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DOE OSTI2024

Radio measurements of the depth of air-shower maximum at the Pierre Auger Observatory

The (AERA), part of the Pierre Auger Observatory, is currently the largest array of radio antenna stations deployed for the detection of cosmic rays, spanning an area of 17 km 2 with 153 radio stations. It detects the radio emission of extensive air showers produced by cosmic rays in the 30–80 MHz band. Here, we report the AERA measurements of the ( X max ), a probe for mass composition, at cosmic-ray energies between 10 17.5 and 10 18.8 eV , which show agreement with earlier measurements with the fluorescence technique at the Pierre Auger Observatory. We show advancements in the method for radio X max reconstruction by comparison to dedicated sets of / air-shower simulations, including steps of reconstruction-bias identification and correction, which is of particular importance for irregular or sparse radio arrays. Using the largest set of radio air-shower measurements to date, we show the radio X max resolution as a function of energy, reaching a resolution better than 15 g cm − 2 at the highest energies, demonstrating that radio X max measurements are competitive with the established high-precision fluorescence technique. In addition, we developed a procedure for performing an extensive data-driven study of systematic uncertainties, including the effects of acceptance bias, reconstruction bias, and the investigation of possible residual biases. These results have been cross-checked with air showers measured independently with both the radio and fluorescence techniques, a setup unique to the Pierre Auger Observatory. Published by the American Physical Society 2024

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2024

Demonstrating Agreement between Radio and Fluorescence Measurements of the Depth of Maximum of Extensive Air Showers at the Pierre Auger Observatory

We show, for the first time, radio measurements of the depth of shower maximum ( X max ) of air showers induced by cosmic rays that are compared to measurements of the established fluorescence method at the same location. Using measurements at the Pierre Auger Observatory we show full compatibility between our radio and the previously published fluorescence dataset, and between a subset of air showers observed simultaneously with both radio and fluorescence techniques, a measurement setup unique to the Pierre Auger Observatory. Furthermore, we show radio X max resolution as a function of energy and demonstrate the ability to make competitive high-resolution X max measurements with even a sparse radio array. With this, we show that the radio technique is capable of cosmic-ray mass composition studies, both at Auger and at other experiments. Published by the American Physical Society 2024

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2020

Direct measurement of the muonic content of extensive air showers between 2 $\times$ 10 17 and 2 $\times$ 10 18 eV at the Pierre Auger Observatory

The hybrid design of the Pierre Auger Observatory allows for the measurement of the properties of extensive air showers initiated by ultra-high energy cosmic rays with unprecedented precision. By using an array of prototype underground muon detectors, we have performed the first direct measurement, by the Auger Collaboration, of the muon content of air showers between 2 $\times$ 10 17 and 2 $\times$ 10 18 eV. We have studied the energy evolution of the attenuation-corrected muon density, and compared it to predictions from air shower simulations. The observed densities are found to be larger than those predicted by models. We quantify this discrepancy by combining the measurements from the muon detector with those from the Auger fluorescence detector at 10 17.5 eV and 10 18 eV. We find that, for the models to explain the data, an increase in the muon density of 38% $±$4%(12%) $±^{21\%}_{18\%}$ for EPOS-LHC, and of 50%(53%) $±$4%(13%) $±^{23\%}_{20\%}$ for QGSJETII-04, is respectively needed.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2021

The UHECR dipole and quadrupole in the latest data from the original Auger and TA surface detectors

