Quartz Bars Research Articles

Operation of the Belle II imaging Time-Of-Propagation (iTOP) detector before and after the first long shutdown

The iTOP detector is a Cherenkov detector specialized on particle identification at Belle II. The SuperKEKB accelerator collides electrons and positrons with a design luminosity of 6⋅10351cm2s. In order to exploit the high collision rate Belle II has a trigger rate of up to 30 kHz. The iTOP detector uses quartz bars as the source of Cherenkov photons. The photons are reflected inside the bars until they hit photomultipliers installed at one end. The spatial distribution and precise arrival times of the detected photons are used to reconstruct the Cherenkov angle and particle flight time. To achieve a good pion–kaon separation the photon arrival times have to be measured with a resolution of 100 ps. Microchannel plate photomultipliers together with dedicated high-speed electronics for 2.7 GSa/s waveform sampling in 8192 channels are used to achieve this requirement. After four years of operation, the experiment entered its first long shutdown phase in 2022. Aging components of iTOP were exchanged and the detector was prepared for data-taking at increasing luminosities and backgrounds after the long shutdown. In this talk the design of the iTOP detector will be shown and experience and results from operation will be discussed together with an outlook on future running conditions.

Применение метода вариации Аллана при исследовании физико-химических процессов на поверхности твердого тела

The Allan variation method is being effectively used to study stability of frequency generators and noise characteristics of the dynamic processes of various physical nature presented in the form of time series. At the same time, the methods of nonlinear dynamics, in particular, of the fractal analysis, are used both in processing the time series and in studying irregularities in profiles or surfaces. By analogy with this, the possibility of introducing the Allan variance method to analyze alterations in the solid body surface during chemical and thermal treatment was evaluated. Introduction of the Allan variance method makes it possible to quantify the roughness components corresponding to the surface defects of a certain size. Alterations in the surface of grounded and polished quartz glass plates were studied, as well as the melted rods during chemical dissolution of the surface layer. The presented graphs and calculated Allan variations for the profiles of various surfaces clearly demonstrate that alterations in the surface relief standard deviation during chemical etching of the quartz plates and bars is associated with the surface defects size. The results of studying the surface stay in good agreement with the estimates made by the fractal analysis method. Introduction of the Allan variance method makes it possible to optimize both the mechanical and the chemical surface treatment mode of various parts during their manufacture

Multifractal analysis of ultrasonically machined surfaces of cylindrical quartz crystals: the effect of the abrasive grits

Since synthetic quartz is essential to produce 3D resonators for numerous applications in precision electronics, in this work the surface topography of cylindrical quartz bars is investigated using the multifractal technique. The cylindrical bars were manufactured with ultrasonic machining using five SiC grits ranging from 6 to 50 μm. The machined surfaces were initially characterized by contact profilometry and scanning electron microscopy (SEM). The multifractality of the machined surfaces was scrutinized using a box-counting method applied to the images obtained with 500X magnification. The multifractal spectrum indicated that the fractal dimension f(α) and the width of the fractal spectrum Δα are dependent on the grit size, but this dependence is not monotonic. The lowest (negative) value for Δf(α) was found for 25 μm grits indicating that for these grits the lower frequency events (grooves with tens μm width occurring along the USM direction) control the surface topography much more than high-frequency events related to brittle microcracking. The abrasive wear due to the continuous slurry recycling in lateral tool-workpiece interfaces contributed to smooth the groove texture as well as the sharpness of microscopic indentations, which remained observed on the surfaces machined with 50 μm grits. The opposite paths observed for the arithmetical mean deviation of the measured profile (Ra) and Δf(α) parameters with the cutting rate measured for each grit size were valuable to differentiate flat-rough and unlevelled-rough topographies in quartz bars.

A modified piezoelectric ultrasonic composite oscillator technique for simultaneous measurement of elastic moduli and internal frictions at varied temperature.

