Plastic Scintillator Films Research Articles

Enhanced performance of a pulsed neutron detector by the plastic scintillator with a photonic crystal.

A detector based on the plastic scintillator film with large-area photonic crystals has been designed and demonstrated for measuring pulsed neutron flux. Compared with the reference detector, the neutron sensitivity and the gamma sensitivity of the detector using the scintillator film with photonic crystals were enhanced by more than 20%, which is attributed to the improved light extraction efficiency and the controllable angular profile of scintillation light by the photonic crystal. The application of the photonic crystals is beneficial to the improvement of the signal-to-noise ratio of the detector in the calibration experiment, thus expanding the lower limit of the measurable neutron flux without sacrificing the ratio of the neutron sensitivity to the gamma sensitivity. This research indicates that photonic crystals play an important role in the fields where scintillation photons need to be extracted and collected as many as possible.

A plastic scintillator film for an electron beam-excitation assisted optical microscope

A plastic scintillator film for use in an electron beam excitation-assisted (EXA) optical microscope is characterized. The thin film scatters an incident electron beam weakly and generates high intensity nanoscale luminescence excited by the beam spot. For high spatial resolution and signal to noise, an EXA microscope requires a thin high-efficiency scintillator film. Homogeneous plastic scintillators with thicknesses ranging from 60 to 2800 nm were fabricated on silicon nitride via spin coating. The emission intensity was examined as a function of film thickness and the accelerating voltage of the incident electron beam. The emission wavelength can be tuned by changing scintillator materials in the film matrix. To demonstrate a plastic scintillator film performance with an EXA microscope, time-lapse images of yeast cells were acquired.

A fast responding tritium in air monitor for use in operational areas of heavy water power reactors

A fast responding and sensitive tritium-in-air monitor, suitable for monitoring in heavy water-based nuclear power reactors has been described. The detector is a flowcell of 6.3 ml volume, made of stainless steel body and Teflon window and packed with 600 mg of 5 μm thick dry plastic scintillator films. It is coupled to a matched pair of photomultipliers and measurement is made in the coincidence mode of counting. Tritium counting efficiency for direct passage of sample air through the detector is 65%. The sampling rate is 1 to 10 1/min. For an uncontaminated detector, in the absence of any background activity, the instrument records only 2 counts/min as background which is equivalent to the passage of 8000 Bq/m 3 (0.01 DAC) of tritium in air. Microprocessor based electronic compensation has been provided for gaseous radionuclide and gamma background interference. Trial runs of the monitor in our nuclear power plants have shown that the monitor can function on a continuous basis in presence of large levels of gamma background and gaseous radionuclide interference.

A new model of luminescence production in a very thin plastic scintillator film

A new model of luminescence production in a very thin (less than 100 μg/cm 2) plastic scintillator film is described. This model contains the thickness of the scintillator film and needs only one parameter to fit to the experimental data. Applications of this model are presented for the response of heavy ions as a function of the energy and for the double-valuedness of the luminescence production on the stopping power of the 16O ion. The calculated results show good agreement with the experiments reported by other authors. This model is useful for heavy ions with low energy.

Response of thin NE102A scintillator films to fission fragments

The pulse height response of NE102A plastic scintillator films to fragment ions from 252Cf spontaneous fission has been investigated as a function of fragment time-of-flight and film thickness t in the range 1–15 μm. For velocities close to the two peaks in the fragment velocity spectrum and for films of either t ≳ 9 μm or t ≲ 3 μm, an approximately linear relationship between response and fragment velocity is found. For films of thickness 3–6 μm or for fragments from symmetric or highly asymmetric fission. deviations from the linear dependence are observed. The response increases rapidly with film thickness in the range t = 3–6 μm and saturates at t ≳ 9 μm for both light and heavy fragments. The possible role of surface effects in these phenomena is discussed.

An on-line tritium-in-water monitor

The paper describes the development and operation of a continuous on-line tritium-in-water monitor for the detection of heavy water leaks into the secondary coolant light water of a heavy water power reactor. The heart of the instrument is its plastic scintillator sponge detector, made from 5 μm thick plastic scintillator films. The sponge weighs only about 1 g and is in the form of disc of 48 mm diameter and 8 mm thickness. The total surface area of the films is about 3000 cm 2. In the coincidence mode of counting, the detector gives 1000 cps for the passage of 3.7 × 10 4 Bq/cm 3 (1 μCi/cm 3) of tritiated water. The background in 6 cm thick lead shielding in the laboratory is 0.2 cps, and inside the reactor building it is below 1 cps. The monitor presently scans 18 sample lines in sequence for 5 min each and gives a printout for the activity in each line.

