Liquid Scintillator Solvent Research Articles

Tuning the decay time of liquid scintillators

The choice of an appropriate viscosity of a liquid scintillator solvent can lead to the fine tuning of its decay time. We present herein the photophysical and scintillation properties of liquid scintillators containing pyrene and 9,10-diphenylanthracene as the primary and secondary fluorophores, respectively, being dissolved either in toluene, diisopropylnaphthalene or mixtures of these two solvents. By modifying the dynamic viscosity, the photoluminescence decay time can be easily chosen in the range 40–120 ns. For all liquid scintillators the light yields were satisfying, and the scintillation decays were slightly different, ranging from 36 up to 125 ns.

Light attenuation length of high quality linear alkyl benzene as liquid scintillator solvent for the JUNO experiment

The Jiangmen Underground Neutrino Observatory (JUNO) is a multipurpose neutrino experiment with a 20-kiloton liquid scintillator detector designed to determine the neutrino mass hierarchy, and to precisely measure the neutrino oscillation parameters. Linear alkyl benzene (LAB) will be used as the solvent for the liquid scintillation system in the central detector of JUNO. For this purpose, we have prepared LAB samples and measured their light attenuation lengths. An attenuation length of 25.8 m, comparable to the diameter of the JUNO detector, was observed for one sample. The procedure for preparing the samples and the results of the measurements are reported.

A theoretical study on geometry, bonding nature, and stability of several anhydrous and hydrated In(III), Gd(III) and Yb(III) complexes in liquid scintillator solvents

The structure, bonding nature, and stability properties of several anhydrous and hydrate In-, Gd-, and Yb-carboxylates (M-CBX) and β-diketonates (M-BDK) used in neutrino liquid scintillator detectors have been investigated in two liquid scintillator (LS) solvents by density functional theory (DFT). Bonding energy and quantum theory of atoms in molecule (QTAIM) analyses reveal that the order of stability of these complexes is M-acetylacetone (M-ACAC)>M-tetramethyl-heptane-3,5-dionate (M-THD)>M-ethyl-hexanoate (M-EHA)≈M-methyl-valerate (M-MVA)≈M-tri-methyl-hexanate (M-TMHA) in LS solvent, while for the same ligand, binding energies increase in the order of Gd-L<Yb-L<In-L, which is inversely related to the metal ionic size. Therefore, In(ACAC)3 with better stability property might be more suitable for neutrino experiments than other metal-complexes. QTAIM study also shows that although electrostatic interaction dominates the metal-ligand bonding in In-, Gd-, and Yb-CBX complexes, some slight covalent character can be found in the In-CBX complexes. Calculated changes of Gibbs free energy (ΔG) of the solvent extraction reactions reveal that the products of the solvent extraction are mainly hydrated compounds. Therefore, more sophisticate method should be used to synthesize anhydrous complexes, which are supposed to have better solubility in LS solvent. The calculated ΔG values of potential dehydration reactions show that only limited types of hydrate Gd- and Yb-complexes can dehydrate in the gas phase at room temperature, while the situation is different in LS solvent. It is expected that our calculations can provide some useful information for future neutrino detection, radiochemical composition study of earth, and some other applications involving neutron capture.

Comparative theoretical study of the structures and stabilities of four typical gadolinium carboxylates in different scintillator solvents.

The structural properties and stabilities of four typical gadolinium carboxylates (Gd-CBX) in toluene, linear alkyl benzene (LAB), and phenyl xylyl ethane (PXE) solvents were theoretically studied using density functional theory (DFT/B3LYP with the basis sets 6-311G(d) and MWB54) and the polarizable continuum model (PCM). The average Gd-ligand interaction energies (E int, corrected for dispersion) and the values of the energy gap between the highest occupied molecular orbital and lowest unoccupied molecular orbital (ΔHL) for the gadolinium complexes were calculated to compare the relative stabilities of the four Gd-CBX molecules in the three liquid scintillator solvents. According to the calculations, the values of E int and ΔHL for Gd-CBX in LAB are larger than the corresponding values in PXE and toluene. Gd-CBX may therefore be more compatible with LAB than with PXE and toluene. It was also found that, in the three scintillator solvents, the stabilities of the four Gd-CBX molecules increase in the order Gd-2EHA < Gd-2MVA < Gd-pivalate < Gd-TMHA.

Characterizing a fast-response, low-afterglow liquid scintillator for neutron time-of-flight diagnostics in fast ignition experiments.

The characteristics of oxygen-enriched liquid scintillators with very low afterglow are investigated and optimized for application to a single-hit neutron spectrometer for fast ignition experiments. It is found that 1,2,4-trimethylbenzene has better characteristics as a liquid scintillator solvent than the conventional solvent, p-xylene. In addition, a benzophenon-doped BBQ liquid scintillator is shown to demonstrate very rapid time response, and therefore has potential for further use in neutron diagnostics with fast time resolution.

Theoretical study of structure and stability of small gadolinium carboxylate complexes in liquid scintillator solvents.

