scholarly journals Feasibility of X-ray beam nanofocusing with compound refractive lenses

2021 ◽  
Vol 28 (2) ◽  
pp. 419-428
Author(s):  
V. G. Kohn ◽  
M. S. Folomeshkin
Keyword(s):  
Refractive Index ◽  
Photon Energy ◽  
Radiation Absorption ◽  
Beam Size ◽  
Radiation Wavelength ◽  
Transverse Beam ◽  
X Ray ◽  
Effective Aperture ◽  
Material Refractive Index ◽  
Lens Material

A more general analytical theory of X-ray beam propagation through compound refractive lenses (CRLs) than the earlier study by Kohn [(2003). JETP, 97, 204–215] is presented. The problem of nanofocusing with CRLs is examined in detail. For a CRL with a relatively large aperture the focusing efficiency is limited by the radiation absorption in the lens material. The aperture does not affect the focusing process and it is replaced by the effective aperture. The X-ray transverse beam size at the focus is then by a factor of γ = β/δ times smaller than the transverse beam size just behind the CRL. Here, δ and β are the real and imaginary parts of the CRL material refractive index n = 1 − δ + iβ. In this instance, to improve focusing efficiency, it is advantageous to decrease the CRL aperture and increase the photon energy E. However, with increasing photon energy, the material absorption decreases, which results in the CRL aperture impact on the transverse beam size. The latter leads to the fact that with a proper CRL length the beam size is independent of both the aperture and photon energy but depends only on the CRL material electron density and is approximately equal to w c = λ/(8δ)1/2, where λ denotes the radiation wavelength, as predicted by Bergemann et al. [(2003). Phys. Rev. Lett, 91, 204801].

Arsenic segregation in polysilicon

1983 ◽  
Vol 41 ◽  
pp. 154-155 ◽  
Author(s):  
P.E. Batson ◽  
C.R.M. Grovenor ◽  
D.A. Smith ◽  
C. Wong
Keyword(s):  
Incident Beam ◽  
Silicon Wafers ◽  
Chemical Polishing ◽  
Bright Field Image ◽  
Beam Size ◽  
Stem Analysis ◽  
Bright Field ◽  
Twin Boundaries ◽  
X Ray ◽  
Line Scan

In this work As doped polysilicon was deposited onto (100) silicon wafers by APCVD at 660°C from a silane-arsine mixture, followed by a ten minute anneal at 1000°C, and in one case a further ten minute anneal at 700°C. Specimens for TEM and STEM analysis were prepared by chemical polishing. The microstructure, which is unchanged by the final 700°C anneal,is shown in Figure 1. It consists of numerous randomly oriented grains many of which contain twins.X-ray analysis was carried out in a VG HB5 STEM. As K α x-ray counts were collected from STEM scans across grain and twin boundaries, Figures 2-4. The incident beam size was about 1.5nm in diameter, and each of the 20 channels in the plots was sampled from a 1.6nm length of the approximately 30nm line scan across the boundary. The bright field image profile along the scanned line was monitored during the analysis to allow correlation between the image and the x-ray signal.

Soft X-ray photon energy calibration using multilayer mirror

2020 ◽  
Author(s):  
Kiranjot ◽  
Mangalika Sinha ◽  
R. K. Gupta ◽  
P. K. Yadav ◽  
Mohammed H. Modi
Keyword(s):  
Photon Energy ◽  
Energy Calibration ◽  
X Ray ◽  
Multilayer Mirror

scholarly journals Monte Carlo Modeling and Design of Photon Energy Attenuation Layers for >10× Quantum Yield Enhancement in Si-Based Hard X-ray Detectors

Instruments ◽  
2021 ◽  
Vol 5 (2) ◽  
pp. 17
Author(s):  
Eldred Lee ◽  
Kaitlin M. Anagnost ◽  
Zhehui Wang ◽  
Michael R. James ◽  
Eric R. Fossum ◽  
...  
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Quantum Yield ◽  
Photon Energy ◽  
High Efficiency ◽  
High Energy ◽  
Yield Enhancement ◽  
X Ray ◽  
Simulation Results ◽  
Conversion Efficiencies

High-energy (>20 keV) X-ray photon detection at high quantum yield, high spatial resolution, and short response time has long been an important area of study in physics. Scintillation is a prevalent method but limited in various ways. Directly detecting high-energy X-ray photons has been a challenge to this day, mainly due to low photon-to-photoelectron conversion efficiencies. Commercially available state-of-the-art Si direct detection products such as the Si charge-coupled device (CCD) are inefficient for >10 keV photons. Here, we present Monte Carlo simulation results and analyses to introduce a highly effective yet simple high-energy X-ray detection concept with significantly enhanced photon-to-electron conversion efficiencies composed of two layers: a top high-Z photon energy attenuation layer (PAL) and a bottom Si detector. We use the principle of photon energy down conversion, where high-energy X-ray photon energies are attenuated down to ≤10 keV via inelastic scattering suitable for efficient photoelectric absorption by Si. Our Monte Carlo simulation results demonstrate that a 10–30× increase in quantum yield can be achieved using PbTe PAL on Si, potentially advancing high-resolution, high-efficiency X-ray detection using PAL-enhanced Si CMOS image sensors.

