Theoretical study and design of a CARM type millimeter wave source

In Nuclear Fusion external heating sources play a role of paramount relevance for the twofold role of plasma heating and instability suppression. The effectiveness of Electron Cyclotron (EC) waves in Tokamaks have been experimentally demonstrated since the early 80’s of the last century (see e. g. the pioneering work by R.M. Gilgenbach et al., 1980). Nowadays EC systems plays a pivotal role in magnetic fusion devices and their need in future experimental reactors is out of doubt. The physical reasons underlying these choices stems from the fact that electron cyclotron radiation can be coupled effectively to the plasma, producing a localized and controlled energy deposition. Within this framework an important tool has been provided by the electron cyclotron masers (ECM) sources, namely gyrotronlike device, extensively used because able to provide sufficiently large power in the millimeter and sub-millimeter region. The gyrotrons provide the most mature and reliable technology in the field of millimeter-wave tubes, their use is however hampered by the fact that they meet some difficulty of operation (in terms of delivered power and efficiency) in the spectral range above 200 GHz. The possibility of exploiting different generators of powerful millimeter-wave coherent radiation has therefore been suggested. In this context a research and development program has been undertaken at ENEA Frascati Center, aimed at realizing a microwave tube based on a Cyclotron Auto-Resonance Maser (CARM) oscillator, characterized by a high value of the Doppler up-shift interaction allowing a consistent reduction of the static magnetic field in the interaction cavity and enhanced efficiency with a moderately relativistic beam due to the auto resonance mechanism. The price to be paid is the necessity of exploiting high quality electron beams, with velocity spread below 0.5%, in order to ensure appropriate mode selection, enough gain to oscillate and adequate beam-wave power transfer with the required efficiency. The low beam quality has been the main element that has affecting the performances of the first CARM experiments on the eve of the last century. Most of the them used already existing high-voltage accelerators producing electron beams with currents of several kA. They were powered by modulators having non-appropriate waveform with respect to flat-top ripple. The beam was emitted from a cold cathode and then blasted toward the small aperture, used either to scratch out the largest part of the beam and as an emittance filter. This mechanism never succeeded to deliver a beam with appropriate characteristics. Even though the data relevant to the beam qualities are rather insufficient, serious doubts can be raised on the reliability of such drivers for CARM operation. The research line associated with the present Ph.D. thesis, developed at ENEA with the CARM project team, has gone through different phases, the first of which has been the understanding of the physical mechanisms underlying the operation of the different devices (Gyrotron, FEL, CARM, Gyro-Backward. . . ). A significant part of the thesis has been devoted to the design of the various components of the CARM device, including the cathode, the principal magnet and the radiation confining cavity. Most of the design effort has been devoted to the production of a beam with suited characteristic for the CARM operation. Successively, particular care has been devoted in putting in evidence the relative pro’s and con’s and noticeable efforts has been devoted to the understanding of the factors which have limited the CARM efficiency in the past experiments. In chapter 1 we review the relevant issues to the thermonuclear fusion as a clean solution for the world energy demand putting in evidence the requirements for a commercial power fusion plant. In particular the studies, undertaken under auspices of the European Fusion Development Agreement (EFDA) for a different configuration of a DEMOnstration fusion reactor, get out the importance of the efficiency for the Heating and Current Drive (H&CD) systems. We report a short description of the physical mechanism governing the fusion reaction. We discussed the role played by the plasma instabilities in a Tokamak plant and the necessity of their suppression or control. We put therefore in evidence the necessity of additional H&CD devices in Tokamak plants and analyze the required characteristics in terms of frequency and power. In chapter 2 we describe the design of the ENEA CARM facility. We start with the analysis of a thermionic gun and perform accurate simulation determine the conditions for the generation of a high quality beam, in terms of the longitudinal velocity spread. The simulation are benchmarked with an analytical modeling of the beam transport by means of the generalization of the Courant-Snyder formalism which simplifies the beam transport design for this device, demanding for an accurate control of the beam transverse dimension. The forthcoming chapter 3 contains a thorough analysis of CARM interaction, carried out using previous theoretical formulation providing the coupled beam-wave evolution equations. The theory is then confronted with that of U-FEL systems. The results of this efforts is that of providing a set of semi-analytical formulae useful for a quick design of the device. The relevant reliability has been benchmarked using the home-made code GRAAL and tested for a variety of study cases. Furthermore, a “universal” scaling formula describing the CARM performance embedding inhomogeneous broadening effects and the beam current, as it happens in the case of U-FEL, has been derived for monitoring the accuracy and for diagnosing the calculations during the numerical experiments. The concluding chapter 4 deals with the CARM oscillator configuration. It contains the description of the system, the evaluation of the gain and saturation mechanism and the design of the radiation confining cavity with particular reference to the relevant optimization of the suppression of the spurious modes

