Van De Graaff ion Beams as a Useful Instrument of Scintillation Study of Crystals
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V.K.EGOROV, A.P.ZUEV IPTM RAS, Chernogolovka, Moscow Region, 142432 Russia
ABSTRACT The search of new efficient scintillators can be simplified by the application of ion beams. The beam flux density of the order magnitude 1012-1014 ions/cm 2sec can be easily achieved. The light yield visualization takes place even for weak scintillators as PbF 2 under excitation by such beams. The light response of crystals for ion beams with EB= 1-2 MeV is not connected with the Cherenkov's radiation. Ion excitation enables one to find the crystals with surface scintillation. Measurement were performed by means of 0.15-2.0 MeV H', D' and 4He' ions with current 0.1-10 nA. Quantitative values of the light yield for the cubic phase of monocrystal PbF 2 in random and channeling were obtained. Restrictions of the technique applicability are discussed.
INTRODUCTION It has long been known that when the beams of charged particles with moderate energies obtained at electrostatic accelerator interact with some materials (e.g. with SiO 2) active optical fluorescence is observed. As a rule, in this case the same optical lines as under other types of excitation (-y- and X-rays, electron beams, vacuum ultraviolet and laser) are seen [1]. It's natural, since the energy losses of various types of excitations form finally electron-hole pairs, which recombine under certain conditions initiating light emission by a particular mechanism (trap radiation recombination, cross-luminescence, etc.). Crystals being fluorescented under y- and charge particle excitation are usually named scintillators. In the present work an attempt is made to study the scintillation of crystals using beams of charged particles with moderate energies so that to create an efficient procedure for the search of fast
heavy scintillators.
BACKGROUND Van de Graaff accelerator is the mainframe device for such a procedure. Energy range of 0.5-2.0 Mev convenient for the study of crystals by Rutherford backscattering of ions appears to be quite acceptable for the scintillation measurements as well. 323 Mat. Res. Soc. Symp. Proc. Vol. 348. 01994 Materials Research Society
The depth of ions penetration into a crystal is the natural restriction of this procedure. For He' ions it usually makes up several microns and 10-20 Lm for H÷ ones. However, unlike for RBS, channeling and nuclear resonance measurements, the requirement for time stability of the ion beam current increases greatly when beams of charged particles are used for scintillation investigations. The use of charged particle beams for scintillation spectroscopy realizes a number of advantages of their application as compared to traditional methods of scintillation studies. The flux density 1012-1014 particles/cm 2sec (current of the beam is 1.6160 nA at 01 mm) being some orders of magnitude greater than the illumination of an isotope source of the ionizing radiation, can be easily reached using the ion irradiation. The density of an excitation obtained by election subsystem at ionic stopping appears to be much higher as com
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