Bobine Tesla

Résumé

thumb|Bobine Tesla (Nikola Tesla Memorial Centre, Smiljan, Croatie). La bobine Tesla, ou transformateur de Tesla, est une machine électrique fonctionnant avec du courant alternatif à haute fréquence et permettant de produire de très hautes tensions. Elle porte le nom de son inventeur, Nikola Tesla, qui l'a mise au point vers 1891. L'appareil consiste en deux ou trois circuits de bobinage couplés et accordés par résonance. Il n'y a pas de noyau métallique comme dans les transformateurs électriques classiques : c'est un transformateur à noyau d'air. La version électromécanique du circuit, inventée par Nikola Tesla, dite conventionnelle, a été améliorée tout au long du . La version à semi-conducteurs de puissance a permis d'alléger le dispositif d'alimentation à la fin des années 1990, mais avec une construction plus complexe. Il est relativement facile aujourd'hui de fabriquer une bobine Tesla pour produire des éclairs artificiels. De nombreux amateurs ont construit leur propre versio

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https://fr.wikipedia.org/wiki/Bobine_Tesla

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In this study, we deal with the design and implementation of microsystems for electron spin resonance (ESR) applications. Three different microsystems are designed with different approaches for microwave magnetic field generation, ESR detection and sample handling. To the best of our knowledge, these microsystems are the first ever realized fully integrated solutions providing X-band ESR spectroscopy functionality on a single silicon chip. The first microsystem implements absorption mode ESR detection by means of a differential approach. It consists of two pairs of planar excitation/detection coils, a voltage controlled oscillator (VCO), a low noise amplifier (LNA) and a mixer. The excitation/detection coil pairs are identical. The excitation coil has a diameter of 300 microns, and it also functions as the LC-tank inductor of the VCO. The detection coil, which is placed in the middle of the excitation coil, has a diameter of 100 microns. The ESR sample is placed over one of the detection coils. This coil functions as the sample coil, while the empty coil functions as the reference coil. The excitation coils generate the microwave magnetic field acting on the detection coils. In the presence of ESR, the induced voltage on the sample coil differs from the induced voltage on the reference coil. This difference is amplified by the LNA and down-converted by the mixer. Two such microsystems with operating frequencies at 6 and 8 GHz are prototyped on a single standard CMOS chip with an area of 8.6 mm2. The ESR spin sensitivities achieved with the 6 and 8 GHz microsystems are 6.7×1010 and 3.9×1010 spins/GHz1/2, respectively. The second microsystem is an improved version of the first microsystem, with a slightly different topology. Furthermore, LNAs are implemented with SiGe bipolar transistors for higher gain with lower noise figure. It is also prototyped on a single silicon chip with an area of 4 mm2. The ESR spin sensitivity achieved with this microsystem is 3×1010 spins/GHz1/2. The third microsystem implements dispersion mode ESR detection by means of a differential approach in frequency domain. It consists of two VCOs, a mixer, a high frequency buffer, and a frequency divider. The VCO LC-tank inductor has a diameter of 100 microns, and it functions both as the excitation and detection coil. The two coils are placed perpendicularly in order to prevent injection locking. The VCO outputs are multiplied by the mixer, and a difference frequency output is generated. This output is amplified by the high frequency buffer. Its frequency is then divided by the frequency divider, and a 1-bit digital frequency output is generated. In the presence of ESR, the center frequencies of one of the VCOs changes slightly. This change is observed at the output in the form of frequency. This microsystem is prototyped on a standard CMOS chip with an area of 1 mm2. The ESR spin sensitivity achieved with this microsystem is 2×1010 spins/GHz1/2. The realized microsystems already have performances comparable to commercial systems. Their performances can further be improved; and they may be used in different micro scale applications of ESR spectroscopy and imaging.

EPFL2007

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The cost of omnidirectionality: extracting and labelling the echoes

Julien Olivier Thierry Rüegg

This report explains all theoretical and practical aspects of a 2D room re- construction algorithm based on euclidean geometry. Detailed theoretical explanations about the procedure are given in the first part. In the second part, a precise description of the implementational choices, issues, strengths and weaknesses is given in order for the user to run the software correctly and be able to modify and improve it with more simplicity.

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H- ion source for CERN's Linac4 accelerator

Stefano Mattei

Linac4 is the new negative hydrogen ion (H-) linear accelerator of the European Organization for Nuclear Research (CERN). Its ion source operates on the principle of Radio-Frequency Inductively Coupled Plasma (RF-ICP) and it is required to provide 50 mA of H- beam in pulses of 600 us with a repetition rate up to 2 Hz and within an RMS emittance of 0.25 pi mm mrad in order to fullfil the requirements of the accelerator. This thesis is dedicated to the characterization of the hydrogen plasma in the Linac4 H- ion source. We have developed a Particle-In-Cell Monte Carlo Collision (PIC-MCC) code to simulate the RF-ICP heating mechanism and performed measurements to benchmark the fraction of the simulation outputs that can be experimentally accessed. The code solves self-consistently the interaction between the electromagnetic field generated by the RF coil and the resulting plasma response, including a kinetic description of charged and neutral species. A fully-implicit implementation allowed to simulate the high density regime of the Linac4 H- ion source, ensuring the energy conservation while maintaining the computational resources tractable. We studied the capacitive to inductive transition characteristic of the initial phase of the pulsed discharge. The simulation results were confirmed by time-resolved photometry measurements and allowed quantifying the effect of the hydrogen pressure and of the external magnetic cusp field on the transition dynamics. This provided insights into possible modifications to the magnetic cusp field configuration to maximize the power deposited to the plasma. The optimal ion source configuration maximizes the density of volume produced H-, the flux of H0 atoms onto the cesiated molybdenum plasma electrode surface at the origin of H- emission, and minimizes the electron density and energy in the beam formation region. We simulated the high-density regime (10^19 m-3) representative of the nominal operation of the Linac4 ion source during beam extraction. We performed a parametric study of the RF current, hydrogen pressure and magnetic configuration (cusp and filter) to assess their impact on the plasma parameters. The simulation results allowed assessment of these parameters and provided guidelines for the optimization of the ion source operational and design parameters. The simulation results of electron density, electron energy and hydrogen dissociation degree showed excellent agreement with optical emission spectroscopy measurements both as a function of RF coil current and magnetic configuration. The outputs of these simulations provide crucial inputs to beam formation and extraction physics models. Dedicated PIC software packages are being developed that will eventually shed insight into essential beam parameters such as the intensity and emittance of the H° beam and the intensity of the co-extracted electrons.

EPFL2017

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H- ion source for CERN's Linac4 accelerator

Stefano Mattei

EPFL2017

EPFL2007