Anisotropic expansion of a thermal dipolar Bose gas

We report on the anisotropic expansion of ultracold bosonic dysprosium gases at temperatures above quantum degeneracy and develop a quantitative theory to describe this behavior. The theory expresses the post-expansion aspect ratio in terms of temperature and microscopic collisional properties by incorporating Hartree-Fock mean-field interactions, hydrodynamic effects, and Bose-enhancement factors. Our results extend the utility of expansion imaging by providing accurate thermometry for dipolar thermal Bose gases, reducing error in expansion thermometry from tens of percent to only a few percent. Furthermore, we present a simple method to determine scattering lengths in dipolar gases, including near a Feshbach resonance, through observation of thermal gas expansion.Comment: main text and supplement, 11 pages total, 4 figure

Coherence scanning interferometry for additive manufacture

Additive manufacture (AM) of metal components is a rapidly maturing technology; but given the large number of interrelated process parameters, it remains difficult to control to high precision. It has been observed that processing conditions may be associated with specific features in the surface texture [1], creating a drive to achieve fast, and reliable topographic measurement of metal AM surfaces. One of the most developed metal AM processes, selective laser melting (SLM), still produces parts that exhibit rough surface textures with dense distributions of features at a wide range of lateral and vertical scales, aspect ratios, and reflective properties; with the additional complication of the presence of high slopes, undercuts and surface recesses. These features make metal AM surfaces challenging to measure by both tactile and optical means [2,3]

Optimisation of surface topography characterisation for metal additive manufacturing using coherence scanning interferometry

The surface topography of metal additive manufactured (AM) parts can be challenging to measure due to the presence of complex features, such as high slopes, step like recesses and protuberances, and local variations in reflectance. Recent innovations in coherence scanning interferometry (CSI) technology, such as high dynamic range of exposure and adjustable data acquisition rates for noise reduction, have augmented the baseline sensitivity of a measurement. This enhanced sensitivity expands the capability of CSI instruments to measure surface textures with high slopes or low reflectance, making CSI a potentially valuable tool for process development and quality control of metal AM. This study presents an empirical sensitivity analysis of a CSI system for the top and side surfaces of metal AM parts made from different materials (Ti-6Al-4V and Al-Si-10Mg) and processes (laser powder bed fusion (LPBF) and electron beam powder bed fusion (EBPBF)). The aim of this work is to demonstrate the feasibility of using CSI for characterisation of metal AM surfaces, and to evaluate the effectiveness of relevant CSI measurement settings. Topographic measurements are described through the use of ISO 25178-2 areal surface texture parameters Sq and Sdq and are analysed for data coverage, measurement time and area. The results show that the CSI technique can provide surface topography measurements for metal AM surfaces with a wide range of surface features. Finally, recommendations for optimisation of future measurements on metal AM surfaces using CSI are provided

True-color 3D surface metrology for additive manufacturing using interference microscopy

Coherence scanning interferometry (CSI) is widely used for surface topography characterisation. With the ability to measure both rough surfaces with the high slopes and optical finishes, CSI has made contibutions in fields from industrial machining to optical fabrication and polishing [1,2]. While the low coherence sources for CSI are typically broadband and suitable for color imaging, the metrology is usually performed without regards for the color information [3]. We present color surface topography measurements from a CSI instrument designed to provide true color images in addition to areal surface topography of additive manufactired samples. The addition of color measurements enables contamination and defect detection along with blemish and discoloration identification

First Single Particle Measurements of the Proton and Antiproton Magnetic Moments

We report a new comparison of the proton (p) and antiproton $(\bar{p})$ magnetic moments. In nuclear magnetons, $\mu_p/\mu_N$ = 2.792 846 (7) [2.5 ppm], while $\mu_{\bar{p}}/\mu_N$ = 2.792 845 (12) [4.4 ppm]. The unprecedented accuracy of the antiproton measurement is 680 times more precise than previous work. These first single-particle measurements provide a stringent test of CPT invariance. Our comparison, $\mu_{\bar{p}}/\mu_p$ = -1.000 000 (5) [5.0 ppm], is consistent with the prediction of the CPT theorem. We also report the observation of a single proton spin flip, opening a path to improved precision by an additional factor of $10^3$ or $10^4$.Physic

Optimisation of surface measurement for metal additive manufacturing using coherence scanning interferometry

Surface topography measurement for metal additive manufacturing (AM) is a challenging task for contact and non-contact methods. In this paper, we present an experimental investigation of the use of coherence scanning interferometry (CSI) for measurement of AM surfaces. Our approach takes advantage of recent technical enhancements in CSI, including high dynamic range for light level and adjustable data acquisition rates for noise reduction. The investigation covers several typical metal AM surfaces made from different materials and AM processes. Recommendations for measurement optimisation balance three aspects: data coverage, measurement area and measurement time. This study also presents insight into areas of interest for future rigorous examination, such as measurement noise and further development of guidelines for the measurement of metal AM surfaces

Coherence scanning interferometry for additive manufacture

Additive manufacture (AM) of metal components is a rapidly maturing technology; but given the large number of interrelated process parameters, it remains difficult to control to high precision. It has been observed that processing conditions may be associated with specific features in the surface texture [1], creating a drive to achieve fast, and reliable topographic measurement of metal AM surfaces. One of the most developed metal AM processes, selective laser melting (SLM), still produces parts that exhibit rough surface textures with dense distributions of features at a wide range of lateral and vertical scales, aspect ratios, and reflective properties; with the additional complication of the presence of high slopes, undercuts and surface recesses. These features make metal AM surfaces challenging to measure by both tactile and optical means [2,3]