Scintillation

About: Scintillation is a research topic. Over the lifetime, 14022 publications have been published within this topic receiving 187694 citations.

Absorption dose measuring apparatus for intensity modulated radio therapy

Abstract: An intensity modulated radio therapy (IMRT) dosimeter measuring a three-dimensional absorption dose distribution in a transparent plastic phantom readily and accurately. In the IMRT dosimeter, radiation beams are directed to a phantom assembly having a scintillation fiber block sandwiched between two blocks of the phantom. As an intensity of light proportional to the radiation beam is emitted from one side of the scintillation fiber block, its profile is measured by an image sensor. Then, the three-dimensional absorption dose distribution is obtained from the light intensity distribution data. By summing the three-dimensional absorption dose distribution data measured with the radiation beam at different angles, an integrated three-dimensional absorption dose distribution in the phantom can be calculated readily and accurately.

Scintillation and spectroscopic properties of Ce3+-doped YAlO3 and Lux(RE)1-xAlO3(RE=Y3+ and Gd3+) scintillators

Abstract: Scintillation properties like photoelectron yield and light yield of Ce3+-doped YAlO3 and mixed Lux(RE)1−xAlO3 (RE=Y3+ and Gd3+) perovskite crystals are presented. The photoelectron yields increase almost linearly with γ-ray energy but a small non-linearity is observed around 40 keV. Scintillation and spectroscopic properties like UV or X-ray excited emission, laser excited emission, excitation and absorption spectra and photo- and scintillation decay of the different crystals are compared. The influence of intrinsic absorption and reflecting tape on the yields are discussed. Selected YAlO3:Ce showed the highest light yield of 25,000 phels/MeV and an energy resolution of 4.5% for 662 keV γ-radiation. The γ-ray linear absorption coefficient increases with Lu content and that of LuAlO3:Ce is almost 10 times higher than that of YAlO3:Ce.

Quenching correction for volumetric scintillation dosimetry of proton beams

Abstract: Volumetric scintillation dosimetry has the potential to provide fast, high-resolution, three-dimensional radiation dosimetry. However, scintillators exhibit a nonlinear response at the high linear energy transfer (LET) values characteristic of proton Bragg peaks. The purpose of this study was to develop a quenching correction method for volumetric scintillation dosimetry of proton beams. Scintillation light from a miniature liquid scintillator detector was measured along the central axis of a 161.6 MeV proton pencil beam. Three-dimensional dose and LET distributions were calculated for 85.6, 100.9, 144.9 and 161.6 MeV beams using a validated Monte Carlo model. LET values were also calculated using an analytical formula. A least-squares fit to the data established the empirical parameters of a quenching correction model. The light distribution in a tank of liquid scintillator was measured with a CCD camera at all four beam energies. The quenching model and LET data were used to correct the measured light distribution. The calculated and measured Bragg peak heights agreed within ±3% for all energies except 85.6 MeV, where the agreement was within ±10%. The quality of the quenching correction was poorer for sharp low-energy Bragg peaks because of blurring and detector size effects. The corrections performed using analytical LET values resulted in doses within 1% of those obtained using Monte Carlo LET values. The proposed method can correct for quenching with sufficient accuracy for dosimetric purposes. The required LET values may be computed effectively using Monte Carlo or analytical methods. Future detectors should improve blurring correction methods and optimize the pixel size to improve accuracy for low-energy Bragg peaks.

Pulsar scintillations from corrugated reconnection sheets in the interstellar medium

Abstract: We show that surface waves along interstellar current sheets closely aligned with the line of sight lead to pulsar scintillation properties consistent with those observed. This mechanism naturally produces the length and density scales of the ISM scattering lenses that are required to explain the magnitude and dynamical spectrum of the scintillations. In this picture, the parts of warm ionized interstellar medium that are responsible for the scintillations are relatively quiescent, with scintillation and scattering resulting from weak waves propagating along magnetic domain boundary current sheets, which are both expected from helicity conservation and have been observed in numerical simulations. The model statistically predicts the spacing and amplitudes of inverted parabolic arcs seen in Fourier-transformed dynamical spectra of strongly scintillating pulsars with only 3 parameters. Multi-frequency, multi-epoch low frequency VLBI observations can quantitatively test this picture. If successful, in addition to mapping the ISM, this may open the door to precise nanoarcsecond pulsar astrometry, distance measurements, and emission studies using these 10AU interferometers in the sky.