The sources of ultra-high-energy cosmic rays are still unknown, but assuming standard physics, they are expected to lie within a few hundred megaparsecs from us. Indeed, over cosmological distances cosmic rays lose energy to interactions with background photons, at a rate depending on their mass number and energy and properties of photonuclear interactions and photon backgrounds. The universe is not homogeneous at such scales, hence the distribution of the arrival directions of cosmic rays is expected to reflect the inhomogeneities in the distribution of galaxies; the shorter the energy loss lengths, the stronger the expected anisotropies. Galactic and intergalactic magnetic fields can blur and distort the picture, but the magnitudes of the largest-scale anisotropies, namely the dipole and quadrupole moments, are the most robust to their effects. Measuring them with no bias regardless of any higher-order multipoles is not possible except with full-sky coverage. In this work, we achieve this in three energy ranges (approximately $8$--$16~EeV$, $16$--$32~EeV$, and $32$--$\infty~EeV$) by combining surface-detector data collected at the Pierre Auger Observatory until 2020 and at the Telescope Array (TA) until 2019, before the completion of the upgrades of the arrays with new scintillator detectors. We find that the full-sky coverage achieved by combining Auger and TA data reduces the uncertainties on the north-south components of the dipole and quadrupole in half compared to Auger-only results.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2020

A Search for Ultra-high-energy Neutrinos from TXS 0506+056 Using the Pierre Auger Observatory

Results of a search for ultra-high-energy neutrinos with the Pierre Auger Observatory from the direction of the blazar TXS 0506+056 are presented. They were obtained as part of the follow-up that stemmed from the detection of high-energy neutrinos and gamma rays with IceCube, Fermi-LAT, MAGIC, and other detectors of electromagnetic radiation in several bands. The Pierre Auger Observatory is sensitive to neutrinos in the energy range from 100 PeV to 100 EeV and in the zenith-angle range from θ = 60° to θ = 95°, where the zenith angle is measured from the vertical direction. No neutrinos from the direction of TXS 0506+056 have been found. The results were analyzed in three periods: one of 6 months around the detection of IceCube-170922 A, coinciding with a flare period of TXS 0506+056, a second one of 110 days during which the IceCube collaboration found an excess of 13 neutrinos from a direction compatible with TXS 0506+056, and a third one from 2004 January 1 up to 2018 August 31, over which the Pierre Auger Observatory has been taking data. The sensitivity of the Observatory is addressed for different spectral indices by considering the fluxes that would induce a single expected event during the observation period. For indices compatible with those measured by the IceCube collaboration the expected number of neutrinos at the Observatory is well below one. Spectral indices as hard as 1.5 would have to apply in this energy range to expect a single event to have been detected.

79 ASTRONOMY AND ASTROPHYSICS↗

NASA NTRS1973

A new technique for Auger analysis of surface species subject to electron-induced desorption

A method is presented to observe surface species subject to electron-induced desorption by Auger electron spectroscopy. The surface to be examined is moved under the electron beam at constant velocity, establishing a time independent condition and eliminating the time response of the electron spectrometer as a limiting factor. The dependence of the Auger signal on the surface velocity, incident electron current, beam diameter, and desorption cross section are analyzed. The method is illustrated by the Auger analysis of PTFE, in which the fluorine is removed by electron induced desorption.

Pepper, S. V.↗

NASA NTRS1975

Auger electron spectroscopy at high spatial resolution and nA primary beam currents

An experimental Auger microprobe system is described which incorporates a field-emission electron gun and total beam currents in the nanoampere range. The distinguishing characteristics of this system include a large multistation UHV specimen chamber, pulse counting and fully digital Auger signal-processing techniques, and digital referencing methods to eliminate the effects of beam instabilities. Some preliminary results obtained with this system are described, and it is concluded that field-emission electron sources can be used for high-resolution Auger electron spectroscopy with primary-beam spots of less than 100 nm and beam currents of the order of 1 nA.

Todd, G.↗

NASA NTRS1977

Auger spectroscopy analysis in adhesion, friction and wear studies

The paper reviews the current use of Auger electron spectroscopy in adhesion, friction, wear and lubrication studies. Conventional Auger spectroscopy is adopted to complement LEED studies of the adhesion of metal single crystals. In addition, Auger cylindrical mirror analysis is applied to the study of changes in surface chemistry during dynamic friction and wear experiments on polycrystalline metals and alloys. Important conclusions are that (1) segregation of alloying elements to the surface of metals can alter adhesion behavior; (2) hydrocarbons are adsorbed readily to clean iron surfaces at 23 C; (3) transfer from one surface to another for dissimilar materials in contact can be followed in sliding or rubbing friction studies; and (4) the friction process can enhance surface activity for metals with hydrocarbons.

