The Ka-Band High Power Klystron Amplifier Design Program of INFN

In the framework of the Compact Light XLS project, a short ultra-high gradient linearizer working on the third harmonic of the main linac frequency is requested. Increasing gradients and reducing dimensions are requirements for XLS and all next generation linear accelerators. Actually, ultra-compact normal conducting accelerating structures, operating in the Ka-band regime ranging from 100 to 150 MV/m are required to achieve ultra-high gradients for research, industrial and medical applications. To fulfill these strong requirements, the R&D of a proper Ka-band klystron with RF power output and a high efficiency is mandatory. This contribution reports the design of a possible klystron amplifier tube operating on the TM010 mode at 36 GHz, the third harmonic of the 12 GHz linac frequency, with an efficiency of 42% and a 20 MW RF power output. This contribution discusses also the high-power DC gun, the beam focusing channel and the RF beam dynamics

A novel harmonic klystron configuration for high power microwave frequency conversion

A new frequency converter, operating at significantly higher power and efficiency than previous devices, is described in this paper. The proposed device is implemented as a klystron structure where a new design principle is used. New analytical formulas and a specific design procedure are proposed. The klystron frequency multiplier can be suitable for telecommunications and non-lethal weapon, scientific and medical particle accelerators while the most interested exploitations are in the field of high gradient particle acceleration and FEL devices for which no performant sources exist. The advanced klystron multiplier can replace all the low level circuitry for frequency multiplication as a less expensive alternative. Efficiencies in the range of 60% in the K-band range with power levels of 30 MW are possible without phase noise, sideband generation, jitter or chirp effects. The presented design principle is applicable to other bands or power levels.Comment: 14 pages, 12 figure

Multiphysics Design of a Klystron Buncher

Abstract: The Multiphysics design of a 130 GHz klystron Buncher cavity is described in this paper. In this high frequency range, dimensions are critical and expose the device to multiple physics effects, due to the power dissipations, affecting the electromagnetic performances. The proposed device is integrated with a carbon nanotube cold cathode in order to reduce thermal expansion and an opportune airflow controls the temperature. The multiphysics design is performed on COMSOL in order to ensure the desired behavior in operative conditions. Electromagnetic fields and scattering parameters have been computed when the Buncher is subjected to multiple physics factors. The appropriate geometries and materials and can be found

Design, Test and Analysis of a Gyrotron Cavity Mock-Up Cooled Using Mini Channels

In 2016, we have designed, built and finally tested at the FE200 facility in Le Creusot (France) a planar mock-up mimicking the water-cooled cylindrical resonance cavity of the European 170 GHz, 1 MW gyrotron to be used for electron cyclotron plasma heating in ITER. The aim of the mock-up is the characterization of the cooling capability of the cavity. A Glidcop® target is heated with an electron beam gun with resulting peak heat fluxes relevant for the full-size cavity. Underneath the target surface, whose temperature is monitored by means of a pyrometer, a set of parallel semi-circular mini-channels, with diameter of 1.5 mm, allows the flow of pressurized water, entering the mockup at ~ 9 bar and 40 °C. Several thermocouples measure the target temperature, at different distances from the heated target surface. The experimental results show that the mock-up is capable to withstand a heat fluxes of 21 MW/m2, while the cooling system keeps the heated surface below ~ 400 °C, for flow conditions comparable to those of the full-size cavity. The test results are used to first calibrate the uncertain model parameters and then, with frozen parameters, to validate a previously developed CFD model, showing good agreement with the experiment. In view of its reliability, this model might eventually be a useful tool for the simulation of the full-size gyrotron cavity operation

European 1 MW, 170 GHz CW Gyrotron Prototype for ITER - long-pulse operation at KIT -

The upgraded EU 1 MW, 170 GHz continuous wave (CW) industrial prototype gyrotron (TH1509U) for Electron Cyclotron Resonance Heating and Current Drive (ECRH&CD) in ITER was tested at the Karlsruhe Institute of Technology (KIT). The gyrotron surpassed the performance of the previous TH1509 tube. In particular, TH1509U delivered (i) 0.9 MW in 180 s pulses (max. pulse length of the KIT test stand) and (ii) more than 1 MW at a pulse length limited to 40 s, due to a problem with the test stand cooling circuit at that time. In addition, it was possible to demonstrate gyrotron operation at (iii) 0.5 MW in 1600 s pulses

Global pressures, specific responses: effects of nutrient enrichment in streams from different biomes

