A5081868538- Particle accelerators and beam dynamics
- Particle Accelerators and Free-Electron Lasers
- Superconducting Materials and Applications
- Gyrotron and Vacuum Electronics Research
- Magnetic confinement fusion research
- Physics of Superconductivity and Magnetism
- Photocathodes and Microchannel Plates
- Plasma Diagnostics and Applications
- Nuclear Physics and Applications
- Laser Design and Applications
- Atomic and Subatomic Physics Research
- Acoustic Wave Resonator Technologies
- Quantum, superfluid, helium dynamics
- Ammonia Synthesis and Nitrogen Reduction
- Electron and X-Ray Spectroscopy Techniques
- Superconducting and THz Device Technology
- Quantum and electron transport phenomena
- Advanced X-ray Imaging Techniques
- Spacecraft and Cryogenic Technologies
- Parallel Computing and Optimization Techniques
- Semiconductor materials and devices
- Photonic and Optical Devices
- Advanced MEMS and NEMS Technologies
- Laser-Plasma Interactions and Diagnostics
- Fuzzy Logic and Control Systems
Helmholtz-Zentrum Berlin für Materialien und Energie
2016-2025
University of Siegen
2016-2024
Folkwang University of the Arts
2018-2024
Technical University of Darmstadt
2021
Brno University of Technology
2019
Budker Institute of Nuclear Physics
2011
Deutsches Elektronen-Synchrotron DESY
2010
Cornell University
1992-2005
Fraunhofer Society
2002-2004
Albert Einstein College of Medicine
2003
BASICS Introductory Overview Cavity Fundamentals and Fields Superconductivity Essentials Electrodynamics of Normal Superconductors Maximum Surface PERFORMANCE OF SUPERCONDUCTING CAVITIES Fabrication Preparation Multicell Field Flatness Tuning Testing Residual Resistance Multipacting Thermal Breakdown Emission The Quest for High Gradients Alternate Materials to Solid Niobium COUPLERS AND TUNERS Mode Excitation Its Consequences Higher Order Couplers Coupling Power the Beam Input Windows Tuners...
The photoinjector test facility at DESY, Zeuthen site (PITZ), was built to develop and optimize photoelectron sources for superconducting linacs high-brilliance, short-wavelength free-electron laser (FEL) applications like the in Hamburg (FLASH) European x-ray (XFEL). In this paper, detailed characterization of two laser-driven rf guns with different operating conditions is described. One experimental optimization beam parameters performed an accelerating gradient about $43\text{ }\text{...
An MIMD multiprocessor digital signal-processing (DSP) chip containing four 64-b processing elements (PE's) interconnected by a 128-b pipelined split transaction bus (STBus) is presented. Each PE contains 32-b RISC core with DSP enhancements and single-instruction, multiple-data vector coprocessor 16-b MAC/s reduction unit. PEs are connected to the STBus through reconfigurable dual-ported snooping L1 cache memories that support shared memory multiprocessing using modified-MESI data coherency...
Abstract Vacuum thermal treatments (baking) are known to improve the superconducting properties of RF surface layer niobium cavities, and employed as a last processing step increase their efficiency determined by intrinsic quality factor Q$_0$. A specific method perform baking has been used. It consists in annealing an evacuated cavity with local heaters installed on its outer cryostat which ensures exterior vacuum protects from oxidation. Such set-up number advantages it does not require...
Many next-generation, high-gradient accelerator applications, from energy-recovery linacs to accelerator-driven systems (ADS) rely on continuous wave (CW) operation for which superconducting radio-frequency (SRF) are the enabling technology. However, while SRF cavities dissipate little power, they must be cooled by liquid helium and many CW accelerators complexity as well investment operating costs of cryoplant can prove prohibitive. We investigated ways reduce dynamic losses improving...
Trapped magnetic flux is known to be one cause of residual losses in bulk niobium superconducting radio frequency cavities. In the Meissner state an ambient field should expelled from material. Disturbances such as lattice defects or impurities have ability inhibit expulsion external during transition so that trapped. We investigated effect treatment history has on trapped and which leads minimal trapping. For purpose, we measured fraction samples representing cavities with different typical...
