scholarly journals Fluorescence of pyrene-doped polystyrene films from room temperature down to 4 K for wavelength-shifting applications

2021 ◽  
Vol 16 (12) ◽  
pp. P12029
Author(s):  
H. Benmansour ◽  
E. Ellingwood ◽  
Q. Hars ◽  
P.C.F. Di Stefano ◽  
D. Gallacher ◽  
...  
Keyword(s):  
Room Temperature ◽  
Light Yield ◽  
Liquid Argon ◽  
Strongly Correlated ◽  
Particle Detectors ◽  
Time Constants ◽  
Ultraviolet Excitation ◽  
Emission Lifetime ◽  
Fluorescence Light ◽  
The Common

Abstract In liquid argon-based particle detectors, slow wavelength shifters (WLSs) could be used alongside the common, nanosecond scale, WLS tetraphenyl butadiene (TPB) for background mitigation purposes. At room temperature, pyrene has a moderate fluorescence light yield (LY) and a time constant of the order of hundreds of nanoseconds. In this work, four pyrene-doped polystyrene films with various purities and concentrations were characterized in terms of LY and decay time constants in a range of temperature between 4 K and 300 K under ultraviolet excitation. These films were found to have a LY between 35 and 50% of that of evaporated TPB. All light yields increase when cooling down, while the decays slow down. At room temperature, we observed that pyrene purity is strongly correlated with emission lifetime: highest obtainable purity samples were dominated by decays with emission time constants of ∼ 250–280 ns, and lower purity samples were dominated by an ∼ 80 ns component. One sample was investigated further to better understand the monomer and excimer emissions of pyrene. The excimer-over-monomer intensity ratio decreases when the temperature goes down, with the monomer emission dominating below ∼ 87 K.

scholarly journals Direct comparison of PEN and TPB wavelength shifters in a liquid argon detector

2021 ◽  
Vol 81 (12) ◽  
Author(s):  
M. G. Boulay ◽  
V. Camillo ◽  
N. Canci ◽  
S. Choudhary ◽  
L. Consiglio ◽  
...  
Keyword(s):  
Large Scale ◽  
Light Yield ◽  
Target Material ◽  
Liquid Argon ◽  
The Other ◽  
Polyethylene Naphthalate ◽  
Scintillation Light ◽  
Particle Detectors ◽  
Wavelength Shifter ◽  
Efficient Detection

AbstractA large number of particle detectors employ liquid argon as their target material owing to its high scintillation yield and its ability to drift ionization charge over large distances. Scintillation light from argon is peaked at 128 nm and a wavelength shifter is required for its efficient detection. In this work, we directly compare the light yield achieved in two identical liquid argon chambers, one of which is equipped with polyethylene naphthalate (PEN) and the other with tetraphenyl butadiene (TPB) wavelength shifter. Both chambers are lined with enhanced specular reflectors and instrumented with SiPMs with a coverage fraction of approximately 1%, which represents a geometry comparable to the future large scale detectors. We measured the light yield of the PEN chamber to be  39.4$$\,\pm \,$$ ± 0.4(stat)$$\,\pm \,$$ ± 1.9(syst)% of the yield of the TPB chamber. Using a Monte Carlo simulation this result is used to extract the wavelength shifting efficiency of PEN relative to TPB equal to 47.2$$\,\pm \,$$ ± 5.7%. This result paves the way for the use of easily available PEN foils as a wavelength shifter, which can substantially simplify the construction of future liquid argon detectors.

scholarly journals Scintillation light increase of carbontetrafluoride gas at low temperature

2021 ◽  
Vol 16 (12) ◽  
pp. P12033
Author(s):  
K. Mizukoshi ◽  
T. Maeda ◽  
Y. Nakano ◽  
S. Higashino ◽  
K. Miuchi
Keyword(s):  
Low Temperature ◽  
Particle Physics ◽  
Spin Structure ◽  
Room Temperature ◽  
Light Yield ◽  
Weakly Interacting Massive Particles ◽  
Particle Detection ◽  
Scintillation Light ◽  
Dark Matter Search ◽  
Particle Detectors

