33 research outputs found
Untersuchungen zum technischen und teilchenoptischen Design kompakter Speicherringe fĂŒr Ionen
Die vorliegende Arbeit befasst sich mit der Berechnung und dem Bau von elektrostatischen Speicherringen. Eine solche Maschine kann als eine Kreuzung zwischen elektrostatischen Fallen und "klassischen" magnetischen Ringen angesehen werden. Kompakte Bauform, gute ZugĂ€nglichkeit der Elemente und vergleichsweise niedrigen Kosten werden mit hoher FlexibilitĂ€t in Bezug auf mögliche Experimente kombiniert. Im 1. Kapitel werden zunĂ€chst die Unterschiede der Bewegung von Ionen in elektrostatischen und magnetischen Speicherringen untersucht. Die MassenunabhĂ€ngigkeit der Teilchenbewegung bei gegebener Energie und Ladung in rein elektrostatischen Feldern erlaubt es, unterschiedlichste Ionen im Prinzip in direkter Folge in einen elektrostatischen Ring einzuschieĂen, ohne dass die Felder der optischen Elemente verĂ€ndern werden mĂŒssen. Die Felder in den fĂŒr einen Speicherring notwendigen StrahlfĂŒhrungskomponenten werden berechnet, die zugehörigen Bewegungsgleichungen aufgestellt und in linearer NĂ€herung gelöst. Dabei werden zunĂ€chst die Bahnen einzelner Teilchen untersucht und dann das Strahlverhalten insgesamt durch Ăbergang auf einen Matrizenformalismus beschrieben. Die aus dieser Darstellung resultierenden Trajektorien stellen eine starke Vereinfachung dar. Die Untersuchung der realen Teilchenbewegung mit Einfluss von Randfeldern, Positionierungsfehlern und die Berechnung der dreidimensionalen Feldverteilung ist Gegenstand des 2. Kapitels. Ein kritischer Punkt bei der Bewegung von Teilchen in Ringbeschleunigern sind durch Feldfehler induzierten Resonanzerscheinungen. Zur Diskussion der verschiedenen möglichen Resonanzen werden im 3. Kapitel die Effekte durch zusĂ€tzliche Dipol- und Quadrupolfelder analysiert, dargestellt und schlieĂlich anhand eines Resonanzdiagramms erlĂ€utert. In den geplanten Speicherring werden Ionen in einem einzigen Bunch, mit einer Ausdehnung von rund dem halben Ringumfang, injiziert. Ihre Lebensdauer hĂ€ngt wesentlich von dem erzielbaren Vakuumenddruck ab. Die vorgesehenen Getterpumpen weisen eine sehr hohe Pumpleistung fĂŒr die meisten Gase auf. Ihre Wirkungsweise wird im 4. Kapitel beschrieben und praktische Aspekte ihrer Handhabung diskutiert. FĂŒr den Betrieb eines Speicherrings ist es notwendig, die Parameter des umlaufenden Strahls zu jeder Zeit zu kennen und gegebenenfalls modifizieren zu können. Zentrales Element des Kontroll- und Diagnosesystems sind Strahlpositionsmonitore. In elektrostatischen Pickup-Elektroden induziert der Strahl beim Durchgang Spannungen ĂŒber die eine Positionsbestimmung möglich ist. Die Wirkungsweise dieser Sonden wird in der zweiten HĂ€lfte des 4. Kapitels diskutiert und Methoden zur Signalaufbereitung und -analyse beschrieben. Die allgemeinen Ergebnisse der Ăberlegungen zu elektrostatischen Speicherringen aus den ersten Kapiteln werden schlieĂlich auf spezielle FĂ€lle ĂŒbertragen. Im Rahmen dieser Arbeit wurden verschiedene EntwĂŒrfe fĂŒr einen elektrostatischen Speicherring angefertigt und ein Viertelringsegment zu Testzwecken entworfen und aufgebaut. Die Ergebnisse sind Inhalt des abschlieĂenden 5. Kapitels. Mit den in dieser Arbeit vorgestellten Methoden ist es möglich, elektrostatische Speicherringe detailliert zu berechnen und an die experimentellen Rahmenbedingungen anzupassen. SĂ€mtliche Rechnungen wurden im Hinblick auf den geplanten Bau eines Rings fĂŒr Teilchen mit Energien bis 50 keV durchgefĂŒhrt
Experimental Evidence for Electric Surface Resistance in Niobium
Identifying the loss mechanisms of niobium cavities enables an accurate determination of applications for future accelerator projects and points to research topics required to mitigate current limitations. For several cavities an increasing surface resistance above a threshold field, saturating at higher field has been observed. Measurements on samples give evidence that this effect is caused by the surface electric field. The measured temperature and frequency dependence is consistent with a model that accounts for these losses by interface tunnel exchange between localized states in dielectric oxides and the adjacent superconductor
Longitudinal beam profile measurements at CTF3 using a streak camera