In this work, a modified piezoelectric ultrasonic composite oscillator technique (M-PUCOT) is developed for measuring a material's elastic moduli and internal frictions, as a function of temperature. Different from the traditional PUCOT that employs two quartz bars as the drive and gauge, here, a single small piezoelectric transducer (PZT) ring is used to drive and sense longitudinal or torsional vibration in a cylinder specimen. Because of the strong piezoelectric effect and relatively large bandwidth of the PZTs compared to their quartz counterpart, the frequency match condition between the transducer and the specimen is not required in this M-PUCOT. For high temperature measurement, a fused quartz spacer, whose resonance frequency matches the specimen's, is bonded between the transducer and the specimen to provide thermal insulation. First, the united equivalent circuit of the transducer- (spacer) -specimen composite system was derived. Then, Young's modulus, longitudinal friction, shear modulus, and torsional friction were explicitly obtained by measuring the resonance frequency and antiresonance frequency of the 2- or 3-component system's electrical susceptance curve using an impedance analyzer. The accuracy of this method was validated both by measuring the system's amplitude-frequency curves using a laser vibrometer and through finite element simulations. The repeatability error of the M-PUCOT is only ∼0.2% for moduli measurement and ∼2.5% for internal friction measurement, which is very promising for studying the moduli and internal friction variations during damage, fatigue, and phase transitions. Finally, the M-PUCOT was employed to measure the variations in moduli and internal frictions of an Fe64Ni36 Invar alloy from room temperature to 500 °C. Results show that above the ferromagnetic phase transition temperature Tc, both moduli reach their maxima, and both internal frictions reach their minima. The proposed M-PUCOT is expected to be widely used in the near future for its quick measurement, high repeatability, and low cost.

Performance of the Belle II imaging Time-Of-Propagation (iTOP) detector in first collisions

The iTOP detector is a novel Cherenkov detector developed for barrel particle identification at Belle II, an upgrade of the previous Belle experiment at KEK. The SuperKEKB accelerator, an upgrade of KEKB, collides electrons and positrons with a design luminosity of 8⋅1035cm−2s−1. In order to exploit the high collision rate, Belle II has a trigger frequency of up to 30 kHz. The iTOP detector uses quartz bars as source of Cherenkov photons. The photons are reflected inside the bars until they hit photomultipliers at one end. The spatial distribution and precise arrival times of the detected photons are used to reconstruct the Cherenkov angle. The photon arrival times have to be measured with a resolution better than 100 ps to achieve a good pion–kaon separation. Microchannel plate photomultipliers together with dedicated high-speed electronics for 2.7 GSa/s waveform sampling are used to achieve this timing resolution. The iTOP detector consists of 16 modules with 512 channels each, in total the detector has 8192 channels. First collisions were recorded in spring 2018. A phase of physics operation with a ramp up to full luminosity starts in March 2019. The design of the iTOP detector is shown and experience and results from initial operation are discussed together with an outlook on future running conditions.

Characterisation of the fused silica surface quality with a [formula omitted]-source

A method to characterise the quality of a fused silica surface using a β-source is presented. Two fused silica bars (5×10×400mm3) were fabricated for the Cherenkov detector for proton Flux Measurement installed at vacuum chamber of the Super Proton Synchrotron at CERN. The resolution of such device is defined by the collection efficiency of the Cherenkov light, which is produced by relativistic charged particles in the fused silica. Thus, the surface quality of the radiator should be as good as possible to avoid light losses. The method is based on the scanning of the radiator surface with a 90Sr radioactive source and measurements of the Cherenkov light rate, detected by a PMT attached to the quartz bars. The data have been compared with a Monte-Carlo simulation, providing an estimation of the radiator’s probability of the total internal reflection and inefficient area at the edges of the bars.

The Belle II imaging Time-of-Propagation (iTOP) detector

High precision flavor physics measurements are an essential complement to the direct searches for new physics at the LHC ATLAS and CMS experiments. Such measurements will be performed using the upgraded Belle II detector that will take data at the SuperKEKB accelerator. With 40x the luminosity of KEKB, the detector systems must operate efficiently at much higher rates than the original Belle detector. A central element of the upgrade is the barrel particle identification system. Belle II has built and installed an imaging-Time-of-Propagation (iTOP) detector. The iTOP uses quartz optics as Cherenkov radiators. The photons are transported down the quartz bars via total internal reflection with a spherical mirror at the forward end to reflect photons to the backward end where they are imaged onto an array of segmented Micro-Channel Plate Photo-Multiplier Tubes (MCP-PMTs). The system is read out using giga-samples per second waveform sampling Application-Specific Integrated Circuits (ASICs). The combined timing and spatial distribution of the photons for each event are used to determine particle species. This paper provides an overview of the iTOP system.

