The diffraction detector for the EMD of the CSNS

On 23rd August 2018, the China Spallation Neutron Source (CSNS) located in Dongguan operated 4 neutron instruments. In the future, twenty neutron spectrometers will be built to provide multidisciplinary platforms for scientific research by national institutions, universities, and industries. Engineering Material Diffractometer (EMD), which will be used for strain measurements in engineering materials and components, will be constructed at the Beamline 8 in 2022. A novel thermal neutron detector, which will comply with the requirements of EMD application, is being developed. This detector will consist of 6LiF/ZnS(Ag) scintillation screens, wavelength shifting fiber (WLSF) arrays, a silicon photomultiplier (SiPM) and Application Specific Integrated Circuit (ASIC) read-out electronics. Each scintillation screen will be inclined with respect to the incident neutron beam at a grazing angle θ = 17°. Such geometry will not only improve the spatial resolution of detectors but also the neutron detection efficiency. The prototype of detector module has been tested at the neutron Beamline 20 at the CSNS. The experimental results obtained for this prototype illustrate that the pixel size of detector module is 3 mm and the detection efficiency exceeds 40% at the neutron wavelength of 1 Å. Based on these results, we design and manufacture the final version of the detector for the EMD application, which is characterized by low power consumption, highly integrated and easy to install. 70 such detectors will be installed till the end of 2021.

Development and performance evaluation of a multi-layer boron-lined detector for the CPHS-SANS instrument

A position-sensitive thermal neutron detector module based on multi-layer boron-lined tubes has been developed. It is designed for the CPHS (compact pulsed hadron source) SANS (small-angle neutron scattering) instrument [Loong et al. (2012). Phys. Procedia, 26, 8–18]. The detector module consists of 64 boron-lined tubes, arranged into an eight row by eight column structure. Several key aspects of the development of the detector prototype are briefly covered, including the detector module structure design, the readout electronic system and the digital filter of neutron waveforms. Preliminary characterization reveals that the detector module could achieve an average axial spatial resolution of 5.62 mm and a good position linearity. The detection efficiency measurement shows that more than 30% efficiency can be achieved for thermal neutrons on the CPHS. A virtual experiment was conducted to evaluate the performance of the multi-layer boron-lined tubes in SANS measurement; the effect of inside detector scattering of the multi-layer detector was simulated. The result shows that, by implementing proper data reduction, the impact of inside detector scattering on the Q (momentum transfer) value and Q resolution is negligible.

Performance Improvement of Spaceborne Carbon Dioxide Detection IPDA LIDAR Using Optimization of Optical Detector and Amplifier Linearity

The spaceborne double-pulse integrated-path differential absorption (IPDA) light detection and ranging (LIDAR) system was found to be helpful in observing atmospheric CO2 and understanding the carbon cycle. The airborne experiments of a scale prototype of China’s planned spaceborne IPDA LIDAR was implemented in 2019. A problem with data inversion caused by the detector module nonlinearity was found. Through many experiments, the amplifier circuit board (ACB) of the detector module was proved to be the main factor causing the nonlinearity. Through amplifier circuit optimization, the original bandwidth of the ACB was changed to 1 MHz by using a fifth-order active filter. Compared with the original version, the linearity of optimized ACB is improved from 42.6% to 0.0747%. The optimized ACB was produced and its linearity was verified by experiments. In addition, the output waveform of the optimized ACB changes significantly, which will affect the random error (RE) of the optimized IPDA LIDAR system. Through the performance simulation, the RE of more than 90% of the global area is less than 0.728 ppm. Finally, the transfer model of the detector module was given, which will be helpful for the further optimization of the CO2 column-averaged dry-air mixing ratio (XCO2) inversion algorithm.

SOFTWARE AT MOBILE SPECTROMETER WITH CZT-DETECTOR

The technology is based on a semiconductor CdZnTe-portable (almost the size of a mobile phone) gamma-ray spectrometer with high resolution, which provides high efficiency of rapid identification of radionuclides and assessment of radiation dose from low to moderately high levels. The CdZnTe gamma-ray spectrometer is a highly efficient device based on the use of CdZnTe (CZT) semiconductor detectors operating at room temperature with very low power consumption, a digital multichannel analyzer, and a microcomputer. CdZnTe-portable spectrometer is a self-contained device and consists of three modules - a detector module, a multichannel analyzer, and a microcomputer. The detector module contains a high-quality CdZnTe detector, a preamplifier, and a high voltage power supply for the detector. There are detector modules with different volumes of the CZT detector from 5 mm3 to 1600 mm3. It is possible to use a multi-detector system. The analyzer module contains an amplifier, a digital signal processor, a low voltage power supply, and a computer interface. The microcomputer software interacts with the multichannel analyzer, analyzes gamma spectra, and provides the accumulation of time profiles of the dose of gamma radiation, communication with other information systems. Spectrometric measurements in real-time make it possible to use "electronic collimation" technologies to build a map of the radiation field and localize sources of ionizing radiation, with the subsequent certification of identified sources, creation of an effective radiation monitoring system with the functions of certification of ionizing sources radiation. The corresponding software allows you to solve the following tasks – building a three-dimensional map of the fields of ionizing radiation of various degrees of spatial detailing, taking into account the radiation energy, localization, and certification of gamma radiation sources. The special laboratory kit is based on μSPEC microspectrometers. A LattePanda single board computer is used to control the operation of spectrometers, collect and analyze data. LattePanda – A Windows 10 Computer with integrated Arduino. This explains the choice of LattePanda. Windows 10 application allows you to use the WinSPEC software to control the multichannel analyzer operation supplied with the spectrometer. The built-in Arduino allows you to remote control the movement of the radiation source during laboratory experiment. Both the traditional problems of calibrating spectrometers (energy calibration and efficiency curves), including those for various source geometries, processing the measured spectra using standard programs, calculating the activity of sources, and the problem of creating a spectra processing program and a spectrometer control program are considered. The values of the minimum detectable activity are given.

Data Acquisition System Prototype of the ITER Diagnostic Divertor Neutron Flux Monitor Testing at Research Nuclear Facilities

The Divertor nuclear flux monitor (DNFM) is one of the ITER neutron diagnostics. This diagnostic consists of the three same subsystems. Each subsystem concludes the detector module with fission chambers (FCs) and the data acquisition system (DAQ). To solve the task of the neutron flux measurements in the range of 7 orders of magnitude and 1 ms of time resolution the multidetector module is used. To confirm the possibility of the neutron flux measurements in a wide range using such a detector module and to evaluate the characteristics of the DAQ prototype a number of tests were carried out under conditions of the intense neutron radiation. The detector module and the DAQ, which are the prototype of the equipment planned for use on site were used for the tests. The tests were carried out at the plasma neutron diagnostic stand based on the NG-24M neutron generator and at the IBR-2 pulsed reactor of the Joint Institute for Nuclear Research. During the tests at the plasma neutron diagnostic stand the data for the calibration of the DNFM DAQ measuring channels were collected. During the tests at the IBR-2 pulsed reactor the signals from the measuring channels of the DNFM subsystem were obtained while the neutron flux was changed. This report shows the test results and the subsystem calibration techniques.