scholarly journals MoCA: A Monte Carlo code for Comptonisation in Astrophysics

2018 ◽  
Vol 619 ◽  
pp. A105 ◽  
Author(s):  
Francesco Tamborra ◽  
Giorgio Matt ◽  
Stefano Bianchi ◽  
Michal Dovčiak
Keyword(s):  
Monte Carlo ◽  
Optical Thickness ◽  
Thermal Emission ◽  
Single Photon ◽  
Spherical Geometry ◽  
Accretion Disc ◽  
Monte Carlo Code ◽  
X Ray ◽  
First Results ◽  
Good Agreement

We present a new Monte Carlo code for Comptonisation in Astrophysics (MoCA). To our knowledge MoCA is the first code that uses a single photon approach in a full special relativity scenario, and including also Klein–Nishina effects as well as polarisation. In this paper we describe in detail how the code works, and show first results from the case of extended coronae in accreting sources Comptonising the accretion disc thermal emission. We explored both a slab and a spherical geometry, to make comparison with public analytical codes more easy. Our spectra are in good agreement with those from analytical codes for low/moderate optical depths, but differ significantly, as expected, for optical depths larger than a few. Klein–Nishina effects become relevant above 100 keV depending on the optical thickness and thermal energy of the corona. We also calculated the polarisation properties for the two geometries, which show that X-ray polarimetry is a very useful tool to discriminate between them.

MONTE CARLO CODE FOR STUDY OF THE RESPONSE FUNCTION OF Si(Li) DETECTORS FOR X-RAYS

1999 ◽  
Vol 09 (03n04) ◽  
pp. 135-141
Author(s):  
KÁROLY TŐKÉSI ◽  
TAKESHI MUKOYAMA
Keyword(s):  
Monte Carlo ◽  
Present Model ◽  
Monte Carlo Code ◽  
X Rays ◽  
Model Calculations ◽  
X Ray ◽  
Line Shapes ◽  
Calculated Line ◽  
The Individual ◽  
Good Agreement

For more detailed understanding of the line shape of X-ray peaks observed with Si ( Li ) detectors, a new Monte Carlo code was developed and tested in the range of incident X-ray energy less than 5 keV. In our simulation the individual elastic and inelastic processes in the solid and the charge collection probabilities in the different region of detectors are taken into account. The results of our model calculations are compared with experimental data. In general, good agreement is found between the experimental and calculated line shapes. This fact demonstrates the validity of the present model.

scholarly journals A deep X-ray view of the bare AGN Ark 120

2019 ◽  
Vol 623 ◽  
pp. A12 ◽  
Author(s):  
A. Marinucci ◽  
D. Porquet ◽  
F. Tamborra ◽  
S. Bianchi ◽  
V. Braito ◽  
...  
Keyword(s):  
Compton Scattering ◽  
Single Photon ◽  
Accretion Disc ◽  
Compact Objects ◽  
Monte Carlo Code ◽  
Polarization Signal ◽  
X Ray ◽  
Inverse Compton Scattering ◽  
Inverse Compton ◽  
Hot Corona

Context. The spectral shape of the hard X-ray continuum of Active Galactic Nuclei (AGN) can be ascribed to inverse Compton scattering of optical/UV seed photons from the accretion disc by a hot corona of electrons. This physical process produces a polarization signal which is strongly sensitive to the geometry of the scattering medium (i.e. the hot corona) and of the radiation field. Aims. MoCA (Monte Carlo code for Comptonisation in Astrophysics) is a versatile code which allows for different geometries and configurations to be tested for Compton scattering in compact objects. A single photon approach is considered as well as polarisation and Klein–Nishina effects. In this work, we selected four different geometries for the scattering electrons cloud above the accretion disc, namely an extended slab, an extended spheroid and two compact spheroids. Methods. We discuss the first application of the MoCA model to reproduce the hard X-ray primary continuum of the bare Seyfert 1 galaxy Ark 120, using different geometries for the hot corona above the accretion disc. The lack of extra-Galactic absorption along the line of sight makes it an excellent target for studying the accretion disc-corona system. We report on the spectral analysis of the simultaneous 2013 and 2014 XMM-Newton and NuSTAR observations of the source. Results. A general agreement is found between the best fit values of the hot coronal parameters obtained with MoCA and the ones inferred using other Comptonisation codes from the literature. The expected polarization signal from the best fits with MoCA is then presented and discussed, in view of the launch in 2021 of the Imaging X-ray Polarimetry Explorer (IXPE). Conclusions. We find that none of the tested geometries for the hot corona (extended slab and extended/compact spheroids) can be statistically preferred, based on spectroscopy solely. In the future, an IXPE observation less than 1 Ms long will clearly distinguish between an extended slab or a spherical hot corona.

