28 research outputs found
Continuous bunch-by-bunch spectroscopic investigation of the micro-bunching instability
Electron accelerators and synchrotrons can be operated to provide short
emission pulses due to longitudinally compressed or sub-structured electron
bunches. Above a threshold current, the high charge density leads to the
micro-bunching instability and the formation of sub-structures on the bunch
shape. These time-varying sub-structures on bunches of picoseconds-long
duration lead to bursts of coherent synchrotron radiation in the terahertz
frequency range. Therefore, the spectral information in this range contains
valuable information about the bunch length, shape and sub-structures. Based on
the KAPTURE readout system, a 4-channel single-shot THz spectrometer capable of
recording 500 million spectra per second and streaming readout is presented.
First measurements of time-resolved spectra are compared to simulation results
of the Inovesa Vlasov-Fokker-Planck solver. The presented results lead to a
better understanding of the bursting dynamics especially above the
micro-bunching instability threshold.Comment: 12 pages, 11 figure
Detuning Properties of RF Phase Modulation in the Electron Storage Ring KARA
In electron storage rings, it is possible to increase the electron bunch length by applying a phase modulation on the radio frequency accelerating field by choosing appropriate parameters for the modulation. Such a bunch lengthening effect improves beam parameters such as the beam lifetime, which can help us to get better beam stability. The dependence of the bunch lengthening on the modulation frequency, the so-called detuning property, tends to have a peak with asymmetric slopes around it. The modulation amplitude and the beam current also affect the properties of the detuning condition of such bunch lengthening. We have investigated the detuning property with systematic measurements at the electron storage ring KARA. The experimental results agree with the theoretical model and the simulation results
Synergy Analysis Methodology For Decreasing Fuel Cell Production Costs
For meeting CO2 emission targets in the mobility sector, decarbonization efforts of referring applications are necessary. Fuel cell electric vehicles powered by hydrogen demonstrate a viable option to achieve those targets, especially taking the targets of heavy-duty applications into consideration. Higher ranges, short fueling durations and locally emission-free transport represent advantages offered by fuel cells in comparison to internal combustion engines or battery-electric powertrains.
However, production costs of fuel cells are still a drawback. Latest analyses show that the utilization of scale effects even in early technology adaption phases can heavily decrease production costs. As the cell structure of fuel cells and electrolyzers show many similarities, the assumption of production synergies is made. Taking advantage of referring synergies, increased production volumes and thus decreased production cost are assumed for fuel cells.
This paper introduces a methodology to identify synergies between fuel cell and electrolyzer production. The methodology is used to evaluate a company's production process portfolio on the example of the three alternative coating processes, based on an initial evaluation of the processes and the use of the Analytic Network Process. The application of the methodology results in synergy coefficients for production processes, using the examples of slot die, gravure and spray coating. The coefficients are transferred into an overall benefit of a production process portfolio. Finally, the effect of the considered synergies between fuel cell and electrolyzer production on the overall benefit of a company's production process portfolio is visualized. This paper is concluded with a critical review of the methodology and a summary of further research
Detuning Properties of RF Phase Modulation in the Electron Storage Ring KARA
In electron storage rings, it is possible to increase the electron bunch length by applying a phase modulation on the radio frequency accelerating field by choosing appropriate parameters for the modulation. Such a bunch lengthening effect improves beam parameters such as the beam lifetime, which can help us to get better beam stability. The dependence of the bunch lengthening on the modulation frequency, the so-called detuning property, tends to have a peak with asymmetric slopes around it. The modulation amplitude and the beam current also affect the properties of the detuning condition of such bunch lengthening. We have investigated the detuning property with systematic measurements at the electron storage ring KARA. The experimental results agree with the theoretical model and the simulation results
Systematic Studies of the Micro-Bunching Instability at Very Low Bunch Charges
At KARA, the KArlsruhe Research Accelerator of the KIT synchrotron, the so
called short bunch operation mode allows the reduction of the bunch length down
to a few picoseconds. The micro- bunching instability resulting from the high
degree of longitudinal compression leads to fluctuations in the emitted THz
radiation, referred to as bursting. For extremely compressed bunches at KARA,
bursting occurs not only in one but in two different bunch-current ranges that
are separated by a stable region. This work presents measurements of the
bursting behavior in both regimes. Good agreement is found between data and
numerical solutions of the Vlasov-Fokker-Planck equation.Comment: 6 pages, 5 figures, to be submitte
Extensive Copy-Number Variation of Young Genes across Stickleback Populations
MM received funding from the Max Planck innovation funds for this project. PGDF was supported by a Marie Curie European Reintegration Grant (proposal nr 270891). CE was supported by German Science Foundation grants (DFG, EI 841/4-1 and EI 841/6-1). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
Analysis of Impact of Humidity and Temperature on Excimer Laser Ablation of Polyethylene Terephthalate, Polymethylmethacrylate, and Porcine Corneal Tissue
Background and Objectives
To analyze the impact of humidity and temperature on excimer laser ablation of polyethylene terephthalate (PET), polymethylmethacrylate (PMMA) and porcine corneal tissue, and an ablation model to compensate for the temperature and humidity changes on ablation efficiency.
Study Design/Materials and Methods
The study was conducted using an AMARIS 1050RS (Schwind eye‐tech‐solutions) placed inside a climate chamber at ACTS. Ablations were performed on PET, PMMA, and porcine cornea. The impact of a wide range of temperature (~18°C to ~30°C) and relative humidity (~25% to ~80%) on laser ablation outcomes was tested using nine climate test settings. For porcine eyes, change in defocus was calculated from the difference of post‐ablation to pre‐ablation average keratometry readings. Laser scanning deflectometry was performed to measure refractive change achieved in PMMA. Multiple linear regression was performed using the least square method with predictive factors: temperature, relative humidity, time stamp. Influence of climate settings was modeled for pulse energy, pulse fluence, ablation efficiency on PMMA and porcine cornea tissue.
Results
Temperature changes did not affect laser pulse energy, pulse fluence (PET), and ablation efficiency (on PMMA or porcine corneal tissue) significantly. Changes in relative humidity were critical and significantly affected laser pulse energy, high fluence and low fluence. The opposite trend was observed between the ablation performance on PMMA and porcine cornea.
Conclusions
The proposed well‐fitting multi‐linear model can be utilized for compensation of temperature and humidity changes on ablation efficiency. Based on this model, a working window for optimum operation has been found (temperature 18°C to 28°C and relative humidity 25% to 65%) for a maximum deviation of ±2.5% in ablation efficiency in PMMA and porcine corneal tissue