Uncertainty Modeling and Analysis of the European X-ray Free Electron Laser Cavities Manufacturing Process

This paper reports on comprehensive efforts on uncertainty quantification and global sensitivity analysis for accelerator cavity design. As a case study object the TESLA shaped superconducting cavities, as produced for the European X-ray Free Electron Laser (EXFEL), are selected. The choice for these cavities is explained by the available measurement data that can be leveraged to substantiate the simulation model. Each step of the manufacturing chain is documented together with the involved uncertainties. Several of these steps are mimicked on the simulation side, e.g. by introducing a random eigenvalue problem. The uncertainties are then quantified numerically and in particular the sensitivities give valuable insight into the systems behavior. We also compare these findings to purely statistical studies carried out for the manufactured cavities. More advanced, adaptive, surrogate modeling techniques are adopted, which are crucial to incorporate a large number of uncertain parameters. The main contribution is the detailed comparison and fusion of measurement results for the EXFEL cavities on the one hand and simulation based uncertainty studies on the other hand. After introducing the quantities of physical interest for accelerator cavities and the Maxwell eigenvalue problem, the details on the manufacturing of the EXFEL cavities and measurements are reported. This is followed by uncertainty modeling with quantification studies

Conformational Parameters and Hydrodynamic Behavior of Poly(2-Methyl-2-Oxazoline) in a Broad Molar Mass Range

In this work, we report our results on the hydrodynamic behavior of poly(2-methyl-2-oxazoline) (PMeOx). PMeOx is gaining significant attention for use as hydrophilic polymer in pharmaceutical carriers as an alternative for the commonly used poly(ethylene glycol) (PEG), for which antibodies are found in a significant fraction of the human population. The main focus of the current study is to determine the hydrodynamic characteristics of PMeOx under physiological conditions, which serves as basis for better understanding of the use of PMeOx in pharmaceutical applications. This goal was achieved by studying PMeOx solutions in phosphate-buffered saline (PBS) as a solvent at 37 °C. This study was performed based on two series of PMeOx samples; one series is synthesized by conventional living cationic ring-opening polymerization, which is limited by the maximum chain length that can be achieved, and a second series is obtained by an alternative synthesis strategy based on acetylation of well-defined linear poly(ethylene imine) (PEI) prepared by controlled side-chain hydrolysis of a defined high molar mass of poly(2-ethyl-2-oxazoline). The combination of these two series of PMeOx allowed the determination of the Kuhn–Mark–Houwink–Sakurada equations in a broad molar mass range. For intrinsic viscosity, sedimentation and diffusion coefficients, the following expressions were obtained: η=0.015M0.77, s0=0.019M0.42 and D0=2600M−0.58, respectively. As a result, it can be concluded that the phosphate-buffered saline buffer at 37 °C represents a thermodynamically good solvent for PMeOx, based on the scaling indices of the equations. The conformational parameters for PMeOx chains were also determined, revealing an equilibrium rigidity or Kuhn segment length, (A) of 1.7 nm and a polymer chain diameter (d) of 0.4 nm. The obtained value for the equilibrium rigidity is very similar to the reported values for other hydrophilic polymers, such as PEG, poly(vinylpyrrolidone) and poly(2-ethyl-2-oxazoline), making PMeOx a relevant alternative to PEG

Solid Energetic Material Based on Aluminum Micropowder Modified by Microwave Radiation

The paper discusses the application of pulsed microwave radiation for the modification of crystalline components of a high-energy material (HEsM). The model aluminized mixture with increased heat of combustion was studied. The mixture contained 15 wt.% aluminum micron powder, which was modified by microwave irradiation. It was found that the HEM thermogram has an exo-effect with the maximum at 364.3 °C. The use of a modified powder in the HEM composition increased the energy release during combustion by 11% from 5.6 kJ/g to 6.2 kJ/g. The reason for this effect is the increase in the reactivity of aluminum powder after microwave irradiation. In this research, we confirmed that the powders do not lose the stored energy, even as part of the HEM produced on their basis. A laser projection imaging system with brightness amplification was used to estimate the speed of combustion front propagation over the material surface. Measurement of the burning rate revealed a slight difference in the burning rates of HEMs based on irradiated and non-irradiated aluminum micropowders. This property can be demanded in practice, allowing a greater release of energy while maintaining the volume of energetic material

