Benchmark calculations for electron velocity distribution function obtained with Monte Carlo Flux simulations

Modern, multi-modular plasma modeling requires accurate and versatile methods for the determination of the electron velocity distribution function from which rate coefficients of electron impact processes as well as electron transport quantities are determined. In this paper we propose as a solution a modified version of a strongly overlooked method developed in the early 90\u27s, namely, Monte Carlo Flux (MCF). The improvement lies in a criterion for the otherwise somewhat empirical selection of the time-step used in the method. We show that an MCF based code highlights and overcomes the limitations of two-terms codes such as BOLSIG+ and it is much faster than a conventional Monte Carlo. Moreover, MCF is in excellent agreement with the multi-term method for a wide range of reduced electric fields, being at the same time much simpler to implement and to extend to more general cases than the latter. Explicit illustrations of the Markov matrices representing short-time kinetics are presented to gain insight into the method. The two-dimensional velocity distribution and its expansion into Legendre polynomials are discussed for electrons in argon.</p

FATTORI UMORALI PROTETTIVI COME STRUMENTI PER LA GENERAZIONE DI VACCINI EFFICACI CONTRO L'INFEZIONE DA HIV

The present study includes several works which have common goal to further clarify the humoral correlates of protection against HIV infection, present in those populations that naturally can remain IgG-seronegative, despite a long-term exposure to HIV (ESNs), or are able to control for a long time the same infection (LTNPs, ECs). In fact, the first part of the thesis is concerned about the study of protective humoral parameters which would characterize a cohort of 45 HIV-infected individuals at different clinical stages (10 AI, Acute Infection, 10 LTNPs, 8 ECs, 7 AIDS, 10 HAART +); a cohort consisting of South African mothers infected with HIV subtype C, coupled with their infants, some of which are seronegative (as a particular ESN group), and finally, a cohort of women in Cambodian ESN, whose B cells, in their cervicovaginal secretions, were used to construct a library of Fab IgA phage-k/\uf06c, which was screened for specificity to HIV-gp41. The results showed that heterogeneous humoral responses were observed in groups of HIV seropositive subjects. The high variability of total or gp41-specific IgA among all patients groups, supported their role as a biomarker. Infact, significant differences were detected in AI and in LTNP for IgA to gp41 and in IgG to gp120, respectively. Moreover, three domains of gp41, HR1, IDE and MPER, elicited antibodies that were effectively transmitted to ESN babies. In such babies, epitopes overlapping the 2F5 (ELDKWAS), but not the 4E10 epitope, were neutralization targets in two out of four viruses tested. Finally, the Fabs IgA from ESN women blocked efficiently transcytosis of HIV-1 with IC90 <50-150 ng ml-1. However, all results showed good neutralizing activity of ESN Fabs. The efficiency of the Fabs in protecting the epithelial cells from free-HIV and CD4+ cells HIV-infectied, suggests that the low concentration of IgA, present in genital secretions, could be active in vivo. Our findings highlight important epitopes in gp41 that appear to be associated with exposure, but without infection, and would be important to consider for vaccine design. From these assumptions it has been possible to continue the study to design and produce immunogenic proteins which could elicit the humoral immune response, observed in the above categories. Thus we produced chimeric proteins, consisting of the carrier system of VLPs (Virus-Like Particles). In particular, have been used VLPs expressing regions and domains of HIV-gp41, produced in the first case in the baculovirus system, and in the second case, by the conjugation of gp41-peptides to VLPs, from bacteriophage Q\u3b2, AP205. All results showed that sera from immunized animals showed a high reactivity with individual HIV proteins expressed in VLPs. Results of TZM-bl based neutralization assay show that combined sera from animals independently immunized with gp140- or full-length-gp41-expressing VLPs have an additive/synergistic effect in the neutralization activity of HIV pseudoviruses. The peptides to which aminoacid strings were added to either the C-terminus or N-terminus of core epitope in HR1 region prior to VLP coupling could induced a strong specific immune response and HIV-1 neutralizing antibodies; high level of gp41 specific antibodies and neutralizing activity were also raised against MPR region. Antibody-dependent cell cytotoxicity (ADCC) activity was induced by one of the two MPR epitopes, whereas no ADCC activity was associated to HR1 region. These results may have relevant implications for the development of new vaccinal approaches against HIV infection

