No Arabic abstract
In recent works we discussed the feasibility of the radar detection technique as a new method to probe high-energy cosmic-neutrino induced plasmas in ice. Using the different properties of the induced ionization plasma, an energy threshold of several PeV was derived for the over-dense scattering of a radio wave off the plasma. Next to this energy threshold the radar return power was determined for the different constituents of the plasma. It followed that the return signal should be detectable at a distance of several hundreds of meters to a few kilometers, depending on the plasma constituents and considered geometry. In this article we describe a more detailed modeling of the scattering process by expanding our model to include the full shower geometry, as well as the reflection off the under-dense plasma region. We include skin-effects, as well as the angular dependence of the scattered signal. As a first application of this more detailed modeling approach, we provide the effective area and sensitivity for a simplified detector setup. It follows that, depending on the detailed plasma properties, the radar detection technique provides a very promising method for the detection of neutrino induced particle cascades at energies above several PeV. Nevertheless, to determine the feasibility of the method more detailed information about the plasma properties, especially its lifetime and the free charge collision rate, are needed.
We report the observation of radar echoes from the ionization trails of high-energy particle cascades. These data were taken at the SLAC National Accelerator Laboratory, where the full electron beam ($sim$10$^9$ e$^-$ at $sim$10 GeV/e$^-$) was directed into a plastic target to simulate an ultra high-energy neutrino interaction. This target was interrogated with radio waves, and coherent radio reflections from the cascades were detected, with properties consistent with theoretical expectations. This is the first definitive observation of radar echoes from high-energy particle cascades, which may lead to a viable neutrino detection technology for energies $gtrsim 10^{16}$ eV.
We present a particle-level model for calculating the radio scatter of incident RF radiation from the plasma formed in the wake of a particle shower. We incorporate this model into a software module (RadioScatter), which calculates the collective scattered signal using the individual particle equations of motion, accounting for plasma effects, transmitter and receiver geometries, refraction at boundaries, and antenna gain patterns. We find appreciable collective scattering amplitudes with coherent phase for a range of geometries, with high geometric and volumetric acceptance. Details of the calculation are discussed, as well as the implementation of RadioScatter into GEANT4. A laboratory test of our model, currently scheduled at SLAC in 2018, with the goal of measuring the time-dependent characteristics of the reflecting plasma, is also described. Prospects for a future in-ice, high-energy neutrino detector, along with comparison to current detection strategies, are presented.
TARA (Telescope Array Radar) is a cosmic ray radar detection experiment colocated with Telescope Array, the conventional surface scintillation detector (SD) and fluorescence telescope detector (FD) near Delta, Utah, U.S.A. The TARA detector combines a 40 kW, 54.1 MHz VHF transmitter and high-gain transmitting antenna which broadcasts the radar carrier over the SD array and within the FD field of view, towards a 250 MS/s DAQ receiver. TARA has been collecting data since 2013 with the primary goal of observing the radar signatures of extensive air showers (EAS). Simulations indicate that echoes are expected to be short in duration (~10 microseconds) and exhibit rapidly changing frequency, with rates on the order of 1 MHz/microsecond. The EAS radar cross-section (RCS) is currently unknown although it is the subject of over 70 years of speculation. A novel signal search technique is described in which the expected radar echo of a particular air shower is used as a matched filter template and compared to waveforms obtained by triggering the radar DAQ using the Telescope Array fluorescence detector. No evidence for the scattering of radio frequency radiation by EAS is obtained to date. We report the first quantitative RCS upper limits using EAS that triggered the Telescope Array Fluorescence Detector.
Radar and optical simultaneous observations of meteors are important to understand the size distribution of the interplanetary dust. However, faint meteors detected by high power large aperture radar observations, which are typically as faint as 10 mag. in optical, have not been detected until recently in optical observations, mainly due to insufficient sensitivity of the optical observations. In this paper, two radar and optical simultaneous observations were organized. The first observation was carried out in 2009 to 2010 using Middle and Upper Atmosphere Radar (MU radar) and an image-intensified CCD camera. The second observation was carried out in 2018 using the MU radar and a mosaic CMOS camera, Tomo-e Gozen, mounted on the 1.05-m Kiso Schmidt Telescope. In total, 331 simultaneous meteors were detected. The relationship between radar cross sections and optical V-band magnitudes was well approximated by a linear function. A transformation function from the radar cross section to the V-band magnitude was derived for sporadic meteors. The transformation function was applied to about 150,000 meteors detected by the MU radar in 2009--2015, large part of which are sporadic, and a luminosity function was derived in the magnitude range of $-1.5$ to $9.5$ mag. The luminosity function was well approximated by a single power-law function with the population index of $r = 3.52{pm}0.12$. The present observation indicates that the MU radar has capability to detect interplanetary dust of $10^{-5}$ to $10^{0}$ g in mass as meteors.
The flux of high-energy neutrinos passing through the Earth is attenuated due to their interactions with matter. Their transmission probability is modulated by the neutrino interaction cross section and affects the arrival flux at the IceCube Neutrino Observatory, a cubic-kilometer neutrino detector embedded in the South Pole ice sheet. We present a measurement of the neutrino-nucleon cross section between 60 TeV--10 PeV using the high-energy starting events (HESE) sample from IceCube with 7.5 years of data.