Grid-controlled extraction of pulsed ion beams

Humphries, S.; Burkhart, C.; Coffey, S.K.; Cooper, G. W.; Len, L. K.; Savage, M. E.; Woodall, D. M.; Rutkowski, H.L.; Oona, H.; Shurter, R. B.

doi:10.1063/1.336401

Cited by 32 publications

(8 citation statements)

References 7 publications

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“…These lead to strong modulation of the extracted beam current using a multiaperture anode 19 or concave extraction electrodes. [20][21][22][23] One can also minimize the diameter of the extraction aperture relative to the plume radius so that only paraxial plasma ions are extracted, reducing beam divergence after injection. Of course, this also lowers the extracted current density.…”

Section: B Extraction Dynamicsmentioning

confidence: 99%

The DCU laser ion source

Yeates¹,

Costello

Kennedy

2010

Review of Scientific Instruments

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Laser ion sources are used to generate and deliver highly charged ions of various masses and energies. We present details on the design and basic parameters of the DCU laser ion source ͑LIS͒. The theoretical aspects of a high voltage ͑HV͒ linear LIS are presented and the main issues surrounding laser-plasma formation, ion extraction and modeling of beam transport in relation to the operation of a LIS are detailed. A range of laser power densities ͑I ϳ 10 8 -10 11 W cm −2 ͒ and fluences ͑F = 0.1-3.9 kJ cm −2 ͒ from a Q-switched ruby laser ͑full-width half-maximum pulse duration ϳ35 ns, = 694 nm͒ were used to generate a copper plasma. In "basic operating mode," laser generated plasma ions are electrostatically accelerated using a dc HV bias ͑5-18 kV͒. A traditional einzel electrostatic lens system is utilized to transport and collimate the extracted ion beam for detection via a Faraday cup. Peak currents of up to I ϳ 600 A for Cu + to Cu 3+ ions were recorded. The maximum collected charge reached 94 pC ͑Cu 2+ ͒. Hydrodynamic simulations and ion probe diagnostics were used to study the plasma plume within the extraction gap. The system measured performance and electrodynamic simulations indicated that the use of a short field-free ͑L =48 mm͒ region results in rapid expansion of the injected ion beam in the drift tube. This severely limits the efficiency of the electrostatic lens system and consequently the sources performance. Simulations of ion beam dynamics in a "continuous einzel array" were performed and experimentally verified to counter the strong space-charge force present in the ion beam which results from plasma extraction close to the target surface. Ion beam acceleration and injection thus occur at "high pressure." In "enhanced operating mode," peak currents of 3.26 mA ͑Cu 2+ ͒ were recorded. The collected currents of more highly charged ions ͑Cu 4+ -Cu 6+ ͒ increased considerably in this mode of operation.

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Section: B Extraction Dynamicsmentioning

confidence: 99%

The DCU laser ion source

Yeates¹,

Costello

Kennedy

2010

Review of Scientific Instruments

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“…The width of the ion sheath around the wires is determined by the balance between the plasma ion flux and space-charge-limited current flowing through the sheath [5,7]. These sheath regions work as a barrier for plasma electrons.…”

Section: Resultsmentioning

confidence: 99%

“…Hence the beam optics and the beam current waveform are expected to be unstable in such a ''plasma prefill'' mode [4 -6]. In order to eliminate such a beam-extraction mode, one can apply a negative bias voltage on a fine metallic mesh attached to the anode [7,8].…”

Section: Introductionmentioning

confidence: 99%

Extraction of high-intensity ion beams from a laser plasma by a pulsed spherical diode

Oguri

Kashiwagi

Kaneko

et al. 2005

Phys. Rev. ST Accel. Beams

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High-current Cu ion beams were extracted from a laser-produced plasma using a pulsed high-voltage multiaperture diode driven by an induction cavity. The amplitude and the duration of the extraction voltage were 130 kV and 450 ns, respectively. During the extraction, explosive beam divergence due to the strong space-charge force was suppressed by the focusing action of the gap between concentric hemispheres. Modulation of the extracted beam flux due to the plasma prefill in the gap has been eliminated by using a biased control grid put on the anode holes. By means of this extraction scheme we obtained a rectangular beam pulse with a rise time as short as 100 ns. The beam current behind the cathode was limited to 0:1 A, owing to space-charge effects, as well as to poor geometrical transmission through the cathode sphere. From the measurement of the extracted beam current density distribution along the beam axis and the beam profile measurement, we found a beam waist slightly downstream of the spherical center of the diode structure. The measured beam behavior was consistent with numerical results obtained via a 3D particle code. No serious degradation of the beam emittance was observed for the grid-controlled extraction scheme.

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“…Humphries and co-workers developed a technique for reduction in ion beam noise level by the use of wire meshes to reflect plasma electrons and to limit pure ion flow by its own space charge [31]. In the case of space-charge-limited flow the extracted ion beam current is independent of the plasma fluctuation level and random plasma generation at the cathode spots.…”

Section: B Beam Noise and Pulse Shape Reproducibilitymentioning

confidence: 99%

Vacuum arc ion sources: recent developments and applications

Brown

Окс

2005

IEEE Trans. Plasma Sci.

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The vacuum arc ion source has evolved over the past twenty years into a standard laboratory tool for the production of high current beams of metal ions, and is now used in a number of different embodiments at many laboratories around the world. The primary application of this kind of source has evolved to be ion implantation for material surface modification. Another important use is for injection of high current beams of heavy metal ions into the front ends of particle accelerators, and much excellent work has been carried out in recent years in optimizing the source for reliable accelerator application. The source also provides a valuable tool for the investigation of the fundamental plasma physics of vacuum arc plasma discharges. As the use of the source has grown and diversified, at the same time the ion source performance and operational characteristics have been improved in a variety of different ways also. Here we review the growth and status of vacuum arc ion sources around the world, and summarize some of the applications for which the sources have been used. _________________________Index Terms -Ion source, vacuum arc, cathode spot, metal ion beam, ion implantation 1

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Grid-controlled extraction of pulsed ion beams

Cited by 32 publications

References 7 publications

The DCU laser ion source

The DCU laser ion source

Extraction of high-intensity ion beams from a laser plasma by a pulsed spherical diode

Vacuum arc ion sources: recent developments and applications

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