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Laser Separation of Silicon Isotopes

#0750


Work out of the Laser Separation of Silicon Isotopes Technology Principles

Tech Area / Field

  • PHY-OPL/Optics and Lasers/Physics
  • MAT-SYN/Materials Synthesis and Processing/Materials

Status
3 Approved without Funding

Registration date
18.09.1996

Leading Institute
TRINITI, Russia, Moscow reg., Troitsk

Collaborators

  • A&R Materials, Inc., USA, NJ, Edgewater

Project summary

Recently, a great interest has been evoked in isotopes of medium mass elements, specifically in isotopes of carbon, nitrogen, oxygen and silicon. A super pure silicon isotope 28Si, for example, could find its application in nucroelectronics.

As a rule, the cost price of isotopes produced by traditional methods (rectification, chemical exchange and centrifugation) is rather high. One of the most important methods of reducing cost prices of isotope productions using of lasers or its combination with traditional ones. This has been demonstrated for carbon isotope separation on the base of selective multiphoton dissociation of freon molecules (22CF2HC1) by CO2 - laser radiation.

At present, a brand - new technology of carbon isotope separation using lasers has been developed and industrial facilities in TRINITI and NIIEFA have been built.

The most important goal of further laser method development is demonstration of its multipurpose applicability, i.e. visibility of using the equipment built for isotope separation of other elements. On this case the laser method of silicon isotope separation is an urgent problem: its solution will permit to combine the above - mention goal with rising demand for suppresser selecon (28Si) and other isotopes. Till now, laser isotope separation of silicon, has been considered to be less promising than that of carbon for reasons that:


- the most suitable initial compound using for effective dissociation required using of substantially higher laser beam density (>10 j/cm2). However, optical materials (KCl, KBr) do not sustain such energy density;
- there remained an unsolved problem of radical acceptors and creation of optimal chemical cycle as at SiF4 dissociation an involatile product (SiF4) can form.

The progress made lately in the development of technology for laser isotope separation of carbon allows applying to that of silicon.

Firstly, in engineering facilities tested now in the field of laser molecule dissociation an energy density of 20j/cm2 is achieved without any contact of laser beam with optical materials of low radiation resistance.

Secondly, a very perspective radical acceptor (HJ) has been found which makes possible to bring off a multistage laser enrichment of carbon isotopes when the product of the first stage dissociation is a starting compound for the second stage and so on. Such case is realized in the system

CF2Cl2 hv/HI ® CF2HCl hv/HI ® CF2HI hv/HI ® CF2H2 ,

where after a single radiation of gas mixture as a result of a three - stage process of laser isotope enrichment a highly enriched product CF2H2 forms.

There exist sufficient grounds to conclude that in the system SiF4 + HI a similar scheme could be realized:

SiF4 h/HI ® SiF3H h/HI ® SiF2HI h/HI ® SiF2H h/HI ® SiFH2I h/HI ® SiH3F


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