Isomeric fluorescence sensors for wide range detection of ionizing radiations

In order to achieve a wider range of ionizing radiations detection,novel fluorescence sensing materials have been developed that utilize the fluorescence enhancement phenomenon caused by the intramolecular photoinduced electron transfer(PET)effect.Two perylene diimide isomers PDI-P and PDI-B were designed and synthesized,and their molecular structures were characterized by high-resolution Fourier transform mass spectrometry(HRMS),nuclear magnetic resonance hydrogen and carbon spectroscopy(~1H and~(13)C NMR).The interaction between ionizing radiation and fluorescent molecules was simulated by HCl titration.The results show that combining PDIs and HCl can improve fluorescence through the retro-PET process.Despite the similarities in chemical structures,the fluorescent enhancement multiple of PDI-B with aromatic amine as electron donor is much higher than that of PDI-P with alkyl amine.In the direct irradiation experiments of ionizing radiation,the emission enhancement multiples of PDI-P and PDI-B are 2.01 and 45.4,respectively.Furthermore,density functional theory(DFT)and time-dependent density functional theory(TDDFT)calculations indicate that the HOMO and HOMO-1 energy ranges of PDI-P and PDI-B are 0.54 e V and 1.13 e V,respectively.A wider energy range has a stronger driving force on electrons,which is conducive to fluorescence quenching.Both femtosecond transient absorption spectroscopy(fs-TAS)and transient fluorescence spectroscopy(TFS)tests show that PDI-B has shorter charge separation lifetime and higher electron transfer rate constant.Although both isomers can significantly reduce LOD during PET process,PDI-B with aromatic amine has a wider detection range of 0.118—240 Gy due to its larger emission enhancement,which is a leap of three orders of magnitude.It breaks through the detection range of gamma radiation reported in existing studies,and provides theoretical support for the further study of sensitive and effective new materials for ionizing radiation detection.

闪烁晶体——辐射探测用单晶

Phosphor converts excitation energy into light,resulting in lumminescence.The luminescence caused by radiation is called scintillation.Since the discovery of the scintillation in NaI∶Tl crystal in 1948,a series of materials with profound scintillating characteristics have been developed and have found wide applications for radiation detection in different fields such as nuclear physics,high energy physics,medical diagnostic imaging,geophysics exploration,clandestine explosive finding and many industrial measuring systems. Inorganic scintillating crystals have superior characteristics over their organic counterparts and some kinds of ceramics,glasses and powders that do have their scintillation effects.We will confine ourselves mainly to inorganic scintillating crystals in this presentation..

Development of gated fiber detectors for laser-induced strong electromagnetic pulse environments

With the development of laser technologies,nuclear reactions can happen in high-temperature plasma environments induced by lasers and have attracted a lot of attention from different physical disciplines.However,studies on nuclear reactions in plasma are still limited by detecting technologies.This is mainly due to the fact that extremely high electromagnetic pulses(EMPs)can also be induced when high-intensity lasers hit targets to induce plasma,and then cause dysfunction of many types of traditional detectors.Therefore,new particle detecting technologies are highly needed.In this paper,we report a recently developed gated fiber detector which can be used in harsh EMP environments.In this prototype detector,scintillating photons are coupled by fiber and then transferred to a gated photomultiplier tube which is located far away from the EMP source and shielded well.With those measures,the EMPs can be avoided which may result that the device has the capability to identify a single event of nuclear reaction products generated in laser-induced plasma from noise EMP backgrounds.This new type of detector can be widely used as a time-of-flight(TOF)detector in high-intensity laser nuclear physics experiments for detecting neutrons,photons,and other charged particles.

