Automated precision alignment of optical components for hydroxide catalysis bonding

We describe an interferometric system that can measure the alignment and separation of a polished face of a optical component and an adjacent polished surface. Accuracies achieved are ∼ 1μrad for the relative angles in two orthogonal directions and ∼ 30μm in separation. We describe the use of this readout system to automate the process of hydroxide catalysis bonding of a fused-silica component to a fused-silica baseplate. The complete alignment and bonding sequence was typically achieved in a timescale of a few minutes, followed by an initial cure of 10 minutes. A series of bonds were performed using two fluids - a simple sodium hydroxide solution and a sodium hydroxide solution with some sodium silicate solution added. In each case we achieved final bonded component angular alignment within 10 μrad and position in the critical direction within 4 μm of the planned targets. The small movements of the component during the initial bonding and curing phases were monitored. The bonds made using the sodium silicate mixture achieved their final bonded alignment over a period of ∼ 15 hours. Bonds using the simple sodium hydroxide solution achieved their final alignment in a much shorter time of a few minutes. The automated system promises to speed the manufacture of precision-aligned assemblies using hydroxide catalysis bonding by more than an order of magnitude over the more manual approach used to build the optical interferometer at the heart of the recent ESA LISA Pathfinder technology demonstrator mission. This novel approach will be key to the time-efficient and low-risk manufacture of the complex optical systems needed for the forthcoming ESA spaceborne gravitational waves observatory mission, provisionally named LISA

Stellar Activity and its Implications for Exoplanet Detection on GJ 176

We present an in-depth analysis of stellar activity and its effects on radial velocity (RV) for the M2 dwarf GJ 176 based on spectra taken over 10 years from the High Resolution Spectrograph on the Hobby-Eberly Telescope. These data are supplemented with spectra from previous observations with the HIRES and HARPS spectrographs, and V- and R-band photometry taken over 6 years at the Dyer and Fairborn observatories. Previous studies of GJ 176 revealed a super-Earth exoplanet in an 8.8-day orbit. However, the velocities of this star are also known to be contaminated by activity, particularly at the 39-day stellar rotation period. We have examined the magnetic activity of GJ 176 using the sodium I D lines, which have been shown to be a sensitive activity tracer in cool stars. In addition to rotational modulation, we see evidence of a long-term trend in our Na I D index, which may be part of a long-period activity cycle. The sodium index is well correlated with our RVs, and we show that this activity trend drives a corresponding slope in RV. Interestingly, the rotation signal remains in phase in photometry, but not in the spectral activity indicators. We interpret this phenomenon as the result of one or more large spot complexes or active regions which dominate the photometric variability, while the spectral indices are driven by the overall magnetic activity across the stellar surface. In light of these results, we discuss the potential for correcting activity signals in the RVs of M dwarfs.Comment: Accepted for publication in Ap

Construction of rugged, ultrastable optical assemblies with optical component alignment at the few microradian level

A method for constructing quasimonolithic, precision-aligned optical assemblies is presented. Hydroxide-catalysis bonding is used, adapted to allow optimization of component fine alignment prior to the bond setting. We demonstrate the technique by bonding a fused silica mirror substrate to a fused silica baseplate. In-plane component placement at the submicrometer level is achieved, resulting in angular control of a reflected laser beam at the sub-10-μrad level. Within the context of the LISA Pathfinder mission, the technique has been demonstrated as suitable for use in space-flight applications. It is expected that there will also be applications in a wide range of areas where accuracy, stability, and strength of optical assemblies are important

Stable Isotope Geochemistry and Paleohydrology of the Poison Strip Sandstone, Early Cretaceous, Eastern Utah

The Poison Strip Sandstone Member is a unique unit in the early Cretaceous Cedar Mountain Formation of eastern Utah. A previous chemostratigraphic study of the Poison Strip Sandstone at the Ruby Ranch Road (RRR) section east of Green River, Utah produced a noteworthy dataset with interesting δ18O results (Ludvigson et al., 2015). The Poison Strip at the type section of the Ruby Ranch Member contains poikilotopic calcite cements that yield δ18O values that range between -16 and -13.5‰ VPDB (Ludvigson et al, 2015). These isotopic values represent a major departure from the typical δ18O values of about -8‰ VPDB documented during earlier studies of the Cedar Mountain formation and have either major paleoclimatic or later diagenetic implications for the unit. Through detailed petrographic, diagenetic, and stable isotopic analysis, we were able to determine that that the atypical δ18O values produced from the poikilotopic calcite cements of the Poison Strip Sandstone are the result of deep burial diagenesis. The precipitation of poikilotopic calcite cements were likely influenced by petroleum migration through the basin and may have also been impacted by hydrothermal fluids. Preliminary temperature and depth estimates of 2 – 3km and 73 to 90° C were calculated from the intergranular volumes and isotopic data

Sounding The Trumpet: Educating For Jubilee

Series 7: Altadena, Southern California / Jubilee (2000-2012): English Files, Notebook 8https://digitalcommons.fuller.edu/kinsler-tee/1052/thumbnail.jp