The structural properties of three small gadolinium carboxylate complexes in three liquid scintillator solvents (pseudocumene, linear alkylbenzene, and phenyl xylylethane) were theoretically investigated using density functional theory (B3LYP/LC-RECP) and polarizable continuum model (PCM). The average interaction energy between gadolinium atom and carboxylate ligand (E(int)) and the energy difference of the highest singly occupied molecular orbital and lowest unoccupied molecular orbital (Δ(SL)) were calculated to evaluate and compare the relative stability of these complexes in solvents. The calculation results show that the larger (with a longer alkyl chain) gadolinium carboxylate complex has greater stability than the smaller one, while these gadolinium carboxylates in linear alkylbenzene were found to have greater stability than those in the other two solvents.

Timing properties and pulse shape discrimination of LAB-based liquid scintillator

Linear Alkyl Benzene (LAB) is a promising liquid scintillator solvent in neutrino experiments because it has many appealing properties. The timing properties of LAB-based liquid scintillator have been studied through ultraviolet and ionization excitation in this study. The decay time of LAB, PPO and bis-MSB is found to be 48.6 ns, 1.55 ns and 1.5 ns, respectively. A model can describe the absorption and re-emission process between PPO and bis-MSB perfectly. The energy transfer time between LAB and PPO with different concentrations can be obtained via another model. We also show that the LAB-based liquid scintillator has good (n, γ) and (α, γ) discrimination power.

Theoretical study of UV-Vis light absorption of some impurities in alkylbenzene type liquid scintillator solvents

Special chemical impurities may greatly decrease the light transparency of liquid scintillator (LS) solvents in the wavelength region 350–450 nm, which is of great importance to the neutrino experiments. The absorption wavelengths and oscillator strengths of two types of impurities (thiocarbonyls and nitrobenzene derivatives) and some similar compounds were calculated using TD-DFT in three scintillator solvents (toluene, pseudocumene, and linear alkyl benzene). Influences of these impurity molecules on LS solvent’s optical transmission in 350–450 nm were analyzed and compared with each other.

Measurement of the refractive index of the LAB-based liquid scintillator and acrylic at RENO

In this paper, we describe the first measurement of the refractive index of the linear alkyl benzene (LAB)-based liquid scintillator and acrylic used at the Reactor Experiment for Neutrino Oscillation (RENO). The refractive index of a material is an important optical property and the prism spectrometer is the most common device for measuring the refractive index. Using the minimum deviation technique, which requires an exact measurement of the apex angle, we determined the refractive indices at six different wavelengths and then fitted them. We also compared the refractive index of the LAB-based liquid scintillator with the refractive indices of other liquid scintillator solvents commonly used in reactor neutrino experiments.

生分解性液体シンチレータの化学成分

Chemical constituents of the commercially available "biodegradable" liquid scintillator solvents were elucidated by means of GC/MS analysis etc., as either the mixture of monosubstituted benzenes with the alkyl chain of carbon 10 to 13, or 1-(3,4-dimethylphenyl)-1-phenyl-ethane.

The affinity of [ 3H]quinuclidinyl benzilate and some other radioligands for glass microfiber and cellulose filters in some common liquid scintillation solvents

The optimum conditions for measuring radioactivity in the filtration assay of muscarinic cholinoceptors with tritiated quinuclidinyl benzilate are to use Whatman GF B filters and to add a simple toluene scintillant to them while they are still damp. Practically all the radioactive material is then slowly extracted into the scintillant and high counting efficiencies are obtained after 24 h. Dried filters, or dry filters in control experiments in the absence of receptor, adsorb much of the radioactivity with a 30% reduction in counting efficiency. Other scintillants were able to extract the radioactive material from dry filters, but were generally not preferable to toluene. The GF B filters performed better than other glass microfiber and cellulose filters in terms of retention of receptor-bound ligand, rapid filtration rates, and low filter blanks. Toluene is unsuitable as a scintillant with GF B filters for some other radioligands examined.

Progress in the development of water-miscible non-hazardous liquid scintillation solvents: T.F. Kellogg, Department of Biochemistry, Mississippi State University, Mississippi State, MS 39762, USA

Progress in the development of water-miscible non-hazardous liquid scintillation solvents: T.F. Kellogg, Department of Biochemistry, Mississippi State University, Mississippi State, MS 39762, USA

Noble gas solubility measurement in liquid scintillator solvents

A method based on the use of gaseous radioactive tracers was devised for the measurement of gas solubilities in liquids. With this method solubilities of krypton and xenon in liquid scintillator solvents were examined at 15–40°C. Solubility data obtained show that the amount of krypton which can be introduced into liquid scintillators is biggest in toluene-based liquid scintillators and decreases in the order of methanol>dioxan>ethyleneglycol. For xenon the solubility decreases in the order of dioxan>methanol>ethyleneglycol. Independent of the kind of solvent the solubility both of krypton and xenon was found to decrease progressively with increasing temperature.

