Search results for "methods"
showing 10 items of 4526 documents
Measurement of edge residual stresses in glass by the phase-shifting method
2011
Abstract Control and measurement of residual stress in glass is of great importance in the industrial field. Since glass is a birefringent material, the residual stress analysis is based mainly on the photoelastic method. This paper considers two methods of automated analysis of membrane residual stress in glass sheets, based on the phase-shifting concept in monochromatic light. In particular these methods are the automated versions of goniometric compensation methods of Tardy and Senarmont. The proposed methods can effectively replace manual methods of compensation (goniometric compensation of Tardy and Senarmont, Babinet and Babinet–Soleil compensators) provided by current standards on th…
On the photoelectron spectrum ofp-benzoquinone
2001
A high-resolution photoelectron spectrum of p-benzoquinone in the low energy (9.5–11.5 eV) region is reported and analyzed with the aid of simulations based on high-level ab initio calculations. The results generally support the notion that the two prominent spectral features in this region are each due to a pair of final ion states. The lower energy feature beginning near 10 eV is due to oxygen lone-pair ionizations, while that beginning near 11 eV comes from π electron removal. Contrary to previous interpretations of the spectrum, however, the results of this study indicate that the two π states are nearly degenerate, with the strongest peak in the photoelectron spectrum representing a co…
A theoretical study of the lowest electronic states of azobenzene: the role of torsion coordinate in the cis-trans photoisomerization
2003
In the present paper we report the results of a multiconigurational computational study on potential- energy curves of azobenzene along the NN twisting to clarify the role of this coordinate in the decay of the S2(pp*) and S1(np*) states. We have found that there is a singlet state, S3 at the trans geometry, on the basis of the doubly excited coniguration n 2 p* 2 , that has a deep minimum at about 90 of twisting, where it is the lowest excited singlet state. The existence of this state provides an explanation for the short lifetime of S2(pp*) and for the wavelength-dependence of azobenzene photochem- istry. We have characterized the S1(np*) state by calcu- lating its vibrational frequencie…
Valence-band splitting energies in wurtzite InP nanowires : Photoluminescence spectroscopy and ab initio calculations
2010
We investigated experimentally and theoretically the valence-band structure of wurtzite InP nanowires. The wurtzite phase, which usually is not stable for III-V phosphide compounds, has been observed in InP nanowires. We present results on the electronic properties of these nanowires using the photoluminescence excitation technique. Spectra from an ensemble of nanowires show three clear absorption edges separated by 44 meV and 143 meV, respectively. The band edges are attributed to excitonic absorptions involving three distinct valence-bands labeled: A, B, and C. Theoretical results based on “ab initio” calculation gives corresponding valence-band energy separations of 50 meV and 200 meV, r…
Photomicrography of skin by ultraviolet light.
1971
Skin sections superimposed on fine-grained photographic plates were exposed to ultraviolet light (2580 A wavelength). The images obtained, which reproduced the microanatomy of tissue in the process of ultraviolet photoabsorption, were studied under the microscope. Since absorption is proportional to the concentration of such biologically important chromophore-bearing substances as nueleoproteins and melanoproteins, the method gives information on the content and distribution of these substances in normal and altered tissue.
The Time Calibration System of KM3NeT: The Laser Beacon and the Nanobeacon
2015
The KM3NeT collaboration has started the construction of a deep sea neutrino telescope in the Mediterranean with an instrumented volume of several cubic kilometers. The objective of the KM3NeT telescope is to observe cosmic neutrinos. For this, the detector will consist of a tri-dimensional array of optical modules, each one composed of a pressure resistant glass sphere housing 31 small area photomultipliers. An important element of the KM3NeT detector is the system for the relative time calibration between optical modules with a precision of about 1 ns. The system comprises two independent devices: a nanobeacon inside each optical module for calibration of optical modules in the same verti…
Time of flight measurements based on FPGA using a breast dedicated PET
2014
In this work the implementation of a Time-to-Digital Converter (TDC) using a Nutt delay line FPGA-based and applied on a Positron Emission Tomography (PET) device is going to be presented in order to check the system’s suitability for Time of Flight (TOF) measurements. In recent years, FPGAs have shown great advantages for precise time measurements in PET. The architecture employed for these measurements is described in detail. The system developed was tested on a dedicated breast PET prototype, composed of LYSO crystals and Positive Sensitive Photomultipliers (PSPMTs). Two distinct experiments were carried out for this purpose. In the first test, system linearity was evaluated in order to …
Charge reconstruction in large-area photomultipliers
2018
Large-area PhotoMultiplier Tubes (PMT) allow to efficiently instrument Liquid Scintillator (LS) neutrino detectors, where large target masses are pivotal to compensate for neutrinos' extremely elusive nature. Depending on the detector light yield, several scintillation photons stemming from the same neutrino interaction are likely to hit a single PMT in a few tens/hundreds of nanoseconds, resulting in several photoelectrons (PEs) to pile-up at the PMT anode. In such scenario, the signal generated by each PE is entangled to the others, and an accurate PMT charge reconstruction becomes challenging. This manuscript describes an experimental method able to address the PMT charge reconstruction …
Operation and first results of the NEXT-DEMO prototype using a silicon photomultiplier tracking array
2013
NEXT-DEMO is a high-pressure xenon gas TPC which acts as a technological test-bed and demonstrator for the NEXT-100 neutrinoless double beta decay experiment. In its current configuration the apparatus fully implements the NEXT-100 design concept. This is an asymmetric TPC, with an energy plane made of photomultipliers and a tracking plane made of silicon photomultipliers (SiPM) coated with TPB. The detector in this new configuration has been used to reconstruct the characteristic signature of electrons in dense gas, demonstrating the ability to identify the MIP and "blob" regions. Moreover, the SiPM tracking plane allows for the definition of a large fiducial region in which an excellent e…
Lowering the radioactivity of the photomultiplier tubes for the XENON1T dark matter experiment
2015
The low-background, VUV-sensitive 3-inch diameter photomultiplier tube R11410 has been developed by Hamamatsu for dark matter direct detection experiments using liquid xenon as the target material. We present the results from the joint effort between the XENON collaboration and the Hamamatsu company to produce a highly radio-pure photosensor (version R11410-21) for the XENON1T dark matter experiment. After introducing the photosensor and its components, we show the methods and results of the radioactive contamination measurements of the individual materials employed in the photomultiplier production. We then discuss the adopted strategies to reduce the radioactivity of the various PMT versi…