322,974 research outputs found
Design, fabrication and high power RF test of a C-band accelerating structure for feasibility study of the SPARC photo-injector energy upgrade
No full textThe energy upgrade of the SPARC photo-injector from 160 to more than 260 MeV will be done by replacing a low gradient 3m S-Band structure with two 1.4m high gradient C-band structures. The structures are travelling wave, constant impedance sections, have symmetric waveguide input couplers and have been optimized to work with a SLED RF input pulse. A prototype with a reduced number of cells has been fabricated and tested at high power in KEK (Japan) giving very good performances in terms of breakdown rates (≈ 10-6 bpp /m) at high accelerating gradient (>50 MV/m). The paper illustrates the design criteria of the structures, the fabrication procedure and the high power RF test results. Copyright © 2011 by IPAC'11/EPS-AG
Beam coupling impedance simulation and RF measurements of a passive extraction septum for particle absorbing in the CERN Proton Synchrotron
No full textWe present a study of the beam coupling impedance due to trapped modes of a new protection septum that will be installed in the CERN Proton Synchrotron (PS) during the Long Shutdown 1 (LS1). The interaction between the particle field and the discontinuities inside the septum generates electromagnetic fields localized in a particular region inside the device. These resonances, producing narrow peaks in the coupling impedance, can be potential source of beam instabilities for high intensity particle accelerators like PS. The final outcome of these studies is the basis for the acceptance of the septum installation in section 15 of the PS ring
Beam-Wall Interaction in the CERN Proton Synchrotron for LHC Upgrade
No full textCoupling impedances and wakefields are fundamental quantities to characterize the electromagnetic interaction of a particle beam with the surrounding environment. In particular, collective effects, triggered by these self-induced fields, may play an important role in beam stability and machine performance. Within the framework of the LHC Injectors Upgrade project, since a significantly higher beam intensity is planned for the CERN Proton Synchrotron (PS), wakefields are expected to increase their influence on the beam dynamics, and their evaluation is becoming important. In this paper we present the results of recent measurements of the longitudinal broadband coupling impedance by means of incoherent quadrupole synchrotron frequency shift as a function of beam intensity. A detailed evaluation of the contribution of several machine installations to the total impedance budget is also presented and compared with the measurements
Transverse beam coupling impedance of the CERN Proton Synchrotron
No full textBeam coupling impedance is a fundamental parameter to characterize the electromagnetic interaction of a particle beam with the surrounding environment. Synchrotron machine performances are critically affected by instabilities and collective effects triggered by beam coupling impedance. In particular, transverse beam coupling impedance is expected to impact beam dynamics of the CERN Proton Synchrotron (PS), since a significant increase in beam intensity is foreseen within the framework of the LHC Injectors Upgrade (LIU) project. In this paper we describe the study of the transverse beam coupling impedance of the PS, taking into account the main sources of geometrical impedance and the contribution of indirect space charge at different energies. The total machine impedance budget, determined from beam-based dedicated machine measurement sessions, is also discussed and compared with the theoretical model
Introduction to carbon nanotubes: fabrication and properties
No full textOwing to their surprising properties, carbon nanotubes (CNT) have recently raised a great deal of interest, both from scientific and engineering point of view. The development in understanding phenomena, preparing materials, designing and realizing devices dealing with carbon nanotubes is such a fast growing area that is almost impossible to exhaustively present: here it will be only given a reasoned list of the main themes focused on the production of CNT based systems
Impedance studies for the PS Finemet loaded longitudinal damper
No full textThe impedance of the Finemet® loaded longitudinal damper cavity, installed in the CERN Proton Synchrotron straight section 02 during the Long Shutdown 2013-2014, has been evaluated [1]. Time domain simulations with CST Particle Studio have been performed in order to get the longitudinal and transverse impedance of the device and make a comparison with the longitudinal impedance that was measured for a single cell prototype
Functionalised single-walled carbon nanotubes modified microsensors for the selective response of epinephrine in presence of ascorbic acid
No full textModified stainless steel microelectrodes (microwire diameter: 300 mm) were assembled using functionalized singlewalled
carbon nanotubes (SWCNTs) deposited by the EPD method (electrophoretical deposition process). The
functionalized SWCNTs, which covered the microelectrode surfaces, showed an improved sensitivity and selectivity
toward the electrochemical detection of epinephrine. These chemical sensors hampered the voltammetric responses of
ascorbic acid (AA) and uric acid (UA), while the electrochemical oxidation of epinephrine was significantly
enhanced. Using the differential pulse voltammetry (DPV) technique, epinephrine showed a very well resolved peak
centered around 240mV, while 1 mM of AA (present in the same solution) was not detected. The corresponding
permeability and permselectivity parameters were also evaluated for ascorbic acid and uric acid. To investigate the
sensor selectivity, a comparative study performed using microsensors assembled with non functionalized carbon
nanotubes, deposited on the microelectrode surfaces by a chemical vapor deposition (CVD) technique, was also
carried out. This study was useful to highlight that the presence, or the absence of electrostatic barriers on SWCNT<s
walls (due to the presence of some chemical functional groups), can be able to control the electrochemical response of
these sensors. This optimization resulted in microsensors with a good linear range (2 – 100 mM) epinephrine; a good
sensitivity (28.1 A M 1 cm 2) and interelectrodes reproducibility (RSD%¼7.0, n¼6), a detection of limit (LOD¼
3s) of 2 mM; a response time of 6 s; a significant operational stability (of 13 hours in continuous working conditions)
and long term stability (1 month)
Coupling of single wall carbon nanotubes and L-histidine on Ag microwires: new architectures for the assembling of NAD+ sensors
No full textreduction are shown. A series of Ag-microelectrodes have been assembled with different architectures. The Ag-modified microelectrodes have been
characterized and cyclic voltammetry (CV) experiments demonstrated that the electrochemical response is strongly correlated to their molecular
architecture and the Ag/SWNT/l-histidine microwires offer the best performances for NAD+ detection
CVD-based techniques for the synthesis of nanographites and nanodiamonds
No full textWe report about some Chemical Vapor Deposition approaches used
to produce a variety of C-sp2 and C-sp3 crystalline nanostructures. The methodologies
developed in our laboratories provide custom-made solutions for the fabrication
of specific carbon nanomaterials with properties tailored for applications in the field
of nanotechnology
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