研究目的
To develop next generation gamma-ray Cherenkov detectors for the National Ignition Facility to improve sensitivity, reduce temporal response, and lower energy threshold for fusion reaction history and ablator areal density measurements.
研究成果
The first phase for next generation GCD at NIF has demonstrated the viability for making relatively clean reaction history measurements in a high radiation environment. The results support proceeding to the next phases, including the implementation of a pulse-dilation photomultiplier tube and the design of a NIF-specific 'Super' GCD.
研究不足
The precursor signal and snout gamma background can interfere with the Cherenkov signal, potentially corrupting the tail of the prompt signal and broadening the burn width measurement. Mitigation strategies are under consideration to improve signal-to-background ratio.
1：Experimental Design and Method Selection:
The study involves the insertion of the existing coaxial GCD-3 detector into a reentrant well within 4 m of the implosion at the National Ignition Facility. The methodology includes comparing GCD-3 signals with those of GRH at the same gamma-ray energy threshold to assess background issues.
2：Sample Selection and Data Sources:
Data from two NIF shots were taken at thresholds of 2.9 MeV and 8 MeV, normalized by the PMT sensitivity and total neutron yield.
3：9 MeV and 8 MeV, normalized by the PMT sensitivity and total neutron yield.
List of Experimental Equipment and Materials:
3. List of Experimental Equipment and Materials: GCD-3 detector, GRH 6m diagnostic, pressurized gas cells (SF6 and CO2), photomultiplier tubes (PMTs), and Cassegrain optics.
4：Experimental Procedures and Operational Workflow:
The GCD-3 was operated at different gamma-ray energy thresholds to measure reaction history and ablator gamma signals. Background measurements were also conducted by evacuating the GCD gas cell for a 'null' shot.
5：Data Analysis Methods:
Deconvolution of signals was performed to extract reaction history, with and without background subtraction, to assess the impact of background on signal quality.
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