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1. Hardware, methodology and applications of 2 + D backscatter Mössbauer spectroscopy with simultaneous x-ray and γ-ray detection

   https://doi.org/10.1088/1361-6501/ad044b  

   O’Brien, Jack ; Ahmadian Baghbaderani, Hasan ; Keller, Frederico O. ; Dempsey, Nora ; H Lewis, Laura ; Stamenov, Plamen ( November 2023 , Measurement Science and Technology)

   A unique method is presented for the acquisition and analysis of⁵⁷Fe backscatter Mössbauer spectra with simultaneous detection of the resonant 14.4 keVγ-rays and the characteristic 6.4 keV x-rays, using a custom-built multi-parameter analyser constructed on the basis of commercial analogue to digital converters and high-speed digital latches. The system allows for the simultaneous registration of Doppler-modulation velocities and photon energies, with up to 4096 and 8192 digital channels respectively. This arrangement is in contrast to most related systems, which detect at a single narrow energy window per detector. Samples of arbitrary atomic structure, morphology and surface topography can be studied without altering the setup or the analysis procedure, provided that the samples are at least micrometre sized. The hardware and software that are used to acquire data with minimal dead time are described and the custom and self-contained methods for post-measurement energy discrimination, background correction and velocity-axis folding are discussed. The data are fit using a general Hamiltonian model for the nuclear energy levels of⁵⁷Fe and a quantum mechanical description of the angular momentum coupling is utilised, with consideration of the crystalline and chemical disorder of the sample under examination. Three examples of distinct magnetic systems, with thicknesses ranging from$5\text{μ}$m to 6 mm, that were studied using this method are presented, these are: an amorphous CoFeB-based ribbon with ultra-soft coercivity for high-frequency applications, magnetically hard Nd-Fe-B thick films on Si substrates, examined in both as-deposited and annealed states, and a sample from the nickel-rich iron meteorite NWA 6259 that contains the atomically ordered, elevated coercivity,$L{1}_0$phase of FeNi, tetrataenite. The wide applicability and usefulness of this method is thus demonstrated on three distinct sample morphologies that required little to no surface preparation prior to examination.

    

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2. Coordinating rolling software upgrades for cellular networks

   https://doi.org/10.1109/ICNP.2017.8117537  

   Qureshi, Mubashir Adnan ; Mahimkar, Ajay ; Qiu, Lili ; Ge, Zihui ; Zhang, Max ; Broustis, Ioannis ( October 2017 , International Conference on Network Protocols)

   Cellular service providers continuously upgrade their network software on base stations to introduce new service features, fix software bugs, enhance quality of experience to users, or patch security vulnerabilities. A software upgrade typically requires the network element to be taken out of service, which can potentially degrade the service to users. Thus, the new software is deployed across the network using a rolling upgrade model such that the service impact during the roll-out is minimized. A sequential roll-out guarantees minimal impact but increases the deployment time thereby incurring a significant human cost and time in monitoring the upgrade. A network-wide concurrent roll-out guarantees minimal deployment time but can result in a significant service impact. The goal is to strike a balance between deployment time and service impact during the upgrade. In this paper, we first present our findings from analyzing upgrades in operational networks and discussions with network operators and exposing the challenges in rolling software upgrades. We propose a new framework Concord to effectively coordinate software upgrades across the network that balances the deployment time and service impact. We evaluate Concord using real-world data collected from a large operational cellular network and demonstrate the benefits and tradeoffs. We also present a prototype deployment of Concord using a small-scale LTE testbed deployed indoors in a corporate building. 

