A versatile beamline for soft x-ray reflectivity, absorption, and fluorescence measurements at Indus-2 synchrotron source.

A versatile beamline for performing reflectivity, fluorescence, and absorption experiments in the soft x-ray region of 100-1500 eV is commissioned on a bending magnet port of the Indus-2 synchrotron source. A high vacuum 2-axis reflectometer with x, y, and z sample scanning stages is installed. This reflectometer is used to measure the reflectivity of large samples up to 300 mm in length and 5 kg in weight. This feature is useful for characterizing x-ray optical elements, such as mirrors, gratings, and multilayers. A flange mounted silicon drift detector is installed in the downstream of the reflectometer for soft x-ray fluorescence measurements. The soft x-ray absorption measurements are carried out in the total electron yield and partial fluorescence yield modes. Integration of three different experimental techniques in the experimental station makes the beamline versatile for materials science applications as it provides structural, chemical, and electronic state information by performing the required experiments in an identical environment. The beamline uses a varied line spacing plane grating monochromator and gives a high flux (∼109 to 1011 photon/s) with a moderate resolution (λ/Δλ ~1000-5000). A three-mirror-based higher harmonic setup is incorporated to get rid of harmonics and to get a high spectral purity monochromatic beam with less than 0.1% harmonic content. In the present article, the beamline optical scheme, mechanical configuration, and details of the experimental setups are presented, along with a few representative results of each experimental mode.

BL-02: a versatile X-ray scattering and diffraction beamline for engineering applications at Indus-2 synchrotron source.

A hard X-ray engineering applications beamline (BL-02) was commissioned recently and started operation in March 2019 at the Indian synchrotron source, Indus-2. This bending-magnet-based beamline is capable of operating in various beam modes, viz. white, pink and monochromatic beam. The beamline utilizes the X-ray diffraction technique in energy-dispersive and angle-dispersive modes to carry out experiments mainly focused on engineering problems, viz. stress measurement, texture measurement and determination of elastic constants in a variety of bulk as well as thin-film samples. An open-cradle six-circle diffractometer with ∼12 kg load capacity allows accommodation of a wide variety of engineering samples and qualifies the beamline as a unique facility at Indus-2. The high-resolution mode of this beamline is suitably designed so as to carry out line profile analysis for characterization of micro- and nano-structures. In the present article the beamline is described starting from the beamline design, layout, optics involved, various operational modes and experimental stations. Experiments executed to validate the beamline design parameters and to demonstrate the capabilities of the beamline are also described. The future facilities to be incorporated to enhance the capabilities of the beamline are also discussed.

Experimental setup to measure thermal waves generated by X-ray absorption using pyroelectric sensor.

Pyroelectric detectors are widely used for infrared radiation detection, whereas these can also be used in the X-ray region. They have multiple advantages when used at synchrotron radiation sources, such as (a) can be used with a white beam (high flux), (b) have a flat spectral response, and (c) can be used both as a detector and as a sample. However, when used in the hard X-ray region, absorption in the detector plays an important role depending upon the thickness of the detector. Hence, the estimation of the responsivity of the detector is important. In this paper, we report an improved experimental setup for the measurement of a pyroelectric signal in the hard X-ray region. The responsivity (V/W) of a pyroelectric detector for absorbed radiation in the hard x-ray region is measured. Measurements of the K-edge x-ray absorption fine structure of 10-µm copper and nickel foils are carried out using a LiTaO3 pyroelectric detector and compared with the measurements carried out using an ionization chamber as a sensor for the same foils. Absorption spectra near the Ta LIII and LII edges in LiTaO3, measured using a LiTaO3 crystal both as a sample and as a sensor, are also reported in this paper.

Simultaneous measurements of X-ray reflectivity and grazing incidence fluorescence at BL-16 beamline of Indus-2.

A new multipurpose x-ray reflectometer station has been developed and augmented at the microfocus beamline (BL-16) of Indus-2 synchrotron radiation source to facilitate synchronous measurements of specular x-ray reflectivity and grazing incidence x-ray fluorescence emission from thin layered structures. The design and various salient features of the x-ray reflectometer are discussed. The performance of the reflectometer has been evaluated by analyzing several thin layered structures having different surface interface properties. The results reveal in-depth information for precise determination of surface and interface properties of thin layered materials demonstrating the immense potential of the combined measurements of x-ray reflectivity and grazing incidence fluorescence on a single reflectometer.

A microfocus X-ray fluorescence beamline at Indus-2 synchrotron radiation facility.

A microfocus X-ray fluorescence spectroscopy beamline (BL-16) at the Indian synchrotron radiation facility Indus-2 has been constructed with an experimental emphasis on environmental, archaeological, biomedical and material science applications involving heavy metal speciation and their localization. The beamline offers a combination of different analytical probes, e.g. X-ray fluorescence mapping, X-ray microspectroscopy and total-external-reflection fluorescence characterization. The beamline is installed on a bending-magnet source with a working X-ray energy range of 4-20 keV, enabling it to excite K-edges of all elements from S to Nb and L-edges from Ag to U. The optics of the beamline comprises of a double-crystal monochromator with Si(111) symmetric and asymmetric crystals and a pair of Kirkpatrick-Baez focusing mirrors. This paper describes the performance of the beamline and its capabilities with examples of measured results.