Abstract Scintillation detector is widely used for the particle detection in the field of particle physics. Particle detectors containing fluorine-19 (19F) are known to have advantages for Weakly Interacting Massive Particles (WIMPs) dark matter search, especially for spin-dependent interactions with WIMPs due to its spin structure. In this study, the scintillation properties of carbontetrafluoride (CF4) gas at low temperature were evaluated because its temperature dependence of light yield has not been measured. We evaluated the light yield by cooling the gas from room temperature (300 K) to 263 K. As a result, the light yield of CF4 was found to increase by (41.0 ± 4.0stat. ± 6.6syst.)% and the energy resolution was also found to improve at low temperature.

Characterization and catalytic properties of a saponite clay modified by acid activation

Clay Minerals ◽  
1997 ◽  
Vol 32 (4) ◽  
pp. 633-643 ◽  
Author(s):  
F. Kooli ◽  
W. Jones
Keyword(s):  
Infrared Spectroscopy ◽  
Room Temperature ◽  
Textural Properties ◽  
Acid Sites ◽  
Single Type ◽  
Activation Process ◽  
Acid Activation ◽  
Strongly Correlated ◽  
Lewis Site ◽  
Adsorbed Pyridine

AbstractA natural saponite was acid activated at room temperature or 90°C with different acid/clay ratios and the products were characterized by powder X-ray diffraction, infrared spectroscopy and thermogravimetry. The leaching of Mg from the octahedral sheets is enhanced by an increase in the acid/clay ratio and by an increase in temperature of activation. Textural properties are reported, and it appears that they are strongly correlated to the presence of a noncrystalline silica phase which is formed during the acid activation process. The desorption of cyclohexylamine indicates that for samples activated at 90°C the number of acid sites in the acidactivated saponites decreases following severe acid treatment. Infrared spectroscopy of adsorbed pyridine on samples after calcination at 500°C suggests that acid activation at 90°C produces a single type of Bronsted site but two types of Lewis sites whereas activation at room temperature results in only one type of Lewis site in addition to a Brønsted site. The two Lewis sites are suggested to originate from residual Al in the clay structure and to AI exsolved from the layers during activation. The dehydration of pentan-1-ol has been used as a further probe to measure acidity by monitoring the degree of conversion and selectivity for the different samples.

Molecule-Based Magnets—An Overview

MRS Bulletin ◽  
2000 ◽  
Vol 25 (11) ◽  
pp. 21-30 ◽  
Author(s):  
Joel S. Miller ◽  
Arthur J. Epstein
Keyword(s):  
Low Temperature ◽  
Vapor Deposition ◽  
Room Temperature ◽  
Chemical Vapor ◽  
Magnetic Ordering ◽  
Low Density ◽  
Materials Properties ◽  
The Common ◽  
New Processing ◽  
Very High

Molecule-based magnets are a broad, emerging class of magnetic materials that expand the materials properties typically associated with magnets to include low density, transparency, electrical insulation, and low-temperature fabrication, as well as combine magnetic ordering with other properties such as photoresponsiveness. Essentially all of the common magnetic phenomena associated with conventional transition-metal and rare-earth-based magnets can be found in molecule-based magnets. Although discovered less than two decades ago, magnets with ordering temperatures exceeding room temperature, very high (∼27.0 kOe or 2.16 MA/m) and very low (several Oe or less) coercivities, and substantial remanent and saturation magnetizations have been achieved. In addition, exotic phenomena including photoresponsiveness have been reported. The advent of molecule-based magnets offers new processing opportunities. For example, thin-film magnets can be prepared by means of low-temperature chemical vapor deposition and electrodeposition methods.

