The development,performances and applications of the monochromatic X-rays facilities in(0.218–301)keV at NIM,China

Space scientific exploration is rapidly becoming the primary battlefield for humankind to explore the universe.Countries worldwide have launched numerous space exploration satellites.Accurate calibration of the detectors on the ground is a crucial element for space science satellites to obtain observational results.For the purpose of providing calibration for various satellite-borne detectors,multiple monochromatic X-rays facilities have been built at the National Institute of Metrology,P.R.China(NIM).These facilities mainly pertain to grating diffraction and Bragg diffraction,and the energy range of the produced monochromatic X-rays is 0.218–301 ke V.These facilities have a high performance in terms of energy stability,monochromaticity,and flux stability.The monochromaticity was greater than 3.0%.The energy stability of the facility is 0.02%at 25 ke V over 8 h,and the flux stability was within 1.0%at 25 ke V over 8 h.Calibration experiments on the properties of satellite-borne detectors,such as energy linearity,energy resolution,detection efficiency,and temperature response,can be conducted at the facilities.Thus far,the calibration of two satellites has been completed by the authors,and the work on three other satellites is in progress.This study will contribute to the advancement of X-ray astronomy the development of Chinese space science.

Establishment and study of a polarized X-ray radiation facility

With the advancement in X-ray astronomical detection technology,various celestial polarization detection projects have been initiated.To meet the calibration requirements of polarimeters on the ground,a polarized X-ray radiation facility was designed for this study.The design was based on the principle that X-rays incident at 45°on a crystal produce polarized X-rays,and a second crystal was used to measure the polarization of the X-rays produced by the facility after rotation.The effects of different diaphragm sizes on the degree of polarization were compared,and the facility produced X-rays with polarization degrees of up to 99.55±0.96%using LiF200 and LiF220 crystals.This result revealed that the polarization of incident X-rays is one of the factors affecting the diffraction efficiency of crystals.The replacement of different crystals can satisfy the calibration requirements of polarized X-ray detectors with more energy points in the energy range(4-10)keV.In the future,the facility should be placed in a vacuum environment to meet the calibration requirements at lower energies.

Strategies and recommendations for the management of gastrointestinal surgery during the COVID-19 pandemic:experience shared by Chinese surgeons

Novel coronavirus disease-2019(COVID-19),caused by severe acute respiratory syndrome coronavirus 2(SARS-CoV-2),is an ongoing public-health pandemic worldwide.Although SARS-CoV-2 has been known to spread primarily through respiratory droplets,recent evidence also supports fecal/oral as an additional route of transmission,raising concerns over gastrointestinal(GI)transmission of the infection.Herein,we,as the front-line Chinese GI surgeons,would like to share our experience and lessons in the combat against COVID-19.It is essential to create science-based,rational,and practical strategies during the outbreak of COVID-19.Here,we provide multi-institutional consensus on minimizing disease transmission while continuing to provide care from all aspects for patients in GI surgery,including outpatient clinics,inpatient units,gastrointestinal endoscopy centers,and adjustments in perioperative care.Our experiences and recommendations are worth sharing and may help to establish specific infection-control and outcome measures.