scholarly journals Monte Carlo derivation of filtered tungsten anode X-ray spectra for dose computation in digital mammography

2015 ◽  
Vol 48 (6) ◽  
pp. 363-367 ◽  
Author(s):  
Lucas Paixão ◽  
Bruno Beraldo Oliveira ◽  
Carolina Viloria ◽  
Marcio Alves de Oliveira ◽  
Maria Helena Araújo Teixeira ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Digital Mammography ◽  
Relative Difference ◽  
Monte Carlo Code ◽  
Solid State Detector ◽  
X Ray ◽  
Direct Radiography ◽  
State Detector ◽  
Tungsten Anode ◽  
Good Agreement

Abstract Objective: Derive filtered tungsten X-ray spectra used in digital mammography systems by means of Monte Carlo simulations. Materials and Methods: Filtered spectra for rhodium filter were obtained for tube potentials between 26 and 32 kV. The half-value layer (HVL) of simulated filtered spectra were compared with those obtained experimentally with a solid state detector Unfors model 8202031-H Xi R/F & MAM Detector Platinum and 8201023-C Xi Base unit Platinum Plus w mAs in a Hologic Selenia Dimensions system using a direct radiography mode. Results: Calculated HVL values showed good agreement as compared with those obtained experimentally. The greatest relative difference between the Monte Carlo calculated HVL values and experimental HVL values was 4%. Conclusion: The results show that the filtered tungsten anode X-ray spectra and the EGSnrc Monte Carlo code can be used for mean glandular dose determination in mammography.

Experimental measurements and Monte Carlo modelling of the XSTRAHL 150 superficial X-ray therapy unit

2014 ◽  
Vol 14 (1) ◽  
pp. 43-55
Author(s):  
Fayez H. H. Al-Ghorabie
Keyword(s):  
Monte Carlo ◽  
Theoretical Calculations ◽  
Beam Quality ◽  
Patient Treatment ◽  
Experimental Measurements ◽  
Monte Carlo Code ◽  
X Ray ◽  
Percentage Depth Dose ◽  
Depth Dose ◽  
Good Agreement

AbstractBackgroundSuperficial X-ray therapy units are used for the treatment of certain types of skin cancer and some severe dermatological conditions. The performance assessment and beam characteristics of the superficial unit are very important to ensure accurate dose delivery during patient treatment. Both experimental measurements and Monte Carlo calculations can be used for this purpose.PurposeThis study aims to investigate whether it is possible to reproduce experimentally measured data for the XSTRAHL 150 superficial X-ray unit with simulations using the BEAMnrc Monte Carlo code.Materials and MethodsThe experimental procedure applied in this study included the following: experimental measurements of different X-ray spectra, half-value layers, percentage depth dose and beam profiles. Monte Carlo modelling of the XSTRAHL 150 unit was performed with the BEAMnrc code. The validity of the model was checked by comparing the theoretical calculations with experimental measurements.ResultsThere was good agreement (∼1%) between experimentally measured and simulated X-ray spectra. Results of half-value layers obtained from simulated and measured spectra showed that there was a maximum of 3·6% difference between BEAMnrc and measurements and a minimum of 2·3%. In addition, simulated percentage depth dose and profile curves have been compared against experimental measurements and show good agreement (within 2% for the depth dose curves and 3–5% for beam profile curves, depending on the applicator size).ConclusionThe results of this study provide information about particles’ interaction in different kilovoltage and filter combinations. This information is useful for X-ray tube design and development of new target/filter combinations to improve beam quality in superficial X-ray radiotherapy. The data presented here may provide a base for comparison and a reference for other or potential new users of the XSTRAHL 150 X-ray unit.