Szintillationslichtausbeuten anorganischer und organischer Kristalle für energiereiche Deuteronen, α-Teilchen und Elektronen

1966 ◽  
Vol 21 (7) ◽  
pp. 1075-1080
Author(s):  
W. Schött ◽  
A. Flammersfeld
Keyword(s):  
Electronic Circuit ◽  
Pulse Height ◽  
Light Yield ◽  
Organic Crystals ◽  
Height Ratio ◽  
Scintillation Light ◽  
Time Constants ◽  
Inverse Effect ◽  
Short Time ◽  
Α Particles

The scintillation light yield S of three anorganic [NaJ (Tl), KJ (Tl), CsJ (Tl)], of two organic (p-terphenyl, anthracene) crystals, and of plastic NE 102 by bombardement with deuterons in the energy range from 10,0—27,5 MeV, α-particles from 8,0—55,0 MeV, and electrons has been measured. The time constants of the electronic circuit have been chosen to τ1 = 0,5 sec and τ2 = 2,0 µsec. The pulse-height ratios SD/Sβ and Sα/Sβ are slightly different for the two time constants. The anorganic crystals have a higher pulse-height ratio for the short time constant, whereas the organic crystals and plastic show the inverse effect.

scholarly journals Artificial two-dimensional polar metal by charge transfer to a ferroelectric insulator

2019 ◽  
Vol 2 (1) ◽  
Author(s):  
W. X. Zhou ◽  
H. J. Wu ◽  
J. Zhou ◽  
S. W. Zeng ◽  
C. J. Li ◽  
...  
Keyword(s):  
Carrier Density ◽  
Room Temperature ◽  
Electronic Devices ◽  
General Concept ◽  
Polar Phase ◽  
Strongly Correlated ◽  
Two Dimensional ◽  
Single System ◽  
Oxide Interfaces ◽  
Mobile Carrier

Abstract Integrating multiple properties in a single system is crucial for the continuous developments in electronic devices. However, some physical properties are mutually exclusive in nature. Here, we report the coexistence of two seemingly mutually exclusive properties-polarity and two-dimensional conductivity-in ferroelectric Ba0.2Sr0.8TiO3 thin films at the LaAlO3/Ba0.2Sr0.8TiO3 interface at room temperature. The polarity of a ∼3.2 nm Ba0.2Sr0.8TiO3 thin film is preserved with a two-dimensional mobile carrier density of ∼0.05 electron per unit cell. We show that the electronic reconstruction resulting from the competition between the built-in electric field of LaAlO3 and the polarization of Ba0.2Sr0.8TiO3 is responsible for this unusual two-dimensional conducting polar phase. The general concept of exploiting mutually exclusive properties at oxide interfaces via electronic reconstruction may be applicable to other strongly-correlated oxide interfaces, thus opening windows to new functional nanoscale materials for applications in novel nanoelectronics.

Growth and Heat Resistance of Salmonella enteritidisin Refrigerated and Abused Eggs

1993 ◽  
Vol 56 (11) ◽  
pp. 927-931 ◽  
Author(s):  
A. MAHDI SAEED ◽  
CAROL W. KOONS
Keyword(s):  
Heat Resistance ◽  
Salmonella Enteritidis ◽  
Room Temperature ◽  
Storage Temperature ◽  
Phase 1 ◽  
Shell Eggs ◽  
Growth Inhibitory ◽  
Significant Barrier ◽  
The Common ◽  
Salmonella Survival

The effect of storage temperature on the growth and heat resistance of Salmonella enteritidis (SE) in eggs artificially inoculated with 20 CFU per egg has been investigated. SE organisms grew to a stationary phase (1 × 109 CFU/ml of egg) within 2–3 d after storing the eggs at room temperature (23°C), while minimal or no growth occurred in similarly inoculated eggs that were refrigerated at 4°C. None of the common methods of egg cooking was found totally effective in eliminating SE organisms in massively contaminated eggs. SE organisms survived in significantly higher proportions of the eggs that were stored at 23°C than in refrigerated eggs after cooking by different methods (P < 0.05). Higher rates of Salmonella survival after cooking were detected in the eggs that were stored at room temperature for 5 d or longer than in eggs stored for shorter time (P < 0.05). Data from this study indicated: i) storage abuse of eggs can be a major factor in increasing the prevalence of eggborne SE infections by increasing the infectious load and heat resistance of the SE organisms in the contaminated eggs, and ii) that breaking and pooling of eggs immediately before cooking can minimize the substantial multiplication of SE organisms from slightly contaminated eggs. Refrigeration, therefore, can be a significant barrier against SE infections through its growth inhibitory and heat resistance-reducing effects on the SE organisms in contaminated shell eggs as well as in large volumes of liquid eggs intended for pasteurization.