Improved spatial resolution and lower-dose pediatric CT imaging: a feasibility study to evaluate narrowing the X-ray photon energy spectrum

2014 ◽  
Vol 44 (8) ◽  
pp. 1026-1030
Author(s):  
Mark G. Benz ◽  
Matthew W. Benz ◽  
Steven B. Birnbaum ◽  
Eric Chason ◽  
Brian W. Sheldon ◽  
...  
Keyword(s):  
Energy Spectrum ◽  
Feasibility Study ◽  
Spatial Resolution ◽  
Photon Energy ◽  
Ct Imaging ◽  
X Ray ◽  
Pediatric Ct ◽  
Photon Energy Spectrum

Analytical account for off-axis effects in X-ray radiation of free electron lasers

2021 ◽  
Vol 64 (1) ◽  
pp. 21-28
Author(s):  
K.V. Zhukovsky ◽  
Keyword(s):  
Free Electron ◽  
Finite Size ◽  
Photon Radiation ◽  
Beam Parameter ◽  
Beam Size ◽  
Free Electron Lasers ◽  
Airy Functions ◽  
X Ray ◽  
Harmonic Radiation ◽  
Gain Length

We give analytical description of generation of harmonics of the undulator radiation (UR) with account for the finite electron beam size, emittance, off-axis beam deviation and electron energy spread, as well as for the constant magnetic components and field harmonics effects. We give exact analytical expressions for the generalized Bessel and Airy functions, which describe the spectrum line shape and intensities in the two-frequency bi-harmonic undulator with account for the above factors. The obtained analytical formulae distinguish contributions of each field component and every undulator and beam parameter on the harmonic radiation in free electron lasers (FEL). The effect of the field on the harmonic radiation is analyzed with account for the beam finite size and its off-axis deviation. The phenomenological model is employed for the FEL modeling; with its help we study the harmonic generation, including even ones, in the experiments LCLS and LEUTL. We demonstrate analytically that strong second FEL harmonic in X-ray FEL at the wavelengths λ = 0.75nm in the LCLS experiment is caused by the deviation of the electron trajectories off the axis in 15 μm on the gain length 1.6 m, which is comparable with the beam size; the strong second FEL harmonic in the LEUTL experiment at the wavelength λ = 192nm can be attributed to interaction of the electrons in wide, ~ 0.2 mm, beam with the photon radiation at the gain length 0.87 m. The modeling results fully agree with the measurements. The developed formalism allows the analysis of projected and built FELs and their radiation, helps minimizing losses and correcting magnetic fields; it also shows physical background and reasons for each harmonic radiated power in the FEL.

scholarly journals Synthesis and Characterisation of Thin Films of Bismuth Triiodide for Semiconductor Radiation Detectors

2014 ◽  
Vol 2014 ◽  
pp. 1-3 ◽  
Author(s):  
Alka Garg ◽  
Monika Tomar ◽  
Vinay Gupta
Keyword(s):  
Thin Films ◽  
Absorption Coefficient ◽  
Room Temperature ◽  
Active Material ◽  
Visible Region ◽  
Radiation Detectors ◽  
Radiation Absorption ◽  
X Rays ◽  
X Ray ◽  
Bismuth Iodide

Bismuth iodide is a potentially active material for room temperature radiation detector, as it is well reported in the literature that it has both wide energy band gap and high atomic absorption coefficient. Crystalline films of high atomic number and high radiation absorption coefficient can absorb the X-rays and convert them directly into electrical charges which can be read by imaging devices. Therefore, it was proposed to grow thin films of Bismuth iodide on glass substrate using thermal evaporation technique in vacuum to avoid the inclusion of impurities in the films. The structural studies of the films were carried out using XRD and optical absorption measurement was carried out in the UV/VIS region using spectrophotometer. All Bismuth iodide films grown at room temperature are polycrystalline and show X-ray diffraction peaks at angles reported in research papers. The optical transmission spectra of BiI3 films show a high transmission of about 80% in visible region with a sharp fall near the fundamental absorption at 650 nm. Resistivity of the as-grown film was found to be around 1012 ohm-cm suitable value for X-ray detection application. Films were subjected to scanning electron microscopy to study the growth features of both as-grown and annealed films.

Soft X-ray refractive index by reconciling total electron yield with specular reflection: experimental determination of the optical constants of graphite

2018 ◽  
Vol 25 (5) ◽  
pp. 1433-1443
Author(s):  
C. Jansing ◽  
H. Wahab ◽  
H. Timmers ◽  
A. Gaupp ◽  
H.-C. Mertins
Keyword(s):  
Refractive Index ◽  
Optical Constants ◽  
Specular Reflection ◽  
Complex Refractive Index ◽  
Reflection Spectra ◽  
Total Electron Yield ◽  
Total Electron ◽  
X Ray ◽  
Electron Yield ◽  
Saturation Effects

The complex refractive index of many materials is poorly known in the soft X-ray range across absorption edges. This is due to saturation effects that occur there in total-electron-yield and fluorescence-yield spectroscopy and that are strongest at resonance energies. Aiming to obtain reliable optical constants, a procedure that reconciles electron-yield measurements and reflection spectroscopy by correcting these saturation effects is presented. The procedure takes into account the energy- and polarization-dependence of the photon penetration depth as well as the creation efficiency for secondary electrons and their escape length. From corrected electron-yield spectra the absorption constants and the imaginary parts of the refractive index of the material are determined. The real parts of the index are subsequently obtained through a Kramers–Kronig transformation. These preliminary optical constants are refined by simulating reflection spectra and adapting them, so that measured reflection spectra are reproduced best. The efficacy of the new procedure is demonstrated for graphite. The optical constants that have been determined for linearly polarized synchrotron light incident with p- and s-geometry provide a detailed and reliable representation of the complex refractive index of the material near π- and σ-resonances. They are also suitable for allotropes of graphite such as graphene.

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