using a time-integrated space-resolved keV spectroscope and pinhole camera, potential helium-like titanium Kα x-ray backlighting （radiography） line source is studied as a function of laser wavelength, ratio of pre-pulse intensity to main pulse intensity, and laser intensity （from 7.25 to ～ 11.3 × 10^15 W/cm2）. One-dimensional radiography using a grid consisting of 5 #m Au wires on 16 μm period and the pinhole-assisted point projection is tested. The measurements show that the size of the helium-like titanium Ka source from a simple foil target is larger than 100 ~m, and relative x-ray line emission conversion efficiency ~x from the incident laser light energy to helium- like titanium K-shell spectrum increases significantly with pre-pulse intensity increasing, increases rapidly with laser wavelength decreasing, and increases moderately with main laser intensity increasing. It is also found that a gold gird foils can reach an imaging resolution better than 5-μm featured with high contrast. It is further demonstrated that the pinhole-assisted point projection at such a level will be a novel two-dimensional imaging diagnostic technique for inertial confinement fusion experiments.

Numerical simulation for all-optical Thomson scattering X-ray source

Energy spectra, angular distributions, and temporal profiles of the photons produced by an all-optical Thomson scat- tering X-ray source are explored through numerical simulations based on the parameters of the SILEX-I laser system （800 nm, 30 fs, 300 TW） and the previous wakefield acceleration experimental results. The simulation results show that X-ray pulses with a duration of 30 fs and an emission angle of 50 mrad can be produced from such a source. Using the optimized electron parameters, X-ray pulses with better directivity and narrower energy spectra can be obtained. Besides the electron parameters, the laser parameters such as the wavelength, pulse duration, and spot size also affect the X-ray yield, the angular distribution, and the maximum photon energy, except the X-ray pulse duration which is slightly changed for the case of ultrafast laser-electron interaction.

Studying a kind of portable ultra-bright microfocus x-ray source

This paper studies the properties of a kind of portable ultra-bright microfocus x-ray source with the Monte-Carlo method in detail. The new x-ray source consists of an electron-emission system, an electrostatic focusing system and a metal target. A crystal Lanthanum Hexaboride cathode, a Wehnelt grid and an extracted electrode compose the triode electrode electron-gun system. Two equal radius cylinder electrodes form the focusing system. The key factors determining the focus properties of the electron beam such as the ratio Dw/H, grid bias Vg, and the properties of the extracted electrode arc numerically studied. The calculated results reveal that when Dw/H, Vg, the length of the extracted electrode, and the distance between the grid and the extracted electrode equals 5, q）.6 kV, 10 mm, and 8 mm respectively, the electron beam focal spot can be concentrated down to 9 μm in radius and a reasonable focal length about 72.5 mm can be achieved, at the same time, the cathode emission currents can be as high as 30 mA.

Low Energy Plasma Focus as an Intense X-ray Source for Radiography

Study on X-ray emission from a low energy (1.8 kJ) plasma focus devicepowered by a 9 μF capacitor bank, charged at 20 kV and giving peak discharge current of about 175kA by using a lead-inserted copper-tapered anode is reported. The X-ray yield in different energywindows is measured as a function of hydrogen filling pressure. The maximum yield in 4π-geometry isfound to be (27.3+-1.1) J and corresponding wall plug efficiency for X-ray generation is 1.52+-0.06%. X-ray emission, presumably due to bombarding activity of electrons in current sheath at theanode tip was dominant, which is confirmed by the pinhole images. The feasibility of the device asan intense X-ray source for radiography is demonstrated.

Phase Imaging Using Laser-produced X-ray Sources

A possible novel application of hard x-ray emitted during laser-plasma interaction was discussed. We established an Optical Transform Function to study the joint effect of the spectral distribution and temporal profile of the laser-produced x-ray on x-ray phase imaging. Though the laser-produced x-ray pulse duration is short and incoherent, the analysis confirms that the current x-ray phase imaging theory still holds for laser-produced x-ray phase imaging.