Effect of dimensional expansion on carrier transport behaviors of the hexagonal Bi-based perovskite crystals

All-inorganic Cs_(3)Bi_(2)I_(9)(CBI)halide perovskites are sought to be candidate for photoelectrical materials because of their low toxicity and satisfactory stability.Unfortunately,the discrete molecular[Bi2I9]3−clusters limit the charge-transport behaviors.Herein,the defect halide perovskite based on trivalent Bi^(3+)is expanded to Cs_(3)Bi_(2)I_(6)Br_(3)(CBIB).Centimeter-size CBIB single crystal(Φ15×70 mm^(3))was grown by the vertical Bridgeman method.The powder X-ray diffraction analysis shows that CBIB has structure with lattice parameters of a=b=8.223Å,c=10.024Å,α=β=90°andγ=120°.The density functional theory(DFT)calculations demonstrate that the charge density distribution was enhanced after the dimensional expansion.The enhancement of carrier transport ability of(00l)in-plane is characterized before and after dimensional improvement.The obtained CBIB(001)exhibited an electron mobility up to 40.03 cm^(2)V^(−1)s^(−1)by time-of-flight(TOF)technique,higher than 26.46 cm^(2)V^(−1)s^(−1)of CBI(001).Furthermore,the X-ray sensitivity increases from 707.81μC Gy^(−1)cm^(−2)for CBI(001)to 3194.59μC Gy−1 cm^(−2)for CBIB(001).This research will deepen our understanding of Bi-based perovskite materials and afford more promising strategies for lead-free perovskite optoelectronic devices modification.

Organic–inorganic hybrid perovskite scintillators for mixed field radiation detection

Sensitive and fast detection of neutrons and gamma rays is vital for homeland security,high-energy physics,and proton therapy.Fast-neutron detectors rely on light organic scintillators,andγ-ray detectors use heavy inorganic scintillators and semiconductors.Efficient mixed-field detection using a single material is highly challenging due to their contradictory requirements.Here we report hybrid perovskites(C_(8)H_(12)N)_(2)Pb(Br_(0.95)Cl_(0.05))_(4)that combine light organic cations and heavy inorganic skeletons at a molecular level to achieve unprecedented performance for mixed-field radiation detection.High neutron absorption due to a high density of hydrogen,strong radiative recombination within the highly confined[PbX_(6)]^(4-)layer,and sub-nanometer distance between absorption sites and radiative centers,enable a light yield of 41000 photons/MeV,detection pulse width of 2.97 ns and extraordinary linearity response toward both fast neutrons andγ-rays,outperforming commonly used fast-neutron scintillators.Neutron energy spectrum,time-of-flight based fast-neutron/γ-ray discrimination and neutron yield monitoring were all successfully achieved using(C_(8)H_(12)N)_(2)Pb(Br_(0.95)Cl_(0.05))_(4)detectors.We further demonstrate the monitoring of reaction kinetics and total power of a nuclear fusion reaction.We envision that molecular hybridized scintillators open a new avenue for mixed-field radiation detection and imaging.

Properties study of ZnO:Ga crystal on pulsed radiation detections

In this paper, properties on pulsed radiation detections of ZnO：Ga crystal grew by a magnetron sputtering method were studied. The time response to pulsed laser, pulsed hard X rays and single α particles, the energy response to pulsed hard X ray, the scintillation efficiency to γ rays, the response to pulsed proton, and the relations of the light intensity varied with the proton energy were measured and analyzed in detail. Results show that the ZnO：Ga crystal has potential applications in the regime of pulse radiation detection.

Realization of an integrated seeding and compensating potato planter based on one-way clutch

