Generation and transport of a low energy intense ion beam

This paper summarizes experimental results on the injection and transport of intense, wide cross-section H ϩ plasmã PB!, and ion beams~IB!, in vacuum and ambient H ϩ plasma across an applied B-field. The injection of plasma and ion beams into magnetic confinement devices have the potential to heat and support current in these systems~e.g., field-reversed configurations!. The translational energies of the PB and IB ranged between E pb ϭ 60 to 120 eV and E IB ϭ 60 to 120 keV, with temperatures and densities in the range of T b ; 2 to 10 eV, n b ; 10 12 to 10 13 cm Ϫ3 , and T b ; 200 eV, n b 10 10 to 10 11 cm Ϫ3 , respectively. Compared to earlier studies~Peter, 1979;Wessel et al., 1988 Wessel et al., , 1990!, this research extends the experimental parameter space to higher beam current densities~up to 30 A0cm 2 ! and higher B-field strengths up to 1.6 kG. The PB and IB were both about 10 cm in diameter at the injection port, and the ratio of beam specific energy to ambient B-field specific energy, b, was in the range of 0.1 to 10. Ratios of beam Larmor radius to beam size, r, ranged from 10 Ϫ1 to 1 and 1 to 10 for the PB and IB, respectively. Cross B-field propagation of the PB in vacuum was undeflected as a whole with a sharp increase~one order or more! in the current density of the central beam core at B-field levels . 1 kG accompanied by a significant loss of beam peripheral layers, beam "braking" and preferential beam expansion along the B-field lines. Cross B-field propagation of the PB in ambient plasma did not differ substantially from the case without B-field, that is, no deflection of the PB as a whole, which could be due to an insufficient neutralization of the induced E-field inside the PB. Cross B-field propagation of the IB in ambient plasma followed a single particle trajectory deflection with a simultaneous significant loss of IB intensity without any detectable bunching, indicating an adequate shorting of the polarization E-field inside the IB.

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Significance of time-of-flight ion energy spectrum on energy deposition into matter by high-intensity pulsed ion beam

Xin

Zhu

Lei

2010

Laser Part. Beams

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Energy deposition by high-intensity pulsed ion beam into a metal target has been studied with time-of-flight (TOF) of ions which can be related to the original ion kinetic energy E0 and the ion mass with $t_{\rm TOF} \propto 1/\sqrt{2E_{0}/m_{i}}$. It is found that the TOF effect has a profound influence on the kinetic energy distribution of implanted ions and subsequent energy deposition process into the target. The HIPIB of mixed H+ and C+ was extracted from a magnetically insulated ion diode at a peak accelerating voltage of 350 kV, leading to an ion current density of 300 A/cm2 at the target. The widespread ion energy spectrum remarkably varied in shape as arriving at the target surface, from the original Gaussian-like of 80-ns duration to a pulse form of a sharp front and a long tail extending to about 140-ns duration. Energy loss of the mixed ions into a Ti target was simulated utilizing a Monte Carlo method. The energy deposition generally showed a shallowing trend and could be divided into two phases proceeded with sequent arrivals of H+ and C+. Note that, the peak value of deposited energy profile appeared at the beginning of mixed ion irradiation phase, other than the phase of firstly arrived H+ with peak kinetic energy and peak ion current. This study indicated that TOF effect of ions greatly affects the HIPIB-matter interaction with a kinetic energy spectrum of impinging ions at the target, noticeably differing from that of original output of the ion source; consequently, the specific energy deposition phenomena of the widespread ion energy can be studied with the TOF correlation of ion energy and ion current, otherwise not obtainable in common cases assuming fixed ion energy distribution in accordance with the original source output.

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Generation and transport of a low energy intense ion beam

Cited by 14 publications

References 15 publications

Double and multi-pulsed operations of inductive plasma sources

Double and multi-pulsed operations of inductive plasma sources

Propagation of intense plasma and ion beams across B-field in vacuum and magnetized plasma

Significance of time-of-flight ion energy spectrum on energy deposition into matter by high-intensity pulsed ion beam

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