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Title: Enhanced collective focusing of intense neutralized ion beam pulses in the presence of weak solenoidal magnetic fields

Abstract

The design of ion drivers for warm dense matter and high energy density physics applications and heavy ion fusion involves transverse focusing and longitudinal compression of intense ion beams to a small spot size on the target. To facilitate the process, the compression occurs in a long drift section filled with a dense background plasma, which neutralizes the intense beam self-fields. Typically, the ion bunch charge is better neutralized than its current, and as a result a net self-pinching (magnetic) force is produced. The self-pinching effect is of particular practical importance, and is used in various ion driver designs in order to control the transverse beam envelope. In the present work we demonstrate that this radial self-focusing force can be significantly enhanced if a weak (B {approx} 100 G) solenoidal magnetic field is applied inside the neutralized drift section, thus allowing for substantially improved transport. It is shown that in contrast to magnetic self-pinching, the enhanced collective self-focusing has a radial electric field component and occurs as a result of the overcompensation of the beam charge by plasma electrons, whereas the beam current becomes well-neutralized. As the beam leaves the neutralizing drift section, additional transverse focusing can be applied. Formore » instance, in the neutralized drift compression experiments (NDCX) a strong (several Tesla) final focus solenoid is used for this purpose. In the present analysis we propose that the tight final focus in the NDCX experiments may possibly be achieved by using a much weaker (few hundred Gauss) magnetic lens, provided the ion beam carries an equal amount of co-moving neutralizing electrons from the preceding drift section into the lens. In this case the enhanced focusing is provided by the collective electron dynamics strongly affected by a weak applied magnetic field.« less

Authors:
 [1]; ; ;  [2]
  1. Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)
  2. Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)
Publication Date:
OSTI Identifier:
22072429
Resource Type:
Journal Article
Journal Name:
Physics of Plasmas
Additional Journal Information:
Journal Volume: 19; Journal Issue: 5; Other Information: (c) 2012 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 1070-664X
Country of Publication:
United States
Language:
English
Subject:
43 PARTICLE ACCELERATORS; 70 PLASMA PHYSICS AND FUSION TECHNOLOGY; BEAM CURRENTS; BEAM FOCUSING MAGNETS; COMPRESSION; ELECTRIC FIELDS; ELECTROMAGNETIC LENSES; ELECTRONS; HEAVY IONS; ION BEAMS; MAGNETIC FIELDS; PINCH EFFECT; PLASMA; SOLENOIDS

Citation Formats

Dorf, Mikhail A, Davidson, Ronald C, Kaganovich, Igor D, and Startsev, Edward A. Enhanced collective focusing of intense neutralized ion beam pulses in the presence of weak solenoidal magnetic fields. United States: N. p., 2012. Web. doi:10.1063/1.4722999.
Dorf, Mikhail A, Davidson, Ronald C, Kaganovich, Igor D, & Startsev, Edward A. Enhanced collective focusing of intense neutralized ion beam pulses in the presence of weak solenoidal magnetic fields. United States. https://doi.org/10.1063/1.4722999
Dorf, Mikhail A, Davidson, Ronald C, Kaganovich, Igor D, and Startsev, Edward A. 2012. "Enhanced collective focusing of intense neutralized ion beam pulses in the presence of weak solenoidal magnetic fields". United States. https://doi.org/10.1063/1.4722999.
@article{osti_22072429,
title = {Enhanced collective focusing of intense neutralized ion beam pulses in the presence of weak solenoidal magnetic fields},
author = {Dorf, Mikhail A and Davidson, Ronald C and Kaganovich, Igor D and Startsev, Edward A},
abstractNote = {The design of ion drivers for warm dense matter and high energy density physics applications and heavy ion fusion involves transverse focusing and longitudinal compression of intense ion beams to a small spot size on the target. To facilitate the process, the compression occurs in a long drift section filled with a dense background plasma, which neutralizes the intense beam self-fields. Typically, the ion bunch charge is better neutralized than its current, and as a result a net self-pinching (magnetic) force is produced. The self-pinching effect is of particular practical importance, and is used in various ion driver designs in order to control the transverse beam envelope. In the present work we demonstrate that this radial self-focusing force can be significantly enhanced if a weak (B {approx} 100 G) solenoidal magnetic field is applied inside the neutralized drift section, thus allowing for substantially improved transport. It is shown that in contrast to magnetic self-pinching, the enhanced collective self-focusing has a radial electric field component and occurs as a result of the overcompensation of the beam charge by plasma electrons, whereas the beam current becomes well-neutralized. As the beam leaves the neutralizing drift section, additional transverse focusing can be applied. For instance, in the neutralized drift compression experiments (NDCX) a strong (several Tesla) final focus solenoid is used for this purpose. In the present analysis we propose that the tight final focus in the NDCX experiments may possibly be achieved by using a much weaker (few hundred Gauss) magnetic lens, provided the ion beam carries an equal amount of co-moving neutralizing electrons from the preceding drift section into the lens. In this case the enhanced focusing is provided by the collective electron dynamics strongly affected by a weak applied magnetic field.},
doi = {10.1063/1.4722999},
url = {https://www.osti.gov/biblio/22072429}, journal = {Physics of Plasmas},
issn = {1070-664X},
number = 5,
volume = 19,
place = {United States},
year = {2012},
month = {5}
}

Works referencing / citing this record:

Irradiation of materials with short, intense ion pulses at NDCX-II
journal, May 2017


Sheaths in laboratory and space plasmas
journal, July 2013