Luminescence and scintillation characteristics of four selected material systems, namely CsI:Tl(Na), CeF 3 , PbWO 4 and Ce-doped aluminium perovskites XAIO 3 :Ce (X=Y, Lu, Y-Lu) are reviewed. The progress in their physical understanding and related optimisation of their characteristics and technology are demonstrated. The important role of various defect states in the scintillator performance of these materials is stressed, which has led to the need for a deeper study of the processes of energy transfer and storage to achieve their intrinsic limits and full exploitation in scintillation detectors.

Wide Band Gap Scintillation Materials: Progress in the Technology and Material Understanding

Electronic structure and optical properties of the lanthanide activated RE3(Al1−xGax)5O12 (RE=Gd, Y, Lu) garnet compounds

In this paper we summarize the results of a research programme on lead-tungstate (PWO) crystals performed by the CMS Collaboration at CERN, as well as by other groups who promoted the progress of the PWO scintillation crystal technology. Crystal properties, mass production technology, scintillation mechanism, origin of colouring, defects in crystal and radiation induced phenomena, light yield improvement and results of beam tests are described.

Lead tungstate scintillation material

The systematic in the 4f n ? 4f n?1 5d transition energy of divalent lanthanides in inorganic compounds has been studied. Energies were derived from excitation and optical absorption spectra gathered from the literature. Going through the lanthanide series from La2+ to Yb2+, a characteristic variation is observed similar to that known for the trivalent lanthanides and the free atoms and free ions. Once the transition energy is known for one lanthanide in a compound, that of all others in that same compound can be predicted. The value for the Stokes shift between fd excitation and df emission appears independent of the lanthanide ion. For Gd2+ to Yb2+ both the spin-forbidden and the spin-allowed fd-transition energies are discussed.

https://iopscience.iop.org/article/10.1088/0953-8984/15/3/322/pdf

f ? d transition energies of divalent lanthanides in inorganic compounds

The Y3Al2Ga3O12:Ce3+–Cr3+ compound is one of the brightest persistent phosphors, but its persistent luminescence duration is not so long because of the relatively shallow Cr3+ electron trap. To compare the vacuum referred binding energy of the electron trapping state by Cr3+ and lanthanide ions, we selected Yb3+ as a deeper electron trapping center. The Y3Al2Ga3O12:Ce3+–Yb3+ phosphors show Ce3+:5d → 4f green persistent luminescence after blue light excitation. The formation of Yb2+ was confirmed by the increased intensity of absorption due to Yb2+:4f−5d at 585 nm during the charging process. This result indicates that the Yb3+ ions act as electron traps by capturing an electron. From the thermoluminescence glow curves, it was found that the Yb3+ trap makes a much deeper electron trap with a 1.01 eV depth than the Cr3+ electron trap with a 0.81 eV depth. This deeper Yb3+ trap provides a much slower detrapping rate of filled electron traps than the Cr3+-codoped persistent phosphor. In addition, by preparing...

Formation of Deep Electron Traps by Yb3+ Codoping Leads to Super-Long Persistent Luminescence in Ce3+-Doped Yttrium Aluminum Gallium Garnet Phosphors

Methods to suppress damage centres in lead tungstate (PWO) crystals under irradiation are discussed. It is shown that in large size scintillation elements (23 cm in length) the minimization of both electron and hole centers created under irradiation by recharge of structural defects is achieved by proper stoichiometry tuning and additional simultaneous doping of crystals by Y and Nb. The different aspects of the suppression of the recharge process in PWO scintillation crystals are also discussed.

Suppression of the radiation damage in lead tungstate scintillation crystal

Luminescence and scintillation in cerium-activated oxide crystals with complex structure are quenched by co-doping with ytterbium. It was determined that Ce 3+ luminescence is quenched by tunneling ionization and scintillations are suppressed in addition by the destruction of relaxing excited host matrix states by Yb 3+ ions and nonradiative transitions Ce 3+ → (Yb 3+ ) - .

Scintillation quenching in cerium‐doped ytterbium‐based crystals

A compact high power microwave (HPM) source is reported. It generates short pulses by direct excitation of an antenna with a 300 kV Marx generator. Oil insulation is used to protect capacitor banks from breakdown, while discharge gaps are designed to work in air. The Marx generator risetime is less than 50 ns. The disk-cone antenna is also oil-insulated and operates in the self-breakdown regime. Radiated pulse has the duration about 2 ns and the spectrum from 800 MHz to 2 GHz. The HPM source is used for studying the vulnerability of computers and different electronic components. (4 pages)

/pdf/a-compact-high-power-microwave-hpm-source-46g91ubnbw.pdf

A. E. Borisevich

Papers

Suppression of the radiation damage in lead tungstate scintillation crystal

Scintillation quenching in cerium‐doped ytterbium‐based crystals

A compact high power microwave (hpm) source