On an Umbral Point of View of the Gaussian and Gaussian-like Functions

The theory of Gaussian functions is reformulated using an umbral point of view. The symbolic method we adopt here allows an interpretation of the Gaussian in terms of a Lorentzian image function. The formalism also suggests the introduction of a new point of view of trigonometry, opening a new interpretation of the associated special functions. The Erfi ( x ) , is, for example, interpreted as the “sine” of the Gaussian trigonometry. The possibilities offered by the Umbral restyling proposed here are noticeable and offered by the formalism itself. We mention the link between higher-order Gaussian trigonometric functions, Hermite polynomials, and the possibility of introducing new forms of distributions with longer tails than the ordinary Gaussians. The possibility of framing the theoretical content of the present article within a redefinition of the hypergeometric function is eventually discussed

On an Umbral point of view to the Gaussian and Gaussian like functions

In this note we review the theory of Gaussian functions by exploiting a point of view based on symbolic methods of umbral nature. We introduce quasi-Gaussian functions, which are close to Gaussian distribution but have a longer tail. Their use and their link with hypergeometric function is eventually presented

Radio-Frequency Undulators, Cyclotron Auto Resonance Maser and Free Electron Lasers

We discuss a hybrid Free Electron Laser (FEL) architecture operating with a RF undulator provided by a powerful Cyclotron Auto-Resonance Maser (CARM). We outline the design elements to operate a compact X-ray device. We review the essential aspects of wave undulator FEL theory and of CARM devices

Rete capillare, cancro e legge di Kleiber

Lo studio dell’evoluzione dei complessi biologici ha beneficiato dell’utilizzo di leggi di scala che coinvolgono relazioni tra massa e fabbisogno energetico. L’uso congiunto di modelli, quali le leggi di Kleiber e di Murray, ha aperto nuove possibilità per l’analisi quantitativa della crescita delle masse cancerose, della relativa vascolarizzazione ed evoluzione metastatica. In questo articolo si descrivono i risultati essenziali delle ricerche in tali campi e si esaminano come tali studi possano avere un impatto efficace sulla pratica clinic

The Third Dose of BNT162b2 COVID-19 Vaccine Does Not “Boost” Disease Flares and Adverse Events in Patients with Rheumatoid Arthritis

Data on the risk of adverse events (AEs) and disease flares in autoimmune rheumatic diseases (ARDs) after the third dose of COVID-19 vaccine are scarce. The aim of this multicenter, prospective study is to analyze the clinical and immunological safety of BNT162b2 vaccine in a cohort of rheumatoid arthritis (RA) patients followed-up from the first vaccine cycle to the third dose. The vaccine showed an overall good safety profile with no patient reporting serious AEs, and a low percentage of total AEs at both doses (40/78 (51.3%) and 13/47 (27.7%) patients after the second and third dose, respectively (p < 0.002). Flares were observed in 10.3% of patients after the end of the vaccination cycle and 12.8% after the third dose. Being vaccinated for influenza was inversely associated with the onset of AEs after the second dose, at both univariable (p = 0.013) and multivariable analysis (p = 0.027). This result could allow identification of a predictive factor of vaccine tolerance, if confirmed in larger patient populations. A higher disease activity at baseline was not associated with a higher incidence of AEs or disease flares. Effectiveness was excellent after the second dose, with only 1/78 (1.3%) mild breakthrough infection (BI) and worsened after the third dose, with 9/47 (19.2%) BI (p < 0.002), as a probable expression of the higher capacity of the Omicron variants to escape vaccine recognition

