Title: Setup for the crystal purification by the traveling molten zone method.
1Setup for the crystal purification by the
traveling molten zone method. TMZ for XEUS
V. Kozlov1b, M. Leskelä1b, M. Ritala1b, H.
Sipilä2, J. Huovelin1a, H. Kärkkäinen2, E. Kiuru2
and J. Hiltunen2
1aDepartment of Astronomy, University of
Helsinki, Helsinki, Finland 1bDepartment of
Chemistry, University of Helsinki, Helsinki,
Finland 2Metorex International Oy, Espoo, Finland
- Introduction
- The XEUS mission is characterised by ambitious
science goals, which will require substantial
technological advances in many parallel fields.
One of such is the search and development of
compound semiconductors for X-ray and gamma-ray
detectors. Our preliminary studies on TlBr
material have showed that the material quality is
far from perfect. Improved materials are needed
for the future planetary and astrophysics
investigations.
LT
Degassing
Tc / M
F
Z
HBr Preparation Drying
F
FC
PM
- The aim of this work is to construct a traveling
molten zone (TMZ) setup for the crystal
purification. TMZ-method is traditionally used in
semiconductor technology for materials
purification. The TMZ-instrument has been
designed by METOREX International and University
of Helsinki (Department of Chemistry) for the
rectification of thallium halides under various
atmospheres. The system consists of two parts
(see Figure 1) - - Preliminary material treatment
- - TMZ purification
NT
TMZ
M
Tc
Pump
Figure 1. System for the preliminary material
treatment and purification (degassing, TMZ,
vacuum and Tl -fixation).
(Purge) gas system
Vacuum System
- Preliminary material treatment
- The preliminary melting allow to avoid the use of
aggressive atmosphere during prolonged TMZ
cleaning. During preliminary treatment, water and
another components adsorbed are removed using
vacuum or appropriate gas atmosphere and step by
step heating. After full degassing, the raw
material/powder is melt and transferred into TMZ
setup.
Outlet filter
Chemical pump
Filter
Liquid nitrogen trap
Tl-fixation
Flow control
Pressure meter
M
Tc
SM
- TMZ purification
- In the TMZ method the heating ring moves along
the tube/ampoule and creates a molten zone-disk.
Due to the equilibrium between solid-melt-solid
phases the trace components are separated and
collected at opposite sides of the ampoule. The
rate is controlled from 1mm/h to 1mm/day. Because
of the different mobility of elements the
appropriate rate can be chosen according to the
contamination presented. Higher rates can be used
for the annealing and lower ones for the single
crystal growth and re-crystallization. The TMZ
setup is presented in Figure 2.
Heating control HR supply
Step motor control
valve soft valve
decompressor
Figure 2. TMZ purification setup
- Status
- The setup is under the testing and probe running
in METOREX International Oy.
- Acknowledgements
- This work is a part of the consortium High Energy
Astrophysics and Space Astronomy (HESA) financed
by the Academy of Finland and the Finnish
Technology Agency TEKES within the framework of
the Finnish space research programme ANTARES. -