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3. Characterization of Multianode Photomultiplier Tubes for use in the CLAS12 RICH detector

   https://doi.org/10.1016/j.nima.2022.167446  

   Degtiarenko, P. ; Kim, A. ; Kubarovsky, V. ; Raydo, B. ; Smith, A. ; Benmokhtar, F. ( December 2022 , Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment)

   We present results of the detailed study of several hundred Hamamatsu H12700 Multianode Photomultiplier Tubes (MaPMTs), characterizing their response to the Cherenkov light photons in the second Ring Imaging Cherenkov detector, a part of the CLAS12 upgrade at Jefferson Lab. The total number of pixels studied was 25536. The single photoelectron spectra were measured for each pixel at different high voltages and light intensities of the laser test setup. Using the same dedicated front-end electronics as in the first RICH detector, the setup allowed us to characterize each pixel’s properties such as gain, quantum efficiency, signal crosstalk between neighboring pixels, and determine the signal threshold values to optimize their efficiency to detect Cherenkov photons. A recently published state-of-the-art mathematical model, describing photon detector response functions measured in low light conditions, was extended to include the description of the crosstalk contributions to the spectra. The database of extracted parameters will be used for the final selection of the MaPMTs, their arrangement in the new RICH detector, and the optimization of the operational settings of the front-end electronics. The results show that the characteristics of the H12700 MaPMTs satisfy our requirements for the position-sensitive single photoelectron detectors. 

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4. Measuring the 15 O(α, γ) 19 Ne reaction in Type I X-ray bursts using the GADGET II TPC: Hardware

   https://doi.org/10.1051/epjconf/202226011046  

   Wheeler, Tyler ; Adams, A. ; Allmond, J. ; Alvarez Pol, H. ; Argo, E. ; Ayyad, Y. ; Bardayan, D. ; Bazin, D. ; Budner, T. ; Chen, A. ; et al ( January 2022 , EPJ Web of Conferences)

   Liu, W. ; Wang, Y. ; Guo, B. ; Tang, X. ; Zeng, S. (Ed.)

   Sensitivity studies have shown that the 15 O(α, γ) 19 Ne reaction is the most important reaction rate uncertainty affecting the shape of light curves from Type I X-ray bursts. This reaction is dominated by the 4.03 MeV resonance in 19 Ne. Previous measurements by our group have shown that this state is populated in the decay sequence of 20 Mg. A single 20 Mg(βp α) 15 O event through the key 15 O(α, γ) 19 Ne resonance yields a characteristic signature: the emission of a proton and alpha particle. To achieve the granularity necessary for the identification of this signature, we have upgraded the Proton Detector of the Gaseous Detector with Germanium Tagging (GADGET) into a time projection chamber to form the GADGET II detection system. GADGET II has been fully constructed, and is entering the testing phase. 

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5. Shades: 22 Ne( α , n) 25 Mg reaction rate in the Gamow window

   https://doi.org/10.1051/epjconf/202226011031  

   Rapagnani, David ; Ananna, Chemseddine ; Di Leva, Antonino ; Imbriani, Gianluca ; Junker, Matthias ; Pignatari, Marco ; Best, Andreas ( January 2022 , EPJ Web of Conferences)

   Liu, W. ; Wang, Y. ; Guo, B. ; Tang, X. ; Zeng, S. (Ed.)

   Neutron capture reactions are the main contributors to the synthesis of the heavy elements through the s-process. Together with 13 C( α , n) 16 O, which has recently been measured by the LUNA collaboration in an energy region inside the Gamow peak, 22 Ne( α , n) 25 Mg is the other main neutron source in stars. Its cross section is mostly unknown in the relevant stellar energy (450 keV < E cm < 750 keV), where only upper limits from direct experiments and highly uncertain estimates from indirect sources exist. The ERC project SHADES (UniNa/INFN) aims to provide for the first time direct cross section data in this region and to reduce the uncertainties of higher energy resonance parameters. High sensitivity measurements will be performed with the new LUNA-MV accelerator at the INFN-LNGS laboratory in Italy: the energy sensitivity of the SHADES hybrid neutron detector, together with the low background environment of the LNGS and the high beam current of the new accelerator promises to improve the sensitivity by over 2 orders of magnitude over the state of the art, allowing to finally probe the unexplored low-energy cross section. Here we present an overview of the project and first results on the setup characterization. 

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