Fil: Artigas, Joan. Clermont Université. Université Blaise Pascal. Laboratoire Microorganismes: Génome et Environnement; FranceFil: García-Berthou, Emili. Institute of Aquatic Ecology. University of Girona. Girona; SpainFil: Bauer, Delia Elena. Instituto de Limnología Dr. Raúl A. Ringuelet (ILPLA). Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; ArgentinaFil: Castro, Maria I.. Department of Biology. National University of Colombia. Bogotá DC; ColombiaFil: Cochero, Joaquín. Instituto de Limnología Dr. Raúl A. Ringuelet (ILPLA). Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; ArgentinaFil: Colautti, Darío César. Instituto de Limnología Dr. Raúl A. Ringuelet (ILPLA). Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; ArgentinaFil: Cortelezzi, Agustina. Instituto de Limnología Dr. Raúl A. Ringuelet (ILPLA). Facultad de Ciencias Naturales y Museo. Universidad Nacional de La PlataFil: Donato, John C.. Department of Biology. National University of Colombia. Bogotá DC; ColombiaFil: Elosegi, Arturo. Faculty of Science and Technology. The University of the Basque Country. Bilbao; SpainFil: Feijoó, Claudia S.. INEDES. Department of Basic Sciences. National University of Luján. Luján; ArgentinaFil: Giorgi, Adonis. INEDES. Department of Basic Sciences. National University of Luján. Luján; ArgentinaFil: Gómez, Nora. Institute of Aquatic Ecology. University of Girona. Girona; SpainFil: Leggieri, Leonardo. Institute of Aquatic Ecology. University of Girona. Girona; SpainFil: Muñoz, Isabel. Department of Ecology. University of Barcelona. Barcelona; SpainFil: Rodrigues Capítulo, Alberto. Instituto de Limnología Dr. Raúl A. Ringuelet (ILPLA). Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; ArgentinaFil: Romaní, Anna M.. Institute of Aquatic Ecology. University of Girona. Girona; SpainFil: Sabater, Sergi. Catalan Institute for Water Research (ICRA). Scientific and Technological Park of the University of Girona. Girona; Spai

Global pressures, specific responses: effects of nutrient enrichment in streams from different biomes

We assessed the effects of nutrient enrichment on three stream ecosystems running through distinct biomes (Mediterranean, Pampean and Andean). We increased the concentrations of N and P in the stream water 1.6–4-fold following a before–after control–impact paired series (BACIPS) design in each stream, and evaluated changes in the biomass of bacteria, primary producers, invertebrates and fish in the enriched (E) versus control (C) reaches after nutrient addition through a predictive-BACIPS approach. The treatment produced variable biomass responses (2–77% of explained variance) among biological communities and streams. The greatest biomass response was observed for algae in the Andean stream (77% of the variance), although fish also showed important biomass responses (about 9–48%). The strongest biomass response to enrichment (77% in all biological compartments) was found in the Andean stream. The magnitude and seasonality of biomass responses to enrichment were highly site specific, often depending on the basal nutrient concentration and on windows of ecological opportunity (periods when environmental constraints other than nutrients do not limit biomass growth). The Pampean stream, with high basal nutrient concentrations, showed a weak response to enrichment (except for invertebrates), whereas the greater responses of Andean stream communities were presumably favored by wider windows of ecological opportunity in comparison to those from the Mediterranean stream. Despite variation among sites, enrichment globally stimulated the algal-based food webs (algae and invertebrate grazers) but not the detritus-based food webs (bacteria and invertebrate shredders). This study shows that nutrient enrichment tends to globally enhance the biomass of stream biological assemblages, but that its magnitude and extent within the food web are complex and are strongly determined by environmental factors and ecosystem structure.Instituto de Limnología "Dr. Raúl A. Ringuelet

Towards a 1.5 MW, 140 GHz gyrotron for the upgraded ECRH system at W7-X

For the required upgrades of the Electron Cyclotron Resonance Heating system at the stellarator Wendelstein 7-X, the development of a 1.5 MW 140 GHz Continuous Wave (CW) prototype gyrotron has started. KIT has been responsible to deliver the scientific design of the tube (i.e. the electron optics design and the RF design), with contributions from NKUA and IPP. The prototype gyrotron has been ordered at the industrial partner, Thales, France, and is expected to be delivered in 2021. In parallel, a short-pulse pre-prototype gyrotron has been developed at KIT, to provide the means for a first experimental validation of the scientific design in ms pulses, prior to the construction of the CW prototype. This paper reports on the status of the 1.5 MW CW gyrotron development, focusing on the scientific design and its numerical and experimental validation

New Six Ways Waveguide to Microstrip Transition applied in X Band Spatial Power Combiner

A Spatial Power Combiner is proposed using an innovative waveguide to microstrip transition capable to divide the electric field in six equal parts per card. This device can combine 12 MMIC Solid State Power Amplifiers in the whole X Band with 13 dB of return loss and only 2.2 dB losses in a small size, high power and high efficiency system