Study of cosmogenic activation in copper for rare event search experiments

Rare event search experiments using germanium detectors are performed in underground laboratories to minimize the background induced by cosmic rays. However, the cosmogenic activation of cupreous detector components on the ground generates long half-life radioisotopes and contributes to the background level. We measured cosmogenic activation with 142.50 kg of copper bricks after 504 days of exposure at an altitude of 2469.4 m outside the China Jinping Underground Laboratory (CJPL). The specific activities of the cosmogenic nuclides produced in the copper bricks were measured using a low-background germanium gamma-ray spectrometer at CJPL. The production rates at sea level, in units of nuclei/kg/day, were $${18.6 \pm 2.0}$$ 18.6 ± 2.0 for $${^{54}}$$ 54 Mn, $${9.9 \pm 1.3}$$ 9.9 ± 1.3 for $${^{56}}$$ 56 Co, $${48.3 \pm 5.5}$$ 48.3 ± 5.5 for $${^{57}}$$ 57 Co, $${51.8 \pm 2.5}$$ 51.8 ± 2.5 for $${^{58}}$$ 58 Co, and $${39.7 \pm 5.7}$$ 39.7 ± 5.7 for $${^{60}}$$ 60 Co. The measurement will help to constrain cosmogenic background estimation for rare event searches using copper as a detector structure and shielding material. Based on the measured production rates, the impact of the cosmogenic background in cupreous components of germanium detectors on the next generation CDEX-100 experiment was assessed with the expected exposure history above ground.

Application of strip electrode in single-gap RPC

The Resistive Plate Chamber (RPC) is widely used in High Energy Physics experiments as trigger detector to take advantage of its good time resolution and high efficiency. A conventional RPC detector consists of one gas gap covered by graphite layers on both side. The working voltage is applied on these layers and the charge of avalanche dissipates through them. In this paper, a design which removes the graphite layers and uses the readout strips as the electrode is applied to simplify the structure of this detector. This design eliminates the challenge of controlling the uniformity of the graphite layer and simplifies the detector structure.

SAVSDN: A Scene-Aware Video Spark Detection Network for Aero Engine Intelligent Test

Due to carbon deposits, lean flames, or damaged metal parts, sparks can occur in aero engine chambers. At present, the detection of such sparks deeply depends on laborious manual work. Considering that interference has the same features as sparks, almost all existing object detectors cannot replace humans in carrying out high-precision spark detection. In this paper, we propose a scene-aware spark detection network, consisting of an information fusion-based cascading video codec-image object detector structure, which we name SAVSDN. Unlike video object detectors utilizing candidate boxes from adjacent frames to assist in the current prediction, we find that efforts should be made to extract the spatio-temporal features of adjacent frames to reduce over-detection. Visualization experiments show that SAVSDN can learn the difference in spatio-temporal features between sparks and interference. To solve the problem of a lack of aero engine anomalous spark data, we introduce a method to generate simulated spark images based on the Gaussian function. In addition, we publish the first simulated aero engine spark data set, which we name SAES. In our experiments, SAVSDN far outperformed state-of-the-art detection models for spark detection in terms of five metrics.

A Self-Test, Self-Calibration and Self-Repair Methodology of Thermopile Infrared Detector

To improve the reliability and yield of thermopile infrared detectors, a self-test, self-calibration and self-repair methodology is proposed in this paper. A novel micro-electro-mechanical system (MEMS) infrared thermopile detector structure is designed in this method with a heating resistor building on the center of the membrane. The heating resistor is used as the stimuli of the sensing element on chip to achieve a self-test, and the responsivity related with ambient temperature can be calibrated by the equivalent model between electrical stimuli and physical stimuli. Furthermore, a fault tolerance mechanism is also proposed to localize the fault and repair the detector if the detector fails the test. The simulation results with faults simulated by the Monte Carlo stochastic model show that the proposed scheme is an effective solution to improve the yield of the MEMS thermopile infrared detector.

Детектирование терагерцевых электромагнитных волн с помощью проводящих антиферромагнетиков

We investigate a mathematical model of a terahertz electromagnetic wave detector based on a conducting antiferromagnet and a heavy metal. The mechanism of resonant straightening of oscillations is based on the inverse spin Hall effect in a heavy metal under spin pumping from an antiferromagnet. It is shown that the frequency dependence of the constant voltage of the detector has a resonant character with a peak corresponding to the frequency of antiferromagnetic resonance. The sensitivity to an alternating terahertz signal of the proposed detector structure is comparable to the sensitivity of modern detectors based on Schottky and Gunn diodes.

InAs/InAsSb Strained-Layer Superlattice Mid-Wavelength Infrared Detector for High-Temperature Operation

This paper reports an InAs/InAsSb strained-layer superlattice (SLS) mid-wavelength infrared detector and a focal plane array particularly suited for high-temperature operation. Utilizing the nBn architecture, the detector structure was grown by molecular beam epitaxy and consists of a 5.5 µm thick n-type SLS as the infrared-absorbing element. Through detailed characterization, it was found that the detector exhibits a cut-off wavelength of 5.5 um, a peak external quantum efficiency (without anti-reflection coating) of 56%, and a dark current of 3.4 × 10−4 A/cm2, which is a factor of 9 times Rule 07, at 160 K temperature. It was also found that the quantum efficiency increases with temperature and reaches ~56% at 140 K, which is probably due to the diffusion length being shorter than the absorber thickness at temperatures below 140 K. A 320 × 256 focal plane array was also fabricated and tested, revealing noise equivalent temperature difference of ~10 mK at 80 K with f/2.3 optics and 3 ms integration time. The overall performance indicates that these SLS detectors have the potential to reach the performance comparable to InSb detectors at temperatures higher than 80 K, enabling high-temperature operation.

Numerical Analysis of Dark Currents in T2SL nBn Detector Grown by MBE on GaAs Substrate

The paper presents the numerical analysis of the performance of the nBn type-II superlattice barrier detector operated at 230 K. Results of theoretical predictions were compared to the experimental data for the nBn detector composed of AlAs0.15Sb0.85 barrier and InAs (5.096 nm)/InAs0.62Sb0.38 (1.94 nm) superlattice absorber and contact layer. Detector structure was grown on GaAs substrate using molecular beam epitaxy. To determine the position of the electron miniband and the first heavy hole state in the superlattice, we have used a k·p model which can also predict the absorption spectrum and the cut-off wavelength of an absorber layer. As shown, the most important parameters in the nBn structure optimization is the barrier height in the valence band. While the barrier in the conduction band must be high enough to prevent the flow of the electron current from the contact layer to the absorber, the barrier in the valence band must be sufficiently low to ensure the flow and a collection of optically generated holes. The position of the valence band edge for the AlAsSb barrier was changed by changing the valence band bowing parameter for this ternary material. Proper fit of the calculated plot to our experimental data was obtained assuming no bowing in the valence band for AlAsSb barrier.

Design and Numerical Evaluation of a Highly Selective CMOS-Compatible Mid-IR Thermal Emitter/Detector Structure Using Optical Tamm-States

In this work we propose and evaluate a concept for a selective thermal emitter suitable for monolithic on-chip integration suitable for fabrication by conventional CMOS-compatible processes. The concept is based on our recently presented work on vertical-cavity enhanced resonant thermal emission (VERTE). Here we present the application of this concept to a slab waveguide structure, instead of depositing extended dielectric layers forming a one-dimensional photonic crystal. We optimize the dimension by certain design considerations and geneticalgorithm optimization and demonstrate effective absorbing/emitting properties (depending on different slab heights) of such a low-cost structure by exciting so-called optical Tamm-states on the metal-dielectric interface.