photon energy
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Coatings ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 87
Author(s):  
Atef S. Gadalla ◽  
Hamdan A. S. Al-shamiri ◽  
Saad Melhi Alshahrani ◽  
Huda F. Khalil ◽  
Mahmoud M. El Nahas ◽  
...  

In this study, cadmium Sulfide (CdS) thin films were synthesized on quartz substrates using an infrared pulsed laser deposition (IR-PLD) technique under high vacuum (~10−6 Torr) conditions. X-ray diffraction was used to evaluate the structural features. According to X-ray analysis, the deposited CdS films are crystalline and have a favored orientation on a plane (110) of an orthorhombic. The peak intensity and the average crystallite size increases with increasing the film thickness. After annealing at 300 °C, the orthorhombic phase transformed into a predominant hexagonal phase and the same result was obtained by SEM photographs as well. Spectrophotometric measurements of transmittance and reflectance of the CdS films were used to derive optical constants (n, k, and absorption coefficient α). The optical band gap energy was found to be 2.44 eV. The plasma plume formation and expansion during the film deposition have also been discussed. The photocurrent response as a function of the incident photon energy E (eV) at different bias voltages for different samples of thicknesses (85, 180, 220 and 340 nm) have been studied, indicating that the photocurrent increases by increasing both the film thickness and photon energy with a peak in the vicinity of the band edge. Thus, the prepared CdS films are promising for application in optoelectronic field.


2022 ◽  
Author(s):  
R. El-Mallawany ◽  
Weam aboutaleb ◽  
M.A. Naeem ◽  
S.M. Kotb ◽  
M.E. Krar ◽  
...  

Abstract Borotellurite glasses with a composition [(60-X)TeO2-(20+X)B2O3-10Li2O-10Bi2O3] where x= 5-20 in steps of 5 mol% have been synthesized. Glass density, molar volume, oxygen packing density, and many other physical parameters were measured. UV-spectra in the wave length range (200-800) nm have been measured for the whole glass series. The optical energy band gap Eopt , refractive index, and optical basicity were measured. The mass absorption coefficients (μm) are determined experimentally by the HPGe detector and compared with the theoretical values obtained by XCOM program and MCNP5 simulation code within (0.121–1.408) MeV photon energy range. Half value layer (HVL), effective atomic number and electron density (Zeff and Neff), and macroscopic removal cross-section (∑R) were evaluated. The sample [55TeO2 – 25B2O3 – 10Bi2O3 – 10Li2O] possess the highest values of (μm = 1.192 ± 0.033 cm2/g, Zeff = 56.12 e/atom and ∑ R = 0.101499 cm-1) at energy 121 keV also lower values of (HVL = 0.121 cm, TVL = 0.1 cm and MFP = 0.174 cm) at photon energy 121 keV, therefore this sample considered the best gamma ray shielding material among the prepared glasses.


PLoS ONE ◽  
2022 ◽  
Vol 17 (1) ◽  
pp. e0261042
Author(s):  
Xiao-Jun Li ◽  
Yan-Cheng Ye ◽  
Yan-Shan Zhang ◽  
Jia-Ming Wu

Introduction This study presents an empirical method to model the high-energy photon beam percent depth dose (PDD) curve by using the home-generated buildup function and tail function (buildup-tail function) in radiation therapy. The modeling parameters n and μ of buildup-tail function can be used to characterize the Collimator Scatter Factor (Sc) either in a square field or in the different individual upper jaw and lower jaw setting separately for individual monitor unit check. Methods and materials The PDD curves for four high-energy photon beams were modeled by the buildup and tail function in this study. The buildup function was a quadratic function in the form of dd2+n with the main parameter of d (depth in water) and n, while the tail function was in the form of e−μd and was composed by an exponential function with the main parameter of d and μ. The PDD was the product of buildup and tail function, PDD = dd2+n·e−μd. The PDD of four-photon energies was characterized by the buildup-tail function by adjusting the parameters n and μ. The Sc of 6 MV and 10 MV can then be expressed simply by the modeling parameters n and μ. Results The main parameters n increases in buildup-tail function when photon energy increased. The physical meaning of the parameter n expresses the beam hardening of photon energy in PDD. The fitting results of parameters n in the buildup function are 0.17, 0.208, 0.495, 1.2 of four-photon energies, 4 MV, 6 MV, 10 MV, 18 MV, respectively. The parameter μ can be treated as attenuation coefficient in tail function and decreases when photon energy increased. The fitting results of parameters μ in the tail function are 0.065, 0.0515, 0.0458, 0.0422 of four-photon energies, 4 MV, 6 MV, 10 MV, 18 MV, respectively. The values of n and μ obtained from the fitted buildup-tail function were applied into an analytical formula of Sc = nE(S)0.63μE to get the collimator to scatter factor Sc for 6 and 10 MV photon beam, while nE, μE, S denotes n, μ at photon energy E of field size S, respectively. The calculated Sc were compared with the measured data and showed agreement at different field sizes to within ±1.5%. Conclusions We proposed a model incorporating a two-parameter formula which can improve the fitting accuracy to be better than 1.5% maximum error for describing the PDD in different photon energies used in clinical setting. This model can be used to parameterize the Sc factors for some clinical requirements. The modeling parameters n and μ can be used to predict the Sc in either square field or individual jaws opening asymmetrically for treatment monitor unit double-check in dose calculation. The technique developed in this study can also be used for systematic or random errors in the QA program, thus improves the clinical dose computation accuracy for patient treatment.


2022 ◽  
Vol 29 (1) ◽  
Author(s):  
Jeremy Davis ◽  
Andrew Dipuglia ◽  
Matthew Cameron ◽  
Jason Paino ◽  
Ashley Cullen ◽  
...  

