On the Application of a Sandwich of Thin Plastic Scintillators of Various Diameters for Low-Background β-Scintillation Measurements in Anticoincidence

An examination is made of the possibilities of a symmetrical system of two scintillation detectors with thin polymeric scintillators of various diameters for low-background measurements. A high sensitivity is sought in serial determinations of β-activities through the utilization of a screening detector with a thin plastic polymer scintillator connected in an anticoincidence circuit with the measuring detector. Light reflectors and a β-particles backscatterr are applied. A minimum of radiation shielding is utilized. The method is intended for practical measurements of low-level activities in a non-specialized laboratory.     

Untersuchungen zur Autoradiolyse einiger Hg-markierter Diuretika

Lufthaltige wäßrige Lösungen von Mersalyl und von Neohydrin wurden mit ⁶⁰Co-γ-Strahlung bestrahlt und die Quecksilberabspallung polarographisch verfolgt. Wahrend Mersalyl nur metallisches Quecksilber lieferte, entstand aus Neohydrin ionogenes Hg. Die cntsprechenden Radiolyseausbeuten waren G(Hg) = 4,6 und G(Hg²⁺) = 3,9. Durch Zusatz von Theophyllin, Benzylalkohol und den ungesättigten Ausgangsstoffen der quecksilberorganischen Verbindungen wurden sie erheblich vermindert. Die Ergebnisse werden im Hinblick auf die zu erwartende Autoradiolyse der ²⁰³Hg-markierten Siibstanzen diskutiert.     

Delayed recombination and excited state ionization of the Ce3+ activator in the SrHfO3 host

We determine the thermal ionization energy of the excited state of Ce³⁺ in a SrHfO₃ host by a contactless optical method based on the measurement and analysis of delayed recombination decay following UV excitation. We show the applicability of the method for microcrystalline powder samples. The method provides a consistent value of thermal ionization energy of about 0.25 eV, as previously determined by a ther‐ mally stimulated luminescence (TSL) study after UV illumination. We reveal a low temperature contribution to the delayed recombination signal and address its origin. This contribution indicates a complex interaction of the luminescence center with the host lattice neighborhood and the presence of temperature independent losses of fast scintillation light. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Growth and characterization of isotopically enriched 40Ca100MoO4 single crystals for rare event search experiments

Calcium molybdate is considered as a very promising scintillator material for experimental studies of rare processes. This paper reports on the production and characterization of a ⁴⁰Ca¹⁰⁰MoO₄ scintillator. Using the Czochralski technique, a crystal of high optical quality with total mass 0.55 kg, 42 mm diameter (minimum) and 53 mm 1ength of the cylindrical section was produced from isotopically enriched raw materials, containing 96.1% of ¹⁰⁰Mo and 99.964% of ⁴⁰Ca. To satisfy the requirement of low intrinsic radioactivity the purity of the materials was monitored at different stages of the production process and it is shown that the concentration of ²³⁸U and ²³²Th in the final crystal does not exceed 0.05 ppb. The scintillation properties of ⁴⁰Ca¹⁰⁰MoO₄ were measured over the 8 – 300 K temperature range and it is found that the light yield of the ⁴⁰Ca¹⁰⁰MoO₄ crystal is very similar to that of the CaMoO₄ reference scintillator. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Improving the Energy Resolution of BaF2 Scintillators by Cooling

The energy resolution at 662 keV of a BaF₂ scintillator improved from 9.5% at 28 °C to 8.8% at −5 °C. Further cooling deteriorated the resolution. Experiments with a long quartz light guide disprove the idea that the unintentional cooling of the photocathode of the photomultiplier is responsible for the levelling off of the resolution at lower temperatures as suggested by Wisshak et al. We present evidence that irradiation defects at temperatures below 0 °C limit the resolution. This revised version was published online in September 2006 with corrections to the Cover Date.     