Passage of fission fragments through thin film plastic scintillators

The slowing down of fission fragments from the spontaneous fission of 252Cf has been studied in the self-supporting thin films of plastic scintillator NE 102A, using a surface barrier detector. The measured residual energies and hence the energy losses of the mean light and heavy fragments after passing through the thin films of thickness ranging from ∼-100 to 1200 μg/cm 2 of NE 102A are reported. These measurements were carried down to 20.0 MeV and ∼- 14.0 MeV for light and heavy fragments respectively. The shape spectrum parameters from the slowed spectra are determined. The measured energy straggling parameters obtained from these spectra show a maximum around 300 μg/cm 2 of NE 102A and the energy bunching effect due to fission fragments is observed in thicker plastic scintillator films (>300 μg/cm 2). The stopping power obtained from these measurements is compared with the theoretical predictions.

Quantitative investigation of scintillator intensification for light and electron microscope radioautography.

Several reports have indicated that scintillators enhance the intensity of radioautographic reactions. If this were the case, the use of scintillators would shorten the exposure time of radioautographs and the production of radioautographs would be accelerated. It was, therefore, decided to examine the effect of scintillators on the intensity of radioautographs in a quantitative manner over uniformly labeled test specimens. Reaction intensities with or without scintillators were compared using Kodak NTB2 emulsion for light microscopy and Ilford L4 and Sakura NR-H2 emulsion for electron microscopy. In addition, the background fog was quantitatively evaluated. No increase in the intensity of the radioautographs was observed under the following conditions: pretreatment of tissue sections with scintillator solutions before emulsion coating and exposure; treatment with scintillator solutions after emulsion coating but before exposure; treatment with scintillator solutions during exposure; contact with a plastic scintillator film throughout exposure. Heightened reaction intensity was obtained only when scintillators were applied during the histological processing of tissues. The impregnation of tissue blocks with PPO (2,5-Diphenyloxazole) and POPOP (1,4-bis-2-(5-phenyloxazolyl)-benzene) during dehydration, infiltration and Epon embedding produced a 20% increase of reaction intensity in light microscope radioautographs using NTB2 emulsion and a 75% increase in electron microscope radioautographs using L4 emulsion.

Discrimination between different ions using thin scintillator films as time-of-flight detectors

A time-of-flight telescope is described using two thin plastic scintillator films as start- and stop-detectors. The separation of different ions with different energies is achieved both by time measurement and by thin film light response. First experiences with the telescope, now installed at the velocity filter behind the UNILAC at GSI, are reported.

A detector for continuous monitoring of low levels of tritiated water activity in presence of high gamma background

Development of a flow cell type of detector for continuous monitoring of low levels of tritiated water activity in presence of high gamma background is being reported. The cell is packed with 50 mm dia. and 6 μm thick plastic scintillator films. The total surface area of the films is 2800 cm 2 and the total weight is 0.880 g. Background of the unshielded detector is 20 counts per minute which is equivalent to a passage of 0.3 nCi/ml of tritiated water. Gamma response of the detector in 6 cm lead shielding is equivalent to the passage of 0.2 nCi/ml of tritiated water for 1 mR/h field.

Energy loss and straggling of alpha particles in thin homogeneous NE-111 scintillator foils

A method for preparing thin homogeneous plastic scintillator films is described. The films were tested by measuring energy loss and straggling of alpha particles. The results are compared with theoretical predictions. In addition, the detection efficiency of the films was determined.

Response of thin film plastic scintillator to fission fragments

Thin plastic scintillator films of different thicknesses are prepared and their characteristics response to fission fragments from 252Cf is studied. It is observed that the peak to valley ratio of fission fragments depends non-linearly upon the thickness of thin films. This ratio for the heavy fragments is larger than that of the light fragments by a factor of 1.5–1.9 for the whole range of thickness investigated. The laminated structure of the films shows slightly higher gain (≈5 %) but the resolution remains practically the same. The energy loss of fission fragments in plastic scintillator (NE 102A) is measured. A simple system for a “start-detector”, employing such a thin film and a photomultiplier, is also described for the time-of-flight experiments.

Identification of fission activity using thin-film detectors

A method to measure the masses of fission fragments from spontaneously fissioning sources using thin plastic-scintillator film detectors is described. The method has been tested for a 252Cf source and would appear to have significant advantages — in particulae higher efficiency — for experiments using very low counting rates.