The PS 10 MHz High Level RF System Upgrade

In view of the upgrade of the injectors for the High Luminosity LHC, significantly higher bunch intensity is required for LHC-type beams. In this context an upgrade of the main accelerating RF system of the Proton Synchrotron (PS) is necessary, aiming at reducing the cavity impedance which is the source of longitudinal coupled-bunch oscillations. These instabilities pose as a major limitation for the increase of the beam intensity as planned after LS2. The 10 MHz RF system consists in 11 ferrite loaded cavities, driven by tube-based power amplifiers for reasons of radiation hardness. The cavity-amplifier system is equipped with a wide-band feedback that reduces the beam induced voltage. A further reduction of the beam loading is foreseen by upgrading the feedback system, which can be reasonably achieved by increasing the loop gain of the existing amplification chain. This paper describes the progress of the design of the upgraded feedback system and shows the results of the tests on the new amplifier prototype, installed in the PS during the 2015-16 technical stop. It also reports the first results of its performance with beam, observed in the beginning of the 2016 run

Beam-Induced Electron Cloud in the LHC and Possible Remedies

Synchrotron radiation from proton bunches in the LHC creates photoelectrons at the beam screen wall. These photoelectrons are accelerated towards the positively charged proton bunch and drift across t he beam pipe between successive bunches.When they hit the opposite wall, they generate secondary electrons which can in turn be accelerated by the next bunch if they are slow enough to survive. We sum marize the results of an intensive research program set up atCERN and discuss recent multipacting tests as well as the importance of several key parameters, such as photon reflectivity, photoelectron and secondary electron yield.Then, based on analytic estimates and simulation results, we discuss possible solutions to avoid the fast build-up of an electron cloud with potential implications for bea m stability and heat load on the cryogenic system

La cittadinanza digitale tra riflessioni teoriche e implicazioni educative

Questo breve articolo intende trattare il tema attualissimo e rilevante della cittadinanza digitale attraverso la lente della riflessione pedagogica per denotare un elemento legato sia alle elaborazioni teoriche sia alle pratiche e alle politiche educative. Il concetto di cittadinanza digitale sarà analizzato in prospettiva diacronica, esaminando le modificazioni che ha subito nel corso degli anni, condizionate da profonde trasformazioni economiche, sociali, culturali e tecnologiche. Parallelamente sarà sviluppata una considerazione sull’alfabetizzazione digitale e sui modelli delle competenze digitaliche assumono valore nello sviluppo della cittadinanza digitale

A Time Resolved Measurement of Photoelectron Production at EPA

A time resolved experiment to measure the photoelectron production was carried out at the EPA machine (Electron-Positron Accumulator for LEP)[1] in June 1998. We used an existing synchrotron radiation beam line with a stainless steel test chamber[2] and irradiated the inner surface of the test chamber to produce photoelectrons. The generated photoelectrons were collected by an electrode and analysed by an oscilloscope. In this report we discuss the experimental layout and present the results of the data analysis

ДВОСТОРОННІЙ ПЕРЕТВОРЮВАЧ СВІТЛОВОЇ ЕНЕРГІЇ В ЕЛЕКТРИЧНУ НА ОСНОВІ ІЗОТИПНИХ ПЕРЕХОДІВ

The method of n+Si/nSi/SiO2 /n+ITO bifacial solar cells fabrication by pyrolitical spraying was elaborated. This structure contains only isotype junctions. The spectral sensitivity is situated in the 350–1200nm wavelength region and is independent on the illumination direction. The photoelectrical parameters of solar cells obtained on silicon wafer (4,5 Ohm.cm) are following: at frontal illumination Voc=0,425V, Isc=32,63mÀ/cm2 , FF=68,3%, Eff=9,47%; at rear illumination Voc=0,392V, Isc =13,20mÀ/cm2 , FF=69,3%, Eff=3,60%.Разработан способ получения двусторонних солнечных элементов n+Si/nSi/SiO2/n+ITO на основе изотипных переходов методом пиролитической пульверизации. Область спектральной чувствительности разработанной структуры расположена в интервале длин волн 350–1200нм и не зависит от направления освещения. Основные параметры для элемента на основе КЭФ-4,5 следующие: при фронтальном освещении Vxx=0,425В, Iкз=32,63мА/cм2, FF=68,3%, к.п.д.=9,47%; при тыльном освещении Vxx=0,392В, Iкз=13,20 мА/cм2, FF=69,3%, к.п.д.=3,60%.Розроблено спосіб отримання двосторонніх сонячних елементів n+Sі/nSі/SіO2/n+ІTO на основі ізотипних переходів методом піролітичної пульверизації. Область спектральної чутливості розробленої структури розташована в інтервалі довжин хвиль 350-1200нм і не залежить від напрямку освітлення. Основні параметри для елемента на основі КЭФ-4,5 наступні: при фронтальному освітленні Vxx=0,425В, Ікз=32,63мА/cм2, FF=68,3%, к.к.д.=9,47%; при тильному освітленні Vxx=0,392В, Ікз=13,20 мА/cм2, FF=69,3%, к.к.д.=3,60%