arXiv subjects

Junli Li

Publications and source records attributed to Junli Li.

32 records · Page 2Linked to original sources

arXiv2020

Preliminary Design of a FADC Readout System for the Alpha/Beta Discrimination in a Large Area Plastic Scintillation Detector

This paper describes a FADC Readout system developed for the tap water $α/β$ dose monitoring system which is based on EJ444 phoswich scintillation detector and wavelength shifting fiber readout. The Readout system contains dual sampling channels that can supply sampling rate up to 1 GSPS, 14-Bit vertical resolution and adequate effective number of bits (9.7 Bits at 10 MHz), which is optimum for the discrimination of the minimal difference between alpha/beta signals. Moreover, the system is based on a ZYNQ SoC which provides high data throughput speed, low latency and excellent flexibility. As for the discrimination algorithms, a simple least-square classification method is used to discriminate the $α/β$ signals and shows high discrimination capability. Besides, the front-end electronics and high voltage supply modules are also briefly introduced in the paper.

physics.ins-det↗

arXiv2020

Oxygen depletion hypothesis remains controversial: a mathematical model of oxygen depletion during FLASH radiation

Background: Experiments have reported low normal tissue toxicities during FLASH radiation, but the mechanism has not been elaborated. Several hypotheses have been proposed to explain the mechanism. The oxygen depletion hypothesis has been introduced and mostly studied qualitatively. Methods: We present a computational model to describe the time-dependent change of oxygen concentration in the tissue. The kinetic equation of the model is solved numerically using the finite difference method. The model is used to analyze the FLASH effect with the oxygen depletion hypothesis, and the brain tissue is chosen as an example. Results: The oxygen distribution is determined by the oxygen consumption rate of the tissue and the distance between capillaries. The change of oxygen concentration with time after radiation has been found to follow a negative exponential function, and the time constant is determined by the distance between capillaries. When the dose rate is high enough, the same dose results in the same change of oxygen concentration regardless of dose rate. The analysis of FLASH effect in the brain tissue based on this model does not support the explanation of the oxygen depletion hypothesis. Conclusions: The oxygen depletion hypothesis remains controversial because oxygen in most normal tissues cannot be depleted by FLASH radiation according to the mathematical analysis with this model and experiments on the expression and distribution of the hypoxia-inducible factors.

physics.med-ph↗

arXiv2018

Measurements of Radon Concentrations Using CR-39 Detectors in China JinPing Underground Laboratory (2015-2016)

Radon background is one of the most critical influences on the ultra-low background and rare-event physical experiments in underground laboratories. To conduct a comprehensive investigation of the radon concentrations in China JinPing underground Laboratory (CJPL), long-term cumulative measurements were carried out using time-integrated passive radon dosimeters containing CR-39 solid-state nuclear track detectors at four sites of CJPL-I. The measurements lasted from May 30,2015 to March 16,2016, a total of 290 days, and the total effective measurement time is 6,953 hours. In the main experiment hall equipped with the ventilation system, the average annual radon concentrations were (55+/-7) Bq m^-3, (58+/-10) Bq^m-3and (53+/-9) Bq m^-3 in three locations respectively. In the storage tunnel without any radon reduction facility, the average annual radon concentrations increased to (345+/-15) Bq m^-3, reflecting the original average annual radon concentration levels in the underground laboratory. Compared with the measured results in the period from 2010 to 2011, the average radon concentration in the main experimental hall was reduced from (86+/-25) Bq m^-3 to (58+/-10) Bq m^-3 due to the well-running ventilation system. Compared with other international underground laboratories, radon concentrations in CJPL-I were at an intermediate level and can meet the demand for low background and rare-event physical experiments.

physics.ins-det↗

arXiv2017

Gross beta determination using a scintillating fiber array detector for drinking water

A scintillating fiber array measurement system for gross beta is developed to achieve real-time monitoring of radioactivity in drinking water. The detector consists of 1,096 scintillating fibers, both sides of the fibers connect to a photomultiplier tube, and they are placed in a stainless steel tank. The detector parameters of working voltage, background counting rate and stability of the detector were tested, and the detection efficiency was calibrated using a standard solution of potassium chloride. Through experiment, the background counting rate of the detector is 38.31 cps and the detection efficiency for $β$ particles is 0.37 cps per Bq per liter; the detector can reach its detection limit of 1.0 Bq per liter for $β$ particles within 100 minutes without pre-concentration.

physics.ins-det↗

arXiv2017

Compton suppression in BEGe detectors by digital pulse shape analysis

A new method of pulse shape discrimination (PSD) for BEGe detectors is developed to suppress Compton-continuum by digital pulse shape analysis (PSA), which helps reduce the Compton background level in gamma ray spectrometry. A decision parameter related to the rise time of a pulse shape was presented. The method was verified by experiments using 60Co and 137Cs sources. The result indicated that the 60Co Peak to Compton ratio and the Cs-Peak to Co-Compton ratio could be improved by more than two and three times, respectively.

physics.ins-det↗

arXiv2016

Neutron background measurements at China Jinping underground laboratory with a Bonner Multi-sphere Spectrometer

