119229407
Fermi Bubbles as a Result of Star Capture in the Galactic Center
A*, with a capture rate < 10 5 yr 1 and energy release � 10 52 erg per one capture can produce shocks in the halo, which accelerate electrons to the energy 1 TeV. These electrons generate radio emission via synchrotron radiation, and gamma-rays via inverse Compton scattering with the relic and the galactic soft photons. Estimates of the diffusion coefficient from the observed gamma-ray flux explains consistently the necessary maximum energy of electrons and sharp edges of the bubble. The recently discovered Fermi bubbles are symmetric gamma-ray structures derived from the Fermi LAT data in the energy range 1-100 GeV. The bubbles elongate above and below the Galactic plane for about 8 kpc and their radius is about 3 kpc . Observations show a very sharp outer boundary of the bubble. The gamma-ray intensity sharply drops outward the bubbles [1]. The origin of the bubble is still enigmatic and up to now a few models were presented in the literature. Our group assumed that the Fermi bubbles originated from star capture events which occurred in the GC every 10 4 −10 5 years [2]. These events form giant shocks propagating through the central part of the Galactic halo and thus produce accelerated electrons with energies ≤ 10 TeV whose scattering on background photons is responsible for the bubble gamma-ray emission. Processes of particle acceleration by the bubble shocks in terms of sizes of the envelope, maximum energy of accelerated particles, etc. may differ significantly from those obtained for SNs that may lead to the maximum energy of accelerated protons much larger than can be reached in SNRs. In this respect, we assume that acceleration of protons in Fermi bubbles may contribute to the total flux of the Galactic cosmic rays (CR) above the ’knee’ break (≥ 10 15 eV).
10177650
Clarification of the three-body decay of 12C (12.71 MeV).
Using beta decays of a clean source of 12N produced at the IGISOL facility, we have measured the breakup of the 12C (12.71 MeV) state into three alpha particles with a segmented particle detector setup. The high quality of the data permits solving the question of the breakup mechanism of the 12.71 MeV state, a longstanding problem in few-body nuclear physics. Among existing models, a modified sequential model fits the data best, but systematic deviations indicate that a three-body description is needed.
22794424
Dipole and spin-dipole resonances in charge-exchange reactions on 12C.
The [sup 12]C([ital n],[ital p])[sup 12]B reaction was studied using the white neutron source at the Los Alamos Meson Physics Facility/Weapon Neutron Research Center with a continuous incident neutron energy from 60 to 260 MeV. Double differential cross sections were measured in the angular range 11[degree][le][theta][sub lab][le]37[degree]. Using the neutron time-of-flight facility at the Indiana University Cyclotron Facility, we also studied the [sup 12]C([ital p],[ital n])[sup 12]N reaction at [ital E][sub [ital p]]=186 MeV and the [sup 12]C([ital [rvec p]],[ital [rvec n]])[sup 12]N reaction at [ital E][sub [ital [rvec p]]]=160 and 186 MeV. Double differential cross sections were measured between [theta][sub lab]=0[degree] and [theta][sub lab]=50[degree] in 5[degree] steps. Spin observables [ital D][sub [ital N][ital N]], [ital A][sub [ital Y]], and [ital P] were measured at [theta][sub lab]=5[degree],9[degree],13[degree] with [ital E][sub [ital [rvec p]]]=160 MeV and [theta][sub lab]=15[degree],20[degree] with [ital E][sub [ital [rvec p]]]=186 MeV. Angular distributions of differential cross section and spin observables for low-lying transitions in the residual nuclei are compared with disorted-wave impulse approximation (DWIA) calculations. A multipole decomposition analysis was performed to study the giant dipole and giant spin-dipole resonances. The contributions of the quasifree reaction in the giant resonance region was subtracted. The empirical results ofmore » energy distributions for dipole ([Delta][ital L]=1) transition are compared with DWIA calculations using nuclear structure information obtained with a conventional shell model and also with a random phase approximation.« less
5742840
Crystallization in the Thin and Ultrathin Films of Poly(ethylene-vinyl acetate) and Linear Low-Density Polyethylene
The crystallization of poly(ethylene−vinyl acetate) and linear low-density polyethylene (LLDPE) films spun-cast from the polymer/toluene solutions with as-cast thickness from 460 to 10 nm was studied. The lamellar thickness was measured using small-angle X-ray scattering (SAXS) and found to increase from 14 to 21 nm for films thinner than 100 nm. The morphology of LLDPE measured by scanning probe microscopy (SPM) showed an edge-on lamellae for the films thicker than 30 nm and flat-on lamellae for the films thinner than 15 nm. A pseudo-“shish-kebab” tiny crystal structure was observed in between the larger lamellae. Crystallinity was confirmed using attenuated total reflectance−Fourier transformed infrared spectroscopy (ATR-FTIR) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. The shear modulation force microscopy technique (SMFM) was used to measure the melting point, Tm, which was found to decrease for films thinner than 100 nm. The rate of decrease was a function of the annealing pr...
1289258
Energetic electrons associated with magnetic reconnection in the magnetic cloud boundary layer.