Benchmarking of Monte Carlo Flux simulations of electrons in CO2

Electron velocity distribution functions (EVDFs) in CO2 obtained by means of the Monte Carlo Flux (MCF) method are compared with results from two-term and multi-term Boltzmann solvers. The MCF method provides detailed calculations of the EVDF through a highly efficient variance reduction technique. Benchmark calculations of Legendre polynomial coefficients of the EVDF expansion are reported for a wide range of reduced electric fields (E/N), showing excellent agreement with multi-term solutions. Rate coefficients of inelastic processes calculated from two-term Boltzmann solvers differ significantly, up to 70%, from MCF and multi-term solutions, due to the anisotropy of the EVDF. An extension of the method to consider the thermal distribution of the background gas is also presented. This extension, together with an accurate description of the population of rotationally and vibrationally excited states, provides excellent agreement with measured transport coefficients at low E/N. A good agreement is obtained at moderate E/N between experimental values of dissociation rate coefficients and MCF calculations after careful consideration and analysis of several cross sections data sets.</p

Benchmarking of Monte Carlo flux simulations of electrons in CO2

Electron velocity distribution functions (EVDFs) in CO2 obtained by means of the Monte Carlo flux (MCF) method are compared with results from two-term and multi-term Boltzmann solvers. The MCF method provides detailed calculations of the EVDF through a highly efficient variance reduction technique. Benchmark calculations of Legendre polynomial coefficients of the EVDF expansion are reported for a wide range of reduced electric fields (E/N), showing excellent agreement with multi-term solutions. Rate coefficients of inelastic processes calculated from two-term Boltzmann solvers differ significantly, up to 70%, from MCF and multi-term solutions, due to the anisotropy of the EVDF. An extension of the method to consider the thermal distribution of the background gas is also presented. This extension, together with an accurate description of the population of rotationally and vibrationally excited states, provides excellent agreement with measured transport coefficients at low E/N. A good agreement is obtained at moderate E/N between experimental values of dissociation rate coefficients and MCF calculations after careful consideration and analysis of several cross sections data sets

Design of an X-band constant impedance LINAC for compact light project

Within the framework of Horizon 2020 project, Compact Light, in order to provide a high performance, high-gradient X-band technology, for the new generation of hard X-ray FEL, a travelling wave (TW) Linac, working on 2pi/3 mode at 11.9952 GHz, fed by two types of asymmetrically couplers, has been designed. The design was performed using CST Microwave Studio frequency domain solver. First, simulations have been conduct in order to obtain the best trade-off between single cell’s parameters, varying iris aperture. Then, the both couplers, with and without pumping port, has been tuned to avoid reflections at the input port. Finally, the entire structure, with 5 cells, was simulated. The main structure parameters will be present and we will also show and discuss the acceleranting gradient obtained vary with linac lenght and input power

Review of the ELI-NP-GBS low level rf and synchronization systems

The Gamma Beam System (GBS) of ELI-NP is a linac based gamma-source in construction at Magurele (RO) by the European consortium EuroGammaS led by INFN. Photons with tunable energy and with intensity and brilliance well beyond the state of the art will be produced by Compton back-scattering between a high quality electron beam (up to 740 MeV) and a 515 nm intense laser pulse. Production of very intense photon flux with narrow bandwidth requires multi-bunch operation at 100 Hz repetition rate. A total of 13 klystrons, 3 S-band (2856 MHz) and 10 C-band (5712 MHz) will power a total of 14 Travelling Wave accelerating sections (2 S-band and 12 C-band) plus 3 S-band Standing Wave cavities (a 1.6 cell RF gun and 2 RF deflectors). Each klystron is individually driven by a temperature stabilized LLRF module, for a maximum flexibility in terms of accelerating gradient, arbitrary pulse shaping (e.g. to compensate beam loading effects in multi-bunch regime) and compensation of long-term thermal drifts. In this paper, the whole LLRF system architecture and bench test results, the RF reference generation and distribution together with an overview of the synchronization system will be described