A New Orbiting Deployable System for Small Satellite Observations for Ecology and Earth Observation

In this paper, we present several study cases focused on marine, oceanographic, and atmospheric environments, which would greatly benefit from the use of a deployable system for small satellite observations. As opposed to the large standard ones, small satellites have become an effective and affordable alternative access to space, owing to their lower costs, innovative design and technology, and higher revisiting times, when launched in a constellation configuration. One of the biggest challenges is created by the small satellite instrumentation working in the visible (VIS), infrared (IR), and microwave (MW) spectral ranges, for which the resolution of the acquired data depends on the physical dimension of the telescope and the antenna collecting the signal. In this respect, a deployable payload, fitting the limited size and mass imposed by the small satellite architecture, once unfolded in space, can reach performances similar to those of larger satellites. In this study, we show how ecology and Earth Observations can benefit from data acquired by small satellites, and how they can be further improved thanks to deployable payloads. We focus on DORA—Deployable Optics for Remote sensing Applications—in the VIS to TIR spectral range, and on a planned application in the MW spectral range, and we carry out a radiometric analysis to verify its performances for Earth Observation studies

A First Search for coincident Gravitational Waves and High Energy Neutrinos using LIGO, Virgo and ANTARES data from 2007

We present the results of the first search for gravitational wave bursts associated with high energy neutrinos. Together, these messengers could reveal new, hidden sources that are not observed by conventional photon astronomy, particularly at high energy. Our search uses neutrinos detected by the underwater neutrino telescope ANTARES in its 5 line configuration during the period January - September 2007, which coincided with the fifth and first science runs of LIGO and Virgo, respectively. The LIGO-Virgo data were analysed for candidate gravitational-wave signals coincident in time and direction with the neutrino events. No significant coincident events were observed. We place limits on the density of joint high energy neutrino - gravitational wave emission events in the local universe, and compare them with densities of merger and core-collapse events.Comment: 19 pages, 8 figures, science summary page at http://www.ligo.org/science/Publication-S5LV_ANTARES/index.php. Public access area to figures, tables at https://dcc.ligo.org/cgi-bin/DocDB/ShowDocument?docid=p120000

Gamma-Ray Burst observations by the high-energy charged particle detector on board the CSES-01 satellite between 2019 and 2021

In this paper we report the detection of five strong Gamma-Ray Bursts (GRBs) by the High-Energy Particle Detector (HEPD-01) mounted on board the China Seismo-Electromagnetic Satellite (CSES-01), operational since 2018 on a Sun-synchronous polar orbit at a $\sim$ 507 km altitude and 97$^\circ$ inclination. HEPD-01 was designed to detect high-energy electrons in the energy range 3 - 100 MeV, protons in the range 30 - 300 MeV, and light nuclei in the range 30 - 300 MeV/n. Nonetheless, Monte Carlo simulations have shown HEPD-01 is sensitive to gamma-ray photons in the energy range 300 keV - 50 MeV, even if with a moderate effective area above $\sim$ 5 MeV. A dedicated time correlation analysis between GRBs reported in literature and signals from a set of HEPD-01 trigger configuration masks has confirmed the anticipated detector sensitivity to high-energy photons. A comparison between the simultaneous time profiles of HEPD-01 electron fluxes and photons from GRB190114C, GRB190305A, GRB190928A, GRB200826B and GRB211211A has shown a remarkable similarity, in spite of the different energy ranges. The high-energy response, with peak sensitivity at about 2 MeV, and moderate effective area of the detector in the actual flight configuration explain why these five GRBs, characterised by a fluence above $\sim$ 3 $\times$ 10$^{-5}$ erg cm$^{-2}$ in the energy interval 300 keV - 50 MeV, have been detected.Comment: Accepted for publication in The Astrophysical Journal (ApJ