Buckley, D. H.↗

NASA NTRS1980

Relativistic K-shell Auger rates, level widths, and fluorescence yields

Systematic relativistic (Dirac-Hartree-Slater) calculations of atomic K-shell Auger transition probabilities are reported for 25 elements with Z between 18 and 96, inclusive. K-level Auger widths are found to be enhanced by relativistic effects, while total K-level widths are reduced. Relativistic theoretical K-shell fluorescence yields are in excellent agreement with experiment. Theoretical relative intensities of K-LX Auger transitions in heavy elements, calculated in j-j coupling, agree well with measurements; for low Z, configuration interaction and intermediate coupling must apparently be included.

Chen, M. H.↗

NASA NTRS1983

Tool for Guiding An Auger

Auger and Ram have same pitch, which minimizes damage to workpiece and load carried by auger. Auger firmly fastened onto ram shaft by screw and kept from rotating on shaft by slot machined into end of stem and male driving lug that engages slot. Used to install threaded studs in plastic or rubber where impractical to mold them in.

Wesselski, C. J.↗

NASA NTRS1984

Ratioed scatter diagrams - An erotetic method for phase identification on complex surfaces using scanning Auger microscopy

By ratioing multiple Auger intensities and plotting a two-dimensional occupational scatter diagram while digitally scanning across an area, the number and elemental association of surface phases can be determined. This can prove a useful tool in scanning Auger microscopic analysis of complex materials. The technique is illustrated by results from an anomalous region on the reaction zone of a SiC/Ti-6Al-4V metal matrix composite material. The anomalous region is shown to be a single phase associated with sulphur and phosphorus impurities. Imaging of a selected phase from the ratioed scatter diagram is possible and may be a useful technique for presenting multiple scanning Auger images.

Browning, R.↗

NASA NTRS1986

Angle-resolved Auger electron spectra induced by neon ion impact on aluminum

Auger electron emission from aluminum bombarded with 1 to 5 keV neon ions was studied by angle-resolved electron spectroscopy. The position and shape of the spectral features depended on the incident ion energy, angle of ion incidence, and electron take-off angle with respect to the aluminum surface. These spectral dependencies were interpreted in terms of the Doppler shift given to the Auger electron velocity by the excited atom ejected into the vacuum. For oblique ion incidence it is concluded that a flux of high energy atoms are ejected in a direction close to the projection of the ion beam on the target surface. In addition, a new spectral feature was found and identified as due to Auger emission from excited neon in the aluminum matrix.

Pepper, S. V.↗

NASA NTRS1989

Auger electron intensity variations in oxygen-exposed large grain polycrystalline silver

Auger electron spectroscopic studies of the grains in oxygen-charged polycrystal-line silver show significant intensity variations as a function of crystallographic orientation. These intensity variations were observed by studies of the Auger images and line scans of the different grains (randomly selected) for each silver transition energy. The results can be attributed to the diffraction of the ejected Auger electrons and interpreted by corresponding changes in the electron mean-free path for inelastic scattering and by oxygen atom accumulation in the subsurface. The subsurface (second layer) octahedral sites increased in size because of surface relaxation and serve as a stable reservoir for the dissolved oxygen.

Lee, W. S.↗

NASA NTRS1988

Vertically reciprocating auger

The mathematical model and test results developed for the Vertically Reciprocating Auger (VRA) are summarized. The VRA is a device capable of transporting cuttings that result from below surface drilling. It was developed chiefly for the lunar surface, where conventional fluid flushing while drilling would not be practical. The VRA uses only reciprocating motion and transports material through reflections with the surface above. Particles are reflected forward and land ahead of radially placed fences, which prevent the particles from rolling back down the auger. Three input wave forms are considered to drive the auger. A modified sawtooth wave form was chosen for testing, over a modified square wave or sine wave, due to its simplicity and effectiveness. The three-dimensional mathematical model predicted a sand throughput rate of 0.2667 pounds/stroke, while the actual test setup transported 0.075 pounds/stroke. Based on this result, a correction factor of 0.281 is suggested for a modified sawtooth input.

