Tham khảo tài liệu 'wide spectra of quality control part 17', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 470 Wide Spectra of Quality Control geometry to the surface finish and moreover to its internal state of residual stresses. In particular an excessive residual stress is a major cause of crystal breakage which often may occur during crystal cut during surface finishing or even worse only when the crystal is assembled into the detector units. Fig. 37. Comparison between better worst samples at centre position of the slices as shown by the inset as a function of the longitudinal position from the seed The need to produce high-quality crystals is therefore fundamental both to avoid damage during assembly and finishing of crystals. Crystal performance in terms of production of light strongly depends on surface finish therefore crystal tool machining is a crucial process to achieve the high performance needed in the case of scintillating crystals for high energy physics and medical applications. For optimal crystals performance attention has therefore to be paid to the mechanical aspects of the production process from the mechanical point of view this can be guaranteed by adequate quality control methods. If adequate quality inspection of crystals is achieved this has the potential to prevent breaking during the assembly in an array. The authors have reported the experience which was made within the collaboration with CERN to the development of the electromagnetic calorimeter of the Compact Muon Solenoid CMS presently working at CERN. From an industrial point of view the trend is to use smaller and smaller crystals for biomedical instrumentation in such crystals the surface plays an even more relevant role in the production of light. For this reason the final mechanical processing is important for producing high quality crystals. Therefore the experience made for the large crystals of CMS is in general valuable to guide the 471 Quality Control and Characterization of Scintillating Crystals for High Energy Physics and Medical Applications development of suitable quality
