Showing papers by "Charles L. Melcher published in 1999"
24 Oct 1999
TL;DR: In this paper, the authors studied nonproportionality and intrinsic energy resolution of cerium doped YSO, GSO, LSO and LGSO crystals and found that the high proportionality of scintillators is connected with the structure of the crystal and not with the presence of light elements.
Abstract: We have studied nonproportionality and intrinsic energy resolution of cerium doped YSO, GSO, LSO and LGSO crystals. While LSO and YSO have similar light output, GSO and LGSO have ca. 70% and 20% lower light output than LSO, respectively. YSO, as a compound containing fairly light elements, was expected to be proportional for light output vs. energy scale, like YAP:Ce. Surprisingly it is almost the same nonproportionality as LSO and GSO. Nonproportionality of YSO is followed by large values of intrinsic energy resolution. The comparison of nonproportionality of YSO-LSO and YAP LuAP pairs indicates that the high proportionality of scintillators is connected with the structure of the crystal and not with the presence of light elements. To our knowledge, this is the first study of nonproportionality and intrinsic resolution for LGSO.
153 citations
21 Nov 1999-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: In this article, the authors explore both a specular and diffuse surface reflector finish, using LSO crystals that are either polished or etched, and find that the light collection is characterized by a maximum output (based on the photopeak position when excited at the PMT end) and depth-dependent loss factor.
Abstract: We study the relative light collection efficiency for narrow LSO crystals as a function of surface finish and geometry. We explore both a specular and diffuse surface reflector finish, using LSO crystals that are either polished or etched. The crystals have a square cross-section with widths of 1.8, 2.2, 2.5, or 2.6 mm and lengths of 10, 20 or 30 mm. When optically coupled to a PMT on a square end and wrapped with Teflon on 5 sides, we excite them at 5 mm incremental depths with 511 keV photons and measure the photopeak position. The light collection is characterized by a maximum output (based on the photopeak position when excited at the PMT end) and a depth-dependent loss factor. Both the maximum output and loss factor are effectively independent of width, and the maximum output is only weakly dependent on length (6696±612, 5796±432, and 5328±288 photons for 10, 20, and 30 mm lengths). The loss factor is effectively independent of length, with a 0, 18, 27, and 22% reduction at excitation depths of 0, 10, 20, and 30 mm. The light collection is only weakly dependent on surface finish if it is polished or etched beyond a minimum time.
70 citations
24 Oct 1999
TL;DR: In this paper, a perspective pre-shower detector for high energy /spl gamma/rays was proposed and the response of the crystals to high energy gamma/ray was studied.
Abstract: LSO:Ce and LYSO:Ce has been proposed as a perspective pre-shower detector for search for /spl mu/+/spl rarr/e/sup +/ /spl gamma/ decay with the branching-ratio sensitivity of 10/sup -14/ at PSI (Villigen, Switzerland). The detection involves 52.8 MeV /spl gamma/-rays. To study the response of the crystals to high energy /spl gamma/-rays we have chosen Pu-Be neutron source which due to a /sup 9/Be(/spl alpha/,n) reaction gives monoenergetic 4.439 MeV /spl gamma/-rays. We have studied the response of /spl phi/60/spl times/10 mm YSO:0.2%Ce crystal and half disk of /spl phi/60/spl times/10 mm LSO:0.2%Ce. Despite the large background of /sup 176/Lu the high energy /spl gamma/-rays can be detected efficiently. We have also studied the response to lower energy /spl gamma/-rays (from /sup 137/Cs and /sup 60/Co sources) and found the conditions of optimum work, YSO crystal detects 4.439 MeV /spl gamma/-rays primarily by double 511 keV escapes that form a distinct peak on energy spectrum.
3 citations