The yield reduction caused by miss-seeding in potato mechanized sowing is astonishing.The existing research always needs to install a spare compensator on the original seed-metering device.Therefore,problems of complex planter structure and compensated potato seed poor landing accuracy need to be solved urgently.Consequently,a scheme of integrated seeding and compensating potato planter based on one-way clutch is proposed in this paper.Based on a basic‘improved one raw potato planter’and the working principle of one-way clutch,power of seed-metering system is provided through main power transmission one-way clutch by land wheels when the system works properly.However,when miss-seeding detection system with infrared radiation deciding that a miss-seeding incident has happened,the seed-metering power will be replaced by a compensatory motor through compensating one-way clutch at a higher speed.Thus,the idea of catching-up compensation can be realized.After compensation is completed,the system controller disconnects the compensatory motor,and the seed-metering power will naturally switch to the land wheels again.A prototype based on this idea was built.Field tests showed that the accuracy of seed monitoring system is more than 99.9%;the adoption of catching-up compensation scheme does not bring about empty spoon rate rise significantly.Within the range of 0.2-0.8 m/s of the seed-metering chain speed,although the average success compensation rate decreases evidently with the increase of the chain speed,the success compensation rate is still near 70%even at 0.8 m/s,the vast majority of missed seeds can be compensated effectively.

Thermal experiment of silicon PIN detector

The experiment of this paper is the thermal test of the leakage current of silicon PIN detector. Raising temperature may cause the detector to increase leakage current, decrease depletion and increase noise. Three samples are used in the experiment. One （called △E） is the sample of 100 μm in thickness. The other two （called E1 and E2） are stacks of five detectors of 1000 μm in thickness. All of them are 12 mm in diameter. The experiment has been done for 21 hours and with power on continuously. The samples have undergone more than 60 ℃ for about one hour. They are not degenerated when back to the room temperature. The depletion rate is temperature and bias voltage related. With the circuit of the experiment and temperature at 35 ℃, △E is still depleted while E1 and E2 are 94.9% and 99.7% depleted respectively. The noises of the samples can be derived from the values at room temperature and the thermal dependence of the leakage currents. With the addition of the noise of the pre-amplifier, the noises of E1, E2 and △E at 24 ℃ are 16.4, 16.3, and 10.5 keV （FWHM） respectively while at 35 ℃ are about 33.6, 33.1, and 20.6 keV （FWHM） respectively.

A uranyl based coordination polymer showing response to low-dosage ionizing radiations down to 10^(−5) Gy

Radiation detection material is a central component of nuclear technology finding applications in many critical fields.Developing a highly radiation-sensitive material that shows a facilely detectable response to ultra-low dosage of radiation is a long-term research target and remains to be a challenge.Previously reported most optimal chemical radiation dosimeter can detect low-dosage X-andγ-ray radiations down to 10^(−4) Gy.We document here a new photoresponsive coordination polymer showing upgraded radiation detection capabilities with the detection limit on the radiation dose one order of magnitude lower than the previous record.The radiation induced photoluminescence quenching process was elucidated by multiple spectroscopic characterizations.

Correcting for spatially dependent intrinsic efficiency on a germanium double-sided strip detector to improve nuclear forensics response

Purpose The Germanium Gamma-ray Imager(GeGI)is a planar high-purity germanium(HPGe)imaging detector developed by PHDS Co for far-field imaging.This research investigates the detector’s ability for measuring heterogeneous sources in the near field,placed directly on the detector’s faceplate,to perform isotopic mapping for nuclear forensic missions.Methods The intrinsic efficiency is strongly dependent on where the photons interact within the germanium.The efficiency varies by up to 20%within the sensitive volume of the detector.The efficiency was mapped using eight different photons from 123 to 1274 keV emitted from a collimated 154Eu photons.These were measured at 108 locations to interpolate the efficiency at any point on the detector’s face.Results The position and energy dependence are uncorrelated,and thus,the absolute efficiency at any position and for any gamma-ray energy can be calculated by the convolution of the spatial and energy efficiencies.Conclusion The results on this research show that detection efficiency for a planar two-sided strip HPGe is spatially dependent and shows typical energy dependence.The spatial dependence,which does not have any additional energy dependence,can be corrected.A 154Eu source was used in this research and was able to spatially calibrate for photon energies ranging from 100 to 1300 keV.This method is applicable for sources with higher gamma energies.The advantages of the method demonstrated that after initial in-laboratory calibration,a single measurement in the field can be used to efficiently calibrate the HPGe as a function of photon interaction on the crystal.