121554245
Coumarins as wavelength shifters in polystyrene
Abstract A series of commercially available coumarins was tested as wavelength shifters in polystyrene for a tile/fiber calorimeter application. The objective was to find a compound that when incorporated in a polystyrene matrix absorbed in the 400–450 nm wavelength range, fluoresced in the green region of the visible spectrum ( λ em = 450−550 nm), and exhibited both short decay time and high quantum yield. Transmittance, fluorescence, and decay time determinations were performed in order to characterize each coumarin in polystyrene. Two coumarins (C510 and C515) were found to have faster decay times (∼8 ns vs. 12 ns) and superior light output (100–120%) compared to the commonly-used green wavelength shifter, K-27.
135661547
Summary of the radiation damage studies of the SDC dopants in polystyrene
Approximately 80 commercially available fluorescent organic compounds were studied as dopants in a polystyrene matrix for possible use in wavelength shifting (WLS) fibers. The goal was to find a new green- emitting WLS fiber which would outperform in light yield and decay time the currently available fiber doped with K-27. Therefore the fluorescent compounds of interest should exhibit the following spectroscopic characteristics in polystyrene: {lambda}{sub abs} = 400--450 nm,{lambda}{sub em} = 450--550 nm, {tau} = 3--7 ns and quantum efficiency of minimum 0.7. Polystyrene samples doped with different fluorescent compounds were prepared and characterized. Of all the compounds tested, only a series of coumarins exhibited the spectroscopic characteristics of interest. Radiation damage studies had to be performed on these samples in order to condusively determine if they were better candidates than K-27 for green WLS fibers. AU samples except those showing opacity or deep coloration were irradiated. They were, however, separated in two sets. Radiation damage set No. 20 was mainly formed by the coumarin derivatives. Radiation damage set No. 22 was based on the remaining samples. The irradiations were performed at the Phoenix Memorial Laboratory using a {sup 60}Co source. Both sets were exposed to a total dose ofmore » 10 Mrad in air, at a dose rate of 1.8 Mrad/h. Transmittance measurements were recorded before and after irradiation, and after annealing. After irradiation, the samples were annealed in oxygen to accelerate the recovery process.« less
55019383
Gamma-irradiation of coumarins in a polystyrene matrix
Abstract Polystyrene samples doped with commercially available coumarin derivatives were prepared and tested as wavelength shifters for plastic scintillation applications. Radiation damage studies were performed utilizing a 60 Co source. Transmittance and light yield measurements were recorded before and after irradiation (100 kGy), and after annealing of the samples. All samples experienced losses in transmittance and light yield as a result of radiation-induced damage to the polymer and in some cases, the dopant. None of the coumarins examined in this study outperformed the commonly-used green wavelength shifter, K-27, after irradiation.
135204416
Searching for new green wavelength shifters in polystyrene
A series of commercially available fluorescent compounds was tested as wavelength shifters in polystyrene for the tile/fiber SDC calorimeter. The objective was to find a green-fluorescing compound with short decay time (3--7 ns). Transmittance, fluorescence, and decay time measurements were performed in order to characterize each compound in polystyrene. These samples were also studies for radiation-induced damage.
139458138
Final results from the SDC dopant search for new green wavelength shifting (WLS) fibers. Volume 2
This report contains fluorescent spectral graphs of dopant materials for green wavelength shifting fibers.
121346859
Study of the halo nucleus 6He through the direct nuclear reactions
Differential cross sections for quasi-elastic scattering, breakup reaction as well as 1n- and 2n-transfer reactions induced by 6He at 25 MeV/nucleon from a 9Be target are reported. The experimental data were analysed in the context of the coupled-channel calculations. The internal structure of 6He is discussed and further studies are proposed.
