High current photoemission with 10 picosecond uv pulses
The quantum efficiency and the optical damage threshold of various metals were explored with 10 ps, 266 nm, UV laser pulses. Efficiencies for Cu, Y, and Sm were: 1.4, 5, and 7 {times} 10{sup {minus}4}, with damage thresholds about 100, 10, and 30 mJ/cm{sup 2}. This would permit over 1 {mu}C/cm{sup 2} or current densities exceeding 100 kA/cm{sup 2}. High charge and current densities of up to 66 kA/cm{sup 2} were obtained on 0.25 mm diam cathodes, and 21 kA/cm{sup 2} on a 3 mm diam yttrium cathode. The maximum currents were limited by space charge and the dc field. The experiments with small area illumination indicate that the emitted electrons spread transversely due to Coulomb repulsion and their initial transverse velocity. This increases the effective area above the cathode, reduces the space charge effect and increases emission density on the cathode. The quantum efficiency can be increased substantially by enhancing the field on the surface by either a suitable electrode geometry or microstructures on it. 14 refs., 12 figs., 3 tabs.
- Research Organization:
- Brookhaven National Lab., Upton, NY (USA)
- Sponsoring Organization:
- DOE; USDOE, Washington, DC (USA)
- DOE Contract Number:
- AC02-76CH00016
- OSTI ID:
- 6139623
- Report Number(s):
- BNL-45443; CONF-9006242--6; ON: DE91009439
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
BREAKDOWN
CATHODES
COPPER
CRYSTAL STRUCTURE
CURRENT DENSITY
EFFICIENCY
ELECTRODES
ELECTROMAGNETIC RADIATION
ELEMENTS
EMISSION
LASER RADIATION
METALS
MICROSTRUCTURE
PHOTOCATHODES
PHOTODIODES
PHOTOEMISSION
QUANTUM EFFICIENCY
RADIATIONS
RARE EARTHS
SAMARIUM
SECONDARY EMISSION
SEMICONDUCTOR DEVICES
SEMICONDUCTOR DIODES
SPACE CHARGE
TRANSITION ELEMENTS
ULTRAVIOLET RADIATION
YTTRIUM