Influence of a Surface Finishing Method on Light Collection Behaviour of PWO Scintillator Crystals

Rinaldi, D.; Montalto, Luigi; Lebeau, M.; Mengucci, P.

doi:10.3390/photonics5040047

Cited by 10 publications

(10 citation statements)

References 22 publications

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“…The results gave a clear indication of how to choose the optimal surface treatment for improving crystal light collection. In the same paper, the results of GID analysis and light yield test were compared, highlighting the positive contribution of the CMP treatment to the optical performance of crystals (Table 1 in Figure 5) [13]. In fact, CMP generates an amorphized but smoother surface that contributes to an enhanced light yield.…”

Section: Example Of the Use Of The Presented Measurement Techniquesmentioning

confidence: 92%

“…Grazing incidence X-ray diffraction (GID) can be successfully used to investigate the crystalline state of surface or near-surface regions, compositional depth profile, presence of residual stresses, or crystallographic defects due to the growth process or the surface finishing post-production processes [13].…”

Section: Sem Tem and Edx Analysis X-ray Scattering And Reflectivimentioning

confidence: 99%

“…Although anisotropic crystals offer very high performance, they are very sensitive to stress, structural conditions, and defects [13,14]. Small changes in the production parameters or environmental conditions can create unwanted defects that dramatically affect the scintillating behavior, reducing the crystals performance and lifetime.…”

Section: Introductionmentioning

confidence: 99%

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Quality Control and Structural Assessment of Anisotropic Scintillating Crystals

et al. 2019

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Nowadays, radiation detectors based on scintillating crystals are used in many different fields of science like medicine, aerospace, high-energy physics, and security. The scintillating crystals are the core elements of these devices; by converting high-energy radiation into visible photons, they produce optical signals that can be detected and analyzed. Structural and surface conditions, defects, and residual stress states play a crucial role in their operating performance in terms of light production, transport, and extraction. Industrial production of such crystalline materials is a complex process that requires sensing, in-line and off-line, for material characterization and process control to properly tune the production parameters. Indeed, the scintillators’ quality must be accurately assessed during their manufacture in order to prevent malfunction and failures at each level of the chain, optimizing the production and utilization costs. This paper presents an overview of the techniques used, at various stages, across the crystal production process, to assess the quality and structural condition of anisotropic scintillating crystals. Different inspection techniques (XRD, SEM, EDX, and TEM) and the non-invasive photoelasticity-based methods for residual stress detection, such as laser conoscopy and sphenoscopy, are presented. The use of XRD, SEM, EDX, and TEM analytical methods offers detailed structural and morphological information. Conoscopy and sphenoscopy offer the advantages of fast and non-invasive measurement suitable for the inspection of the whole crystal quality. These techniques, based on different measurement methods and models, provide different information that can be cross-correlated to obtain a complete characterization of the scintillating crystals. Inspection methods will be analyzed and compared to the present state of the art.

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Section: Example Of the Use Of The Presented Measurement Techniquesmentioning

confidence: 92%

Section: Sem Tem and Edx Analysis X-ray Scattering And Reflectivimentioning

confidence: 99%

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Quality Control and Structural Assessment of Anisotropic Scintillating Crystals

et al. 2019

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“…Also, electro-polishing has been shown in a number of cases to have a negative impact on the environment [15,16,17,18,19]. There is a similar consideration of the negative effect on the environment during the application of the chemical mechanical polishing technique (CMP), in which chemical and abrasive materials are used [20,21]. AlMangour B. et al [22] investigated the improvement of the surface quality and mechanical properties of 17-4 stainless steel flat samples manufactured by direct metal laser sintering (DMLS).…”