118079649
Cross-section measurement and analysis for the Sm-149 (n, alpha) Nd-146 reaction at 6.0 MeV
We have measured the $^{149}\mathrm{Sm}(n,\ensuremath{\alpha})^{146}\mathrm{Nd}$ cross section at 6.0 MeV to be $0.12\ifmmode\pm\else\textpm\fi{}0.018$ mb. This is the first reported result for this cross section in the MeV region and so should be helpful for constraining nuclear data evaluations (which differ by a factor of 40 for this reaction at this energy) and for testing and improving nuclear models. The experiment was performed at the at the 4.5-MV Van de Graaff accelerator of Peking University. Neutrons were produced via the $^{2}\mathrm{H}(d,n)^{3}\mathrm{He}$ reaction using a deuterium gas target, and absolute neutron flux was determined with a small $^{238}\mathrm{U}$ fission chamber. Alpha particles were detected using a two-section gridded ionization chamber in which two large-area $^{149}\mathrm{Sm}{}_{2}{\mathrm{O}}_{3}$ samples were placed back-to-back so that the cross section and forward/backward ratio were measured for nearly the entire 4$\ensuremath{\pi}$ solid angle. The data were compared to statistical-model predictions using the code talys. Good agreement between the measured and theoretical cross sections could be obtained with a small modification of the $\ensuremath{\alpha}$-optical potential parameters from their default values in talys. However, we were not able to reproduce the measured forward/backward ratio. In addition, using the previously reported $^{147}\mathrm{Sm}(n,\ensuremath{\alpha})^{144}\mathrm{Nd}$ cross section at 6.0 MeV together with our new result, good agreement was found between the measured and predicted cross-section ratio for these two isotopes. Finally, none of the existing evaluated data libraries are in agreement with our new data to within the experimental uncertainties.
53552875
QCD corrections of all structure functions in transverse momentum dependent factorization for Drell-Yan processes
A bstractWe study the one-loop correction in Transverse-Momentum-Dependent(TMD) factorization for Drell-Yan processes at small transverse momentum of the lepton pair. We adopt the so-called subtractive approach, in which one can systematically construct contributions for subtracting long-distance effects represented by diagrams. The perturbative parts are obtained after the subtraction. We find that the perturbative coefficients of all structure functions in TMD factorization at leading twist are the same. The perturbative parts can also be studied with scattering of partons instead of hadrons. In this way, the factorization of many structure functions can only be examined by studying the scattering of multi-parton states, where there are many diagrams. These diagrams have no similarities to those treated in the subtractive approach. As an example, we use existing results of one structure function responsible for Single-Spin-Asymmetry, to show that these diagrams in the scattering of multi-parton states are equivalent to those treated in the subtractive approach after using Ward identity.
119215240
Neutron energy spectrum measurements with a compact liquid scintillation detector on EAST
A neutron detector based on EJ301 liquid scintillator has been employed at EAST to measure the neutron energy spectrum for D-D fusion plasma. The detector was carefully characterized in different quasi-monoenergetic neutron fields generated by a 4.5 MV Van de Graaff accelerator. In recent experimental campaigns, due to the low neutron yield at EAST, a new shielding device was designed and located as close as possible to the tokamak to enhance the count rate of the spectrometer. The fluence of neutrons and ?-rays was measured with the liquid neutron spectrometer and was consistent with 3He proportional counter and NaI(Tl) ?-ray spectrometer measurements. Plasma ion temperature values were deduced from the neutron spectrum in discharges with lower hybrid wave injection and ion cyclotron resonance heating. Scattered neutron spectra were simulated by the Monte Carlo transport Code, and they were well verified by the pulse height measurements at low energies.
120119782
Calculation of half-lives of cluster decay by using proximity potential with a new universal function
Abstract The half-lives of cluster decays are calculated using proximity potential model with a new universal function, and compared to the experimentally measured values and the theoretical ones of liquid drop model. The results of the present calculations show reasonable agreement with the experimental data as well as the half-life calculations of liquid drop model. In the present work, it is certified that proximity potential model with the new universal function can be used successfully to calculate the half-lives of cluster decays for heavy nuclei.