11 research outputs found
RICE Limits on the Diffuse Ultra-High Energy Neutrino Flux
We present new limits on ultra-high energy neutrino fluxes above 100 PeV
based on data collected by the Radio Ice Cherenkov Experiment (RICE) at the
South Pole from 1999-2005. We discuss estimation of backgrounds, calibration
and data analysis algorithms (both on-line and off-line), procedures used for
the dedicated neutrino search, and refinements in our Monte Carlo (MC)
simulation, including recent in situ measurements of the complex ice dielectric
constant. An enlarged data set and a more detailed study of hadronic showers
results in a sensitivity improvement of more than one order of magnitude
compared to our previously published results. Examination of the full RICE data
set yields zero acceptable neutrino candidates, resulting in 95%
confidence-level model dependent limits on the flux
(E_\nu)^2(d\phi/dE_\nu)<10^{-6} GeV/(cm^2s~sr}) in the energy range 10^{17}<
E_\nu< 10^{20} eV. The new RICE results rule out the most intense flux model
projections at 95% confidence level.Comment: Submitted to Astropart. Phy
Self-amplified Cherenkov radiation from a relativistic electron in a waveguide partially filled with a laminated material
The radiation from a relativistic electron uniformly moving along the axis of
cylindrical waveguide filled with laminated material of finite length is
investigated. Expressions for the spectral distribution of radiation passing
throw the transverse section of waveguide at large distances from the laminated
material are derived with no limitations on the amplitude and variation profile
of the layered medium permittivity and permeability. Numerical results for
layered material consisting of dielectric plates alternated with vacuum gaps
are given. It is shown that at a special choice of problem parameters,
Cherenkov radiation generated by the relativistic electron inside the plates is
self-amplified. The visual explanation of this effect is given and a possible
application is discussed.Comment: 8 pages, 4 figures,1 table, the paper is accepted for publication in
the Journal of Physics: Conference Serie
Relativistic theory of inverse beta-decay of polarized neutron in strong magnetic field
The relativistic theory of the inverse beta-decay of polarized neutron, , in strong magnetic field is developed. For the proton
wave function we use the exact solution of the Dirac equation in the magnetic
filed that enables us to account exactly for effects of the proton momentum
quantization in the magnetic field and also for the proton recoil motion. The
effect of nucleons anomalous magnetic moments in strong magnetic fields is also
discussed. We examine the cross section for different energies and directions
of propagation of the initial neutrino accounting for neutrons polarization. It
is shown that in the super-strong magnetic field the totally polarized neutron
matter is transparent for neutrinos propagating antiparallel to the direction
of polarization. The developed relativistic approach can be used for
calculations of cross sections of the other URCA processes in strong magnetic
fields.Comment: 41 pages in LaTex including 11 figures in PostScript, discussion on
nucleons AMM interaction with magnetic field is adde
Observation of soft X-ray Cherenkov radiation in Al
The soft X-ray radiation generated by 5.7 MeV electrons from both an Al foil and a Mylar film in forward direction was experimentally studied. A narrow specific directivity, an ultra-narrow spectral bandwidth and a good consistency between the experiment and theory prove that the Cherenkov radiation (CR) with photon energy near the L-edge of absorption in Al was observed. The results demonstrate that the CR spectral-angular properties and the absolute photon yield can be described well enough using Pafomov's theoretical model and Henke's refractive index database, which is essential for all practical applications
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Research and development to complete construction of a setup for determination of the longitudinal profile and duration of ultrashort bunches. Final report
Here are presented the results of the authors investigations on the construction of a setup for determination of the longitudinal charge distribution function and duration of ultrashort electron bunches via the measurement of the time-profile of the bunch-generated optical transition radiation (OTR) burst. In the Theoretical Part of the Final Report are obtained conditions that determine the adequacy between the time-profile of OTR flash and bunch longitudinal charge distribution function with account of finiteness of the bunch cross-section and bandwidth of the receiver. The competing processes (bremsstrahlung, luminescence) as well as the boundary roughness effect are considered. The Experimental Part presents the justification for the choice of the target - an OTR-emitter, a description of the measurement scheme, and the main characteristics of the units the setup consists of. An account is given of the OTR simulator and of the setup calibration method. Demands are formulated both to the setup as a whole and to its units. Experimental results are given that confirm correctness of the chosen method. In the Appendix the authors consider alternative methods of solution of the problem posed
Radiation protection for surgeons and anesthetists: practices and knowledge before and after training
International audienceThe use of radiological activity in the operating room (OR) and a regulatory decrease of the eye lens dose warrant an assessment of how medical staff are protected from radiation. This study aims to evaluate practices and knowledge in radiation protection (RP) for OR doctors before and after training. A descriptive study of surgeons and anesthetists in a French public hospital center was conducted in 2016. An ad hoc questionnaire concerning occupational practices and knowledge about RP was distributed before and one month after RP training. Among 103 doctors attending the training, 90 answered the questionnaire before the training. Results showed a lack of knowledge and good practice in RP. Most of the participants (86.7%) had never been trained in RP and recognized insufficient knowledge. Most of them (92.2%) wore a lead apron, 50.0% a thyroid-shield, 5.6% lead glasses, 53.3% a passive dosimeter and 17.8% an electronic dosimeter. None of them benefitted from collective protective equipment such as a ceiling suspended screen. The questionnaire following the training was completed by only 35 doctors. A comparison before and after training results showed an improvement in knowledge (scores of correct responses: 5.5/16 before and 9.5/16 after training) but not in RP good practices (scores of correct responses: 3.2/7 before and 3.3/7 after training). One training session appears to be insufficient to improve the application of the safety rules when x-rays are used. Communication needs to be improved regarding RP among anesthetists and surgeons, such as training renewal, workstation analysis in OR related to x-ray use and occupational medical follow-up. Otherwise, radiological risks in OR need to be given better consideration, such as radio-induced cataract risk. It is necessary to encourage the use of dosimeters and protective equipment and to strengthen access to lead glasses and collective protective equipment, such as ceiling suspended screens. All these recommendations ensure the received dose is reduced to as low as is reasonably achievable