|
Atomic vapor laser isotope separation (AVLIS) is a method by which specially tuned lasers are used to separate isotopes of uranium using selective ionization of hyperfine transitions.〔L. J. Radziemski, R. W. Solarz, and J. A. Paisner (Eds.), ''Laser Spectroscopy and its Applications'' (Marcel Dekker, New York, 1987) Chapter 3.〕〔Petr A. Bokhan, Vladimir V. Buchanov, Nikolai V. Fateev, Mikhail M. Kalugin, Mishik A. Kazaryan, Alexander M. Prokhorov, Dmitrij E. Zakrevskii: ''Laser Isotope Separation in Atomic Vapor''. Wiley-VCH, Berlin, August 2006, ISBN 3-527-40621-2〕 In the largest technology transfer in U.S. government history, in 1994 the AVLIS process was transferred to the United States Enrichment Corporation for commercialization. However, on June 9, 1999 after a $100 million investment, USEC cancelled its AVLIS program. The AVLIS process provides high energy efficiency comparable with gas centrifuges, high separation factor, and low volume of radioactive waste. AVLIS continues to be developed by some countries and it presents some specific challenges to international monitoring. Iran is now known to have had a secret AVLIS program. However, since it was uncovered in 2003, Iran has claimed to have dismantled it. A similar technology, using molecules instead of atoms, is molecular laser isotope separation (MLIS). ==Principle== The absorption lines of 235 and 238U differ slightly due to hyperfine structure; for example, the 238U absorption peak shifts from 502.74 nanometers to 502.73 nm in 235U. AVLIS uses tunable dye lasers, which can be precisely tuned, so that only 235U absorbs the photons and selectively undergoes excitation and then photoionization. The ions are then electrostatically deflected to a collector, while the neutral unwanted uranium-238 passes through. The AVLIS system consists of a vaporizer and a collector, forming the separation system, and the laser system. The vaporizer produces a stream of pure gaseous uranium. The laser commonly used is a two-stage tunable pulsed dye laser usually pumped by a copper vapor laser;〔F. J. Duarte and L.W. Hillman (Eds.), Dye Laser Principles (Academic, New York, 1990) Chapter 9.〕〔C. E. Webb, High-power dye lasers pumped by copper vapor lasers, in ''High Power Dye Lasers'', F. J. Duarte (Ed.) (Springer, Berlin, 1991) Chapter 5.〕〔F. J. Duarte, Tunable lasers for atomic vapor laser isotope separation: the Australian contribution, ''Australian Physics'' 47(2), 38-40 (2010).〕 the master oscillator is low-power but highly precise, and its power is increased by a dye laser amplifier acting as optical amplifier. Three frequencies ("colors") of lasers are used for full ionization of uranium-235. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Atomic vapor laser isotope separation」の詳細全文を読む スポンサード リンク
|