Most-probable-number rapid viability PCR method to detect viable spores of Bacillus anthracis in swab samples.

A comparison of Most-Probable-Number Rapid Viability (MPN RV) PCR and traditional culture methods for the quantification of Bacillus anthracis Sterne spores in macrofoam swabs from a multi-center validation study was performed. The purpose of the study was to compare environmental swab processing methods for recovery, detection, and quantification of viable B. anthracis spores from surfaces. Results show that spore numbers provided by the MPN RV-PCR method were typically within 1-log of the values from a plate count method for all three levels of spores tested (3.1x10(4), 400, and 40 spores sampled from surfaces with swabs) even in the presence of debris. The MPN method tended to overestimate the expected result, especially at lower spore levels. Blind negative samples were correctly identified using both methods showing a lack of cross contamination. In addition to detecting low levels of spores in environmental conditions, the MPN RV-PCR method is specific, and compatible with automated high-throughput sample processing and analysis protocols, enhancing its utility for characterization and clearance following a biothreat agent release.

Rapid, high-throughput, culture-based PCR methods to analyze samples for viable spores of Bacillus anthracis and its surrogates.

To rapidly remediate facilities after a biothreat agent release, improved turnaround times are needed for sample analysis. Current methods to confirm the presence of a viable biothreat agent are limited by low sample throughput. We have developed a rapid-viability-polymerase chain reaction (RV-PCR) method to determine the presence of viable spores. The method combines high-throughput sample processing with 96-well PCR analysis, which measures a change in real-time, quantitative PCR response arising from increased target-cell populations during culturing. The method accurately detects 1 to 10 live spores in a high-dead spore background (10(6)). Field tests using approximately 1000 biological indicators, each containing 10(6) spores of the B. anthracis surrogate, Bacillus atrophaeus, exposed to seven lethal and sub-lethal chlorine dioxide levels showed no significant difference (p>0.05) between RV-PCR and standard culturing methods for detecting the percent survival of spores. RV-PCR results were obtained in <17 h compared to 7 days for the standard culturing method. High-throughput sample processing and RV-PCR protocols were also developed and tested for synthetic wipe samples containing reference dirt material. RV-PCR protocols allowed processing and accurate analysis of approximately100 dirty wipe samples (2''x2'' synthetic) containing approximately10 viable B. atrophaeus spores in <24 h. Quantitative RV-PCR protocols based on a Most-Probable-Number (MPN) statistical approach developed for B. anthracis Sterne resulted in more rapid turnaround times than those for traditional culturing and no significant difference in log colony-forming units compared to traditional viability analysis. Integration of RV-PCR assays with high-throughput protocols will allow the processing of 200 wipe samples per day per robot using commercially available automation.

Analysis of interpenetrating polymer networks via quartz crystal microbalance with dissipation monitoring.

A quartz crystal microbalance with dissipation monitoring (QCM-D) was used to assess the physical properties of interpenetrating polymer networks (IPNs) through swelling experiments in ambient humidity and in phosphate-buffered saline (PBS), pH 7.4. The IPNs, based on acrylamide (AAm) and poly(ethylene glycol) (pEG), swell from thin, rigid films when dry (16.7 +/- 5.2 nm on Si/SiO(2)) to expanded, viscoelastic films when hydrated (107 +/- 24.2 nm on Si/SiO2). The dry IPNs could be analyzed using the Sauerbrey relationship, but for the hydrated films it was necessary to interpret QCM-D data with a Kelvin-Voigt viscoelastic model. A complex modulus |G| of 116 +/- 38.1 kPa for the swollen IPN surface on Si/SiO2 was defined by the model. The QCM-D was also employed to quantify the adsorption of human fibrinogen, a protein important in thrombus formation, onto the IPNs. Fibrinogen adsorption studies demonstrated the sensitivity of the QCM-D, as well as confirmed the nonfouling nature of the IPN surface, where less than 5 ng/cm2 of fibrinogen was adsorbed.

Aerobic biodegradation of methyl tert-butyl ether by aquifer bacteria from leaking underground storage tank sites.

The potential for aerobic methyl tert-butyl ether (MTBE) degradation was investigated with microcosms containing aquifer sediment and groundwater from four MTBE-contaminated sites characterized by oxygen-limited in situ conditions. MTBE depletion was observed for sediments from two sites (e.g., 4.5 mg/liter degraded in 15 days after a 4-day lag period), whereas no consumption of MTBE was observed for sediments from the other sites after 75 days. For sediments in which MTBE was consumed, 43 to 54% of added [U-(14)C]MTBE was mineralized to (14)CO(2). Molecular phylogenetic analyses of these sediments indicated the enrichment of species closely related to a known MTBE-degrading bacterium, strain PM1. At only one site, the presence of water-soluble gasoline components significantly inhibited MTBE degradation and led to a more pronounced accumulation of the metabolite tert-butyl alcohol. Overall, these results suggest that the effects of oxygen and water-soluble gasoline components on in situ MTBE degradation will vary from site to site and that phylogenetic analysis may be a promising predictor of MTBE biodegradation potential.