中国计量科学研究院引进了高温黑体BB3500M作为新的光谱辐射照度基准光源。黑体BB3500M包括辐射腔体和温度反馈系统。辐射腔体由一系列高温热解石墨环组成,可以加热至3 500 K。在光谱辐照度测量中,高温黑体的性能参数和温度测量至关重要。对于黑体的性能参数,着重考察了黑体温度的稳定性和腔底温度的均匀性。在将高温黑体的光谱辐射照度传递给工作标准灯时,黑体的温度可能发生改变。实验观测了一小时内黑体的温度漂移情况。当高温黑体加热至3 016 K时,采用温度反馈系统的BB3500M稳定在±0.3 K。实验光路中设置了限制光栏,用于屏蔽来自黑体腔壁的辐射。黑体腔底辐射环的温度均匀性优于0.2 K。在温度测量中,2 473 K以下的温度可以直接溯源到中国计量科学研究院热工处,对于更高温度的测量需要进行温度延伸。文中从普朗克公式出发,通过多波长亮度比较法进行了温度延伸。实验先在低温区进行延伸证实了方法的可能性,然后进行了高温区的温度延伸。

High temperature blackbody BB 3 500 M was used as the primary standard of spectral irradiance at national institute of metrology (NIM). The blackbody BB 3 500 M cavity radiator was consisted of a series of pyrolytic-graphite (PG) rings, capable of operating at temperature up to 3 500 K. Feedback control mode was used to stabilize the temperature of the blackbody. The stability of the radiator and the blackbody uniformity were measured. In transferring the spectral irradiance from the blackbody to the working standard lamp, the temperature of the blackbody may change. In the experiment, temperature drift within an hour was tested. When the blackbody was heated up to around 3 016 K, the temperature uncertainty was less than 0.3 K. In the radiation path, an aperture was used to screen the radiation from the cylindrical part of the radiation cavity. However, the temperature was not the same all over the effective area of the graphite bottom. The uniformity of the bottom of BB 3 500 M was found to be within 0.2 K. Results showed that BB 3 500 M was suitable for the primary radiation source. In the temperature measurement, temperature below 2 473 K could be traceable to the heat division of NIM. Then the temperature could be extended through the comparison of the spectral radiance at fixed wavelength. In the experiment, the temperature extend was first investigated in low temperature region no higher than 2 473 to verify its applicability. Results in high temperature region showed good consistence that the temperature divergence was smaller than 0.5 K at 345 nm～360 nm wavelength.