研究目的
To describe a procedure for absolute calibration of Bragg crystals used in X-ray spectroscopy of laser plasmas using a commercial mini-X-ray source.
研究成果
The paper presents a straightforward and cost-effective method for absolute calibration of Bragg crystals using a commercial X-ray source and photon counting techniques. The integrated reflectivity measurements for flat and curved crystals were achieved with reasonable accuracy (errors around 10% or less), making the method useful for X-ray spectroscopy in laser plasma experiments. Future improvements could involve longer data collection times to reduce errors further.
研究不足
The method has error bars in the range of 10–20% for flat crystals and 5–6% for curved crystals, which may not be sufficient for high-precision applications. The angular variation of emission from the foil and potential inaccuracies in distance measurements contribute to systematic errors. The technique is limited to the 4–5 keV energy range and requires careful handling of thermal noise and photon counting statistics.
1：Experimental Design and Method Selection:
The method involves using a commercial X-ray source to pump metallic foils (e.g., vanadium or titanium) to generate K-α emission, followed by photon counting with a CCD detector for calibrating flat and curved Bragg crystals in the 4–5 keV energy range. The design rationale is to achieve absolute calibration without needing absolute calibration of the source or detector.
2：Sample Selection and Data Sources:
Metallic foils such as vanadium or titanium with thicknesses around 10 μm were used. Data were acquired using a CCD detector in photon counting mode.
3：List of Experimental Equipment and Materials:
Equipment includes a commercial mini-X-ray source (Amptek, mini-X), metallic foils (e.g., vanadium, titanium), a CCD detector (Andor DX420-BN), lead shielding, collimators, and an enclosure made of aluminum and lead. Materials also include HOPG and Si(111) crystals for calibration.
4：Experimental Procedures and Operational Workflow:
The X-ray source pumps the foil to produce K-α photons. The CCD detector is placed at specific distances and angles to measure photon counts directly and after reflection from Bragg crystals. Multiple runs with short integration times are used to minimize errors from thermal noise and multiple photon events.
5：Data Analysis Methods:
Data analysis involves background subtraction, Gaussian fitting of photon count histograms, and calculation of integrated reflectivity using solid angle and distance measurements. Error analysis includes statistical errors from fitting and systematic errors from distance measurements.
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