Experiments in fundamental particle physics push forward frontiers of what could be possibly measured, so they imply high requirements on performance of measurement instrumentation. In case scintillation detectors are used, this often means such applications require scintillators with unique characteristics, at least on one or two parameters. Examples of such requirements are:
- high transparency and radiation hardness of PbWO4 crystals for LHS CMS and ALICE detectors [1,2] and even higher radiation hardness for FAIR PANDA detector;
- isotopic purity and extra-low natural radioactivity background of CaMoO4 crystals for Y2L AMoRE detector .
To reach the necessary scintillator performance special attention should be paid to chemical composition of raw materials. E.g., 3d impurities, such as Cr, are detrimental to radiation hard PbWO4 properties at 0.5 ppm level, and U and Th even at content of 0.1 ppm in CaMoO4 create unacceptable background signal.
Development of a pure substance technology includes such components, as finding suitable analytical techniques, development of purification procedures, scaling these procedures to technological processes and establishing control methods. Besides mere final compound purity, technological solution should take into account factors of reliability, scalability, price. Some impurities could be eliminated using efficient small production scale processes (e.g., most of 3d); getting rid of the other at a reasonable cost is possible only in large-scale manufacturing (e.g. rare earths). There are some common approaches, however, every raw material compound purification is a special task.
Concerning raw materials specifications, it is a separate problem to develop one. Some requirements could be logically established, and the proof of other takes extended experimental work.
In this report we summarize our experience on a development and production of high purity raw materials for high performance scintillators, such as PbWO4, CaMoO4 and polycrystalline garnet-based scintillators. It is concluded, that using pure and controlled raw materials both at development and production stages increases success rates.
- M.V. Korjik. “Physics of scintillators, based on oxide single crystals” (in Rus.). Minsk, BGU Press, 2003, 234 p.
- A.E. Dossovitski, A.L. Mikhlin, A. N. Annenkov, “Production of specified raw materials for mass manufacturing of radiation hard scintillation materials”, Nucl. Instrum. Meth. A 486(1-2), 2002, pp. 98-101.
- V.V. Alenkov, O.A. Buzanov, A.E. Dosovitskii, V.N. Kornoukhov, A.L. Mikhlin, P.S. Moseev, N.D. Khanbekov. “Ultrapurification of isotopically enriched materials for 40Ca100MoO4 crystal growth”, Inorganic Materials 49(12), 2013, pp. 1220-1223.