Section: Introductionmentioning

confidence: 99%

Laser Polishing of Additive Manufactured 316L Stainless Steel Synthesized by Selective Laser Melting

et al. 2019

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One of the established limitations of metal additive manufacturing (AM) methods, such as selective laser melting (SLM), is the resulting rough surface finish. Laser polishing is one method that can be used to achieve an improved surface finish on AM printed parts. This study is focused on the laser surface polishing of AM parts using CO2 laser beam irradiation. Despite the fact that several researchers have investigated the traditional abrasive polishing method, there is still a lack of information reporting on the laser surface polishing of metal parts. In this study, AM 316L stainless steel cylindrical samples were polished using CO2 laser beam irradiation in continuous wave (CW) working mode. Two design of experiment models were developed for the optimization of the input processing parameters by statistical analysis of their effect on the resulting roughness. The processing parameters investigated were the laser beam power, the rotational speed of the sample, the number of laser scan passes, the laser beam focal position, and the percentage overlap of the laser tracks between consecutive passes. The characterization of the measured roughness and the modified layer microstructure was carried out using 3D optical and scanning electron microscopy (SEM). A maximum reduction of the roughness from 10.4 to 2.7 µm was achieved and no significant change in the microstructure phase type and micro-hardness was observed.

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“…(LY), which evaluates the production light efficiency; LY is expressed as the number of visible photons emitted per unit of deposited energy (conventionally, number of photons/MeV) and varies depending on the crystal variety, surface and crystal condition [5];…”

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confidence: 99%

Scintillator Crystals: Structure, Characterization and Models for Better Performances

Rinaldi

Montalto

2020

Crystals

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The majority of instrumentation and systems for radiation detection are based on scintillators. Scintillating materials convert high-energy radiation in visible light (visible photons), this light is collected by a photomultiplier and elaborated to obtain information about incident radiation energy spectra and for image reconstruction. Among the variety of scintillating substances and forms, the scintillating crystals offer the best performances in various fields of application. Medicine, Physics, Industry, Earth and Soil science, Aerospace, Astronomy applications and others, require more and more sophisticated and accurate tools to face new and deeper challenges. In this direction, the development of new materials and the improvement of the existing ones is mandatory. A deeper knowledge of the crystal physics as well as all the mechanisms relative to their scintillating behaviour is crucial to accomplish the needs of these applications. Theories and simulations are fundamental to obtain predictive models. Further to these, accurate testing procedures and quality control methodologies play a major role in monitoring the crystal condition and improving the production processes, helping the producers of crystals to enhance the process efficiency and allowing crystals' "end users" to have better performing devices.Medical instrumentation, for diagnostics and imaging, requires high sensitivity, in addition to a fast and reliable response, thereby reducing health risk and increasing both the spatial and time resolution. The different bio-medical instrumentation spans from the PET, to the high-resolution SPECT and Gamma camera, including X-Ray imaging [1]; therefore, each crystal species must be optimized for the relevant purpose.However, security and geological instrumentation require another kind of scintillating crystal, which is durable and stable over time.The design and construction of calorimeters for high-energy physics studies are critical in scintillator development. It is opportune to emphasize the discovery of the Higg's boson at CERN by CMS calorimeter, where about 80,000 large-dimension PbWO 4 (PWO) were used. For the first time, a large-scale production of big crystals (2 cm × 2 cm × 20 cm) was necessary [2,3]. Moreover, the large production scale called for a fast and non-destructive quality control to avoid, among the other quality requirements, the risk of fracture due to internal stress [4]. The implementation of in-line quality control using a fast and non-destructive technique is mandatory for all of the above applications. The different applications have specific requirements, since scintillators must be able to detect photons at different energies. For example, energy detected by PWO crystals at CMS is of the order of 100 Gev and the photon energy for X-Ray imaging decreases down to 20 KeV. Different scintillator parameters are crucial for determining the efficiency and accuracy of detection systems. Among them, we cite some significant parameters such as the following: the Light Yield

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Influence of a Surface Finishing Method on Light Collection Behaviour of PWO Scintillator Crystals

Cited by 10 publications

References 22 publications

Quality Control and Structural Assessment of Anisotropic Scintillating Crystals

Quality Control and Structural Assessment of Anisotropic Scintillating Crystals

Laser Polishing of Additive Manufactured 316L Stainless Steel Synthesized by Selective Laser Melting

Scintillator Crystals: Structure, Characterization and Models for Better Performances

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