Microcombustion Method for the Determination of Carbon‐14‐Labeled Pesticide Residues in Soil

AbstractA dry combustion procedure commonly used for total carbon analysis was modified and used to determine the concentration of 14C‐labeled pesticides in soil. Modifications included replacement of the Ascarite®3 CO2 trap with a solution of an organic base compatible with liquid scintillation solvents, and minor carrier gas flow changes. Recovery of three pesticides from four soils ranged from 83 to 99% and averaged 94%.

Rapid procedure for liquid scintillation counting of animal tissues using a nitric acid digestion procedure and a dioxane-based scintillator

The development of a liquid scintillator solvent that can hold up to 4.5 ml of H 2O per 10 ml of solvent is described. This solvent consists of 1% butyl-PBD and 6% naphthalene in dioxane. A nitric acid digestion system for use in conjunction with this solvent is applicable to a wide range of animal tissues, is relatively rapid, calls for minimum modification from tissue to tissue, and generally yields colorless counting solutions without need for special decolorization techniques. It must be emphasized that this system was designed for ambient temperature operation and is unusable in refrigerated spectrometers.

Sensitivity enhancement for low level activities by complete syntheses of liquid scintillation solvents

Abstract In order to take full advantage of liquid scintillation measurements for low level radioactivity, a large part of the solvent should be synthesized from the material of the sample to be counted. This procedure has been applied to three natural radioactivity dating a large part of the solvent should be synthesized from the material of the sample to be counted. This procedure has been applied to three natural radioactivity dating methods. For carbon-14, the most sensitive and practical of the various liquids investigated is benzene. The compound, in addition to being a good liquid scintillation solvent, contains 92% carbon. The work on the synthesis of benzene for carbon-14 dating is now complete with yields approaching 100% and less than eight hours total chemical preparation time. Furthermore, the isotope effect for carbon has been proven to be small and reproducible to better than 1/2%. A synthesis of benzene for low level tritium measurements has also been developed. Benzene contains 8 % hydrog...

Quenching of the scintillation process in plastics by oxygen

Spectral evidence has been obtained to indicate that fluorescence quenching by air in polyvinyltoluene scintillators is probably produced by oxidation products containing the carbonyl group. The evidence for the chemical nature of the quencher has been obtained indirectly by demonstrating that analogous carbonyl compounds cause a similar shift in the fluorescence spectra and produce quenching when incorporated in polyvinyltoluence scintillators. The lower order of magnitude of quenching by air in liquid scintillation solvents at room temperature is due in part to the absence of oxidation products.

N,N,N, trimethylborazine as a liquid scintillator solvent for thermal neutron detection

The compound, N,N,N, trimethylborazine, is shown to be an efficient solvent for the liquid scintillation process. Additionally, the natural boron-10 content of the compound enables the system to be used for the detection of thermal neutrons according to the reaction B 10(n,α)Li 7. In this respect, the system is unuual in that the compound serves as both the neutron target and the scintillator solvent. When compared with conventional boron-loaded scintillators, the borazine system exhibits a number of significant advantages. This paper describes the various characteristics and properties of the new scintillator recipe.

Determination of tritium in whole cells and cellular fractions of Bacillus megaterium using liquid scintillation techniques

Noncombustive methods for the determination of tritium in Bacillus megaterium using liquid scintillation techniques have been developed. The key step involves the dissolution of the cell wall with lysozyme. A fractionation scheme that separates B. megaterium into six soluble fractions, all of which are suitable for incorporation into liquid scintillation solvents, has been developed. Tritiated leucine incorporation was directly proportional to bacterial growth and incorporation was principally into the protein fraction. Tritiated thymidine was not a stable precursor, being converted to thymine, but a portion was incorporated into the nucleic acid fraction. Tritiated diaminopimelic acid was incorporated into the cell wall fraction. It is suggested that these methods have equal applicability for other lysozyme-sensitive organisms, not only for the determination of tritium, but also for other radioisotopes. It is further suggested that, as new cell wall depolymerizing enzymes become available, the methods may be of general applicability.

Practical aspects of internal-sample liquid scintillation counting

The appearance of commercially available equipment has made it practicable for chemists and biochemists to consider the use of liquid-scintillation counting for the assay of radioactive samples. The method offers excellent sensitivity for weak beta-emitting isotopes, including tritium. This is because of its 4π geometry for samples as large as several grams. The disadvantages of the technique are discussed in detail. The equipment is several times as expensive as most other counting apparatus. It is more complex to understand and to maintain. The method involves certain prerequisites of the sample material. These include adequate solubility in the rather limited group of alkyl benzene and polyther solvents that suffice as liquid-scintillation solvents, absence of color, and freedom from quenching action upon the scintillation phenomenon. Toluene remains the solvent of choice, but its usefulness has been broadened through the use of 2-ethylhexanoic acid and a quarternary ammonium base which form toluene-soluble salts with many cations and anions. The applicability of liquid-scintillation counting to any counting problems should be evaluated specifically. In general, however, some of the applications in which it appears to be the method of choice include nearly all tritium counting, assaying C 14 and S 35 samples of low specific activity, any type of counting where speed and ease of sample preparation are necessary, and the counting of volatile compounds.