Presented in this paper are the description and test results of a new stationary thermometry system used to map temperature outer surface 1.5 GHz superconducting single-cell cavities during operation at 1.6 K. The comprises 764 removable carbon thermometers whose signals multiplexed scanned by Macintosh computer. A complete can be obtained as little 0.1 s resolution about 0.2 mK. Alternatively, it has been demonstrated that if acquisition time is increased several seconds, then on order 30...
Nb$_3$Sn is currently the most promising material other than niobium for future superconducting radiofrequency cavities. Critical fields above 120 mT in pulsed operation and about 80 CW have been achieved cavity tests. This large compared to lower critical field as derived from London penetration depth, extracted low surface impedance measurements. In this paper direct measurements of depth which superheating are presented. The first vortex measured under DC RF fields. combined results...
Many proposals for next generation light sources based on single pass free electron lasers or energy recovery linac facilities require a continuous wave (cw) driven superconducting linac. The effective beam loading in such machines is very small and principle the cavities can be operated at bandwidth of few Hz with less than kW rf power. However, power reserve required to ensure field stability. A major error source mechanical microphonics detuning niobium cavities. To understand influence...
For many new accelerator applications, superconducting radio frequency systems are the enabling technology. In particular for CW much effort is being expended to minimize power dissipation (surface resistance) of niobium cavities. Starting in 2009, we suggested a means reducing residual resistance by performing thermal cycle [O. Kugeler et al., Proceedings 14th International Conference on RF Superconductivity (2009), p. 352], procedure warming up cavity after initial cooldown about 20 K and...
Abstract In order to determine optimal parameters of vacuum thermal processing superconducting radiofrequency niobium cavities exhaustive information on the initial chemical state and its modification upon a heat treatment is required. present work composition surface ultra-high baking at 200 ∘ C–400 C similar ‘medium-temperature baking’ ‘furnace explored in-situ by synchrotron x-ray photoelectron spectroscopy (XPS). Our findings imply that below critical thickness <mml:math...
Views Icon Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Twitter Facebook Reddit LinkedIn Tools Reprints and Permissions Cite Search Site Citation J. Knobloch; The "Q disease" in Superconducting Niobium RF Cavities. AIP Conf. Proc. 11 July 2003; 671 (1): 133–150. https://doi.org/10.1063/1.1597364 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Dropdown Menu input auto suggest...
The HoBiCaT facility has been set up and operated at the Helmholtz-Zentrum-Berlin BESSY since 2005. Its purpose is testing superconducting cavities in cw mode of operation it was successfully demonstrated that TESLA pulsed technology can be used for with only minor changes. Issues were addressed comprise elevated dynamic thermal losses cavity walls, necessary modifications cryogenics processing, optimum choice operational parameters such as temperature or bandwidth, characterization higher...
Photocathodes are a limiting factor for the next generation of ultrahigh brightness photoinjectors. We studied behavior superconducting Pb cathode in cryogenic environment rf gun cavity to measure quantum efficiency, its spatial distribution, and work function. will also discuss how surface contaminants modify performance photocathode as well we possibilities remove these contaminants.
A scalable mapping system for superconducting RF (SRF) cavities is presented. Currently, it combines local temperature measurement with 3D magnetic field along the outer surface of resonator. This allows observation dynamic effects that have an impact on properties a cavity, such as normal to phase transition or quench. The was developed single cell 1.3 GHz TESLA-type but can be easily adopted arbitrary other cavity types. data acquisition rate 500 Hz all channels simultaneously (i.e., 2 ms...
Low temperature superconductors ideally exhibit the Meissner-effect, i.e. magnetic flux is expelled from material during superconducting transition. We report about complete suppression of Meissner-effect in two differently surface-treated niobium samples by means polarized neutron radiography. Both were studied Meissner phase, T < Tc = 9.25[K] with an external field Bext 6.3mT and for 0. Neutron radiographs both recorded, imaging depolarization spin > 6.4mT, 6.3mT, After turning off at a...