On the calibration measurement of stripline beam position monitor for the ELI-NP facility

Stripline Beam Position Monitor (BPM) will be installed in the Compton Gamma Source in construction at the ELI Nuclear Physics facility in Romania. A test bench for the calibration of BPM has been built to characterize the device with stretched wire measurement in order to get the BPM response map. A full S-parameters characterization is performed as well to measure the electrical offset with the “Lambertson method”. This paper discusses the extensive simulations performed with full 3D electromagnetic CAD codes of the above measurements to investigate measurement accuracy, possible measurement artefacts and beam position reconstruction

Design realization and commissioning of RF Power system and accelerating structures for a Gamma Source

Thanks to the recent technological progress in the fields of high power lasers and high brightness linac accelerators, new Gamma and X ray sources based on electron-photon interaction are under development in several laboratory world-wide. These kind of sources uses Inverse Compton scattering in the collision between a relativistic high quality electron beam and high power optical laser pulses to generate secondary photon beams of unique performances. These photon beams are suitable for a wide range of applications and open new perspectives in many research fields. In particular gamma rays in the energy interval between 1-20~MeV are of great interest for basic research and application studies in the fields of nuclear physics and photonics. In this framework, a very innovative Compton source is under construction in Magurele (RO), by the EuroGammaS association, with the aim to generate photon beams in that energy range, characterized by unprecedented performances in terms of mono-chromaticity, brilliance, spectral density, tunability and polarization. The realization of this source called ELI-NP-GBS is in the framework of the European Extreme Light infrastructure (ELI) project that pursues the creation of an international laser research infrastructure. The challenging parameters of this source rely on the performances of the Linac and in particular of his radiofrequency (RF) system. The electron accelerator is a high brightness normal conducting RF Linac consisting of two S-band (2856 MHz) and twelve C-band (5712 MHz) RF structures. The main advantages of using a Linac accelerator are the energy "tunability" and the excellent electron beam quality that is possible to obtain. The accelerator will be operated at a repetition rate of 100 Hz. For every RF pulse up to 32 electron bunches, each one carrying 250 pC of charge, separated by 16 ns, will be accelerated. The Linac is required to achieve a normalized emittance in both planes better than 0.5 mm mrad and energy spread below 0.1\%. To guarantee these performances in a reliable and stable way, innovative and advance RF components have been developed. The aim of this thesis is the study, design and commissioning of the main components of RF system used for the realization of a state of the art gamma source such as the ELI-NP-GBS. High power RF sources driven by solid state modulators have to feed the accelerating structures with high pulse to pulse amplitude stability and RF pulse uniformity in order to minimize the electron beam energy spread. An innovative C-band High Order Mode (HOM) damped RF cavity has been conceived and designed in order to avoid beam emittance and energy spread degradation due to the Beam Break-Up instability along the Linac. In addition the S-band RF Gun has been realized with an innovative technique called "Gasket-clamping technique'' and implements new radiofrequency features to sustain the 100 Hz repetition rate operation. All these devices have been realized and tested and the results obtained are reported in this work. Taking into account the extremely good results obtained by RF Gun realized with the gasket-clamping technique, in the last part of this dissertation, it has been explored the possibility to extend this fabrication procedure to the realization of an entire travelling wave Linac structure. This technique, thanks to the use of RF/vacuum special gaskets, allows avoiding the brazing process thus reducing the fabrication costs, the risk of failure and improving the performances of the device in terms of reachable peak electric field. To demonstrate the feasibility of the implementation of such technique an accurate electromagnetic and mechanical design of an S-band travelling wave structure has been performed

Influence of Non-Linearity in Losses Estimation of Magnetic Components for DC-DC Converters

In this paper, the problem of estimating the core losses for inductive components is addressed. A novel methodology is applied to estimate the core losses of an inductor in a DC-DC converter in the time-domain. The methodology addresses both the non-linearity and dynamic behavior of the core magnetic material and the non-uniformity of the field distribution for the device geometry. The methodology is natively implemented using the LTSpice simulation environment and can be used to include an accurate behavioral model of the magnetic devices in a more complex lumped circuit. The methodology is compared against classic estimation techniques such as Steinmetz Equation and the improved Generalized Steinmetz Equation. The validation is performed on a practical DC-DC Buck converter, which was utilized to experimentally verify the results derived by a model suitable to estimate the inductor losses. Both simulation and experimental test confirm the accuracy of the proposed methodology. Thus, the proposed technique can be flexibly used both for direct core loss estimation and the realization of a subsystem able to simulate the realistic behavior of an inductor within a more complex lumped circuit

Microbially-enhanced composting of olive mill solid waste (wet husk): Bacterial and fungal community dynamics at industrial pilot and farm level.

Bacterial and fungal community dynamics during microbially-enhanced composting of olive mill solid waste (wet husk), used as a sole raw material, were analysed in a process carried out at industrial pilot and at farm level by the PCR-DGGE profiling of the 16 and 26S rRNA genes. The use of microbial starters enhanced the biotransformation process leading to an earlier and increased level of bacterial diversity. The bacterial community showed a change within 15 days during the first phases of composting. Without microbial starters bacterial biodiversity increased within 60 days. Moreover, the thermophilic phase was characterized by the highest bacterial biodiversity. By contrast, the biodiversity of fungal communities in the piles composted with the starters decreased during the thermophilic phase. The biodiversity of the microbial populations, along with physico-chemical traits, evolved similarly at industrial pilot and farm level, showing different maturation times

Design of high gradient, high repetition rate damped C-band rf structures

The gamma beam system of the European Extreme Light Infrastructure–Nuclear Physics project foresees the use of a multibunch train colliding with a high intensity recirculated laser pulse. The linac energy booster is composed of 12 traveling wave C-band structures, 1.8 m long with a field phase advance per cell of 2π=3 and a repetition rate of 100 Hz. Because of the multibunch operation, the structures have been designed with a dipole higher order mode (HOM) damping system to avoid beam breakup (BBU). They are quasiconstant gradient structures with symmetric input couplers and a very effective damping of the HOMs in each cell based on silicon carbide (SiC) rf absorbers coupled to each cell through waveguides. An optimization of the electromagnetic and mechanical design has been done to simplify the fabrication and to reduce the cost of the structures. In the paper, after a review of the beam dynamics issues related to the BBU effects, we discuss the electromagnetic and thermomechanic design criteria of the structures. We also illustrate the criteria to compensate the beam loading and the rf measurements that show the effectiveness of the HOM damping

RF Design of the X-band Linac for the EuPRAXIA@SPARC_LAB Project

We illustrate the RF design of the X-band linac for the upgrade of the SPARC_LAB facility at INFN-LNF (EuPRAXIA@SPARC_LAB). The structures are travelling wave (TW) cavities, working on the 2π/3 mode, fed by klystrons with pulse compressor systems. The tapering of the cells along the structure and the cell profiles have been optimized to maximize the effective shunt impedance keeping under control the maximum value of the modified Poynting vector, while the couplers have been designed to have a symmetric feeding and a reduced pulsed heating. In the paper we also present the RF power distribution layout of the accelerating module and a preliminary mechanical design