研究目的
To investigate the detection efficiency of microchannel plate (MCP) detectors to direct impacts for both positively and negatively charged micron and submicron sized iron particles, and to characterize these detectors for space-based dust density studies.
研究成果
The MCP detection efficiency was found to be (6 ± 1)% for positively charged dust and (9 ± 3)% for negatively charged dust particles. This result can help further define dust density when space-based MCP detectors encounter nanograin dust regions. The study also suggests that previous estimates of nanograin number densities derived by CAPS in the vicinity of Enceladus may be a factor of 10–20 too high.
研究不足
The study was limited to low velocity (0.02 to 0.3 km/s) dust particles, and the detection efficiency for higher velocity particles remains to be tested. Additionally, the possibility of individual channel destruction in the MCP due to dust impacts was not reliably determined.
1：Experimental Design and Method Selection:
A double-stack MCP detector in a chevron configuration was mounted as a target in a dust accelerator. A range of particle velocities and masses were used for a comprehensive examination.
2：Sample Selection and Data Sources:
The dust used was a mixture of spherical iron particles with radii in the range of 60 nm < r < 2 μm. Con?rmed and recorded iron impactors ranged in charge from 0.2 fC < q < 0.9 fC for positive dust, and 0.6 fC < q < 1.0 fC for negatively charged dust.
3：2 fC < q < 9 fC for positive dust, and 6 fC < q < 0 fC for negatively charged dust.
List of Experimental Equipment and Materials:
3. List of Experimental Equipment and Materials: DEL MAR MCP 25-10E double stack, in a Chevron orientation, dust accelerator.
4：Experimental Procedures and Operational Workflow:
The process of accelerating dust is achieved by contact between dust particles in a reservoir and a high-voltage tungsten needle. The needle and chamber are biased to a high potential, up to 20 kV. The dust reservoir potential is then pulsed causing dust particles to swirl inside the reservoir. A dust particle contacting the needle becomes electrically charged, and accelerated toward the grounded exit aperture.
5：Data Analysis Methods:
The detection efficiency was calculated by the ratio of detected signals to total confirmed dust strikes, with uncertainty calculated using Poisson statistics.
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