Spatial displays as a means to increase pilot situational awareness

Experiences raise a number of concerns for future spatial-display developers. While the promise of spatial displays is great, the cost of their development will be correspondingly large. The knowledge and skills which must be coordinated to ensure successful results is unprecedent. From the viewpoint of the designer, basic knowledge of how human beings perceive and process complex displays appears fragmented and largely unquantified. Methodologies for display development require prototyping and testing with subject pilots for even small changes. Useful characterizations of the range of differences between individual users is nonexistent or at best poorly understood. The nature, significance, and frequency of interpretation errors associated with complex integrated displays is unexplored and undocumented territory. Graphic displays have intuitive appeal and can achieve face validity much more readily than earlier symbolic displays. The risk of misleading the pilot is correspondingly greater. Thus while some in the research community are developing the tools and techniques necessary for effective spatial-display development, potential users must be educated about the issues so that informed choices can be made. The scope of the task facing all is great. The task is challenging and the potential for meaningful contributions at all levels is high indeed

A Componential Approach to the Investigation of Individual Differences in Time-Sharing (dual-Task Performance, Information Processing)

185 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1986.Time-sharing ability as an individual differences variable in dual-task performance was examined using a componential model. Five proposed components were assessed: (1) serial processing ability, (2) an internal model of the system dynamics, (3) maintenance of different operations in working memory, (4) adaptation to rapidly changing dynamic conditions, and (5) parallel processing ability. The approach combined methodologies from experimental psychology and from individual differences research.Forty subjects were given four single-task pretests, they then performed a compensatory tracking task in various dual-task combinations administered during six sessions over a period of three days. At the conclusion of the experiment the subjects had to perform three different dual-task transfer tasks.The results of a factor analysis and a series of stepwise multiple-regression analyses revealed two important dimensions of individual differences in dual-task performance: (1) individual differences in cognitive style linked to the concept of field dependence/independence, and (2) individual differences in time-sharing ability.The individual differences in cognitive style were identified by the first derived factor. It was defined by the measures that represented serial and parallel processing. Based on the opposing signs, positive for the serial processing measures and negative for the parallel processing measures, it was concluded that this factor is bipolar, representing two distinct strategies of dual-task performance. Multiple-regression analysis and correlational analysis suggested that the strategy differences may be linked to individual differences in field dependence/independence.Individual differences in time-sharing ability were identified by the second derived factor of the factor analysis and through multiple-regression analysis. Based on the results the concept of a 'process-specific' time-sharing ability was introduced.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD

Atomic, Molecular and Cluster Science with the Reaction Microscope Endstation at FLASH2

The reaction microscope (REMI) endstation for atomic and molecular science at the free-electron laser FLASH2 at DESY in Hamburg is presented together with a brief overview of results recently obtained. The REMI allows coincident detection of electrons and ions that emerge from atomic or molecular fragmentation reactions in the focus of the extreme-ultraviolet (XUV) free-electron laser (FEL) beam. A large variety of target species ranging from atoms and molecules to small clusters can be injected with a supersonic gas-jet into the FEL focus. Their ionization and fragmentation dynamics can be studied either under single pulse conditions, or for double pulses as a function of their time delay by means of FEL-pump–FEL-probe schemes and also in combination with a femtosecond infrared (IR) laser. In a recent upgrade, the endstation was further extended by a light source based on high harmonic generation (HHG), which is now available for upcoming FEL/HHG pump–probe experiments

Photoelectron spectroscopy of laser-dressed atomic helium

© 2020 authors. Photoelectron emission from excited states of laser-dressed atomic helium is analyzed with respect to laser intensity-dependent excitation energy shifts and angular distributions. In the two-color exteme ultraviolet (XUV)-infrared (IR) measurement, the XUV photon energy is scanned between 20.4 eV and the ionization threshold at 24.6 eV, revealing electric dipole-forbidden transitions for a temporally overlapping IR pulse (≈1012Wcm-2). The interpretation of the experimental results is supported by numerically solving the time-dependent Schrödinger equation in a single-active-electron approximation

The FLASH Facility: Advanced Options for FLASH2 and Future Perspectives

Since 2016, the two free-electron laser (FEL) lines FLASH1 and FLASH2 have been run simultaneously for users at DESY in Hamburg. With the installation of variable gap undulators in the new FLASH2 FEL line, many new possibilities have opened up in terms of photon parameters for experiments. What has been tested so far is post-saturation tapering, reverse tapering, harmonic lasing, harmonic lasing self-seeding and two-color lasing. At the moment, we are working on concepts to enhance the capabilities of the FLASH facility even further. A major part of the upgrade plans, known as FLASH2020, will involve the exchange of the fixed gap undulators in FLASH1 and the implementation of a new flexible undulator scheme aimed at providing coherent radiation for multi-color experiments over a broad wavelength range. The recent achievements in FLASH2 and the current status of plans for the further development of the facility are presented

Differential Measurement of Electron Ejection after Two-Photon Two-Electron Excitation of Helium

We report the measurement of the photoelectron angular distribution of two-photon single-ionization near the $2p^2$ $^1D^e$ double-excitation resonance in helium, benchmarking the fundamental nonlinear interaction of two photons with two correlated electrons. This observation is enabled by the unique combination of intense extreme ultraviolet pulses, delivered at the high-repetition-rate free-electron laser in Hamburg (FLASH), ionizing a jet of cryogenically cooled helium atoms in a reaction microscope. The spectral structure of the intense self-amplified spontaneous emission free-electron laser pulses has been resolved on a single-shot level to allow for post selection of pulses, leading to an enhanced spectral resolution, and introducing a new experimental method. The measured angular distribution is directly compared to state-of-the-art theory based on multichannel quantum defect theory and the streamlined $R$-matrix method. These results and experimental methodology open a promising route for exploring fundamental interactions of few photons with few electrons in general