Glass Block Research Articles

Studies of magnetic shielding for phototubes

Phototubes associated with a Cherenkov counter, with a wall of scintillation counters for time-of-flight measurements and with a wall of lead glass blocks of an electro-magnetic calorimeter will operate in the fringe field of a superconducting solenoid in the GlueX experiment. The solenoid will be operated with a central magnetic field of ≈2.5T. The maximum fringe field in the vicinity of the phototubes will be approximately 150G. Various techniques for magnetic shielding of phototubes were studied using a 1-m diameter Helmholtz coil arrangement operated with a maximum central field of 200G. Results are presented.

Phonons in an inhomogeneous continuum: Vibrations of an embedded nanoparticle

The spectrum of acoustic vibrational modes of an inhomogeneous elastic continuum are analyzed with application to a spherical nanoparticle embedded in an infinite glass block. The relationship of these modes to the discrete vibrational spectrum of a free sphere is studied. The vibrational modes of a sphere with a fixed surface are relevant in some situations. Comparisons are also made to calculations of mode frequency and damping based on complex valued frequency.

Design of delay elements in a binary optical true-time-delay device that uses a White cell.

A White-cell-based binary optical true-time-delay device has two parts: the controller, or switching engine, and the delay elements. Here we discuss in detail the design of both glass blocks and lens trains as delay elements. Glass blocks can be used in our design for delays ranging from one to a few hundred picoseconds. Lens trains are suitable for longer delays. We also analyze the loss associated with each design and give design limits.

Coherent measurement of short laser pulses based on spectral interferometry resolved in time.

We propose a new method for measuring the phase and the amplitude of a short laser pulse that is based on shearing interferometry in the spectral domain combined with time gating. The method has several features in common with spectral interferometry for direct electric-field reconstruction, in particular, fast and direct reconstruction of the phase. Accurate measurement of the phase added to an 80-fs pulse by a block of F4 glass demonstrates the technique.

Study of gel development during SON68 glass alteration using atomic force microscopy. Comparison with two simplified glasses

Literature mentions several physicochemical studies concerning the characterisation of the alteration films that are formed during the dissolution of the nuclear glasses. Up to now, however, no study had been undertaken on the evolution of the alteration film thickness by in situ technique. This study proposes to carry out atomic force microscopy (AFM) in liquid and dry conditions in order to measure the shrinkage or swelling of the alteration film. This work is performed on the glass SON68 and on two glasses with simplified compositions. The results obtained reveal a shrinkage of the alteration film for the simplified glasses and, in situ (underwater), a slight swelling for the SON68 glass caused by the formation of crystalline phase (phyllosilicates) on the surface. In all three cases, when alteration progresses, it increases the density of the gel and the volume occupied by the alteration products tends to be equal to the volume initially occupied by the glass (called isovolumetric alteration). Finally, the drying leads to an important shrinkage. These results could be used to evaluate the potential impact of the internal cracks of an industrial glass block.

Constitutive modeling of fracture waves

A fracture wave (FW) in a brittle material is a narrow transition region (border) of a continuous fracture zone, which may be associated with the damage accumulation process initiated by propagation of shock waves. In multidimensional structures the fracture wave may behave in an unusual way. The high-speed photography of penetration of a borosilicate (Pyrex) glass block [N. K. Bourne, L. Forde, and J. E. Field, Proc. SPIE 2869, 626 (1997)] shows a visible fracture zone with an apparent flat front although the projectile is a hemispherically nosed rod. A strain-rate-sensitive model is being developed and employed for analysis of the role of the complex stress state and kinetic description of the damage accumulation to describe the process of the impact. Numerical analysis is conducted with a one-dimensional wave propagation code employing the model and with the LS-DYNA2D hydrocode in which the model has been implemented. The analysis demonstrates that (i) the second (plastic) shock wave is superseded by quicker FW relaxing stress behind the elastic precursor, and (ii) the FW front flattening is apparently caused by the change in the acoustic directional properties. This change is associated with the phase-like transition due to the damage accumulation within the FW. In particular, the FW transition separates a highly anisotropic zone of material characterized acoustically by longitudinal and shear waves in front of the FW from a nearly isotropic region of the material characterized only by bulk waves behind the FW.

