Recent measurements using acoustic gas thermometry have determined the value of the Boltzmann constant, k, with a relative uncertainty less than 1 × 10-6. These results have been supported by a measurement with a relative uncertainty of 1.9 × 10-6 made with dielectric-constant gas thermometry. Together, the measurements meet the requirements of the International Committee for Weights and Measures and enable them to proceed with the redefinition of the kelvin in 2018. In further support, we provide a new determination of k using a purely electronic approach, Johnson noise thermometry, in which the thermal noise power generated by a sensing resistor immersed in a triple-point-of-water cell is compared to the noise power of a quantum-accurate pseudo-random noise waveform of nominally equal noise power. The experimental setup differs from that of the 2015 determination in several respects: a 100 Ω resistor is used as the thermal noise source, identical thin coaxial cables made of solid beryllium-copper conductors and foam dielectrics are used to connect the thermal and quantum-accurate noise sources to the correlator so as to minimize the temperature and frequency sensitivity of the impedances in the connecting leads, and no trimming capacitors or inductors are inserted into the connecting leads. The combination of reduced uncertainty due to spectral mismatches in the connecting leads and reduced statistical uncertainty due to a longer integration period of 100 d results in an improved determination of k = 1.380 649 7(37) × 10-23 J K-1 with a relative standard uncertainty of 2.7 × 10-6 and a relative offset of 0.89 × 10-6 from the CODATA 2014 recommended value. The most significant terms in the uncertainty budget, the statistical uncertainty and the spectral-mismatch uncertainty, are uncorrelated with the corresponding uncertainties in the 2015 measurements.

中文翻译：

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通过约翰逊噪声测温法对玻尔兹曼常数进行改进的电子测定


最近使用声学气体测温法的测量确定了玻尔兹曼常数 k 的值，相对不确定度小于 1 × 10-6。这些结果得到了介电常数气体测温法相对不确定度为 1.9 × 10-6 的测量的支持。总之，这些测量结果满足国际度量衡委员会的要求，并使他们能够在 2018 年继续重新定义开尔文。为了进一步支持，我们使用纯电子方法约翰逊噪声测温法提供了新的 k 测定方法，其中将浸没在水三相点池中的传感电阻器产生的热噪声功率与标称噪声功率相等的量子精确伪随机噪声波形的噪声功率进行比较。该实验设置在几个方面与 2015 年的测定有所不同：使用 100 Ω 电阻器作为热噪声源，使用由实心铍铜导体和泡沫电介质制成的相同细同轴电缆来连接热和量子精确度相关器的噪声源，以最小化连接引线中的阻抗的温度和频率敏感性，并且没有微调电容器或电感器插入连接引线中。由于连接引线中的光谱不匹配而减少的不确定性以及由于 100 d 的较长积分周期而减少的统计不确定性相结合，改进了 k = 1.380 649 7(37) × 10-23 J K-1 的测定，其中相对标准不确定度为 2.7 × 10-6，与 CODATA 2014 建议值的相对偏移为 0.89 × 10-6。 不确定性预算中最重要的项、统计不确定性和光谱失配不确定性与 2015 年测量中相应的不确定性不相关。