A flow gas low-pressure multi-wire proportional chamber(LPMWPC)with an active area of 180 mm×80 mm has been developed for the flying time test of the recoil nuclei on super heavy nuclear experiments.The LPMWPC detector can be operated in single as well as double step operational modes.In the case of double step operational mode with a high gas amplification factor,signals fromα-particles reside well above the electronic noise.The gas leakage rate and time resolution obtained from theα239Pu source are shown and discussed at the condition of 3 mbar Isobutane gas.It was shown that the time resolution was better than 2.9 ns at the best work condition,and the detecting efciency was larger than 98%at the low energyαparticles.So the LPMWPC is fit to measure the flying time in the super heavy nuclear fragments experiment.
We present a new idea to understand the structure of nuclei and compare it to the liquid drop model. After discussing the probability that the nuclear system may be a fractal object with the characteristic of self-similarity,the irregular nuclear structure properties and the self-similarity characteristic are considered to be an intrinsic aspect of the nuclear structure properties. For the description of nuclear geometric properties, the nuclear fractal dimension is an irreplaceable variable similar to the nuclear radius. In order to determine these two variables, a new nuclear potential energy formula which is related to the fractal dimension is put forward and the phenomenological semiempirical Bethe–Weizsa¨cker binding energy formula is modified using the fractal geometric theory. One important equation set with two equations is obtained, which is related to the concept that the fractal dimension should be a dynamic parameter in the process of nuclear synthesis. The fractal dimensions of the light nuclei are calculated and their physical meanings are discussed. We compare the nuclear fractal mean density radii with the radii calculated by the liquid drop model for the light stable and unstable nuclei using rational nuclear fractal structure types. In the present model of fractal nuclear structure there is an obvious additional feature compared to the liquid drop model, since the present model can reflect the geometric information of the nuclear structure, especially for nuclei with clusters, such as the α-cluster nuclei and halo nuclei.
In study of dark matter density distributions,there are three types of dark matter halo distributions of galaxies and clusters of galaxies.The NFW(Navarro-Frenk-White)profile[1]ρ(r)NFW=ρ0/(r/rr0)(1+(r/rs))^2(1),whereρ0 and rs are paramenters from halo to halo.The Burkert profile isρ(r)Burkert=ρ0/(1+r/r0)(1+(r/r0)^2),and isothermal profileρ(r)ISO=ρ0/(1+(r/rs))^2,whereρ0,r0 is the center density and radius of dark matter halos.The curves of(1),(2)and(3)are shown in Fig.1.Fig.1 shows that there exist the cored density profile and cuspy problem in the Burkert profile,Quasi ISo profile and NFW profile.
Higgs Portal dark matter have been supposed due to the two facts that dark matter has a gravitational force and has no strong interaction and electromagnetic interaction.A natural logic is the possibility of hiding dark matter.That is,the dark matter does not have the interaction of standard model.Dark matter may be hidden sector.The standard model particles are in the visible sector.The Higgs sector of the Standard Model enjoys a special feature that it can couple to the hidden sector at the renormalizable level.Ref.[1]has discussed the relationship between the standard model and hidden sector.Let H be Higgs field andΦ,be the“hidden Higgs field”in hidden sector.There are a“Higgs portal”interaction term between H andΦas Vportal=λhΦH+HΦ+Φ.
The performance of a double sided silicon strip detector(DSSSD),which is used for the position and energy detection of heavy ions,is reported.The analysis shows that although the incomplete charge collection(ICC)and charge sharing(CS) effects of the DSSSD give rise to a loss of energy resolution,the position information is recorded without ambiguity.Representations of ICC/CS events in the energy spectra are shown and their origins are confirmed by correlation analysis of the spectra from both the junction side and ohmic side of the DSSSD.
