The DCU laser ion source

Journal Article · Thu Apr 15 00:00:00 EDT 2010 · Review of Scientific Instruments

DOI:https://doi.org/10.1063/1.3374123· OSTI ID:22053974

Yeates, P ^[1]; Costello, J T; Kennedy, E T ^[1]

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1. National Centre for Plasma Science and Technology (NCPST), Dublin (Ireland)

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 (LIS). The theoretical aspects of a high voltage (HV) 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{approx}10{sup 8}-10{sup 11} W cm{sup -2}) and fluences (F=0.1-3.9 kJ cm{sup -2}) from a Q-switched ruby laser (full-width half-maximum pulse duration {approx}35 ns, {lambda}=694 nm) 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 kV). 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{approx}600 {mu}A for Cu{sup +} to Cu{sup 3+} ions were recorded. The maximum collected charge reached 94 pC (Cu{sup 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 mm) 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{sup 2+}) were recorded. The collected currents of more highly charged ions (Cu{sup 4+}-Cu{sup 6+}) increased considerably in this mode of operation.

• OSTI ID: 22053974
• Journal Information: Review of Scientific Instruments, Vol. 81, Issue 4; Other Information: (c) 2010 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0034-6748
• Country of Publication: United States
• Language: English

Related Subjects

43 PARTICLE ACCELERATORS
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
BEAM TRANSPORT
BEAM-PLASMA SYSTEMS
COPPER
COPPER IONS
DRIFT TUBES
EFFICIENCY
ELECTRIC POTENTIAL
ELECTROSTATIC LENSES
EXTRACTION
FARADAY CUPS
ION BEAMS
ION PROBES
ION SOURCES
PLASMA
PLASMA DIAGNOSTICS
POWER DENSITY
Q-SWITCHING
RUBY LASERS
SIMULATION