Docstoc

Shanghai Institute

Document Sample
Shanghai Institute Powered By Docstoc
					Cubic Lead Fluoride Crystal
   Growth and Property

             Qun Deng
   Shanghai Institute of Ceramics
   Chinese Academy of Sciences
           Calor02, Qun Deng, SICCAS   1
                          Outline

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


                        Calor02, Qun Deng, SICCAS   2
                        Introduction

n   Density: 7.77 g/cm3
n   Refractive Index: 1.82 at 400nm
n   Radiation Length: 0.93 cm
n   Moliere Radius: 2.22 cm
n   Energy Resolution: 3.2% at 1 GeV *
n   Growth difficulty: very easy to be oxidation
    during crystal gorwth

*F.E. Mass et al., Calor2000

                          Calor02, Qun Deng, SICCAS   3
          Raw Material Preparation

n   PbF2 raw material was synthesized by
    combining PbCO3 and HF at high
    temperature.
n   PbCO3 + HF ® PbF2 + CO2 + H2O
n   Products were put in vacuum oven and
    baked at 120°C for few hours.
n   XRD results confirmed that the final product
    is orthorhombic PbF2 powder.

                   Calor02, Qun Deng, SICCAS       4
Crystal Growth
Bridgman Technology




                              PbF2




  Calor02, Qun Deng, SICCAS          5
            Oxygen Scavenger (I)




Lead fluoride crystal ingot grown without oxygen scavenger



                     Calor02, Qun Deng, SICCAS               6
      Oxygen Scavenger (II)




Lead fluoride crystal grown with oxygen scavenger


                Calor02, Qun Deng, SICCAS           7
       Longitudinal Transmission




Absorption edge of PbF2 crystals can be as good as 245 nm

                    Calor02, Qun Deng, SICCAS               8
Transversal Transmission (I)




     Crystal Size: 30×30×175 mm


          Calor02, Qun Deng, SICCAS   9
              Inclusions in Crystal




Needle like      Tabular shape             Irregular shape
inclusions       inclusions                Inclusions


                   Calor02, Qun Deng, SICCAS                 10
           Inclusions in Crystal(cont.)

n   The composition of needle-like inclusions
    are lead oxide or lead fluoro-oxide.
n   The composition of tabular and irregular
    shape inclusions are orthorhombic lead
    fluoride.
n   Inclusions can be eliminated by:
    n   doping certain amount of oxygen scavenger
    n   increasing the temperature gradient
    n   reducing the crucible downward rate
                     Calor02, Qun Deng, SICCAS      11
Absorption at 300 nm




     Calor02, Qun Deng, SICCAS   12
Absorption of Cerium doped crystal




           Calor02, Qun Deng, SICCAS   13
        Absorption at 300 nm (cont.)

n   Ce ions in raw materials may responsible
    for 300 nm absorption in lead fluoride
    crystals.
n   Absorption at 300nm can be attributed to
    5d ® 4f transition of Ce ions




                  Calor02, Qun Deng, SICCAS    14
Transversal Transmission




    Crystal Size: 30×30×186 mm


         Calor02, Qun Deng, SICCAS   15
        Radiation Hardness




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

                 Calor02, Qun Deng, SICCAS           16
Large Size Crystal Sample




     Ingot Size: 75×75×270 mm

        Calor02, Qun Deng, SICCAS   17
                      Summary
n   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.
n   Inclusions and scattering centers are successfully
    eliminated from the crystal. Very good homogeneity of
    large size crystals are achieved.
n   Ce ions in raw material is found to be responsible for
    300 nm absorption in lead fluoride crystal.
n   The absorption edge of PbF2 can be as good as 245
    nm.
n   PbF2 crystal still keeps good transmission after 10
    krad irradiation.

                      Calor02, Qun Deng, SICCAS              18

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:2
posted:3/23/2014
language:Unknown
pages:18