Activities: G. Carotenuto I CALOCUBE Collaboration Meeting, Firenze, 20/06/2014 Activities: - SCINTILLATOR CRYSTAL COMPOSITION DETERMINATION BY EDS - OPTICAL CHARACTERIZATION OF THE CsI SCINTILLATOR - INDIVIDUATION OF OPTICAL-GRADE ADHESIVES FOR THE PHOTODIODE-SCINTILLATOR COUPLING - ADHESIVE THICKNESS OPTIMIZZATION G. Carotenuto Institute for Polymers, Composites and Biomedical Materials - CNR
DETERMINATION OF THE AS-RECEIVED SAMPLE ELEMENTAL COMPOSITION According to the performed analysis by Energy-Dispersive X-Ray Spectroscopy (EDS), the received sample is made of CeI. A little amount of oxygen is also present on the sample surface (CeI oxidation to Ce2O). Tallium should be present in very low amount.
OPTICAL SPECIMEN CHARACTERISTICS Precise optical measurements on UV/Vis-absorbing solid materials require: (i) quite small sample thickness for strongly absorbing materials, (ii) uniform thickness to reduce light loss by reflection, and (iii) very smooth sample surfaces to reduce light loss by diffusion. 25 mm A = -log(I/I0) = a·l (Lambert’s law) l = pathway a = absorptivity < 300 nm
Drawbacks with water-soluble samples TRADITIONAL APPROACH FOR THE PREPARATION OF SOLID SAMPLES FOR OPTICAL CHARACTERIZATION Cutting Drawbacks with water-soluble samples • Sample solubility in the lubricant and the suspending media used for polishing (water of allumina suspensions) • Sample contamination by oils and grasses present in the diamond pastes Polishing
PREPARATION OF THIN SECTIONS BY SAMPLE DISSOLUTION IN SOLVENT/NON-SOLVENT MIXTURE The sample is put in EtOH or an EtOH/ACN solution and leaved up to solvent saturation, then more EtOH is added up to achieve the desired thickness. Solvent/non-solvent mixture Stirring Crystal slice Acetonitrile 40-60°C Organic solvents that can be used in combination with EtOH to dissolve CsI are: Heat can be used to control the sample dissolution process - Chloroform - Aceton
ROUGHNESS OF THE CsI SAMPLE SURFACE According to the scanning electron microscopy (SEM) investigation of the obtained sample surface, the surface roughness is usually very low. CsI slice under 254nm 1cm
The beam size was ca. 8.6mm with HP diode-array spectrophotometer DETERMINATION OF THE BEAM POSITION FOR THE SAMPLE THICKNESS MEASUREMENT UV-light The beam size was ca. 8.6mm with HP diode-array spectrophotometer
CsI CRYSTAL CUTTING • Slicing of the CsI crystal was obtained by an arc saw • The surfaces were made smooth by using sand papers (100 and 200) CsI slices after treatment with different types of sand papers REMARKS - The CsI slices are moisture-sensible and require to be stored under dry air. Slices obtained from the CsI cubic crystal - CsI may be toxic (thyroid) and prolonged exposure to this substance can produce target organs damage.
CsI CRYSTAL COLORATION Prolonged treatment of CsI crystals with quite protic solvents (e.g., water) causes the material turning yellow, because of iodine (I2) formation. 1. Hydrolysis of the salt: CsI + H2O CsOH + HI Color less 2. Iodidric acid decomposition: 2HI H2 + I2 Color less Yellow
ABSORPTION SPECTROSCOPY PerkinElmer Lambda-850 Double-beam spectrophotometer (monochromator spectrometer)
OPTICAL MEASUREMENTS Thickness has been accurately measured by a caliber in the exact point where the spectrophotometer reads.
UV and Visible absorption of CsI UV-VISIBLE ABSORPTION SPECTRUM A = -log(I/I0) = k·l (Lambert’s law) l = pathway k = absorptivity UV and Visible absorption of CsI
UTRAVIOLECT ABSORPTION BEHAVIOUR
DATA FITTING BY SIGMOIDAL FUNCTIONS
MEASUREMENTS BY DIODE-ARRAY SPECTROPHOTOMETER (HP) Thickness = 0.699 mm
EMISSION SPECTROSCOPY PerkinElmer LS-55 Sample Sampling area
FLUORESCENCE OF SAMPLES AT 254nm 1 Crystal 2 Slice 3 Thin layer
Optical-grade EVA for photovoltaics OPTICAL-GRADE ADHESIVE ALTERNATIVE TO SILICONE GLUE Ethylene-vinyl-acetate copolymer Hot-melt adhesive Optical-grade EVA for photovoltaics
FLUORESCENT FILM THICKNESS OPTIMIZATION TO AVOID LIGHT LOSS BY THE WAVEGUIDE EFFECT 0.6mm
CONCLUSIONS Optical grade samples for absorption and emission spectroscopic characterization can be prepared by controlled dissolution of the CsI scintillator crystals in liquid solvents. Evatane 33-45 PV can be used as adhesive for the photodiode-CsI crystal coupling. An Evatane- 33-45 PV thickness of 0.8mm is enough to avoid light loss from the film edges.
REQUIRED EQUIPMENTS • Nonio di precisione • Sega diamantata (14 kEuro) • Piano vasculante • Reattivi e solventi