Publications: Other Collaborations

PENGEOM: A general-purpose geometry package for Monte Carlo simulation of radiation transport in complex material structures (New Version Announcement)

Julio Almansa, Francesc Salvat-Pujol, Gloria Díaz-Londoño, Artur Carnicer, Antonio M. Lallena, Francesc Salvat

Computer Physics Communications 264, 107962 (2021)

A new version of the code system pengeom, which provides a complete set of tools to handle different geometries in Monte Carlo simulations of radiation transport, is presented. The distribution package consists of a set of Fortran subroutines and a Java graphical user interface that allows building and debugging the geometry-definition file, and producing images of the geometry in two-and three-dimensions. A detailed description of these tools is given in the original paper [Comput. Phys. Commun. 199 (2016) 102113] and in the code manual included in the distribution package. The present new version corrects a bug in the Fortran subroutines, and it includes various improvements of the Java graphical user interface. New Version Program Summary Program Title: pengeom CPC Library link to program files: https://doi. org/10.17632/zgswr8kyf5. 1 Licensing provisions: CC BY NC 3.0 Programming language

PENGEOM—A general-purpose geometry package for Monte Carlo simulation of radiation transport in material systems defined by quadric surfaces

Julio Almansa, Francesc Salvat-Pujol, Gloria Díaz-Londoño, Artur Carnicer, Antonio M Lallena, Francesc Salvat

Computer Physics Communications 199, 102–113 (2015)

The Fortran subroutine package pengeom provides a complete set of tools to handle quadric geometries in Monte Carlo simulations of radiation transport. The material structure where radiation propagates is assumed to consist of homogeneous bodies limited by quadric surfaces. The pengeom subroutines (a subset of the penelope code) track particles through the material structure, independently of the details of the physics models adopted to describe the interactions. Although these subroutines are designed for detailed simulations of photon and electron transport, where all individual interactions are simulated sequentially, they can also be used in mixed (class II) schemes for simulating the transport of high-energy charged particles, where the effect of soft interactions is described by the random-hinge method. The definition of the geometry and the details of the tracking algorithm are tailored to optimize simulation speed. The use of fuzzy quadric surfaces minimizes the impact of round-off errors. The provided software includes a Java graphical user interface for editing and debugging the geometry definition file and for visualizing the material structure. Images of the structure are generated by using the tracking subroutines and, hence, they describe the geometry actually passed to the simulation code.

Particle shape and orientation in laser diffraction and static image analysis size distribution analysis of micrometer sized rectangular particles

AP Tinke, A Carnicer, R Govoreanu, G Scheltjens, L Lauwerysen, N Mertens, K Vanhoutte, ME Brewster

Powder Technology 186(2), 154-167 (2008)

Laser diffraction (LD) and static image analysis (SIA) of rectangular particles [United States Pharmacopeia, USP30-NF25, General Chapter <776>, Optical Miroscopy.] have been systematically studied. To rule out sample dispersion and particle orientation as the root cause of differences in size distribution profiles, we immobilize powder samples on a glass plate by means of a dry disperser. For a defined region of the glass plate, we measure the diffraction pattern as induced by the dispersed particles, and the 2D dimensions of the individual particles using LD and optical microscopy, respectively. We demonstrate a correlation between LD and SIA, with the scattering intensity of the individual particles as the dominant factor. In theory, the scattering intensity is related to the square of the projected area of both spherical and rectangular particles. In traditional LD the size distribution profile is dominated by the maximum projected area of the particles (A). The diffraction diameters of a rectangular particle with length L and breadth B as measured by the LD instrument approximately correspond to spheres of diameter ØL and ØB respectively. Differences in the scattering intensity between spherical and rectangular particles suggest that the contribution made to the overall LD volume probability distribution by each rectangular particle is proportional to A2/L and A2/B. Accordingly, for rectangular particles the scattering intensity weighted diffraction diameter (SIWDD) explains an overestimation of their shortest dimension and an underestimation of their longest dimension. This study analyzes various samples of particles whose length ranges from approximately 10 to 1000 μm. The correlation we demonstrate between LD and SIA can be used to improve validation of LD methods based on SIA data for a variety of pharmaceutical powders all with a different rectangular particle size and shape.

Design strategies for optimizing holographic optical tweezers set-ups

Estela Martín-Badosa, Mario Montes-Usategui, A Carnicer, J Andilla, E Pleguezuelos, I Juvells

Journal of Optics A: Pure and Applied Optics 9(8), S267 (2007)

We provide a detailed account of the construction of a system of holographic optical tweezers. While a lot of information is available on the design, alignment and calibration of other optical trapping configurations, those based on holography are relatively poorly described. Inclusion of a spatial light modulator in the set-up gives rise to particular design trade-offs and constraints, and the system benefits from specific optimization strategies, which we discuss.

HoloTrap: Interactive hologram design for multiple dynamic optical trapping

Encarni Pleguezuelos, Artur Carnicer, Jordi Andilla, Estela Martín-Badosa, Mario Montes-Usategui

Computer Physics Communications 176(11-12), 701-709 (2007)

This work presents an application that generates real-time holograms to be displayed on a holographic optical tweezers setup; a technique that allows the manipulation of particles in the range from micrometres to nanometres. The software is written in Java, and uses random binary masks to generate the holograms. It allows customization of several parameters that are dependent on the experimental setup, such as the specific characteristics of the device displaying the hologram, or the presence of aberrations. We evaluate the software's performance and conclude that real-time interaction is achieved. We give our experimental results from manipulating 5 μm microspheres using the program.