Riverscarlsen8338

Sources of negative ions such as H- are essential elements of proton accelerators and tokamaks. They have limited lifetime. The replacement of an ion source is a costly process causing delays in the operation of the entire machine. The hot tungsten filament is the key element that limits the lifetime of the H- ion source at the Los Alamos Neutron Science Center (LANSCE) facility. An accurate model, which describes the filament physics and provides a reliable estimate on its lifetime, may significantly improve the operation of the facility. Here, we describe such a model, including a comprehensive list of relevant physical processes from first principles. The model can be used to describe different regimes of operation using diagnostics data as input parameters. It has been benchmarked against the data collected during the production cycle at LANSCE and shows good agreement with experimental data.Coherent scatter x-ray imaging systems are sensitive to material structure and chemical composition, and generate soft-material images with contrast superior to conventional transmission x-ray imaging. For practicality in medical or security applications, the image data acquisition time should be less then 10 min. Our approach is a multi-beam projection imaging design. Previously, as a development stage, we implemented a synchrotron-based system with five coplanar pencil beams and continuous motion of the object. In the work reported here, we developed a more practical coherent scatter projection imaging system using a conventional x-ray tube source. The object is irradiated by an array of up to three rows by five columns of pencil beams, and motorized stages translate the object through the beams for step-and-shoot acquisition. For the same tube loading, broad spectrum beams, such as 110 kVp filtered with 2.25 mm Al, were found to provide a higher signal-difference-to-noise ratio between soft materials in scatter images than lower kVp, more heavily filtered beams that have a narrower, lower intensity spectrum. The shortest acquisition time for a 6.0 × 10.0 cm2 object with 6000 pixels was 8.8 min. The width of a sharp edge in the scatter image was consistent with the pencil beam diameter. Contrast-detail performance was similar to our synchrotron-based system. In this first x-ray tube-based system, for simplicity, the transmitted x rays are measured through attenuators using the same flat-panel detector that measures scattered x rays. As a result, the primary image quality was reduced.A multi-purpose in operando optical cell with temperature and gas pressure control is described. This device allows for in operando Raman spectroscopy measurements for different applications. Its original design includes a temperature control from room temperature up to 1000°C and a heating stage that provides uniform and stable thermal conditions. The pressure control of the cell ranges from 10-1 Pa to 6 MPa, and it is compatible with different gases. Both oxidizing and reducing gases are allowed to pass through the sample surface under study. The device has been calibrated and applied to collect Raman spectra for different reaction systems under various operating temperatures and pressures.In situ monitoring of mechanochemical reactions of soft matter is feasible by synchrotron diffraction experiments. However, so far, reactions of hard materials in existing polymer milling vessels failed due to insufficient energy input. In this study, we present the development of a suitable setup for in situ diffraction experiments at a synchrotron facility. The mechanochemical transformation of boehmite, γ-AlOOH, to corundum, α-Al2O3, was chosen as a model system. The modifications of the mill's clamping system and the vessels themselves were investigated separately. Starting from a commercially available Retsch MM 400 shaker mill, the influence of the geometrical adaptation of the setup on the milling process was investigated. Simply extending the specimen holder proved to be not sufficient because changes in mechanical forces need to be accounted for in the construction of optimized extensions. DT-061 Milling vessels that are suitable for diffraction experiments and also guarantee the required energy input as well as mechanical stability were developed. The vessels consist of a steel body and modular polymer/steel rings as x-ray transparent windows. In addition, the vessels are equipped with a gas inlet and outlet system that is connectable to a gas analytics setup. Based on the respective modifications, the transformation of boehmite to corundum could be observed in an optimized setup.This paper proposes a synchronous demodulation technology based on sample-and-hold which shows significant advantages in the application of precision sensors. The traditional synchronous demodulation methods are discussed, and then the working principle of the proposed method is theoretically analyzed in detail. It is found that the proposed method can not only effectively suppress the harmonic components caused by the signal source but is also beneficial to improving the dynamic range of precision sensors. The eddy current sensor is adopted as an example of precision sensors, and a high-precision eddy current displacement sensor prototype was designed and tested. The results show that with the proposed method, the harmonics in the output signal are suppressed more effectively, and the demodulation circuit is relatively simplified. This synchronous demodulation method has an extensive application prospect in precision sensors.In a medical accelerator, real-time monitoring systems of the beam and dose delivered to the