The neutron background spectrum from thermal neutron to 20 MeV fast neutron was measured at the first experimental hall of China Jinping underground laboratory with a Bonner multi-sphere spectrometer. The measurement system was validated by a Cf252 source and inconformity was corrected. Due to micro charge discharge, the dataset was screened and background from the steel of the detectors was estimated by MC simulation. Based on genetic algorithm we obtained the energy distribution of the neutron and the total flux of neutron was (2.69 +/-1.02) *10^-5 cm^-2s^-1

physics.ins-det↗

arXiv2016

Quantitative Analysis and Efficiency Study of PSD Methods for a LaBr3:Ce Detector

The LaBr3:Ce scintillator has been widely studied for nuclear spectroscopy because of its optimal energy resolution (<3%@ 662 keV) and time resolution (~300 ps). Despite these promising properties, the intrinsic radiation background of LaBr3:Ce is a critical issue, and pulse shape discrimination (PSD) has been shown to be an efficient potential method to suppress the alpha background from the 227Ac. In this paper, the charge comparison method (CCM) for alpha and gamma discrimination in LaBr3:Ce is quantitatively analysed and compared with two other typical PSD methods using digital pulse processing. The algorithm parameters and discrimination efficiency are calculated for each method. Moreover, for the CCM, the correlation between the CCM feature value distribution and the total charge (energy) is studied, and a fitting equation for the correlation is inferred and experimentally verified. Using the equations, an energy-dependent threshold can be chosen to optimize the discrimination efficiency. Additionally, the experimental results show a potential application in low-activity high-energy γ measurement by suppressing the alpha background.

physics.ins-det↗

arXiv2014

Quantum Entanglement of Neutrino Pairs

It is practically shown that a pair of neutrinos from tau decay can form a flavor entangled state. With this kind of state we show that the locality constrains imposed by Bell inequality are violated by the quantum mechanics, and an experimental test of this effect is feasible within the earth's length scale. Theoretically, the quantum entanglement of neutrino pairs can be employed to the use of long distance cryptography distribution in a protocol similar to the BB84.

quant-ph↗

arXiv2010

The Parametric Symmetry and Numbers of the Entangled Class of 2 \times M \times N System

We present in the work two intriguing results in the entanglement classification of pure and true tripartite entangled state of $2\times M\times N$ under stochastic local operation and classical communication. (i) the internal symmetric properties of the nonlocal parameters in the continuous entangled class; (ii) the analytic expression for the total numbers of the true and pure entangled class $2\times M \times N$ states. These properties help people to know more of the nature of the $2\times M\times N$ entangled system.

quant-ph↗

arXiv2010

Testing Local Realism in $P \to VV$ Decays

It was found that the vector meson pair from the pseudoscalar decays can form an entangled state. In this work we give out detailed explanations on the polarization correlation of the two entangled vector mesons. It is demonstrated that an experimental test of the Clauser-Horne inequality can be carried out through measuring the azimuthal distribution of four pseudoscalars in the cascade decay $η_c \to VV \to (PP)(PP)$, and the measurement of this process is feasible with the current running experiments in tau-charm factory. Moreover, a brief discussion on the polarization correlation of the two vector mesons from $B \to VV$ decays is also presented.

hep-ph↗

arXiv2009

New Possibilities for Testing Local Realism in High Energy Physics

The three photons from the dominant ortho-positronium decay and two vector mesons from the $η_c$ exclusive decays are found to be in tripartite and high-dimensional entangled states, respectively. These two classes of entangled states possess the Hardy type nonlocality and allow a priori for quantum mechanics vs local realism test via Bell inequalities. The experimental realizations are shown to be feasible, and a concrete scheme to fulfill the test in experiment via two-vector-meson entangled state is proposed.

quant-ph↗

arXiv2009

Classification of the Entangled States of $2 \times N \times N$

We develop a novel method in classifying the multipartite entanglement state of $2\times N\times N$ under stochastic local operation and classical communication. In this method, all inequivalent classes of true entangled state can be assorted directly without knowing the classification information of lower dimension ones for any given dimension $N$. It also gives a nature explanation for the non-local parameters remaining in the entanglement classes while $N\geq 4$ .

quant-ph↗

arXiv2009

Bell Inequalities in High Energy Physics

We review in this paper the research status on testing the completeness of Quantum mechanics in High Energy Physics, especially on the Bell Inequalities. We briefly introduce the basic idea of Einstein, Podolsky, and Rosen paradox and the results obtained in photon experiments. In the tests of Bell inequalities in high energy physics, the early attempts of using spin correlations in particle decays and later on the mixing of neutral mesons used to form the quasi-spin entangled states are covered. The related experimental results in K^0 and B^0 systems are presented and discussed. We introduce the new scheme, which is based on the non-maximally entangled state and proposed to implement in ϕfactory, in testing the Local Hidden Variable Theory. And, we also discuss the possibility in generalizing it to the tau charm factory.

hep-ph↗

arXiv2006

The Feasibility of Testing LHVTs in Charm Factory

It is commonly believed that the LHVTs can be tested through measuring the Bell's inequalities. This scheme, for the massive particle system, was originally set up for the entangled K^0\bar{K^0} pair system from the ϕfactory. In this Letter we show that the J/Ψ-> K^0\bar{K^0} process is even more realistic for this goal. We analyze the unique properties of J/Ψin the detection of basic quantum effects, and find that it is possible to use J/Ψdecay as a test of LHVTs in the future τ-Charm factory. Our analyses and conclusions are generally also true for other heavy Onium decays.

hep-ph↗