Ion source development for ultratrace detection of uranium and thorium

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• 作者：Y. Liu^a ; ; J.C. Batchelder^a ; ^b ; A. Galindo-Uribarri^a ; ^c ; R. Chu^a ; ^c ; S. Fan^a ; ^c ; E. Romero-Romero^a ; ^c ; D.W. Stracener^a
• 关键词：Ion source ; Surface ionization ; Laser ionization ; Uranium ; Thorium
• 刊名：Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
• 出版年：2015
• 出版时间：15 October 2015
• 年：2015
• 卷：361
• 期：Complete
• 页码：267-272
• 全文大小：698 K

文摘

Efficient ion sources are needed for detecting ultratrace U and Th impurities in a copper matrix by mass spectrometry techniques such as accelerator mass spectrometry (AMS). Two positive ion sources, a hot-cavity surface ionization source and a resonant ionization laser ion source, are evaluated in terms of ionization efficiencies for generating ion beams of U and Th. The performances of the ion sources are characterized using uranyl nitrate and thorium nitrate sample materials with sample sizes between 20 and 40 渭g of U or Th. For the surface ion source, the dominant ion beams observed are UO⁺ or ThO⁺ and ionization efficiencies of 2–4% have been obtained with W and Re cavities. With the laser ion source, three-step resonant photoionization of U atoms has been studied and only atomic U ions are observed. An ionization efficiency of about 9% has been demonstrated. The performances of both ion sources are expected to be further improved.