Beam and image experiment of beam deflection electron gun for distributed X-ray sources

Distributed X-ray sources comprise a single vacuum chamber containing multiple X-ray sources that are triggered and emit X-rays at a specific time and location. This process facilitates an application for innovative system concepts in X-ray and computer tomography. This paper proposes a novel electron beam focusing, shaping,and deflection electron gun for distributed X-ray sources.The electron gun uses a dispenser cathode as an electron emitter, a mesh grid to control emission current, and two electrostatic lenses for beam shaping, focusing, and deflection. Novel focusing and deflecting electrodes were designed to increase the number of focal spots in the distributed source. Two identical half-rectangle opening electrodes are controlled by adjusting the potential of the two electrodes to control the electron beam trajectory, and then, multifocal spots are obtained on the anode target. The electron gun can increase the spatial density of the distributed X-ray sources, thereby improving the image quality. The beam experimental results show that the focal spot sizes of the deflected(deflected amplitude 10.5 mm)and non-deflected electron beams at full width at half maximum are 0.80 mm 90.50 mm and 0.55 mm 90.40 mm, respectively(anode voltage 160 kV; beam current 30 mA). The imaging experimental results demonstrate the excellent spatial resolution and time resolution of an imaging system built with the sources, which has an excellent imaging effect on a field-programmable gate array chip and a rotating metal disk.

Optimization of a laser plasma-based x-ray source according to WDM absorption spectroscopy requirements

X-ray absorption spectroscopy is a well-accepted diagnostic for experimental studies of warm dense matter.It requires a short-lived X-ray source of sufficiently high emissivity and without characteristic lines in the spectral range of interest.In the present work,we discuss how to choose an optimum material and thickness to get a bright source in the wavelength range 2A–6A(∼2 keV to 6 keV)by considering relatively low-Z elements.We demonstrate that the highest emissivity of solid aluminum and silicon foil targets irradiated with a 1-ps high-contrast sub-kJ laser pulse is achieved when the target thickness is close to 10μm.An outer plastic layer can increase the emissivity even further.

Broken-up spectra of the loop-top hard X-ray source during a solar limb flare

Solar hard X-rays(HXRs) appear in the form of either footpoint sources or coronal sources. Each individual source provides its own critical information on acceleration of nonthermal electrons and plasma heating. Earlier studies found that the HXR emission in some events manifests a broken-up power-law spectrum, with the break energy around a few hundred keV based on spatially-integrated spectral analysis,and it does not distinguish the contributions from individual sources. In this paper, we report on the brokenup spectra of a coronal source studied using HXR data recorded by Reuven Ramaty High Energy Solar Spectroscopic Imager(RHESSI) during the SOL2017–09–10 T16:06(GOES class X8.2) flare. The flare occurred behind the western limb and its footpoint sources were mostly occulted by the disk. We could clearly identify such broken-up spectra pertaining solely to the coronal source during the flare peak time and after. Since a significant pileup effect on the RHESSI spectra is expected for this intense solar flare, we have selected the pileup correction factor, p = 2. In this case, we found the resulting RHESSI temperature(~30MK) to be similar to the GOES soft X-ray temperature and break energies of 45–60 keV. Above the break energy, the spectrum hardens with time from spectral index of 3.4 to 2.7, and the difference in spectral indices below and above the break energy increases from 1.5 to 5 with time. However, we note that when p = 2 is assumed, a single power-law fitting is also possible with the RHESSI temperature higher than the GOES temperature by ~10MK. Possible scenarios for the broken-up spectra of the loop-top HXR source are briefly discussed.

Influence of tube voltage and current on in-line phase contrast imaging using a microfocus x-ray source

In-line x-ray phase contrast imaging has attracted much attention due to two major advantages： its effectiveness in imaging weakly absorbing materials, and the simplicity of its facilities. In this paper a comprehensive theory based on Wigner distribution developed by Wu and Liu [Med. Phys. 31 2378-2384 （2004）] is reviewed. The influence of x-ray source and detector on the image is discussed. Experiments using a microfocus x-ray source and a CCD detector are conducted, which show the role of two key factors on imaging： the tube voltage and tube current. High tube current and moderate tube voltage are suggested for imaging.

On-Site Calibration Method of Dosimeter Based on X-Ray Source

The real-time monitoring of environmental radiation dose for nuclear fa-cilities is an important part of safety, in order to guarantee the accuracy of the monitoring results regular calibration is necessary. Around nuclear facilities there are so many environmental dosimeters installed dispers-edly, because of its huge quantity, widely distributed, and in real-time monitoring state;it will cost lots of manpower and finance if it were tak-en to calibrate on standard laboratory;what’s more it will make the en-vironment out of control. To solve the problem of the measurement ac-curacy of the stationary gamma radiation dosimeter, an on-site calibra-tion method is proposed. The radioactive source is X-ray spectrum, and the dose reference instrument which has been calibrated by the national standard laboratory is a high pressure ionization. On-site calibration is divided into two parts;firstly the energy response experiment of dosim-eter for high and low energy is done in the laboratory, and the energy response curve is obtained combining with Monte Carlo simulation;sec-ondly experiment is carried out in the field of the measuring dosimeter, and the substitution method to calibrate the dosimeter is used;finally the calibration coefficient is gotten through energy curve correction. In order to verify the accuracy of on-site calibration method, the calibrated dosimeter is test in the standard laboratory and the error is 3.4%. The re-sult shows that the on-site calibration method using X-ray is feasible, and it can improves the accuracy of the measurement results of the stationary γ-ray instrument;what’s more important is that it has great reference value for the radiation safety management and radiation environment evaluation.

