The extraordinary properties of diamond, such as ultrawide bandgap (%5.5 eV), radiation hardness, high resistivity, and high carrier mobility, make it an ideal material for robust radiation detectors yet with a simple structure. [1][2][3][4] In recent years, the quality of chemical vapor deposition (CVD) single-crystal diamond (SCD) has been greatly improved, [5] which makes SCD detectors possible in counting and spectroscopy applications. At present, SCD detectors are widely used in fusion experiments, medical, and fission reactor applications, which are emerging as nextgeneration semiconductor radiation detectors with great potential. [6] Due to the extremely high resistivity of the diamond film [7] (usually > 10 12 Ω cm), the device configuration of the SCD detector is simple, not requiring p-n junctions for low leakage current as any other counterpart. [8,9] In general, the SCD detector utilizes a vertical "sandwich" layout of a metal-semiconductor-metal (MSM) structure with low capacitance, fast response, and low noise. [10] The physical mechanism of SCD detectors is similar to that of other semiconductor detectors, operated by generating current out of ionizing radiation. [11] SCD detectors therefore can be used to measure α-particles, electrons, [12] X-rays, γ-rays, [13] and neutrons. [14] However, these applications rely on the high performance of the detector, in which charge collection efficiency (CCE), energy resolution, and time response are the three leading criteria to evaluate the performance of SCD detectors. The detector's performance greatly depends on the properties of the diamond. [15,16] In addition, accurate neutron monitoring in high-radiation flux of the fission and fusion reactors [17,18] requires algorithms that can distinguish the signals of interests from the background. As SCD detectors are sensitive to γ-rays, it is necessary in these applications to distinguish neutrons from γ-rays background. In fact, high-energy neutron radiation would induce "point-like" ionizations over the entire volume of the SCD, as heavily charged products of the nuclear reaction are greatly localized with their short range. However, this is different from the effects caused by the incident γ-rays. When the MeV

Single‐Crystal Diamond DetectorsA high‐performance single‐crystal diamond (SCD) detector (4.5 × 4.5 × 0.3 mm3) is demonstrated in article number http://doi.wiley.com/10.1002/adpr.202100138 by Chun‐Zhi Zhou, Yi‐Yun Zhang, and co‐workers. Enabled by a machine learning method based on self‐organizing map neural networks as a proof of concept, the SCD detector has demonstrated its potential for accurate pulse shape discrimination, which can effectively distinguish particle radiations in harsh and complex radiation conditions.