The proposed Compact Linear Collider (CLIC) is a multi-TeV electron-positron collider for particle physics based on an innovative two-beam acceleration concept. A high-intensity drive beam powers the main beam of a high-frequency (30 GHz) linac with a gradient of 150 MV/m, by means of transfer structure sections. The aim of the CLIC Test Facility (CTF3) is to make exhaustive tests of the main CLIC parameters and to prove the technical feasibility. One of the points of particular interest is the demonstration of bunch train compression and combination in the Delay Loop and in the Combiner Ring. Thus, detailed knowledge about the longitudinal beam structure is of utmost importance and puts high demands on the diagnostic equipment. Among others, measurements with a streak camera have been performed on the linac part of the CTF3 as well as on the newly installed Delay Loop. This allowed e.g. monitoring of the longitudinal structure of individual bunches, the RF combination of the beam, the behavior during phase shifts and the influence of the installed wiggler. This article first gives an overview of the CTF3 facility, then describes in detail the layout of the long optical lines required for observation of either optical transition radiation or synchrotron radiation, and finally shows first results obtained during the last machine run this year
Industry and outreach event: Milestone M1.12
Report on a dedicated event bringing together potential partners from industry and informing different identified target audiences about the advancement of the design for a next generation, collider complex based large-scale research infrastructure for high-energy particle physics
RF multipoles deliverable
The crab cavities to be installed in the High-Luminosity LHC (HL-LHC) aim to provide an increase in luminosity by restoring head-on collisions and therefore reducing the loss of luminosity due to the crossing angle. The crab cavities rotate the beam by providing z-dependent kicks near the interaction point. Two designs have been cast for this task: the RF dipole (RFD) and the Double Quarter Wave (DQW); a prototype of the latter one has been installed in the SPS and in 2018 the ïŹrst successful crabbing of proton beams was achieved. As the design of both these crab cavities has to be very compact to be able to ïŹt between the two beams, this causes a loss of axial symmetry that gives rise to high order multipoles. This study aims to explore the impact and tolerances of the high order multipoles on beam dynamics by performing DA studies on the HL-LHC lattice
Experimental evidence for electric surface resistance in niobium
Identifying the loss mechanisms of niobium cavities enables an accurate determination of applications for future accelerator projects and points to research topics required to mitigate current limitations. For several cavities an increasing surface resistance above a threshold field, saturating at higher field has been observed. Measurements on samples give evidence that this effect is caused by the surface electric field. The measured temperature and frequency dependence is consistent with a model that accounts for these losses by interface tunnel exchange between localized states in dielectric oxides and the adjacent superconductor.Identifying the loss mechanisms of niobium cavities enables an accurate determination of applications for future accelerator projects and points to research topics required to mitigate current limitations. For several cavities an increasing surface resistance above a threshold field, saturating at higher field has been observed. Measurements on samples give evidence that this effect is caused by the surface electric field. The measured temperature and frequency dependence is consistent with a model that accounts for these losses by interface tunnel exchange between localized states in oxides formed along grain boundaries and the adjacent superconductor
Stability and lifetime study of carbon nanotubes as cold electron field emitters for electron cooling in the CERN extra low energy antiproton ring