Here is reported in situ observation of energetic electrons (∼100-500 keV) associated with magnetic reconnection in the solar wind by the ACE and Wind spacecraft. The properties of this magnetic cloud driving reconnection and the associated energetic electron acceleration problem are discussed. Further analyses indicate that the electric field acceleration and Fermi-type mechanism are two fundamental elements in the electron acceleration processes and the trapping effect of the specific magnetic field configuration maintains the acceleration status that increases the totally gained energy.
120316681
Experimental results of the betatron sum resonance
The experimental observations of motion near the betatron sum resonance, /spl nusub x/+2/spl nusub z/=13, are presented. A fast quadrupole (Panofsky-style ferrite picture-frame magnet with 8 pulsed power supplies) producing a betatron tune shift of the order of 0.03 at rise time of 1 /spl mu/s was used. This quadrupole was used to produce betatron tunes which jumped past and then crossed back through a betatron sum resonance line. The beam response as function of initial betatron amplitudes were recorded turn by turn. The correlated growth of the action variables, J/sub x/ and J/sub z/, was observed. The phase space plots in the resonance frame reveal the features of particle motion near the nonlinear sum resonance region.<<ETX>>
3564025
First results from KamLAND: evidence for reactor antineutrino disappearance.
KamLAND has measured the flux of nu;(e)'s from distant nuclear reactors. We find fewer nu;(e) events than expected from standard assumptions about nu;(e) propagation at the 99.95% C.L. In a 162 ton.yr exposure the ratio of the observed inverse beta-decay events to the expected number without nu;(e) disappearance is 0.611+/-0.085(stat)+/-0.041(syst) for nu;(e) energies >3.4 MeV. In the context of two-flavor neutrino oscillations with CPT invariance, all solutions to the solar neutrino problem except for the "large mixing angle" region are excluded.
14484648
A possible disk mechanism for the 23-day QPO in Mkn 501
Optically, thin two-temperature accretion flows may be thermally and viscously stable, but acoustically unstable. Here, we propose that the O-mode instability of a cooling-dominated optically thin two-temperature inner disk may explain the 23-day quasi-periodic oscillation (QPO) period observed in the TeV and X-ray light curves of Mkn 501 during its 1997 high state. In our model the relativistic jet electrons Compton upscatter the disk soft X-ray photons to TeV energies, so that the instability-driven X-ray periodicity will lead to a corresponding quasi-periodicity in the TeV light curve and produce correlated variability. We analyse the dependence of the instability-driven quasi-periodicity on the mass ( M ) of the central black hole, the accretion rate ( M ˙ ) and the viscous parameter ( α ) of the inner disk. We show that in the case of Mkn 501 the first two parameters are constrained by various observational results, so that for the instability occurring within a two-temperature disk where α  = 0.05–1.0, the quasi-period is expected to lie within the range of 8–100 days, as indeed the case. In particular, for the observed 23-day QPO period our model implies a viscosity coefficient α  ⩽ 0.28, a sub-Eddington accretion rate M ˙ ≃ 0.02 M ˙ Edd and a transition radius to the outer standard disk of r 0  ∼ 60 r g , and predicts a period variation δ P / P  ∼ 0.23 due to the motion of the instability region.
109237518
Tester Board for testing mass-produced SMB modules for CMS Preshower
We have developed a Tester Board to test the electrical characteristics of the System Motherboard (SMB) for the CMS Preshower detector at CERN. The board is designed to test input resistances, output resistances, connections, interconnections and possible short- circuits of a module having up to 640 connector pins. The Tester Board is general-purpose in nature: it could be used to test any electronic module or cable by using dedicated cable sets. The module can detect a variety of problems not detected by either functional tests or the flying probes technique. The design, algorithms and results of using the Tester Board during mass production of CMS Preshower SMBs are presented.
85552284
STUDY ON THE PLANAR UNDULATOR SCHEME WITH FOCUSING PROPERTIES FOR PKU-FEL *
An IR range SASE FEL test facility will be built at Peking University. The project is designed to get the SASE FEL at 7 micron driven by a superconducting accelerator. A hybrid planar Nd-Fe-B undulator is employed and the optimization of the external focus system for the undulator is studied. In the PKU-FEL facility, the electron energy is about 30-40 MeV. The combined function undulator with FODO lattice imposes quite stringent tolerances on the strength of the quads. To solve this problem, the weak natural focusing of the undulator in the vertical plane together with horizontally focusing quads, is proposed to supply the focusing in the facility. The combined function undulator of FOFO lattice and FF lattice in the horizontal plane are studied. Compared with the FODO lattice, the FOFO and FF lattice make the saturation a bit longer and the requirements of the field accuracy for the focusing system are much reduced.
119281810
Study on the spectrum of the injected relativistic protons
About 10TeV gamma-ray emission within 10 pc region from the Galactic Center had been reported by 4 independent groups. Considering that this TeV gamma-ray emission is produced via a hadronic model, and the relativistic protons came from the tidal disruption of stars by massive black holes, we investigate the spectral nature of the injected relativistic protons required by the hadronic model. The calculation was carried on the tidal disruption of the different types of stars and the different propagation mechanisms of protons in the interstellar medium. Compared with the observation data from HESS, we find for the best fitting that the power-law index of the spectrum of the injected protons is about -1.9, when a red giant star is tidally disrupted, and the effective confinement of protons diffusion mechanism is adopted.