Scintillation response of Ce-doped or intrinsic scintillating crystals in the range up to 1 MeV

A hybrid photomultiplier (HPMT) was used to study the scintillation response {N_phels(E) photoelectron and L.Y.(E) light yields and energy resolutions} of various known or newly developed scintillators—namely, Ce-doped crystals (perovskites or garnets), CsI(Tl) and the intrinsic BGO crystal—at different energies in the range 8 keV–1.33 MeV. Detailed comparative studies of the scintillation properties of these crystals are presented. A newly developed fast and heavy LuAG:Ce scintillator is characterized by about a 50% higher L.Y. compared to that of well-known and popular BGO (roughly 12 500 ph/MeV against 8080 ph/MeV, respectively).     

Current Status on Plastic Scintillators Modifications

Recent developments of plastic scintillators are reviewed, from 2000 to March 2014, distributed in two different chapters. First chapter deals with the chemical modifications of the polymer backbone, whereas modifications of the fluorescent probe are presented in the second chapter. All examples are provided with the scope of detection of various radiation particles. The main characteristics of these newly created scintillators and their detection properties are given.     

Characterization of Micro‐ and Nanoscale LuPO4:Pr3+,Nd3+ with Strong UV‐C Emission to Reduce X‐Ray Doses in Radiation Therapy

UV‐C emitting nanoscale scintillators can be used to sensitize cancer cells selectively against X‐rays during radiation therapy, due to the lethal DNA lesions caused by UV‐C photons. Unfortunately, nanoscale particles (NPs) show decreased UV‐C emission intensity. In this paper, the influence of different Nd³⁺ concentrations on the UV‐C emission of micro‐ and nanoscale LuPO₄:Pr³⁺ is investigated upon X‐ray irradiation and vacuum UV excitation (160 nm). Co‐doped LuPO₄ results in increased UV‐C emission independent of excitation source due to energy transfer from Nd³⁺ to Pr³⁺. The highest UV‐C emission intensity is observed for LuPO₄:Pr³⁺,Nd³⁺(1%,2.5%) upon X‐ray irradiation. Finally, LuPO₄ NPs co‐doped with different dopant concentrations are synthesized, and the biological efficacy of the combined approach (X‐rays and UV‐C) is assessed using the colony formation assay. Cell culture experiments confirm increased cell death compared to X‐rays alone due to the formation of UV‐specific DNA damages, supporting the feasibility of this approach.     

Role of hot electron transport in scintillators: A theoretical study

Despite recent intensive study on scintillators, several fundamental questions on scintillator properties are still unknown. In this work, we use ab‐initio calculations to determine the energy dependent group velocity of the hot electrons from the electronic structures of several typical scintillators. Based on the calculated group velocities and optical phonon frequencies, a Monte‐Carlo simulation of hot electron transport in scintillators is carried out to calculate the thermalization time and diffusion range in selected scintillators. Our simulations provide physical insights on a recent trend of improved proportionality and light yield from mixed halide scintillators. (© 2016 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Scintillation of Sol-Gel Derived Lutetium Orthophosphate Doped with Rare Earth Ions

In this paper, the synthesis, the characterization and the scintillation properties of LuPO₄ doped, with several concentrations of Ce³⁺, Eu³⁺ and Tb³⁺ ions, are presented. These materials have been synthesized by sol-gel process. The purity of powders has been verified by X-Ray diffraction and the results confirm the xenotime structure of all the materials. A thermogravimetric analysis allows the obtention of informations on the crystallisation of LuPO₄ and the study of its evolution from the amorphous to crystalline form. The morphology of the powders has been studied by Scanning Electron Microscopy and shows that the powders are constituted of small particles with narrow size distribution. Optical properties have been studied in order to determine the scintillation performances of these materials. The optima are obtained for Ce³⁺, Eu³⁺ and Tb³⁺ concentration of respectively 0.1, 10 and 5% with high scintillation yields. This study thus confirms the potentialities of these materials as scintillators.