Etheridge, Mark↗

NASA NTRS1991

Mapping the composition of planetary surfaces by Auger electron spectroscopy

The feasibility of AES as a remote-sensing technique to map the composition of the sunlit surfaces of planetary bodies without atmospheres is studied. Solar X-rays eject photoelectrons from the planetary surface. The resulting ions relax by emission of fluorescence X-rays or Auger electrons, with energies characteristic of the element which is ionized. The spectrum of Auger electrons and photoelectrons is computed for a variety of elements and for representative lunar rock types illuminated by soft-X-ray line and continuum emission typical of solar long-lived coronal active regions. The Auger electron lines for O, Si, Mg, Al, Fe, and Ca in lunar rocks stand well above the continuum background from photoelectrons and backscattered interplanetary electrons, with typical line-to-continuum ratios from about 20 to over 1000.

Lin, R. P.↗

DOE OSTI2025

CdSe Magic-Size Clusters Deviate from Nanocrystal-Size Scalings for Ultrafast Intraband Relaxation and Auger Recombination

The cluster regime of colloidal semiconductor quantum dots (QDs) occupies an interesting space on the continuum from molecule to bulk material and allow the study of QD properties at extreme quantum confinement limits. For typical QDs, several size-dependent property trends are well established including intraband relaxation rates and universal scaling of Auger recombination with particle volume. Advances in synthesis now allow isolation of atomically precise semiconductor magic-size clusters (MCs), which offer experimental insight regarding how electronic structure changes with particle size in the ultrasmall limit. Here, we report intraband cooling and Auger recombination for several stable CdSe MCs as a function of particle size and observe deviation from QD response in the cluster regime. We additionally show optical signatures ascribed to transient disordering 2 that appear in the single exciton regime for MCs, which point to complexities regarding their implementation.

Auger recombination↗

DOE OSTI2020

Multi-messengers at ultra-high energies with the Pierre Auger Observatory

The Pierre Auger Observatory is an Ultra-High Energy Cosmic Ray (UHECR) detector which has studied cosmic particles with energies above and around 10 18 eV for more than 15 years. It has proved to be the most competitive instrument at these energies and has produced a wealth of valuable results, improving our understanding of UHECRs. A complete understanding of these highest energy particles is crucial to understand the extreme astrophysical events in which they are produced and accelerated, as well as their propagation to Earth. In the same range of energies, UHE photons and neutrinos are of paramount importance as, being electrically neutral, they point back to their origin while charged particles are deflected in the galactic and extragalactic magnetic fields. The flux of extragalactic photons, neutrinos, and cosmic rays are believed to be highly linked, by their origin and their interactions. Each messenger provides different information about the potential sources, and having detection means for all four messengers, including gravitational waves, allows us to shed light on energetic sources of astroparticles. The Pierre Auger Observatory benefits from a large exposure and a good angular resolution, and is efficient in detecting UHE photons and neutrinos. These performances make possible follow-up searches for events detected by gravitational waves, such as the binary mergers observed by the LIGO/Virgo detectors, or any other energetic sources of particles.

Binary black hole mergers↗

DOE OSTI2024

Resonant Auger decay of iodobenzene below the I 4d edge

New data are presented on the resonant Auger decay of iodobenzene (C 6 H 5 I) in the region of the I 4d –1 ionization threshold. The excited molecules decay by participator and spectator processes to populate single-hole valence states and two-hole, one-particle excited states of the cation, providing new information on the structure of C 6 H 5 I + . Excitation of dissociative C 6 H 5 I (I 4d 5/2,3/2 –1 )σ* resonances can, in principle, result in ultrafast dissociation to C 6 H 5 + I** and the subsequent autoionization of I**, but no evidence for this process is observed. Finally, the results are compared with our recent study of the resonant Auger decay of methyl iodide (CH 3 I).

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