Electron cooling is a fundamental process to guarantee the beam quality in low energy antimatter facilities. In extra low energy antiproton, the electron cooler reduces the emittance blowup of the antiproton beam and thus delivers a focused and bright beam to the experiments at the unprecedentedly low kinetic energy of 100Â keV. In order to achieve a cold beam at this low energy, the electron gun of the cooler must emit a monoenergetic and relatively intense electron beam. An optimization of the extra low energy antiproton electron cooler gun involving a cold cathode is studied, with the aim of investigating the feasibility of using carbon nanotubes (CNTs) as cold electron field emitters. CNTs are considered among the most promising field emitting material. However, stability data for emission operation over hundreds of hours, as well as lifetime and conditioning process studies to ensure optimal performance, are still incomplete or missing, especially if the purpose is to use them in operation in a machine such as extra low energy antiproton. This manuscript reports experiments that characterize these properties and ascertain whether CNTs are reliable enough to be used as cold electron field emitters for many hundreds of hours
Inverse-Designed Narrowband THz Radiator for Ultrarelativistic Electrons.
THz radiation finds various applications in science and technology. Pump-probe experiments at free-electron lasers typically rely on THz radiation generated by optical rectification of ultrafast laser pulses in electro-optic crystals. A compact and cost-efficient alternative is offered by the Smith-Purcell effect: a charged particle beam passes a periodic structure and generates synchronous radiation. Here, we employ the technique of photonic inverse design to optimize a structure for Smith-Purcell radiation at a single wavelength from ultrarelativistic electrons. The resulting design is highly resonant and emits narrowbandly. Experiments with a 3D-printed model for a wavelength of 900 ÎŒm show coherent enhancement. The versatility of inverse design offers a simple adaption of the structure to other electron energies or radiation wavelengths. This approach could advance beam-based THz generation for a wide range of applications
Simulations of Space-Charge and Guiding Fields Effects on the Performance of Gas Jet Profile Monitoring
Gas jet based profile monitors inject a usually curtain shaped gas jet across a charged particle beam and exploit the results of the minimally invasive beam-gas interaction to provide information about the beamâs transversal profile. Such monitor will be installed as part of the High Luminosity LHC upgrade at CERN in the Hollow Electron Lens (HEL). The HEL represents a new collimation stage increasing the diffusion rate of halo particles by placing a high intensity hollow electron beam concentrically around the LHC beam. The gas jet monitor will use the fluorescence radiation resulting due to the beam-gas interaction to create an image of the profiles of both hollow electron and LHC beams However, the high beam space-charge and strong guiding magnetic field of the electron beam cause significant displacements of the excited molecules, as they are also ionized, and thus image distortions. This work presents preliminary simulation results showing expected fluorescence images of the hollow electron profile as affected by space-charge and guiding fields using simulation tools such as IPMsim. The influence of the estimated electron beam and gas jet curtain parameters are investigated
Deliverable 2.7: Analysis of the existing sources of blow-up in the SPS by experiments and estimation/measurement of the effect of the crab cavities in the SPS
The Crab Cavities (CCs) may induce emittance growth, driven by phase and amplitude jitter, and lead to a degradation of the High Luminosity LHC (HL-LHC) beam. Furthermore, the tight HL-LHC space constraints call for non-axially symmetric cavity designs that come with higher order non-linearities which can affect the long-term dynamic aperture (DA). In order to study the effect the CCs have on the beam and the engineering challenges to validate the pre-series design, a prototype HL-LHC CC set was installed in the SPS machine in the year-end technical stop (YETS) of 2017-2018, and the first ever CC tests with protons were performed in 2018. This note is a collection of the reports and work done on the emittance growth measurements prior and after the CC installation, as well as simulations and measurements performed to study the CC and SPS non linearities effect. Finally, a summary of the instrumentation observations of the SPS CC experimental measurements is presented