patient are mandatory. In this work, we present a compact current profile detector that has been designed and tested in the framework of the TOP-IMPLART (Intensity Modulated Proton Linear Accelerator for RadioTerapy) project. This project foresees the realization of a proton linear accelerator, currently under construction at ENEA Frascati, for proton therapy applications. The linac produces a pulsed proton beam with 3 µs duration at 50 Hz repetition rate with a pulse current between 0.5 and 50 μA. A large dynamic range and spatial constraints make the use of usual noninterceptive beam diagnostics unfeasible. Therefore, the use of a beam current monitor based on a passive RF cavity working in the TM010 mode has been proposed. This paper reports the electromagnetic design of the device guided by a simplified analytical model. A prototype of such a device has been realized, characterized, and tested on the linac with a 35 MeV beam varying the beam current. The test results in air and in vacuum, together with the signal detection systems used, are presented.The Semilab SE-2000 spectroscopic ellipsometer is a versatile thin film characterization instrument capable of spectroscopic ellipsometry measurements covering a large spectral range from ultraviolet to near infrared within a few seconds and into the mid-infrared in a few minutes. It is suitable for characterizing thin films from monolayers to complex multi-layer laminates and bulk materials. This article demonstrates the unique capabilities of the SE-2000 system by the wide spectral range investigation of Al doped ZnO layers on different substrates and with different layer structures. Using data fits to the Drude dispersion law, the electrical properties of AlZnO were determined despite the presence of other conductive layers. The results were corroborated with four-point-probe measurements on a single AlZnO layer deposited on a glass substrate.We report a new rapid-quench technique for the Kawai-type multi-anvil press several important improvements were made to our previous design. As a result, we are able to routinely quench melts with low glass-forming ability and form glasses. Owing to the use of 3D-printed parts to supply the coolant, the new design is easier to assemble and demonstrates better temperature stability and cooling rate. It was also found that the cooling rate is both pressure- and temperature-dependent. The cooling rate increases with increasing pressure from 6700 °C/s at 1 GPa to 8200 °C/s at 5.5 GPa and decreases with increasing temperature at a rate of 550 °C s-1/100 °C. Taking these dependencies into account, the new rapid-quench design produces more than 15% higher cooling rate compared to the previous design. Moreover, enhancing coolant circulation, which was achieved by using tapered inner anvils with holes, additionally increases the cooling rate by about 4%. As the structure of the rapid-quench assembly differs dramatically from other existing designs, pressure calibration and temperature distribution in the experimental cell and sample capsule were determined for the first time. It was found that the first 0.6 MN of press load is not used to generate pressure due to the hard tungsten components in the assembly. At the current state-of-the-art, it is possible to routinely reach a pressure of 9 GPa and a temperature of 2200 K with the temperature variation not exceeding 70 K within the sample capsule.We conceive and construct an on-site in situ high-pressure time-resolved ultrafast optical spectroscopy instrument that facilitates ultrafast pump-probe dynamics measurements under high pressure conditions. We integrate an ultrafast pump-probe spectroscopy system with a diamond anvil cell (DAC) system. Significantly, both the DAC and the sample are fixed within the light path without motion and rotation throughout the whole ultrafast spectroscopy experiment, including tuning and calibrating the pressure. This instrument thus avoids introducing artifacts due to sample motion or rotation, enabling precision high-pressure ultrafast pump-probe dynamics investigations. As a demonstrating example, we compare the effect of on-site in situ conditions with off-site in situ conditions on the ultrafast dynamics of Sr2IrO4 under 0-44.5 GPa high pressure. Our data and analysis show that conventional possible artifacts are greatly reduced by using the on-site in situ layout. Our work helps the high-pressure ultrafast science investigation develop into a promising new area, which enables the exploration of nonequilibrium excited quantum states in the high-pressure regime.Diagnostic tools are of fundamental importance in experimental research. In plasma physics, probes are usually used to obtain the plasma parameters, such as density, temperature, electromagnetic fields, and waves. This Review focuses on low-temperature plasma diagnostics where in situ probes can be used. Examples of in situ and remote diagnostics will be shown, proven by many experimental verifications. This Review starts with Langmuir probes and then continues with other diagnostics such as waves, beams, and particle collectors, which can provide high accuracy. A basic energy analyzer has been advanced to measure distribution functions with three-dimensional velocity resolution, three directions in real space and time resolution. The measurement of the seven-dimensional distribution function is the basis for understanding kinetic phenomena in plasma physics. Non-Maxwellian distributions have been measured in magnetic reconnection experiments, scattering of beams, wakes of ion beams, etc. The next advance deals with the diagnostics of electromagnetic effects.