Attila Kerekes

Pre-excitation studies for rubidium-plasma generation

The key element in the Proton-Driven-Plasma-Wake-Field-Accelerator (PWFA) project is the generation of highly uniform plasma from Rubidium vapor. A scientifically straightforward, yet highly challenging way to achieve full ionization is to use high power laser which can assure the barrier suppression ionization (BSI) along the 10 m long active region. The Wigner-team in Budapest is investigating an alternative way of uniform plasma generation. The proposed Resonance Enhanced Multi-Photon Ionization (REMPI) scheme can be probably realized by much less laser power. In the following we plan to investigate the resonant pre-excitations of the Rb atoms, both theoretically and experimentally. In the following our theoretical framework is presented together with the status report about the preparatory work of the planned experiment.

Effect of delayed pMDI actuation on the lung deposition of a fixed-dose combination aerosol drug

Graphical abstract Figure. No caption available. ABSTRACT Lack of coordination between the beginning of the inhalation and device triggering is one of the most frequent errors reported in connection with the use of pMDI devices. Earlier results suggested a significant loss in lung deposition as a consequence of late actuation. However, most of our knowledge on the effect of poor synchronization is based on earlier works on CFC devices emitting large particles with high initial velocities. The aim of this study was to apply numerical techniques to analyse the effect of late device actuation on the lung dose of a HFA pMDI drug emitting high fraction of extrafine particles used in current asthma and COPD therapy. A computational fluid and particle dynamics model was combined with stochastic whole lung model to quantify the amount of drug depositing in the extrathoracic airways and in the lungs. High speed camera measurements were also performed to characterize the emitted spray plume. Our results have shown that for the studied pMDI drug late actuation leads to reasonable loss in terms of lung dose, unless it happens in the second half of the inhalation period. Device actuation at the middle of the inhalation caused less than 25% lung dose reduction relative to the value characterizing perfect coordination, if the inhalation time was between 2 and 5 s and inhalation flow rate between 30 and 150 L/min. This dose loss is lower than the previously known values of CFC devices and further support the practice of triggering the device shortly after the beginning of the inhalation instead of forcing a perfect synchronization and risking mishandling and poor drug deposition.

Photon Statistic Measurements of Surface Plasmon Excitation

In this study we present the results of our measurements on photon statistic distributions of the light emitted by surface plasmon oscillations. Time interval statistics, photon-number distribution, auto-correlation and cross-correlation functions of the generated light were determined and compared to those of the exciting laser.

Creation of Blue Light Emitting Color Centers in Nanosized Diamond for Different Applications

Plasma immersion ion implantation and focused ion beam treatment techniques were used to create nitrogen-related complex defect centers in detonation nanodiamond crystals. Helium implantation was used to produce vacancies in the crystal structure, which was followed by the introduction of nitrogen ions (with the same method). Heat treatment at 1,023 K was applied to initiate vacancy diffusion and formation of complex defect centers. The sp2 carbon content of the samples formed during the implantation and the high-temperature annealing was decreased by oxidation at 723 K in air. Changes in the bonding structure were monitored by Raman and infrared spectroscopic measurements after each step of the defect creation process. It was found that the photoluminescence of nanosized diamond changes remarkably as a consequence of different treatments and a new, narrow, intense emission band develops in the deep blue wavelength region. The N3 nitrogen-related complex defect center was considered as source of this fine structured emission band in the luminescence spectrum.

Determination of the Distribution of Inhaled Drugs in Human Airways by Raman Spectroscopy

A novel Raman spectroscopic method has been developed to study the distribution of inhaled drugs and other airborn substances in human airway replicas. A drug from a metered dose inhaler was introduced into a realistic human respiratory tract prepared by 3D printing from computer tomographic data recorded on humans, and the deposited material was collected on silicon substrates fixed to the hollow airway’s walls. The analysis of the covered area was performed by mapping the characteristic Raman peak intensity of the drug over the substrate surface; the amount was determined by integration of the total intensity measured at different points. The Raman mapping method was verified by comparison with optical microscopic images of the same surface area.

Nanoparticle characterization with photon correlation LDA

A completely new photon correlation Laser Doppler Anemometer system was developed to simultaneous particle number, velocity and size measurements down to the nanometer size range. The backscattering arrangement assures the online, in-situ, non-invasive measurements without further fine tuning. Since the measurements are on-line and in situ the particle synthesis process can be monitored with high temporal and spatial resolution. In this way a nanoparticle generator can be analyzed and, for instance, the source of an unwanted broad size distribution may be identified, or the degree of agglomeration and the related properties can be controlled. The accuracy limits of individual velocity and size estimations were investigated with monodisperse paraffin particles separated by Differential Mobility Analyzer. Although the signal-to-noise ratio decreases for nanoparticles, the particle sizing remains robust due to high power increase of the scattered intensity with the size.

Development of a high resolution interferometric system for testing the optical elements in ELI

The development and application of a phase shifting interferometric system for testing optical surfaces is described. Several application examples of this instrument for 3D surface topography diagnostics are presented. After certain expedient reconstruction the system can be used for testing the optical elements and different coatings in ELI (Extreme Light Infrastructure).