Fast fall-time ion beam in neutron generators

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Ion beam with a fast fall time is useful in building neutron generators for the application of detecting hidden, gamma-shielded SNM using differential die-away (DDA) technique. Typically a fall time of less than 1 {micro}s can't be achieved by just turning off the power to the ion source due to the slow decay of plasma density (partly determined by the fall time of the RF power in the circuit). In this paper, we discuss the method of using an array of mini-apertures (instead of one large aperture beam) such that gating the beamlets can be done with low voltage and ... continued below

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Ji, Q.; Kwan, J.; Regis, M.; Wu, Y.; Wilde, S.B. & Wallig, J. August 10, 2008.

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Ion beam with a fast fall time is useful in building neutron generators for the application of detecting hidden, gamma-shielded SNM using differential die-away (DDA) technique. Typically a fall time of less than 1 {micro}s can't be achieved by just turning off the power to the ion source due to the slow decay of plasma density (partly determined by the fall time of the RF power in the circuit). In this paper, we discuss the method of using an array of mini-apertures (instead of one large aperture beam) such that gating the beamlets can be done with low voltage and a small gap. This geometry minimizes the problem of voltage breakdown as well as reducing the time of flight to produce fast gating. We have designed and fabricated an array of 16 apertures (4 x 4) for a beam extraction experiment. Using a gating voltage of 1400 V and a gap distance of 1 mm, the fall time of extracted ion beam pulses is less than 1 {micro}s at various beam energies ranging between 400 eV to 800 eV. Usually merging an array of beamlets suffers the loss of beam brightness, i.e., emittance growth, but that is not an important issue for neutron source applications.

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  • CAARI 2008, 20th International Conference on the Application of Accelerators in Research and Industry, , Fort Worth, Texas USA, August 10-15, 2008

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  • Report No.: LBNL-1577E
  • Grant Number: DE-AC02-05CH11231
  • Office of Scientific & Technical Information Report Number: 949204
  • Archival Resource Key: ark:/67531/metadc931145

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Office of Scientific & Technical Information Technical Reports

Reports, articles and other documents harvested from the Office of Scientific and Technical Information.

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  • August 10, 2008

Added to The UNT Digital Library

  • Nov. 13, 2016, 7:26 p.m.

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  • Jan. 4, 2017, 3:05 p.m.

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Ji, Q.; Kwan, J.; Regis, M.; Wu, Y.; Wilde, S.B. & Wallig, J. Fast fall-time ion beam in neutron generators, article, August 10, 2008; Berkeley, California. (digital.library.unt.edu/ark:/67531/metadc931145/: accessed July 17, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.