Molecular Dynamics Simulation of Homogeneous and Heterogeneous Thermal Bubble Nucleation

2011 ◽  
Author(s):  
Min Chen ◽  
Yunfei Chen ◽  
Juekuan Yang ◽  
Yandong Gao ◽  
Deyu Li
Keyword(s):  
Molecular Dynamics ◽  
Heterogeneous Systems ◽  
Liquid Argon ◽  
Bubble Nucleation ◽  
Dynamics Simulation ◽  
Nucleation Temperature ◽  
The Common ◽  
Solid Walls ◽  
Common Understanding ◽  
Superheat Limit

Thermal bubble nucleation was studied using molecular dynamics for both homogeneous and heterogeneous systems using isothermal-isobaric (NPT) and isothermal-isostress (NPzzT) ensembles. Simulation results indicate that homogeneous thermal bubble nucleation is induced from cavities occurring spontaneously in the liquid when the temperature exceeds the superheat limit. In contrast to published results using NVE and NVT ensembles, no stable nanoscale bubble exists in NPT ensembles, but instead, the whole system changes into vapor phase. For a heterogeneous system composed of a nanochannel with an initial distance of 3.49 nm between the two solid plates, it is found that if the liquid-solid interaction is equal to or stronger than that between liquid argon atoms, the bubble nucleation temperature of the confined liquid argon can be higher than the corresponding homogeneous nucleation temperature, because of the more ordered arrangement of atoms within two solid walls nanometers apart. This observation is in contradiction to the common understanding that homogeneous bubble nucleation temperature sets an upper limit for thermal phase change under a given pressure. Compared to the system where the liquid-solid interaction is the same as that between liquid argon atoms, the system with reduced liquid-solid interaction possesses a significantly reduced bubble nucleation temperature, while the system with enhanced liquid-solid interaction only has a marginally increased bubble nucleation temperature.

Surface oxygen vacancies on Co3O4 mediated catalytic formaldehyde oxidation at room temperature

2016 ◽  
Vol 6 (11) ◽  
pp. 3845-3853 ◽  
Author(s):  
Zhong Wang ◽  
Wenzhong Wang ◽  
Ling Zhang ◽  
Dong Jiang
Keyword(s):  
Catalytic Oxidation ◽  
Room Temperature ◽  
Oxygen Vacancies ◽  
Essential Role ◽  
Surface Oxygen ◽  
Oxidation Reactions ◽  
Major Activity ◽  
Formaldehyde Oxidation ◽  
The Common

This study reveals the essential role played by surface oxygen vacancies in catalytic oxidation reactions, and complements the common viewpoint that Co3+ is the major activity species in Co3O4-based systems.

Electroluminescence from GalnN Quantum Wells Grown on Non-(0001) Facets of Selectively Grown GaN Stripes

2004 ◽  
Vol 831 ◽  
Author(s):  
Barbara Neubert ◽  
Frank Habel ◽  
Peter Bruckner ◽  
Ferdinand Scholz ◽  
Till Riemann ◽  
...  
Keyword(s):  
Low Temperature ◽  
Electric Field ◽  
Quantum Wells ◽  
Room Temperature ◽  
Light Emission ◽  
Low Pressure ◽  
Lower Efficiency ◽  
Strong Light ◽  
The Common ◽  
Piezo Electric

ABSTRACTNon (0001) GalnN QWs have been grown by low pressure MOVPE on side facets of triangular shaped selectively grown GaN stripes. By analysing low temperature photo- and cathodoluminescence and room temperature electroluminescence, we found strong indications, that both, In and Mg are less efficiently incorporated on these side facets compared to the common (0001) plane with even lower efficiency for stripes running along (1–100) compared to (11–20). Nevertheless, we observed strong light emission from these quantum wells, supposed to be at least partly caused by the reduced piezo-electric field.

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