Improved cooling performance of ytterbium-doped glass combined with sapphire

Cooling performance of Yb : glass was improved with an index-matching liquid. 1-bromonaphthalene was used in the interfacial gap of hybrid gain material between Yb : glass and sapphire blocks. Thermal lens effects under an intensity of 20 kW cm−2 were effectively reduced. The improved hybrid gain material Yb : glass and sapphire can increase repetition rates of laser systems.

Modeling of Rock Failure under Explosion of Charge in a Disk-Shaped Slot Cavity

The failure of the concrete and organic glass blocks by the explosion of charges arranged in a slot cavity is investigated. The dependences of the crack kinetics and the character of solid medium failure on the degree of slot filling with explosive and the velocity of explosive detonation are established.

Fiber-linked Faraday effect current sensor by use of a flint glass cell with dielectric-coated retardation-compensated total reflection surfaces.

A new type of Faraday effect optical current transformer has been developed that uses a single block of square flint glass with dielectric-coated total reflection surfaces as the sensing element. Numerical calculation has shown that the coating of two dielectric layers of 45.59-nm-thick Ta2O5 and 448.35-nm-thick SiO2 films on a flint glass surface produces zero retardation total reflection for the 45 degrees incident angle of light at lambda = 840 nm with great incident angle, wavelength, and film thickness tolerances. A fiber-linked current transformer has been constructed and experimentally demonstrated to exhibit high isolation from surrounding currents as well as high stability against mechanical disturbances.

Observation of light propagation by holography with a picosecond pulsed laser

We demonstrate the propagation of a light pulse undergoing refraction and total refraction inside a glass block as well as diffraction at a grating. Observation of a frameless, continuous motion picture of the light propagation is possible by recording of hologram with a picosecond pulsed laser. It is shown that the direction of the pulse changes as a result of refraction, the pulse's speed decreases inside a glass block, and the pulse travels a zigzag path by total refraction. The pulse fronts of the diffracted light propagating parallel to the grating surface are also demonstrated.

Initial studies into the viability of using co-dopants in inorganic glass scintillators to develop a scintillating glass for applications in particle physics experiments

Inorganic glasses are a potential source of affordable scintillators for particle physics; however, for application to calorimetry, dense glasses are required, and oxide glasses with the necessary characteristics have proved difficult to produce. Recent work has demonstrated that cerium-doped heavy metal fluoride (HMF) glasses have many of the required properties, although their performance is limited by the fact that CeF 3 emission is in the near ultraviolet, close to the band edge for transmission in the glass. The light yield from large blocks of glass is, therefore, reduced by self-absorption. The yield is further reduced when the material is exposed to ionising radiation, which causes the formation of colour centres, increasing absorption at short wavelengths. This work reports on initial studies into the addition of rare earth fluorides to Ce-doped HMF glasses as a means of moving the emission wavelength away from the absorption edge and some developments in the manufacture of dense oxide glasses. A number of co-doped glasses have been made and measurements on transmission, scintillation yield and decay time are presented, showing a strong correlation between yield and decay time.

Transmission through a nonlinear thin layer near the critical angle of incidence: application to the sensitive determination of the nonlinear refractive index

Optical transmission, near the critical angle of incidence, through a nonlinear thin layer sandwiched between two linear glass blocks is studied. The transmissivity of the layer in the near-resonant regime is very sensitive to the intensity-induced change of its refractive index. Using this property, we propose a method to determine the nonlinear refractive index n2 of thin films, on the basis of a simple plane-wave model. Experimental results in the picosecond range, using CS2 standard as the nonlinear layer, show the high sensitivity of the method.

Waveguide grating (moire´) microinterferometer for inplane displacement/strain field investigation

Analysis of microelements requires a local approach to their mechanical behavior and material constants distribution. This requires modern full-field measurement tools, among which automated grating (moire) interferometry (GMI) is one of the best-suited measurement methods. A new type of grating microinterferometer is presented. It is based on the concept of an achromatic grating interferometer combined with a glass block waveguide and designed to work with standard optical microscopes. The various types of waveguide plates are presented and discussed. The interferogram obtained may be modified and design for analysis by means of carrier frequency phase shifting methods. The methodology of measurement is described. The usefulness of the microinterferometer is demonstrated by an example of in-plane displacement and strain distribution determination in the two-phase steel polycrystalline material.