Beam tests of an integrated prototype of the ATLAS Forward Proton detector

The ATLAS Forward Proton (AFP) detector is intended to measure protons scattered at small angles from the ATLAS interaction point. To this end, a combination of 3D Silicon pixel tracking modules and Quartz-Cherenkov time-of-flight (ToF) detectors is installed 210 m away from the interaction point at both sides of ATLAS. Beam tests with an AFP prototype detector combining tracking and timing sub-detectors and a common readout have been performed at the CERN-SPS test-beam facility in November 2014 and September 2015 to complete the system integration and to study the detector performance. The successful tracking-timing integration was demonstrated. Good tracker hit efficiencies above 99.9% at a sensor tilt of 14°, as foreseen for AFP, were observed. Spatial resolutions in the short pixel direction with 50 μm pitch of 5.5 ± 0.5 μm per pixel plane and of 2.8 ± 0.5 μm for the full four-plane tracker at 14° were found, largely surpassing the AFP requirement of 10 μm. The timing detector showed also good hit efficiencies above 99%, and a full-system time resolution of 35±6 ps was found for the ToF prototype detector with two Quartz bars in-line (half the final AFP size) without dedicated optimisation, fulfilling the requirements for initial low-luminosity AFP runs.

Design of Cherenkov bars for the optical part of the time-of-flight detector in Geant4

We present the results of studies devoted to the development and optimization of the optical part of a high precision time-of-flight (TOF) detector for the Large Hadron Collider (LHC). This work was motivated by a proposal to use such a detector in conjunction with a silicon detector to tag and measure protons from interactions of the type p + p → p + X + p, where the two outgoing protons are scattered in the very forward directions. The fast timing detector uses fused silica (quartz) bars that emit Cherenkov radiation as a relativistic particle passes through and the emitted Cherenkov photons are detected by, for instance, a micro-channel plate multi-anode Photomultiplier Tube (MCP-PMT). Several possible designs are implemented in Geant4 and studied for timing optimization as a function of the arrival time, and the number of Cherenkov photons reaching the photo-sensor.

Quartz Cherenkov counters for fast timing: QUARTIC

We have developed particle detectors based on fused silica (quartz) Cherenkov radiators read outwith microchannel plate photomultipliers (MCP-PMTs) or silicon photomultipliers (SiPMs) for high precisiontiming (σt ∼ 10-15 ps). One application is to measure the times of small angle protonsfrom exclusive reactions,p+p→p+X+p, at the Large HadronCollider, LHC. They may also be used to measure directional particle fluxes close to external or stored beams.The detectors have small areas (cm2), but need to be active very close( ∼ 4 mm) to the intense LHC beam, and so must be radiation hard and nearly edgeless.We present results of tests of detectors with quartz bars inclined at the Cherenkov angle, and with bars in the form of an“L” (with a 90° corner). We also describe a possible design for a fasttiming hodoscope with few mm2 elements.

Growth of tourmaline single crystals containing transition metal elements in hydrothermal solutions

Interest in the growth of tourmaline single crystals is based on the promising piezoelectric and pyroelectric properties of this material compared to quartz crystals currently in use. Moreover, synthetic tourmaline can be used as a substitute for the natural stone in the jewelry industry similar to other synthetic analogues of gemstones. Single crystals of colored Co-, Ni-, Fe-, (Ni,Cr)-, (Ni,Fe)-, and (Co,Ni,Cr)-containing tourmalines with concentration of transition metal elements up to 16wt% on a seed have been grown from complex boron-containing hydrothermal solutions at a range of temperatures 400–750°C and pressures 100MPa. Experiments were conducted under conditions of a thermal gradient in titanium and chromium–nickel autoclaves. Tourmaline growth on a seed crystal occurs only if separate tourmaline-forming components (monocrystalline corundum and quartz bars) are used as charge. All tourmalines specified above grow in analogous (+) direction of the optical axis with a speed of 0.05mm/day by faces of the trigonal pyramid, except tourmalines containing chromium. They grow in analogous (+0001) direction with a speed 0.05mm/day, and in antilogous (−0001) direction with a speed of 0.01mm/day by faces of the trigonal pyramid and in prism direction with a speed of 0.001mm/day. Along with the large single crystals, a great amount of finest (30–150μm in size) tourmaline crystals was formed during the runs by spontaneous nucleation both on the surface of the seed crystals and in the charge.