Successful transition of synchrotron-based microbeam radiation therapy (MRT) from pre-clinical animal studies to human trials is dependent upon ensuring that there are sufficient and adequate measures in place for quality assurance purposes. Transmission detectors provide researchers and clinicians with a real-time quality assurance and beam-monitoring instrument to ensure safe and accurate dose delivery. In this work, the effect of transmission detectors of different thicknesses (10 and 375 µm) upon the photon energy spectra and dose deposition of spatially fractionated synchrotron radiation is quantified experimentally and by means of a dedicated Geant4 simulation study. The simulation and experimental results confirm that the presence of the 375 µm thick transmission detector results in an approximately 1–6% decrease in broad-beam and microbeam peak dose. The capability to account for the reduction in dose and change to the peak-to-valley dose ratio justifies the use of transmission detectors as thick as 375 µm in MRT provided that treatment planning systems are able to account for their presence. The simulation and experimental results confirm that the presence of the 10 µm thick transmission detector shows a negligible impact (<0.5%) on the photon energy spectra, dose delivery and microbeam structure for both broad-beam and microbeam cases. Whilst the use of 375 µm thick detectors would certainly be appropriate, based upon the idea of best practice the authors recommend that 10 µm thick transmission detectors of this sort be utilized as a real-time quality assurance and beam-monitoring tool during MRT.


2021 ◽  
Author(s):  
Mai He ◽  
Cuihuan Ge ◽  
Kai Braun ◽  
Lanyu Huang ◽  
Xin Yang ◽  
...  

Abstract The quantum optical phenomena, such as single photon emission, in two-dimensional (2D) transition metal dichalcogenides (TMDCs) have triggered extensive researches on 2D material-based quantum optics and devices. By far, most reported quantum optical emissions in TMDCs are based on atomic defects in the material or the local confinement of excitons by introducing local stain or potential. In contrast, energy transfer between two materials could also manipulate the photon emission behaviors in materials, even at the single photon level. Along with the single-photon emission nature of zero-dimensional (0D) quantum dots (QDs) at room temperature, constructing a 0D-2D hybrid heterostructure may provide an effective way to regulate the quantum states related optical emissions of TMDCs. Here, we report on fluorescence blinking, a quantum phenomenon, from MoS2 atomic layers in QD/ MoS2 heterostructure at room temperature. We demonstrate the single-photon nature of the QDs in heterostructures by second-order photon correlation measurements. Based on the transient PL spectroscopy and PL time trajectories, we attribute the fluorescence blinking behavior in MoS2 to the single photon energy transfer from QD to MoS2. Our work opens the possibility to achieve correlated quantum emitters in TMDCs at room temperature by controlling the energy transfer between QD and TMDCs.


Author(s):  
Dennis Mayer ◽  
Fabiano Lever ◽  
Markus Gühr

Abstract The random nature of self-amplified spontaneous emission (SASE) is a well-known challenge for x-ray core level spectroscopy at SASE free-electron lasers (FELs). Especially in time-resolved experiments that require a combination of good temporal and spectral resolution the jitter and drifts in the spectral characteristics, relative arrival time as well as power fluctuations can smear out spectral-temporal features. We present a combination of methods for the analysis of time-resolved photoelectron spectra based on power and time corrections as well as self-referencing of a strong photoelectron line. Based on sulfur 2p photoelectron spectra of 2-thiouracil taken at the SASE FEL FLASH2, we show that it is possible to correct for some of the photon energy drift and jitter even when reliable shot-to-shot photon energy data is not available. The quality of pump-probe difference spectra improves as random jumps in energy between delay points reduce significantly. The data analysis allows to identify coherent oscillations of 1 eV shift on the mean photoelectron line of 4 eV width with an error of less than 0.1 eV.


2021 ◽  
Vol 11 (22) ◽  
pp. 10768
Author(s):  
Ye Chen ◽  
Frank Brinker ◽  
Winfried Decking ◽  
Matthias Scholz ◽  
Lutz Winkelmann

Sub-ångström working regime refers to a working state of free-electron lasers which allows the generation of hard X-rays at a photon wavelength of 1 ångström and below, that is, a photon energy of 12.5 keV and above. It is demonstrated that the accelerators of the European X-ray Free-Electron Laser can provide highly energetic electron beams of up to 17.5 GeV. Along with long variable-gap undulators, the facility offers superior conditions for exploring self-amplified spontaneous emission (SASE) in the sub-ångström regime. However, the overall FEL performance relies quantitatively on achievable electron beam qualities through a kilometers-long accelerator beamline. Low-emittance electron beam production and the associated start-to-end beam physics thus becomes a prerequisite to dig in the potentials of SASE performance towards higher photon energies. In this article, we present the obtained results on electron beam qualities produced with different accelerating gradients of 40 MV/m–56 MV/m at the cathode, as well as the final beam qualities in front of the undulators via start-to-end simulations considering realistic conditions. SASE studies in the sub-ångström regime, using optimized electron beams, are carried out at varied energy levels according to the present state of the facility, that is, a pulsed mode operating with a 10 Hz-repetition 0.65 ms-long bunch train energized to 14 GeV and 17.5 GeV. Millijoule-level SASE intensity is obtained at a photon energy of 25 keV at 14 GeV electron beam energy using a gain length of about 7 m. At 17.5 GeV, half-millijoule lasing is achieved at 40 keV. Lasing at up to 50 keV is demonstrated with pulse energies in the range of a few hundreds and tens of microjoules with existing undulators and currently achievable electron beam qualities.


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