Implementation of a crossed-slit system for fast alignment of sealed polycapillary X-ray optics

A new modification of a table-top laser-driven water-jet plasma X-ray source has been successfully implemented and commissioned at the Extreme Light Infrastructure (ELI) Beamlines user facility. In order to preserve the broadband nature of the source for spectroscopic experiments, a polycapillary lens was initially chosen as the focusing element. Generally, polycapillary X-ray optics have a narrow photon acceptance angle and small field of view, making alignment complicated and time-consuming. This contribution demonstrates a straightforward, reliable and reproducible procedure for aligning polycapillary focusing optics with broadband X-rays. The method involves a pre-alignment step where two X-ray slits are mounted orthogonally on opposite sides of a 3D-printed cylindrical polycapillary holder. This helps to precisely determine the optical axis of the X-ray beam. Subsequent mounting of the polycapillary in the pre-aligned holder with the slits removed allowed for immediate transmission of the X-ray photons through the optics and has provided a good starting point for fine alignment.

Psychophysical effects in double-slit interference patterns: Response to a critique

An experiment was conducted to explore possible psychophysical influences on interference patterns generated by an optical double-slit system. The experiment was motivated by a proposed explanation of the quantum measurement problem by John von Neumann and others, namely that consciousness collapses the quantum wavefunction. The study design generated a single database partitioned into eight differential tests, four in experimental conditions where participants alternately directed their attention toward and away from the optical system, and four in sham conditions when no one was present. The planned analysis was comparison of means in attention-toward vs. attention-away conditions; a secondary analysis added later, but before the data were examined, was comparison of variances. After adjusting the eight mean comparisons for multiple testing, none were statistically significant, but one of the eight variance differences was suggestively significant.To date, 11 of 28 conceptual replications of this experiment, reported by four independent teams, have reported statistically significant outcomes (p < 0.05, two-tail), where only one would be expected by chance. Given the implications of psychophysical effects on our understanding of the role of consciousness in the physical world, we encourage others to attempt to replicate this experiment.

Pyrolitic Graphite Mosaic Crystal Thickness and Mosaicity Optimization for an Extended Source Von Hamos X-ray Spectrometer

Bragg spectroscopy, one of the best established experimental techniques for high energy resolution X-ray measurements, has always been limited to the measurement of photons produced from well collimated (tens of microns) or point-like sources; recently, the VOXES collaboration at INFN National Laboratories of Frascati developed a prototype of a high resolution and high precision X-ray spectrometer working also with extended isotropic sources. The realized spectrometer makes use of Highly Annealed Pyrolitic Graphite (HAPG) crystals in a “semi”-Von Hamos configuration, in which the position detector is rotated with respect to the standard Von Hamos one, to increase the dynamic energy range, and shows energy resolutions at the level of 0.1% for photon energies up to 10 keV and effective source sizes in the range 400–1200 μ m in the dispersive plane. Such wide effective source dimensions are achieved using a double slit system to produce a virtual point-like source between the emitting target and the crystal. The spectrometer performances in terms of reflection efficiency and peak resolution depend on several parameters, among which a special role is played by the crystal mosaicity and thickness. In this work, we report the measurements of the Cu(K α 1 , 2 ) and the Fe(K α 1 , 2 ) lines performed with different mosaicity and thickness crystals in order to investigate the influence of the parameters on the peak resolution and on the reflection efficiency mentioned above.

Consciousness-related interactions in a double-slit optical system

Motivated by a series of reported experiments and their controversial results, the present work investigated if volunteers could causally affect an optical double-slit system by mental efforts alone. The participants' task in the experimental sessions alternated between intending an increase in the (real-time feedback-informed) amount of light diffracted through a specific single slit versus relaxing their intentional effort. In total, 240 sessions contributed by 171 volunteers were recorded. The first 160 sessions were collected in an exploratory mode, and those data revealed statistically significant differences between the intention and relax conditions. The analysis method and variables of interest derived from the exploratory sessions were then pre-registered for the subsequent 80 formal sessions. The formal experiments, based on a directional hypothesis, were not statistically significant. A post hoc meta-analysis based on a bi-directional hypothesis, and applied to the same data, resulted in a 2.75 sigma outcome ($p=6.02\times10^{-3}; \, es=0.31 \pm 0.22$ 95\% CI). Directional and bi-directional analyses applied to an equal number of control sessions, all conducted without observers present, resulted in uniformly non-significant outcomes. Analysis of environmental factors did not reveal any artifactual sources that might have produced the significant bi-directional effect. While the pre-registered analysis did not support the existence of the investigated phenomenon, the post hoc findings warrant further investigation to formally test the bi-directional hypothesis.

Quantitative characterization of the X-ray beam at the Australian Synchrotron Imaging and Medical Beamline (IMBL)

A critical early phase for any synchrotron beamline involves detailed testing, characterization and commissioning; this is especially true of a beamline as ambitious and complex as the Imaging & Medical Beamline (IMBL) at the Australian Synchrotron. IMBL staff and expert users have been performing precise experiments aimed at quantitative characterization of the primary polychromatic and monochromatic X-ray beams, with particular emphasis placed on the wiggler insertion devices (IDs), the primary-slit system and any in vacuo and ex vacuo filters. The findings from these studies will be described herein. These results will benefit IMBL and other users in the future, especially those for whom detailed knowledge of the X-ray beam spectrum (or `quality') and flux density is important. This information is critical for radiotherapy and radiobiology users, who ultimately need to know (to better than 5%) what X-ray dose or dose rate is being delivered to their samples. Various correction factors associated with ionization-chamber (IC) dosimetry have been accounted for, e.g. ion recombination, electron-loss effects. A new and innovative approach has been developed in this regard, which can provide confirmation of key parameter values such as the magnetic field in the wiggler and the effective thickness of key filters. IMBL commenced operation in December 2008 with an Advanced Photon Source (APS) wiggler as the (interim) ID. A superconducting multi-pole wiggler was installed and operational in January 2013. Results are obtained for both of these IDs and useful comparisons are made. A comprehensive model of the IMBL has been developed, embodied in a new computer program named spec.exe, which has been validated against a variety of experimental measurements. Having demonstrated the reliability and robustness of the model, it is then possible to use it in a practical and predictive manner. It is hoped that spec.exe will prove to be a useful resource for synchrotron science in general, and for hard X-ray beamlines, whether they are based on bending magnets or insertion devices, in particular. In due course, it is planned to make spec.exe freely available to other synchrotron scientists.

Fabrication and testing of a newly designed slit system for depth-resolved X-ray diffraction measurements

A new system of slits called `spiderweb slits' have been developed for depth-resolved powder or polycrystalline X-ray diffraction measurements. The slits act on diffracted X-rays to select a particular gauge volume of sample, while absorbing diffracted X-rays from outside of this volume. Although the slit geometry is to some extent similar to that of previously developed conical slits or spiral slits, this new design has advantages over the previous ones in use for complex heterogeneous materials andin situandoperandodiffraction measurements. For example, the slits can measure a majority of any diffraction cone for any polycrystalline material, over a continuous range of diffraction angles, and work for X-ray energies of tens to hundreds of kiloelectronvolts. The design is generated and optimized using ray-tracing simulations, and fabricated through laser micromachining. The first prototype was successfully tested at the X17A beamline at the National Synchrotron Light Source, and shows similar performance to simulations, demonstrating gauge volume selection for standard powders, for all diffraction peaks over angles of 2–10°. A similar, but improved, design will be implemented at the X-ray Powder Diffraction beamline at the National Synchrotron Light Source II.