RF Aspects of Quality Control for Industrial XFEL Cavities Fabrication

Quality control of European XFEL serial cavities allows us not only exception of the use of rejectedcavities for the linac, but also giving a feedback to industry in case of cavity parameters come to their limits.RF check assays not only the electro dynamical characteristics (as frequencies, Q-factors and fields), butalso provides the mechanical revise with a very high accuracy.Automation of this quality control in XFEL data base gave us a powerful tool necessary for big projects such asthe European XFE

Mathematical model of crossing of discrete snow obstacles

The paper is concerned with research of mobility of vehicles, specifically of flotation. The new definition “discrete flotation” is considered. The subject of moving over the snow road surface is considered, especially the crossing of terrain compartments with varying height of snow blanket. The classification of discrete snow obstacles is given separated by the next features: the occurrence of directed anthropogenic factor, the type of formation source, the structure, the degree of shape uniformity of formation source, the stress-strain properties, the composition and the shape of discrete obstacle. The relation describing the shape of snow drifts is given containing the parameters determining the distribution shape, the scale, the area of longitudinal section and the dimension. The relations intended to determine the resistance to moving when crossing the snow drifts and the condition of flotation loss are given

Performance in the vertical test of the 832 nine-cell 1.3 GHz cavities for the European X-ray Free Electron Laser

The successful production and associated vertical testing of over 800 superconducting 1.3 GHz accelerating cavities for the European X-ray Free Electron Laser (XFEL) represents the culmination of over 20 years of superconducting radio-frequency R&D. The cavity production took place at two industrial vendors under the shared responsibility of INFN Milano–LASA and DESY. Average vertical testing rates at DESY exceeded 10 cavities per week, peaking at up to 15 cavities per week. The cavities sent for cryomodule assembly at Commissariat à l’énergie atomique (CEA) Saclay achieved an average maximum gradient of approximately 33  MV/m, reducing to ∼30  MV/m when the operational specifications on quality factor (Q) and field emission were included (the so-called usable gradient). Only 16% of the cavities required an additional surface retreatment to recover their low performance (usable gradient less than 20  MV/m). These cavities were predominantly limited by excessive field emission for which a simple high pressure water rinse (HPR) was sufficient. Approximately 16% of the cavities also received an additional HPR, e.g. due to vacuum problems before or during the tests or other reasons, but these were not directly related to gradient performance. The in-depth statistical analyses presented in this report have revealed several features of the series produced cavities

Analysis of the RF Test Results from the On-Going Cavity Production for the European XFEL

The main Linac of the European XFEL will consist of 100 superconducting accelerator modules, operated at anaverage design gradient of 23.6 MV/m. The fabrication by industry (which includes chemical surface preparation) ofthe required 800 superconducting cavities is now in full swing, with approximately 400 cavities having beendelivered to date. In this interim report, we present an analysis of the RF acceptance tests amassed so far

Uncertainty Modeling and Analysis of the European X-Ray Free Electron Laser Cavities Manufacturing Process

This paper reports on comprehensive efforts on uncertainty quantification and global sensitivity analysis for accelerator cavity design. As a case study object the TESLA shaped superconducting cavities, as produced for the European X-ray Free Electron Laser (EXFEL), are selected. The choice for these cavities is explained by the available measurement data that can be leveraged to substantiate the simulation model. Each step of the manufacturing chain is documented together with the involved uncertainties. Several of these steps are mimicked on the simulation side, e.g., by introducing a random eigenvalue problem. The uncertainties are then quantified numerically and in particular the sensitivities give valuable insight into the system behavior. We also compare these findings to purely statistical studies carried out for the manufactured cavities. More advanced, adaptive, surrogate modeling techniques are adopted, which are crucial to incorporate a large number of uncertain parameters. The main contribution is the detailed comparison and fusion of measurement results for the EXFEL cavities on the one hand and simulation based uncertainty studies on the other hand. After introducing the quantities of physical interest for accelerator cavities and the Maxwell eigenvalue problem, the details on the manufacturing of the EXFEL cavities and measurements are reported. This is followed by uncertainty modeling with quantification studies