Atomic vapor laser isotope separation

An atomic vapor laser isotope separation experiment at LLNL. Green light is from a copper vapor pump laser used to pump a highly tuned dye laser which is producing the orange light.

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.[1][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.[3] 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.[4][5]

A similar technology, using molecules instead of atoms, is molecular laser isotope separation (MLIS).

Principle

The absorption lines of 235U 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.

Laser excitation

The laser commonly used is a two-stage tunable pulsed dye laser usually pumped by a copper vapor laser;[6][7] the master oscillator is tunable, narrow-linewidth, and highly precise.[8] Its power is significantly increased by a dye laser amplifier acting as optical amplifier. Three frequencies ("colors") of lasers are used for full ionization of uranium-235.[9]

For AVLIS in other elements, such as lithium, tunable narrow-linewidth diode lasers are used.[10]

Brief history

The history of AVLIS, as recorded in the open refereed literature, began in the early-mid 1970s in the former Soviet Union and the United States.[11] In the US, AVLIS research was mainly carried out at the Lawrence Livermore National Laboratory although some industrial laboratories were early players. Tunable laser development for AVLIS, applicable to uranium, has also been reported from several countries including Australia (1982-1984), France (1984), India (1994), and Japan (1996).[11]

See also

References

  1. ↑ L. J. Radziemski, R. W. Solarz, and J. A. Paisner (Eds.), Laser Spectroscopy and its Applications (Marcel Dekker, New York, 1987) Chapter 3.
  2. ↑ 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
  3. ↑ Ferguson, Charles D.; Boureston, Jack (March–April 2005). "Laser Enrichment: Separation Anxiety". Council on Foreign Relations. Retrieved 2010-11-22.
  4. ↑ Ferguson, Charles D.; Boureston, Jack (June 17, 2004). "Focusing on Iran's Laser Enrichment Program" (PDF). FirstWatch International. Retrieved 2010-11-22.
  5. ↑ Paul Rogers (March 2006). "Iran's Nuclear Activities". Oxford Research Group. Retrieved 2010-11-22.
  6. ↑ F. J. Duarte and L.W. Hillman (Eds.), Dye Laser Principles (Academic, New York, 1990) Chapter 9.
  7. ↑ 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.
  8. ↑ F. J. Duarte and J. A. Piper, Narrow linewidth high prf copper laser-pumped dye-laser oscillators, Appl. Opt. 23, 1391-1394 (1984).
  9. ↑ ""Annex 3": List of Items to Be Reported to IAEA". Iraqwatch.org. Archived from the original on 2011-05-14. Retrieved 2010-11-22.
  10. ↑ I. E. Olivares, A. E. Duarte, E. A. Saravia, and F. J. Duarte, Lithium isotope separation with tunable diode lasers, Appl. Opt. 41, 2973-2977 (2002).
  11. 1 2 F. J. Duarte (2016). "Tunable laser atomic vapor laser isotope separation". In F. J. Duarte (Ed.). Tunable Laser Applications (3rd ed.). Boca Raton: CRC Press. pp. 371–384. ISBN 9781482261066.
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