·204·2017 The leakage neturon yields and its average enenery as a function of tungsten density at the diameter of50cm were studied and shown in Fig.2(a).Here,R/N is a parameter to describe the porous tungsten density.It is defined to be the density ratio of porous tungsten to natural tungsten.To get a general conclusion,the density of porous tungsten R/N ranges from0.25to1.It can be en that the escaped neutron yield peaks around R/N=0.65.The total energy of the leaking neutrons decreas with granule density.As the tungsten R/N decreas from1to0.65, the neutronics performance is getting better with more neutron yield and higher neutron energy.However,when the tungsten R/N moves toward the area0.65to0.25,it brings out less leaked neutrons with higher total energy.
As shown in Fig.2(b),it shows the proton beam current and heat deposition per unit mass of granules as functions of granular density after ADS evaluations.It is obvious that there would be a continue dropping in the beam current requirement when the density R/N turns from1to0.33.Meanwhile,the heat deposition on the granular target is always less than that in the natural granular(R/N=1)when density R/N>0.55.As the density R/N moves from0.55to0.33,although the beam requirement is still reducing,there is a sharply growth in the heat deposition per unit mass in granules due to decrea of massflow.Although the source effciency is incread when the density lies in the region R/N<0.55,the diffculty of heat removal is also brought in.It can be concluded that the density of porous tungsten is ideal around R/N=0.55when the DGT diameter at50cm.
Fig.2(color online)The leaked neturon yield and energy spectrum(a),Proton beam current and heat deposition per unit mass with tungsten density of DGT(b).
The neutron performance of DGT can be optimized by choosing a reasonable density of porous tungsten accord-ing to the target diameter.In the future industrial grade ADS plant,the target diameter of tungsten DGT probably exceed40cm,the u of porous tungsten can effectively reduce the demand for proton beam current,which is an important improvement for the natural tungsten DGT.At the same time,the thermal deposition on the porous tungsten material is also lower than that in the natural tungsten target.
Reference
[1]L.Yang,W.L.Zhan,Science China Technological Sciences,58(10)(2015)1705.
生铁锅好还是熟铁锅好5-22Neutronics Performance of Den Tungsten Granular Target
Zhang Yaling,Zhang Xunchao,Yan Xuesong and Yang Lei
The gravity driven granularflow spallation target of C-ADS[1]is designed to produce highflux neutron escape from lateral surface to transmute the long-lived radioactive nuclei of spent fuel.The detailed s
imulation of the neutronics performance and activation of den tungsten granular target has been prented in our previous work[2]. Here the efforts have been focus on the stability of the neutron escape from lateral surface.Figures.1and2.showed the laterally leaking neutron energy spectrum and laterally leaking neutron axial distribution of the granular target with different time nodes.It can be en that laterally leaking neutron axial distribution is nearly the same at different time nodes.Therefore,it can be concluded that if the average volume fraction isfixed in the target hopper, the granularflow spallation target can afford a stable external neutron source for subcritical blanket despite that there is a slight change among granule spatial distributions at different time nodes during theflowing.Due to the fact that the granularflow velocity is negligibly small even comparing to the velocity of thermal neutrons,the neutronics of the granularflow target will be nearly the same as that of a static granular target.
2017·205·
Fig.1(color online)Laterally leaking neutron energy spectrum at different time node with the same aver-age volume fraction of0.60.Fig.2(color online)Laterally leaking neutron axial dis-tribution at different time node with the same average volume fraction of0.60.
References
生活垃圾分类制度[1]L.Yang,W.L.Zhan,Sci.China Technol.,Sci.58(2015)1705.
[2]Y.L.Zhang,J.Y.Li,X.C.Zhang,et al.,Nucl.Inst.Meth.B,410(2017)88.
5-23A New IsoDAR Method for Sterile Neutrino Search
with d+9Be Reaction
Chen Liangwen,Cai Hanjie,Emilio Ciuffoli,Jarah Evslin,Zhang Sheng,Chen Xurong and Yang Lei Neutrino oscillations have been obrved in solar and atmosphere neutrino experiments[1,2],and confirmed in-
dependently by accelerator and reactor neutrino experiments[3−5].However,some anomalies have been obrved
in neutrino experiments with different sources,detector principles and detection channels[6−13],which can not be
accommodated within the standard three-flavour neutrino paradigm.The anomalous results may be a sign of
further new physics beyond Standard Model and currently their most popular interpretation is the existence of
sterile neutrino states with mass at the eV scale.Sterile neutrino states are a key issue in arches for new
physics beyond the Standard Model,and their existence and properties would also have important implications in
astrophysics and cosmology.
The“Compact Material Irradiation Facility”(CMIF)is a current project which can provide an inten and
high-energy neutronflux utilizing a deuteron beam impinging on a9Be target.Here,we propo a new method
to produce8Li(therefore neutrino)via bombarding deuteron beam on the9Be target.We adopt two beam-target
configurations to study the feasibility of sterile neutrino arch at the CMIF platform,that is,tup A with75
MeV/u beam energy and a beryllium target that is20cm in diameter and20cm long,and tup B with100MeV/u
beam energy and the same beryllium target dimensions as in tup A.Over afive-years run and with a90%duty
cycle,2.1×1023(4.0×1023)antineutrinos can be created from the8Li beta decay in the tup A(B).穿山甲
We propo to pair the neutrino source with four liquid scintillator detectors,two near and two far detectors,with
九头蛇怪
小人的意思fiducial mass of20tons.This arrangement can help reduce systematic uncertainties,understand the background
as well as monitor the target.The balines for the detectors arefixed as4and10m,which is appropriate to
probe the∆m2∼1eV2region given the propod neutrino source[14,15].To simplify the analysis,we suggest to u the Daya Bay detectors and adopt the same muon veto systems.For the target station,a100meters vertical
overburden is assumed.Since there are four operational reactors at a distance of about5km,the backgrounds that
岗位是什么意思
will mask the oscillation signal are comprid mainly of the reactor neutrino and the cosmogenic muons induced
backgrounds.Both backgrounds have been studied thoroughly by the Daya Bay experiment[16,17].In the context of
胆囊收缩素this proposal,we lect the neutrino events with the constructed energy between6and12MeV.Within this energy
range,the¯νe background from the nearby reactor complex,the background induced by the decay of spallation9Li
and the fast neutrons backgrounds are relevant.Assuming similar average thermal power of each nearby reactor to
黄牛肉tho in the Daya Bay Reactor experiment[16],the reactor neutrino background will be about0.6IBD events/day