Brilliance of novel X-ray source based on bremsstrahlung

A novel X-ray source based on tiny target bremsstrahlung and a low energy tabletop synchrotron was developed in Japan. In this paper, its brilliance formula is deducted and compared with BEAMnrc (EGS4) simulation. The brilliance of a tiny target bremsstrahlung X-ray prototype is discussed.

An active M star with X-ray double flares disguised as an ultra-luminous X-ray source

Here we present research on an ultra-luminous X-ray source （ULX） candidate 2XMM J 140229.91＋542118.8. The X-ray light curves of this ULX candidate in M 101 exhibit features of a flare star. More importantly, the Chandra light curve displays unusual X-ray double flares, which is comprised of two close peaks. The X-ray （0.3-11.0 keV） flux of the first peak was derived from the two-temperature APEC model as ～ 1.1 ±0.1× 10-12 ergcm-2 s-1. The observed flux at its first peak increased by about two orders of magnitude in X-ray as compared to quiescence. The slope of the second fast decay phase is steeper than the slope of the first fast decay phase, indicating that the appearance of a second flare accelerated the cooling of the first flare in a way we do not understand yet. We also observed its optical counterpart using a 2.16 m telescope administered by National Astronomical Observatories, Chinese Academy of Sciences. By optical spectral fitting, it is confirmed to be a late type dMe2.5 star. According to the spectral type and apparent magnitude of its optical counterpart, we estimate the photometric distance to be ～ 133.4 ±14.2 pc. According to the X-ray spectral fitting, a possible explanation is provided. However, more similar close double flares are needed to confirm whether this accelerated cooling event is a unique coincidence or a common physical process during double flaring.

X-ray source population in the polar ring galaxy NGC 660 as observed by Chandra

We present Chandra observations of the nearby polar ring galaxy NGC 660 to study its X-ray source population.Based on our analysis,we detected a total of 23 X-ray sources in the 0.5-8 keV band,with luminosities ranging from~1037 to~1039 erg s-1.Twenty-two of these sources are located offnuclear and have luminosities below the ultraluminous X-ray source(ULX)threshold value of L0.5-8 keV<1039 erg s-1,suggesting that they are likely to be X-ray binary(XRB)candidates.The remaining source is located at the center of the galaxy,suggesting it is an active galactic nucleus(AGN).However,we estimated that four of the detected sources could be associated with background objects.Based on the source count rates in each of the Chandra observations,we found evidence for variability in nine of the 23 sources,including the AGN.However,further investigation with spectral analysis suggested no significant differences in the AGN luminosities between the observations.The X-ray luminosity distribution of the galaxy was found to be generally lower than that expected from previous studies on star forming and collisional ring galaxies.No ULX was also detected in the galaxy,in contrast with what was expected from the galaxy’s SFR and metallicity(i.e.,SFR=14.43±0.19 M⊙yr-1 and Z=0.94±0.01 Z⊙,respectively).These results suggest a deficit in the X-ray sources detected.Based on source hardness ratio distribution,we found evidence that the fainter sources have a harder source spectrum,indicating higher absorption.This further suggests that there could be more X-ray sources that were not detected in the galaxy due to significant obscuration.

Laser Produced Plasma X-Ray Sources for Nanoscale Resolution Contact Microscopy: A Candidate in Cancerous Stem Cells Imaging

Plasma X-ray sources for biological microscopy have been produced by focusing single shots from Nd:glass laser onto carbon rod targets at irradiances between 1 × 1013 W&sdot;cm&minus;2 and 3 × 1013 W&sdot;cm&minus;2 to expose test objects. The optimum parameters needed for obtaining high accurate information on the samples under test namely: the minimum energies and irradiances at a range of angles between the incoming laser beam and the normal to the resist, the depth of exposure of the photoresist as a function of incident laser energy (and irradiance) were concluded in this work.