Photooxidation of dimethylsulfide in the gas phase: A comparison between TiO2–silica and photosensitizer-silica based materials

The photooxidation of dimethylsulfide (DMS) in the gas phase was studied with two different materials, under identical conditions. The first material (TiO2-QZ) is based on titanium dioxide (TiO2) deposited on quartz bars by the sol–gel method. The second one (DCA-SG) is based on the well known photosensitizer, 9,10-dicyanoanthracene (DCA) encapsulated in a sol–gel silica network. In spite of non-optimized conditions, both materials allow the oxidation of DMS in air under irradiation. However, the oxidation products are strikingly different: dimethyldisulfide is the main product detected in the gas phase with TiO2-QZ due to a too short residence time to achieve complete mineralization. With DCA-SG no gaseous product is detected in the treated gaseous flow for more than 100h, due to the exclusive formation of polar dimethylsulfoxide and dimethylsulfone which are totally adsorbed on the highly polar silica gel. The efficiency of this latter reaction depends on the DMS concentration, gas flow and light intensity, but is not affected by the presence of small amounts of water. Singlet oxygen appears to be formed efficiently under these conditions. The saturation of DCA-SG by the oxidation products was demonstrated by several complementary methods, and some possible solutions to regenerate the material are proposed. The complementarities of both TiO2-QZ and DCA-SG could be used to achieve the oxidation of different classes of pollutants.

Study of electrochemical discharge machining technology for slicing non-conductive brittle materials

The electrochemical discharge machining (ECDM) has been proved to be a potential process for the machining of high-strength non-conductive materials. Traveling wire electrochemical discharge machining (TW-ECDM), a newly developed technology, is used to slice the small size (10–30 mm diameter) optical glass and quartz bars. The electrical–thermal etching effect and its feasibility are investigated. The energy release intensities and their physical phenomena under different sizes of discharge wires, power source modulations and methods of electrolyte supply are discussed. The pulsed dc power proves better spark stability and more spark energy release proportion than constant dc power. The input power is modulated to obtain the appropriate frequencies and duty factors for machining glass and quartz materials. The ion translation rate, the electrolyte immersing depth and the concentration of the alkali are found to be the dominant factors of bubbles reaction. Based on the SEM photographs of the workpiece surface, it is noted that the more purple the sparks from the mixed gases of hydrogen and vapor, the better the etching effect is. The V-shape defect occurring at the cut-in and cut-out can be significantly reduced by rotating the workpiece. Finally the appropriate cutting conditions for the quartz and borosilicate optical glass materials are concluded.

Study of electrochemical discharge machining technology for slicing non-conductive brittle materials

The electrochemical discharge machining (ECDM) has been proved to be a potential process for the machining of high-strength non-conductive materials. Traveling wire electrochemical discharge machining (TW-ECDM), a newly developed technology, is used to slice the small size (10–30 mm diameter) optical glass and quartz bars. The electrical–thermal etching effect and its feasibility are investigated. The energy release intensities and their physical phenomena under different sizes of discharge wires, power source modulations and methods of electrolyte supply are discussed. The pulsed dc power proves better spark stability and more spark energy release proportion than constant dc power. The input power is modulated to obtain the appropriate frequencies and duty factors for machining glass and quartz materials. The ion translation rate, the electrolyte immersing depth and the concentration of the alkali are found to be the dominant factors of bubbles reaction. Based on the SEM photographs of the workpiece surface, it is noted that the more purple the sparks from the mixed gases of hydrogen and vapor, the better the etching effect is. The V-shape defect occurring at the cut-in and cut-out can be significantly reduced by rotating the workpiece. Finally the appropriate cutting conditions for the quartz and borosilicate optical glass materials are concluded.

High resolution X-ray Laue topography of thick quartz crystals at SPring-8

High resolution X-ray Laue topography was conducted on the SPring-8 BL-28B2 beamline, operating at a 5–100 keV energy range. The use of this beamline was particularly suitable for characterization of thick samples of giant blocks of natural quartz used as seeds for growing synthetic quartz; and also to understand the propagation mechanism of dislocation lines in synthetic quartz. Area enlargement of Laue topographs by scanning the sample-film stage in the vertical direction was particularly useful for high energy diffraction images, due to their relatively small vertical dimensions. The methodology applied to characterize thick crystals used in the present research, is an effective contribution to develop nearly perfect large dimension seeds and synthetic quartz bars for the next generation of “surface acoustic waves” device substrates.

Kinetics of dissolution and state of silica in hydrothermal solutions of Na 2CO 3 and NaOH, and accelerated method for the quartz crystal characterization against growth rate

Kinetics of dissolution of quartz, its solubility and a heavy phase formation in Na 2CO 3 and NaOH solution under temperature 100°C, 200°C and 320°C and filling of autoclaves at 76% and 79% were studied. The etching surface of quartz bars after the runs is characterized. For the evaluation of entrapped solid inclusions and water-bearing nonstructural contaminations against the growth rate of quartz crystals, the accelerated method was developed.