Numerical simulation of manufacturing silica glass blocks by melting of powder batch

For optimizing the technology of manufacturing blocks of the high-purity silica glass KS-4V, the numerical simulation is performed to examine the melting of cristobalite powder through radiant heating under vacuum and the viscous flow of the glass melt during shaping into large (to 20 kg) cylindrical glass blocks. The characteristic parameters of the melting and the shaping are found, and their dependences on the initial temperature of cristobalite batch and the geometry of blocks are determined. The basic principles of the model, set of equations, and the initial and boundary conditions are described. The main calculation parameters are obtained, and the most practically useful calculated results are presented.

Spray Cooling Under Reduced Gravity Condition

The present paper reports on the results of a series of authors’ parabolic flight experiments on spray cooling in addition to ground-based experiments in which the influence of heater orientation and the behavior of rebounded droplets were especially studied in detail. Water and FC-72 (perfluorocarbon) were employed alternatively as a test liquid sprayed from a single full-cone nozzle onto a Cr-plated surface of an electrically heated copper block for transient cooling experiments or onto a transparent ITO (indium tin oxide) coated surface of a glass block for steady state experiments in a relatively low superheat region. Each experimental run was accomplished within some 15 sec through which a stable reduced gravity condition (0.01 times the terrestrial gravity) was maintained in the aircraft. Cooling curves were obtained over a wide range of each of the following parameters: the wall superheat, the spray volume flux and the Weber number for the spray droplets. It is demonstrated that the gravity dependency of the spray cooling characteristics varies with the spray volume flux and the droplet Weber number. Qualitative interpretations of the observed gravity dependency are provided.

Silicon monolithic microchannel-cooled laser diode array

A monolithic microchannel-cooled laser diode array is demonstrated that allows multiple diode-bar mounting with negligible thermal cross talk. The heat sink comprises two main components: a wet-etched Si layer that is anodically bonded to a machined glass block. The continuous wave (cw) thermal resistance of the 10 bar diode array is 0.032 °C/W, which matches the performance of discrete microchannel-cooled arrays. Up to 1.5 kW/cm2 is achieved cw at an emission wavelength of ∼808 nm. Collimation of a diode array using a monolithic lens frame produced a 7.5 mrad divergence angle by a single active alignment. This diode array offers high average power/brightness in a simple, rugged, scalable architecture that is suitable for large two-dimensional areas.

MONITORING THE STRESSED STATE OF STRUCTURAL GLASS BLOCKS

Based on a polariscope/polarimeter a device for monitoring residual stresses in structural glass blocks is developed that makes it possible to automate the measurement of residual stresses and eliminate the negative effect of the light-diffusing glass-block coating on the interference pattern of the residual-stress distribution in assessing the stressed state of glass articles using the polarization-optical method.

Polymer based electro-optic inline fiber modulator

Poled organic polymer films show great promise for use in integrated photonic devices such as amplitude or phase modulators for telecommunication. We use these polymers in a novel, low loss electro-optic inline fiber modulator. The modulator consists of a fiber half coupler, i.e. a curved fiber which is incorporated into a glass block and polished down close to the core. The coupler is coated with a semitransparent gold electrode, a thin film of our highly electro-optic polymer and an upper silver electrode. The light in the fiber can evanescently couple into the polymer overlay depending on the effective refractive index matching between polymer and fiber core which can be modulated through the electro-optical effect. Preliminary results of our first inline fiber modulators indicate a bandwidth of 100 MHz

Measurement and visualization of vibroacoustic fields caused by impact on solid surfaces

The system for measuring and visualization of vibroacoustic fields, and observation of propagation of acoustic waves of various types on solids surfaces was developed. It is possible to reconstruct the measured vibration or compute modes of vibration (movie, animation) and determine types of acoustic waves and their speeds from the measured data arrays. The vibroacoustic fields of some objects were measured (glass block, steel block, rod, pipe, etc.) in a frequency range from 1 kHz to 10 MHz. The amplitudes of vibrations range from 10 to 2000 nm. Different devices for reception and actuation of vibrations were developed and used: piezoelectric, electromagnetic, microphones, etc. The results of the investigation are presented in CD-ROM (conditions of measurement, animated vibrations, modes).

Adequacy of mathematical models of the glassware annealing process

The adequacy of the previously developed mathematical model of the glass tube annealing process is experimentally confirmed. The model is refined with respect to annealing of construction glass blocks by taking into account the effect of the barometric rarefaction inside the glass block air cavity on the process of the origin and distribution of stresses in the article, and the adequacy of the refined model is experimentally proved.