Research on the Magnetic Field of NGC 7793 P13 and Other Confirmed Pulsating Ultraluminous X-Ray Sources

A pulsating ultraluminous X-ray source(PULX)is a new kind of pulsar(PSR)whose characteristics are different from all known neutron stars.The magnetic field of PULX is suspected to be the main reason to support its supper Eddington luminosity of PULX.NGC 7793 P13,which is the second confirmed PULX,can be easily studied due to its nearby position and isolation from other sources in its host galaxy.In this paper,we calculate its magnetic field to be∼1.0×10^(12) G based on the continued observations from 2016 to 2020.The magnetic field evolution of NGC 7793 P13 is analyzed,which shows that the source has spent about 10^(4) yr for the field decaying from the simulated initial strength 4.0×10^(14) G to the present value.In case of an assumed constant accretion and the limitation of the companion mass,it will be a recycled PSR whose magnetic field is ∼10^(9) G and spin period is a few hundred milliseconds.We estimate the field strength of the other confirmed PULXs and find main range is 10^(13)-10^(14) G.Their positions of the magnetic field and spin period are around or below the magnetars.This is because these PULXs are in the binary systems and are with the spin-up rate that are 2-3 orders higher than the normal binary pulsars.We suggest that PULXs are the accreting magnetars whose multi-pole strong magnetic field can support the supper Eddington luminosity.They would be helpful for studying the evolution of the magnetars,the formation of the binary PSRs above the Eddington spin-up line,and the millisecond PSRs with the magnetic field stronger than ∼10^(9) G.

Is the Variable X-ray Source in M82 due to Gravitational Lensing?

We explore the possibility of attributing the recent discovery of the variable hard X-ray source CXO M82 J095550.2+694047 in M82 to the gravitational magnification by an intervening stellar object along the line of sight acting as a microlens. The duration of the event (> 84 days) allows us to set robust constraints on the mass and location of the microlensing object when combined with the dynamical properties of the Galactic halo, M82 and typical globular clusters. Except for the extremely low probability, the microlensing magnification by MACHO in either the Galactic halo or M82 halo is able to explain the X-ray variability of CXO M82 J095550.2+694047. It is hoped that the lensing hypothesis can be tested soon by measurement of the light curve.

Optical Identifications of Companion Soft X-ray Sources of Mrk 231

We present optical identification results for four ROSAT PSPC soft X-ray companions of Mrk 231 based on the deep BATC 6660 A-band image and the optical spectra obtained by the 60/90cm Schmidt telescope and the 2.16 m telescope at the Xinglong Station, NAOC. Three optical counterparts are quasars with redshifts z> 1 and the remaining X-ray source is probably a background galaxy cluster. Therefore, none of these soft X-ray companions are physically connected with the central X-ray source Mrk 231. Incorporating the previous results of Arp 220 and Mrk 273 (Xia et al. 1998, 1999), we suggest that the apparent soft X-ray associations with ULIRGs are chance coincidence in most cases.

Re-Identification of the 'Enigmatic' X-ray Source 1RXS J114003.0+124112

The ROSAT X-ray source 1RXS J114003.0＋ 124112 was identified as a starburst galaxy at redshift 0.177 by He et al. The authors also noted that the source is almost two orders of magnitude brighter in X-ray than the X-ray-brightest starburst galaxy and it seems to be in a merging system, making this source an enigmatic system demanding further observations. Here we report a re-identification of 1RXS J114003.0＋124112 using observations on the 2.6 m telescope at Byurakan Astrophysical Observatory, Armenia and the SDSS data. The results indicate that the starburst activity is associated with the brighter object of the system, while the fainter object is a typical Seyfert 1 galaxy at a different redshift （0.282）. Therefore, the two objects are not in a merging system, and the Seyfert 1 galaxy naturally accounts for the high X-ray flux. Three more objects reside in the vicinity, but they are all too faint to be responsible for the high X-ray flux.

Pinhole imaging to observe spatial jitters of a triple-pulse X-ray source on the Dragon-Ⅱ LIA

In high-energy flash radiography,scattered photons degrade the acquiring image,which limits the resolving power of interfaces and density of dense object.The application of large anti-scatter grid can reduce the scattered photons remarkably,but this requires a stable source position in order to reduce the loss of signal photons in the grid structure.The pinhole imaging technique is applied to observe spatial jitters of a triple-pulse radiographic source of a linear induction accelerator.Numerical simulations are conducted to analyze the imaging performance with the same or close parameters of the pinhole object and experimental alignment.Experiments are carried out to observe spatial jitters of the source between different measurements.Deviations of the source position between different pulses are measured in each experiment.