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Cubic Lead Fluoride Crystal Growth and Property

Cubic Lead Fluoride Crystal Growth and Property. Qun Deng Shanghai Institute of Ceramics Chinese Academy of Sciences. Outline. Introduction Crystal Growth: Raw Material Preparation; Oxygen Scavenger; Inclusions. Crystal Transmission Properties: Absorption Edge;

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Cubic Lead Fluoride Crystal Growth and Property

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  1. Cubic Lead Fluoride Crystal Growth and Property Qun Deng Shanghai Institute of Ceramics Chinese Academy of Sciences

  2. Outline • Introduction • Crystal Growth: • Raw Material Preparation; • Oxygen Scavenger; • Inclusions. • Crystal Transmission Properties: • Absorption Edge; • Transversal Transmission; • Longitudinal Transmission. • Radiation Hardness

  3. Introduction • Density: 7.77 g/cm3 • Refractive Index: 1.82 at 400nm • Radiation Length: 0.93 cm • Moliere Radius: 2.22 cm • Energy Resolution: 3.2% at 1 GeV * • Growth difficulty: very easy to be oxidation during crystal gorwth *F.E. Mass et al., Calor2000

  4. Raw Material Preparation • PbF2 raw material was synthesized by combining PbCO3 and HF at high temperature. • PbCO3 + HF  PbF2 + CO2 + H2O • Products were put in vacuum oven and baked at 120C for few hours. • XRD results confirmed that the final product is orthorhombic PbF2powder.

  5. Crystal Growth PbF2 Bridgman Technology

  6. Oxygen Scavenger (I) Lead fluoride crystal ingot grown without oxygen scavenger

  7. Oxygen Scavenger (II) Lead fluoride crystal grown with oxygen scavenger

  8. Longitudinal Transmission Absorption edge of PbF2 crystals can be as good as 245 nm

  9. Transversal Transmission (I) Crystal Size: 30×30×175 mm

  10. Inclusions in Crystal Needle like inclusions Tabular shape inclusions Irregular shape Inclusions

  11. Inclusions in Crystal(cont.) • The composition of needle-like inclusions are lead oxide or lead fluoro-oxide. • The composition of tabular and irregular shape inclusions are orthorhombic lead fluoride. • Inclusions can be eliminated by: • doping certain amount of oxygen scavenger • increasing the temperature gradient • reducing the crucible downward rate

  12. Absorption at 300 nm

  13. Absorption of Cerium doped crystal

  14. Absorption at 300 nm (cont.) • Ce ions in raw materials may responsible for 300 nm absorption in lead fluoride crystals. • Absorption at 300nm can be attributed to 5d  4f transition of Ce ions

  15. Transversal Transmission Crystal Size: 30×30×186 mm

  16. Radiation Hardness P. Achenbach et al., Nucl. Instr. And Meth., A416, 357

  17. Large Size Crystal Sample Ingot Size: 75×75×270 mm

  18. Summary • An oxygen scavenger is found to grow lead fluoride crystal by modified bridgman method. Crystal ingot size can be as large as 75×75×270 mm. • Inclusions and scattering centers are successfully eliminated from the crystal. Very good homogeneity of large size crystals are achieved. • Ce ions in raw material is found to be responsible for 300 nm absorption in lead fluoride crystal. • The absorption edge of PbF2 can be as good as 245 nm. • PbF2 crystal still keeps good transmission after 10 krad irradiation.

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