DIRC – A particle identification system for BaBar

The Detection of Internally Reflected Cherenkov light (DIRC) is a novel type of Cherenkov imaging device that has been developed, built and installed as part of the BaBar detector at the asymmetric B-factory PEP-II at SLAC. The DIRC is based on total internal reflection of Cherenkov photons produced and guided within thin, rectangular quartz bars covering the barrel region of BaBar. The photon detector is an array of photomultiplier tubes covering the photon phase space at the backward end of the bars. In its first few months of operation the DIRC performance has been found to achieve the design requirements. This note presents results from cosmic-ray data and an analysis of the first beam collision runs.

Silica transfer and β-quartz growth from supercritical aqueous fluids

Methods used to grow β-quartz crystals include, gas and hydrothermal high-pressure vessels (10–12 ml internal volume) and autoclaves (20, 75 and 100 ml internal volume). The crystals were grown on bar-like α-quartz seeds at temperatures up to 900°C and pressures from 20 to 500 MPa, under isothermal and thermal gradient conditions. Pure water and aqueous solutions of NaOH, K 2CO 3, NaCl, NH 4F, AlF 3, HF, Li 3PO 4 were used as solvents. The nutrient was similar quartz bars or amorphous silica. Impurity elements (Fe, Al, P, Ti, Ge etc.) were added to the nutrient in the form of oxides. The details of silica transfer during the crystal growth process, under supercritical conditions, have been analyzed. It was demonstrated for the first time that in pure water and nearly neutral or alkaline fluids, the direction of silica transfer always coincides with the direct temperature gradient. However, in acidic fluoride fluids and pressures below 80–100 MPa, the direction of silica transfer undergoes inversion and is opposite to the direct temperature gradient. This phenomenon is related to the nonmonotonous and relatively strong temperature and density dependence of the HF dissociation constant which affects quartz solubility. The intensity and direction of silica transfer is substantially dependent on temperature, temperature gradient, density and alkalinity of the solutions, as well as being dependent on the fluoride ion concentrations in acidic solutions. It was shown that only faces {10 1 ̄ 0} and {10 1 ̄ 1} , as well as higher indexed pyramidal {h0 h ̄ l} faces are stable under experimental conditions. The growth rates of faces {10 1 ̄ 0} and {10 1 ̄ 1} are about the same (∼0.02 mm day −1). Impurity elements, except for Ge, are scarce (∼0.001%) in the quartz structure. The results obtained provide an explanation for the growth peculiarities of β-quartz crystals in natural environments.

An internally reflecting Cherenkov detector (DIRC): properties of the fused silica radiators

The DIRC, a new type of ring-imaging Cherenkov detector that images internally reflected Cherenkov light, is being constructed as the main hadronic particle identification component of the BABAR detector at SLAC. The device makes use of 5 meter long fused silica (colloquially called quartz) bars, which serve both as the Cherenkov radiators and as light pipes for transmitting the light to an array of photo-multiplier tubes. This paper describes a program of research and development aimed at determining whether bars that meet the stringent requirements of the DIRC can be obtained from commercial sources. The results of studies of bulk absorption of fused silica, surface finish, radiation damage and bulk inhomogeneities are discussed.

Growth of high temperature β-quartz from supercritical aqueous fluids

Methods have been developed for growing of β-quartz crystals using gas and hydrothermal high-pressure vessels (10–12 ml internal volume), and autoclaves (20, 75, and 100 ml internal volume). The crystals were grown on bar-like α-quartz seeds at temperatures from 580 to 900°C and pressures from 0.5 to 5 kbar under isothermal and thermal gradient conditions. Pure water and aqueous solutions of NaOH, K 2CO 3, NH 4F, AlF 3, HF, Li 3PO 4, etc., were used as solvents. The nutrient was similar quartz bars or amorphous silica. Impurity elements (Fe, Al, P, Ti, Ge, etc.) were added to the nutrient in the form of oxides. It is shown that only the faces {{10 1 0}} and {{10 1 1}}, as well as higher-indexed pyramidal {{ h0 h l}} stable under the experimental conditions used. The growth rates of the {{10 1 0}} and {{10 1 1}} faces were about the same (∼ 0.02 mm/day), giving rise to isometric dipyramidal or prismatic habits. At temperatures above 600°C noticeable growth was observed under the temperature gradient conditions used even from fluids of rather low (0.05 to 0.15 g/cm 3) density. The intensity and direction of silica transfer substantially depended on temperature, temperature gradient, density and the alkalinity of the solutions, as well as on the fluoride ion concentration in acidic solutions. Impurity elements, except for Ge, were low (∼ 0.001%). The results obtained in these experiments can provide an explanation for the growth peculiarities of β-quartz crystals in miarole pegmatites and gas cavities of volcanic rocks.