Calibration and Monte Carlo simulation of a single-photon counting charge-coupled device for single-shot X-ray spectrum measurements

2013 ◽  
Vol 11 (11) ◽  
pp. 110401-110404 ◽  
Author(s):  
Yonghong Yan Yonghong Yan ◽  
Lai Wei Lai Wei ◽  
Xianlun Wen Xianlun Wen ◽  
Yuchi Wu Yuchi Wu ◽  
Zongqing Zhao Zongqing Zhao ◽  
...  
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Single Photon ◽  
Photon Counting ◽  
Single Shot ◽  
Charge Coupled Device ◽  
Single Photon Counting ◽  
X Ray ◽  
Spectrum Measurements

Secondary Fluorescence of 3D Heterogeneous Materials Using a Hybrid Model

2020 ◽  
Vol 26 (3) ◽  
pp. 484-496
Author(s):  
Yu Yuan ◽  
Hendrix Demers ◽  
Xianglong Wang ◽  
Raynald Gauvin
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Analytical Model ◽  
Hybrid Model ◽  
Three Dimensional ◽  
Heterogeneous Materials ◽  
X Ray ◽  
The Monte Carlo Method ◽  
Secondary Fluorescence ◽  
Good Agreement

AbstractIn electron probe microanalysis or scanning electron microscopy, the Monte Carlo method is widely used for modeling electron transport within specimens and calculating X-ray spectra. For an accurate simulation, the calculation of secondary fluorescence (SF) is necessary, especially for samples with complex geometries. In this study, we developed a program, using a hybrid model that combines the Monte Carlo simulation with an analytical model, to perform SF correction for three-dimensional (3D) heterogeneous materials. The Monte Carlo simulation is performed using MC X-ray, a Monte Carlo program, to obtain the 3D primary X-ray distribution, which becomes the input of the analytical model. The voxel-based calculation of MC X-ray enables the model to be applicable to arbitrary samples. We demonstrate the derivation of the analytical model in detail and present the 3D X-ray distributions for both primary and secondary fluorescence to illustrate the capability of our program. Examples for non-diffusion couples and spherical inclusions inside matrices are shown. The results of our program are compared with experimental data from references and with results from other Monte Carlo codes. They are found to be in good agreement.

The Mean Projected Range and Range Straggling of Nd Ions Implanted in Silicon Carbide

2011 ◽  
Vol 474-476 ◽  
pp. 565-569
Author(s):  
Xi Feng Qin ◽  
Shuang Li ◽  
Feng Xiang Wang ◽  
Yi Liang
Keyword(s):  
Silicon Carbide ◽  
Monte Carlo ◽  
Spectrum Analysis ◽  
Monte Carlo Code ◽  
Experiment Data ◽  
Lateral Deviation ◽  
Projected Range ◽  
The Mean ◽  
The Difference ◽  
Good Agreement

In view of the influence of the projected range, the range straggling, and the lateral deviation of ions in materials on the property of device in the fabrication of photoelectric integration devices by ion implantation, the mean projected ranges and range straggling for energetic 200 – 500 keV Nd ions implanted in 6H-SiC were measured by means of Rutherford backscattering followed by spectrum analysis. The measured values are compared with Monte Carlo code (SRIM2006) calculations. It has been found that the measured values of the mean projected range Rp are good agreement with the SRIM calculated values; for the range straggling △Rp, the difference between the experiment data and the calculated results is much higher than that of Rp

First results from the XMCD facility at the Energy-Dispersive EXAFS beamline of the Indus-2 synchrotron source

2019 ◽  
Vol 26 (2) ◽  
pp. 445-449
Author(s):  
N. Patra ◽  
U. G. P. S. Sachan ◽  
S. SundarRajan ◽  
Sanjay Malhotra ◽  
Vijay Harad ◽  
...  
Keyword(s):  
Magnetic Circular Dichroism ◽  
Energy Dispersive ◽  
X Rays ◽  
Beam Direction ◽  
Synchrotron Source ◽  
X Ray ◽  
Synchrotron Beam ◽  
First Results ◽  
Set Up ◽  
Good Agreement

Setting up of the X-ray Magnetic Circular Dichroism (XMCD) measurement facility with hard X-rays at the Energy-Dispersive EXAFS beamline (BL-08) at the Indus-2 synchrotron source is reported. This includes the design and development of a water-cooled electromagnet having a highest magnetic field of 2 T in a good field volume of 125 mm3 and having a 10 mm hole throughout for passage of the synchrotron beam. This also includes the development of an (X–Z–θ) motion stage for the heavy electromagnet for aligning its axis and the beam hole along the synchrotron beam direction. Along with the above developments, also reported is the first XMCD signal measured on a thick Gd film in the above set-up which shows good agreement with the reported results. This is the first facility to carry out XMCD measurement with hard X-rays in India.

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