1,749 research outputs found
Picosecond timing of Microwave Cherenkov Impulses from High-Energy Particle Showers Using Dielectric-loaded Waveguides
We report on the first measurements of coherent microwave impulses from
high-energy particle-induced electromagnetic showers generated via the Askaryan
effect in a dielectric-loaded waveguide. Bunches of 12.16 GeV electrons with
total bunch energy of GeV were pre-showered in tungsten, and
then measured with WR-51 rectangular (12.6 mm by 6.3 mm) waveguide elements
loaded with solid alumina () bars. In the 5-8 GHz
single-mode band determined by the presence of the dielectric in the waveguide,
we observed band-limited microwave impulses with amplitude proportional to
bunch energy. Signals in different waveguide elements measuring the same shower
were used to estimate relative time differences with 2.3 picosecond precision.
These measurements establish a basis for using arrays of alumina-loaded
waveguide elements, with exceptional radiation hardness, as very high precision
timing planes for high-energy physics detectors.Comment: 16 pages, 15 figure
Numerical simulation of electromagnetic fields in complex multi-cavity superconducting radio frequency resonators
This thesis deals with the computation of electromagnetic fields in complex, superconducting resonators, as well as the efficient calculation of the losses of such resonances by the couplers and beampipes. A perturbation approach is used to efficiently assemble the resulting nonlinear eigenvalue problem, which is then solved by using the Newton method. Using the proposed methods, current research questions for the Third Harmonic Module of the FLASH accelerator, the bERLinPro mainlinear accelerator and the BESSY VSR cavity-design are be answered.Diese Arbeit beschäftigt sich mit der Berechnung elektromagnetischer Felder in komplexen, supraleitenden Resonatoren sowie der effizienten Berechnung der Verluste solcher Resonanzen durch die Koppler und Strahlrohre. Ein StÜrungsansatz wird verwendet, um das resultierende nichtlineare Eigenwertproblem effizient zusammenzusetzen, das dann mit der Newton-Methode gelÜst wird. Mit den vorgeschlagenen Methoden werden aktuelle Forschungsfragen fßr das Third Harmonic Modul des FLASH-Beschleunigers, des bERLinPro Haupt-Linearbeschleunigers und des BESSY VSR Resonator-Designs beantwortet
Annual report 2006 // Institute of Safety Research
[no abstract available
Annual report 2006 // Institute of Safety Research
[no abstract available
A point source high power converter target to produce Bremsstrahlung for photonuclear reactions
A continually growing number of applications of radionuclides are known in medicine and various industries. In industries, radionuclides can have different applications depending on the industry in which they are used. For example, they can be employed in the automotive industry for the quality control of the produced metal sheets or accurate thickness measurements; in the oil and gas industry to detect pipe cracks; in the aerospace industry for the use as compact sources of electrical power in spacecraft with long life and almost uniform performance. On the medical side, radionuclides are employed as radiopharmaceuticals to diagnose and treat diseases depending on the radiation that they emit. Three families of radionuclides that emit ι, β-, and Auger electrons are considered for therapy; the family of radionuclides that emit β+ is employed for diagnosis. A relatively new branch called theranostic has been introduced in recent years and is a combination of therapy and diagnostics. The term true theranostic pair refers to pairs of radioisotopes (one β+ emitter and another β- emitter), of the same element conjugated with the same bio-molecule.
To fulfill the high demand for radionuclides, a reliable large-scale production facility that utilizes a low cost and highly efficient method is needed. Up to now, different ways for the production of different radionuclide families have been introduced and built. One of the most conventional methods is using nuclear reactors, which still are being used widely. However, the fleet of radionuclide producing reactors is relatively old and thus no longer reliable (they are scheduled to be taken offline in the next few years). The cyclotron is another method that accelerates protons, deuterons, and alpha particles in a circular path and is mainly used to produce a family of radionuclides that emit β+ with a relatively short half-life. Among the associated problems which they have, low production rates and specific activity are the main. Another radionuclide production method, which is relatively new, is based on photonuclear interaction and uses energetic photons for irradiation of the targets. In order to produce these photons, electron accelerators need to be employed, and then by using a converter, electrons produce photons in an interaction called Bremsstrahlung. This method has a relatively long history in radionuclide production; however, the problem that makes this method unsuitable is the considerable heat generation in the converter target. This problem made the use of this method restricted so that only research areas with a very low input power of incident electrons were of interest. Due to the many advantages of the photonuclear reactions over existing methods, including high production rate and specific activity, low material quantity, low impurities activation, and low post-processing, an in-depth investigation into possible new designs and optimization of the irradiation parts is essential and constitutes the motivation for this Ph.D. work.
This study was performed in the framework of the project entitled âSinergia Project (SNSF): PHOtonuclear Reactions (PHOR): breakthrough research in radionuclides for theranosticsâ funded by the Swiss National Science Foundation and submitted to the European Patent Organisation (No 21212627.0)
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Electromagnetic and Multipactor Stresses on RF Windows in Drift Tube Linear Accelerators
Radio frequency (RF) particle accelerators are a key component to many scientific and industrial endeavors, so their reliable operation is of great concern. An obstacle to reliable operation has been the performance of the RF windows that act as barriers between the vacuum environment of the accelerating cavities and atmospheric conditions in the transmission line. Failures of these windows have a large impact on accelerator availability, and recovering from a window failure is a multiple day event. In order to mitigate these failures, an analysis of the stresses placed on the window has been performed. This dissertation presents simulations of the stresses placed on the window due to the electromagnetic environment and the multipactor effect with a discussion of how to minimize those stresses.The electromagnetic environment was first analyzed using the commercially available CST Microwave Studio software. An analysis of the window geometry in isolation from the accelerating cavity is performed first to minimize the stresses placed on it. Then the analysis of the whole system with the cavity present was performed using an approach that was developed to allow transient simulations of the highly resonant cavity. Simulations show how the signal develops over time, thus allowing adjustments to be made to the driving signal to minimize stresses. Simulations also demonstrate the effect of harmonics and their excitement of higher order modes, and the effect of an off-resonant cavity is briefly discussed.Multipactor is a parasitic phenomenon whereby large electron populations accumulate and is common to accelerator systems. The principles and simulation techniques of multipactor are first presented, and benchmarks are presented to illustrate the validity of the simulations. The conditions of both traveling and standing waves are examined for the effect on multipactor development and electron collisions with the window. The broad analysis of many standing wave conditions allows for mitigation of multipactor in consideration of the signal analyzed in the electromagnetic simulations. Effects of window material and charge accumulation on the window are discussed, and the consideration of the harmonics and higher order modes analyzed previously are shown to have negligible effect on multipactor
Compact State-Space Models for Complex Superconducting Radio-Frequency Structures Based on Model Order Reduction and Concatenation Methods
The modeling of large chains of superconducting cavities with couplers is a challenging task in computational electrical engeneering. The RF properties of the arising segments are described by state-space equations. Their model order is reduced and the reduced-order models are concatenated in accordance with the topology of the complete structure. The scheme enables the investigation of radio-frequency properties of large structures without the application of supercomputers
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