Efficiency calibration of large volume liquid scintillation detectors

An array of seven large (10 cm thick by 20 cm diameter) NE213 scintillation detectors for use in neutron time-of-flight experiments has been calibrated to determine a matrix of relative detection efficiency as a function of incident neutron energy and detector bias. This matrix is then used to determine the relative efficiency for neutron groups in time-of-flight spectra to which an efficiency-optimizing dynamic bias has been applied.     

Performance of a neutron multiplicity filter composed of six liquid scintillation detectors

A neutron multiplicity filter was constructed to investigate the excited states in neutron-deficient nuclei produced via heavy-ion reactions. The arrangement and the performance of the system are discussed and the usefulness of the system is demonstrated.     

A combined neutron and gamma-ray multiplicity counter based on liquid scintillation detectors

Multiplicity counters for neutron assay have been extensively used in materials control and accountability for nonproliferation and nuclear safeguards. Typically, neutron coincidence counters are utilized in these fields. In this work, we present a measurement system that makes use not only of neutron (n) multiplicity counting but also of gamma-ray (γ) multiplicity counting and the combined higher-order multiples containing both neutrons and gamma rays. The benefit of this approach is in using both particle types available from the sample, leading to a reduction in measurement times compared with single-particle measurements. We present measurement results of n, γ, nn, nγ, γγ, nnn, nnγ, nγγ and γγγ multiples emitted by Mixed-Oxide (MOX) samples measured at Idaho National Laboratory (INL). The MOX measurement is compared to initial validation of the detection system done using a ²⁵²Cf source. The dual radiation measuring system proposed here uses extra measurables to improve the statistics when compared to a neutron-only system and allows for extended analysis and interpretation of sample parameters. New challenges such as the effect of very high intrinsic gamma-ray sources in the case of MOX samples are discussed. Successful measurements of multiple rates can be performed also when using high-Z shielding.     

Metrological support of fast wide-range scintillation detectors

Translated from Izmeritel'naya Tekhnika, No. 6, pp. 51–52, June, 1992.     

Water equivalent plastic scintillation detectors in radiation therapy

A review of the dosimetric characteristics and properties of plastic scintillation detectors for use in radiation therapy is presented. The detectors show many desirable qualities when exposed to megavoltage photon and electron beams, including water equivalence, energy independence, reproducibility, dose linearity, resistance to radiation damage and near temperature independence. These detectors do not require the usual conversion and/or correction factors used to convert the readings from common dosemeters to absorbed dose. Due to their small detecting volume, plastic scintillation detectors exhibit excellent spatial resolution. Detector performance, in certain specific cases, can be affected by radiation-induced light arising in the optical fibres that carry the scintillator signal to a photodetector. While this effect is negligible for photon beams, it may not be ignored for electron beams and needs to be accounted for.     

A study of light collection efficiency in scintillation detectors

A group of computer programs was set up to study the light of collection efficiency in scintillation detectors with rectangular cross sections. The input conditions can be chosen arbitrarily, including: the size, light attenuation length and refraction index of the scintillator and light guide, the refraction index of the coupling medium, the reflection characteristics of the walls, and the position of light sources. A few examples are discussed in this article.     

A diffusive light collection system for hard X-ray astronomical scintillation detectors

A novel design of a detector system for hard X-ray astronomy is described which permits large sensitive areas to be constructed on a modular basis. The system also incorporates high quality active shielding without the use of the phoswich system. The development and performance of the diffusive light collection optics are discussed.     

A large area liquid scintillation multiphoton detector

A 60 layer lead-liquid scintillator shower detector, which we call the SLIC, has been used for multiphoton detection in the Fermilab tagged photon spectrometer. The detector has an unimpeded active area which is 2.44 m by 4.88 m and is segmented, by means of teflon coated channels, into 3.17 cm wide strips. The 60 layers in depth are broken into three directions of alternating readouts so that three position coordinates are determined for each shower. At present the readouts are made by 334 photomultiplier tubes coupled to BBQ doped wavelength shifter bars which integrate the entire depth of the detector. It is relatively straightforward to increase the number of readouts to include longitudinal segmentation and to increase the segmentation of the outer region which are at present read out two strips to a readout. The energy and position resolutions of isolated showers are about and 3 mm., respectively. The SLIC has been used to study the K⁻π⁺π⁰ decay of the D⁰ [1], as well as for electron and muon identification in ψ → e⁺e⁻ and ψ → μ⁺μ⁻ plus π⁰ identification in γp → ψχ [8].     

Characteristics of the scintillation responses of small lithium glass detectors to electron excitation

The response characteristics of lithium glass scintillators to electron excitation have been determined for a range of electron energies, lithium concentrations and lithium enrichments. The characteristics determined were the absolute scintillation efficiency and intrinsic resolution. These measurements form part of a study on the possible use of such glasses for the determination of the tritium breeding in fusion reactor blanket experiments.The measurements were undertaken to investigate the effects of the gamma background on the signals arising from the tritium production reactions induced within the glass scintillators. Criteria for the selection of glasses most suitable for tritium breeding are discussed in terms of their measured characteristics.     

Certifying standard specimens for light yield in bismuth germanate single-crystal scintillation detectors

Translated from Izmeritel'naya Tekhnika, No. 5, pp. 45–47, May, 1991.     

Construction and performance of one- and two-dimensional large position-sensitive liquid and plastic scintillation detectors — an application to a neutron polarimeter

Large one- and two-dimensional position-sensitive neutron detectors have been developed. Their shapes are a long block and a square and their sizes are 100×10×7.5 cm³ and 100×100×10 cm³ for one- and two-dimensional detectors, respectively. Both liquid and plastic scintillators are employed as detector materials. Position resolutions are examined by using monoenergetic neutron beams with energies of 61.6 MeV. The obtained position resolutions in FWHM are 3–5 cm and 4–14 cm for one- and two-dimensional detectors, respectively. Position resolutions are poor near the corner of the two-dimensional detector irrespective of scintillator materials. Scintillation light responses have been compared with predictions of Monte Carlo calculations. Neutron polarimeters at an intermediate energy have been developed by utilizing the position sensitivity of these detectors.