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DOE OSTI2019

The Velociprobe: An ultrafast hard X-ray nanoprobe for high-resolution ptychographic imaging

Motivated by the advanced photon source upgrade, a new hard X-ray microscope called "Velociprobe" has been recently designed and built for fast ptychographic imaging with high spatial resolution. We are addressing the challenges of high-resolution and fast scanning with novel hardware designs, advanced motion controls, and new data acquisition strategies, including the use of high-bandwidth interferometric measurements. The use of granite, air-bearing-supported stages provides the necessary long travel ranges for coarse motion to accommodate real samples and variable energy operation while remaining highly stable during fine scanning. Scanning the low-mass zone plate enables high-speed and high-precision motion of the probe over the sample. With an advanced control algorithm implemented in a closed-loop feedback system, the setup achieves a position resolution (3σ) of 2 nm. The instrument performance is evaluated by 2D fly-scan ptychography with our developed data acquisition strategies. A spatial resolution of 8.8 nm has been demonstrated on a Au test sample with a detector continuous frame rate of 200 Hz. Using a higher flux X-ray source provided by double-multilayer monochromator, we achieve 10 nm resolution for an integrated circuit sample in an ultrafast scan with a detector's full continuous frame rate of 3000 Hz (0.33 ms per exposure), resulting in an outstanding imaging rate of 9 x 10 4 resolution elements per second

36 MATERIALS SCIENCE↗

DOE OSTI2010

Quantum master equation for collisional dynamics of massive particles with internal degrees of freedom

We address the microscopic derivation of a quantum master equation in Lindblad form for the dynamics of a massive test particle with internal degrees of freedom, interacting through collisions with a background ideal gas. When either internal or center-of-mass degrees of freedom can be treated classically, previously established equations are obtained as special cases. If in an interferometric setup the internal degrees of freedom are not detected at the output, the equation can be recast in the form of a generalized Lindblad structure, which describes non-Markovian effects. The effect of internal degrees of freedom on center-of-mass decoherence is considered in this framework.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2018

Interferometry of dipole phase in high harmonics from solids

Understanding the temporal profiles of high harmonics is essential for their applications in attosecond science. Microscopically, the dipole phase plays an important role in determining the high-harmonic emission phase. In gas-phase high-harmonic generation, the tunnel-ionized electron spends much of its travel time in the continuum—far from the parent ion, where it accumulates the dipole phase. Therefore, the atomic dipole phase is largely independent of the target atom. In solid-state high-harmonic generation, since the driven electron experiences a periodic potential during the entire travel time, the dipole phase may depend on the electronic structures of source materials. Here, we employ an interferometric method to characterize high harmonics from magnesium oxide and quartz crystals. We measure material-dependent intensity-induced high-harmonic phase delays that we attribute to the intensity-induced changes in the dipole phase originating from the interband polarization. The material-dependent dipole phase can provide a robust platform for high-harmonic spectroscopy of solids.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2017

Design of a dynamic biofilm imaging cell for white-light interferometric microscopy

In microbiology research there is a strong need for next generation imaging and sensing instrumentation that will enable minimally invasive and label-free investigation of soft, hydrated structures such as in bacterial biofilms. White light interferometry (WLI) can provide high resolution images of surface topology without the use of fluorescent labels but is not typically used to image biofilms because there is insufficient refractive index contrast to induce reflection from the biofilm’s interface. The soft structure and water-like bulk properties of hydrated biofilms make them difficult to characterize in situ , especially in a non-destructive manner. In this report, we build on our prior description of static biofilm imaging and describe the design of a dynamic imaging flow cell that enables monitoring the thickness and topology of live biofilms over time using a WLI microscope. The microfluidic system is specifically designed to create a reflective interface on the surface of biofilms while minimizing disruption of fragile structures. The imaging cell was also designed to accommodate limitations imposed by the depth of focus of the microscope’s objective lens. Example images of live biofilm samples are shown in order to illustrate the ability of the flow cell and WLI instrument to 1) support bacterial growth and biofilm development, 2) image biofilm structure that reflects growth in flow conditions, and 3) monitor biofilm development over time non-destructively. In future work, the apparatus described here will enable surface metrology measurements (roughness, surface area, etc.) of biofilms and may be used to observe changes in biofilm structure in response to changes in environmental conditions (e.g., flow velocity, availability of nutrients, and presence of biocides). Furthermore, this development will open new opportunities for the use of WLI in bioimaging.

47 OTHER INSTRUMENTATION↗