Plasma uniformity issues in a 2 x 1 plasma-electrode Pockels cell
- Lawrence Livermore National Lab., CA (United States)
An optical switch based on large-aperture plasma-electrode Pockels cells (PEPC) is an important part of the National Ignition Facility (NIF) laser design. In a PEPC, low-pressure helium discharges (1--2 kA) are formed on both sides of a thin slab of electro-optic material (typically KDP). These discharges form highly conductive, transparent sheets which allow uniform application of a high-voltage (17 kV) across the crystal. A 37 cm x 37 cm PEPC has been in routine operation for two years on the 6 kJ Beamlet laser at LLNL. For the NIF, a module four apertures high by one wide (4 x 1) is required. However, this 4 x 1 mechanical module will be comprised electrically of a pair of 2 x 1 submodules. To achieve uniform electro-optic switching across the entire PEPC aperture, it is important that the plasma density be sufficient high and sufficiently uniform. The authors have observed a number of plasma effects which can degrade plasma uniformity. These include magnetic displacement of the plasma by external return currents and nearby sources of magnetic interference, current channel formation due to plasma self-fields, anode and cathode electrode design, and the potential of the insulated metal housing that surrounds the plasma. They have studied these effects both analytically and experimentally in a 32 cm x 32 cm plastic housing PEPC and more recently in an 80 cm x 40 cm, two-aperture, aluminum-housing PEPC. The results of this work are presented here.
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 323573
- Report Number(s):
- CONF-970559--
- Country of Publication:
- United States
- Language:
- English
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