Metal ion plasmas are produced by vacuum
arcs. These plasma are fully ionized and characterized by the presence
of multiply charged ions (see the Table of ion
charge state distributions). Ions are formed in the plasma and accelerated
by the electric field between extraction electrodes; the final ion energies
are typically from a few to a few hundred keV.
Vacuum arc ion sources are also referred to as Metal Vapor Vacuum Arc (MEVVA) Ion Sources. Over the years, we have developed a "family" of Mevva ion sources (I.G. Brown, "The Physics and Technology of Ion Sources", Wiley, New York, 1989; I.G. Brown, Review of Scientific instruments 65 (1994) 3061; see also Publications):
1. MicroMEVVA
A miniature embodiment, 6 cm long, 1.5 cm in diameter. Beam currents
of 15 mA at 15 kV have been made.
2. MEVVA II
Single-cathode design in which the cathode is a central rod surrounded
coaxially by an alumina insulator and a trigger electrode. Pulse length
typically 250 µs, arc current 50-500 A.
3. MEVVA III
Embodiment residing completely in vacuum, about 5 cm long and 5 cm
in diameter. Ion beam pulses similar to MEVVA II, hundreds of milliamperes,
but limited duty cycle due to thermal load issues.
4. MEVVA IV
16 cathode version, cathodes mounted on revolver (Gatling-gun-like
fashion) allowing changing the cathode material without breaking vacuum.
Operational extractor voltage up to 100 kV.
5. MEVVA V
Similar to MEVVA IV, with 18 cathodes and some improved features to
enhance ease of operation and maintenance. Our ìworkhorseî
for broad beam ion implantation.
6. MEVVA VI
Very broad beam version (ion beam diameter 50 cm) with single cathode.
(see picture at point 10)
7. MEVVA VII
Metal ion source with filtered vacuum
arc plasma with macroparticle-free ion implantation.
(see S. Anders, A. Anders, I. G. Brown, R. A. MacGill, and M. R. Dickinson,
Review Scientific Instruments, vol. 65 (1994) 1319-1321; see also Publications).
8. LEVA
LEVA is an acronym for "Low Energy Vacuum Arc" ion source. 16 cm long,
6 cm in diameter, with 19 beamlet holes with a total ion beam diameter
of 1.5 cm. Low ion energy refers to the range of order 1 keV, achieved
with three-grid-extractor system of almost symmetric potential distribution.
(See Publications)
Modified MEVVA V version with strong axial field in the discharge region. Enhanced ion charge states. (See, E. M. Oks, A. Anders, I. G. Brown, M. R. Dickinson, R. A. MacGill, Nuclear Instruments and Methods in Physics Research B, vol. 127/128 (1997) 779-781; see also Publications).
10. MAGIS
MAGIS is an acronym for "MArx-Generator-based Ion Source". This is a
short-pulse ion source in which the discharge is a high-current vacuum
spark, rather than an arc (i.e., the voltage between anode and cathode
is much higher than the arc-typical 20 Volts). High charge states have
been obtained (up to +8 for tungsten and +6 for copper). (see A.
Anders, I. G. Brown, M. R. Dickinson, and R. A. MacGill, Nuclear Instruments
and Methods in Physics Research B, vol. 127/128 (1997) 992-995; see
also
Publications).
For more information on contact André Anders or Ian Brown.
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