Laser-driven ion sources for high-brightness high-purity ion beams
- Sandia National Labs., Albuquerque, NM (United States); and others
Surface-plasma ion sources are critical to generating high-brightness, high purity ion beams on applied-B ion diodes. The source plasma must meet requirements for species, thickness, purity, degree of ionization, conductivity, formation timescale, and engineering feasibility. Laser ionization schemes have been used on high-power ion diodes with encouraging but inconsistent results in diode impedance and beam purity. The authors are characterizing two laser-driven Li{sup +} schemes for 100--200 cm{sup 2} sources: a single 10 ns Nd:YAG pulse at 0.3--1 J/cm{sup 2}, or the 2-laser LEVIS scheme. Recognizing anode surface contamination as a key issue in 10{sup {minus}5}--10{sup {minus}6} Torr pulsedpower vacuum, they subject well-characterized 0.5 {micro}m LiAg films on stainless substrates to extended 150--400 C heating and plasma discharge sputter cleaning after pumpdown in a test chamber, prior to pulsing the source lasers. A detailed diagnostic set includes absolutely-calibrated, streaked, CCD-imaged spectrographs for plasma properties, 2-color laser deflection for plasma/neutral expansion, ion time-of-flight spectrograph with ionizer for species content, and a tunable narrow-band dye laser for near-resonant absorption. The drive laser uniformity is measured with a CCD. Initial results on uncleaned LiAg show a single laser at >0.3 J/cm{sup 2} can generate thin dense plasma, with acceptable expansion speeds at or below 2 cm/{micro}s.
- Research Organization:
- Sandia National Laboratory
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC04-94AL85000
- OSTI ID:
- 321038
- Report Number(s):
- CONF-970559--
- Country of Publication:
- United States
- Language:
- English
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