bluuebunny/crossref_metadata_2025_split huggingface dataset:
Multi Fluxon Storage and its Implications for Microprocessor Design
Authors: Katam Naveen K , Zha Haipeng , Pedram M , Annavaram M 
Published: June 2020

Abstract
One of the main challenges for single flux quantum (SFQ) technology to successfully implement a microprocessor is to have a compact and robust on-chip memory that can be used for register files and cache memory. In this context, we designed high capacity destructive readout (HC-DRO) cells. The design is based on our insight that each cell can store more than one SFQ pulse with the same area footprint of a regular DRO cell. In our current design, we demonstrate a single HC-DRO cell that can store up to three SFQ pulses thereby enabling us to store the equivalent of two bits of memory in a single cell. We have designed a register file (RF) architecture for a microprocessor and used the HC-DRO cells to reduce the Josephson junction count required for its implementation. The RF architecture presented in this work can also be used for implementing cache memories. We also demonstrate the benefits of doubling the storage density with HC-DRO cells by designing a 2-bit branch predictor circuit block for a 5-stage pipeline microprocessor that dramatically improves the cycles per instruction metric of an SFQ based microprocessor. All the design details are presented in the paper by verifying the design concepts through JSIM simulations and Verilog simulations.
Possible dynamics of Josephson junction arrays connected to high-Q tank circuit
Authors: Kornev Victor K. , Kolotinskiy Nikolay V. 
Published: June 2020

Abstract
Serial Josephson junction arrays connected to high-Q tank circuit are analysed and discussed. Numerical simulation of the systems shows two possible oscillation modes above resonance frequency when the tank impedance is capacitive. These are the inphase oscillation mode and the collectively antiphase oscillation mode. This fact is responsible for complicate switching dynamics, which can block parametric resonance excitation. Stability domains of the modes depend on McCumber parameter of the junctions. Increase in this parameter is favourable to the inphase mode. When the inphased oscillations are feasible, the resonance peak-like peculiarities on IV curve and Shapiro steps can be described with the analytic theory derived earlier for one-junction case and extended over the array systems.
A compact, low-power <1K cooling platform for superconducting nanowire detectors
Authors: Ronson Emily , Chase Simon , Kenny Lee 
Published: June 2020

Abstract
Superconducting nanowire single photon detectors (SNSPD) with high detection efficiency, low dark count rate, small timing jitter and short recovery times require cryogenic cooling. Detector performance is strongly dependent on temperature and though many detectors will operate at ~4K, lower temperatures offer significant performance gains. Fortunately, the technology for sub-Kelvin cooling is now mature and products are available that offer simple operation, with reliable and repeatable performance at relatively low cost. In this paper we review performance data from tests on more than 45 individual sub-Kelvin modules manufactured by Chase Research Cryogenics. We compare modules of different sizes and discuss how modules can be scaled to achieve a range of technical specifications for specialised end-user applications.
Hybrid cooling system with cryocooler and liquid-nitrogen for HTS-SQUID system
Authors: Hato Tsunehiro , Tsukamoto Akira , Adachi Seiji , Tanabe Keiichi 
Published: June 2020

Abstract
We developed a hybrid cooling system consisting of a liquid-nitrogen Dewar and a cryocooler with the aim of cooling HTS-SQUIDs fast at operation sites, extending cooling period time, and avoiding noise increase caused by the cryocooler. Liquid nitrogen is evaporated mainly by thermal inflow into the Dewar. Thus, we tried reducing the thermal inflow into a glass Dewar by cooling its inner surface using a small Stirling cryocooler with a cooling capacity of 16 W at 77 K, and examined the cooling period and the operation procedure. We successfully kept 0.6 liter of liquid nitrogen for one week with 0.2 liter reduction. It was also indicated that long time and low noise operation of HTS-SQUIDs would be possible in the hybrid cooling system by temporarily stopping the cryocooler during measurements.
Progress towards innovative and energy efficient logic circuits
Authors: Pagano Sergio , Salina Gaetano , Napoli Anna , Attanasio Carmine , Barone Carlo , Bobba Fabrizio , Carapella Giovanni , Leo Antonio , Nigro Angela , Cristiano Roberto , Ejrnaes Mikkel , Lisitskiy Mikhail , Martucciello Nadia , Pepe Giovanni Piero , Parlato Loredana , Cirillo Matteo , Lucci Massimiliano , Merlo Vittorio , Messina Antonino , Militello Benedetto 
Published: June 2020

Abstract
The integration of superconductive nanowire logic memories and energy efficient computing Josephson logic is explored. Nanowire memories are based on the integration of switchable superconducting nanowires with a suitable magnetic material. These memories exploit the electro-thermal operation of the nanowires to efficiently store and read a magnetic state. In order to achieve proper memory operation a careful design of the nanowire assembly is necessary, as well as a proper choice of the magnetic material to be employed. At present several new superconducting logic families have been proposed, all tending to minimize the effect of losses in the digital Josephson circuits replacing resistors by adequate combinations of inductors in the logic gates. Among those, the nSQUID concept relies on the propagation of vortices along underdamped Josephson transmission lines. While, in principle, this logic family provides very low dissipation, several issues, such as speed and stability, have yet to be addressed. The current status of design and testing of n-SQUID logic gates and circuits as well as of the design and implementation of the nanowire memories is reported
Measurement of Magnetic Particles by Hexagonal Pseudo Seven-Channel HTS SQUID Array
Authors: Tanaka S , Kabasawa M , Hayashi K , Ohtani T 
Published: June 2020

AbstractWe developed a high-Tc superconducting (HTS) three-channel Superconducting Quantum Interference Device (SQUID) array and applied it to the measurement of a flow of magnetic nano-particles (MNPs).Three magnetometers were positioned in-line with a separation of 2.3 mm. The pick-up loop consisted of a 1 mm × 1 mm square loop; the size of a SQUID washer slit was 5 μm × 60 μm. Using this array, we arranged a hexagonal pseudo seven-channel SQUID array. The signal from the water-diluted MNPs, Resovist, in motion was measured by the array in a DC bias magnetic field and an AC modulation magnetic field. The dependence of the SQUID signal on the angle of the MNP flow to the baseline of the array was measured and discussed. The results suggest that the signal peak values are highly dependent on the flow path angle and that most of the flow path can be identified by the shape of the waveforms. This method is a promising candidate for brain activity investigation of small animals.
High-Resolution Digital SQUID Magnetometer using Sub-Flux Quantum Feedback
Authors: Myoren Hiroaki , Okabe Kosuke , Matsunawa Ryo , Itagaki Kohki , Naruse Masato , Taino Tohru 
Published: June 2020

Abstract
Digital SQUIDs with the single flux quantum (SFQ) feedback have attracted much attention because of the feasibility of realizing a wide dynamic range and high slew rate for digital magnetometers. In order to realize higher resolution, we have studied a digital SQUID with sub-flux quantum feedback. Combining the sub-flux quantum feedback to a feedback loop and the direct SFQ feedback to a main loop triggered by carry SFQ pulses from an up/down counter. In this study, we discuss the method of multi-flux quantum generation and compact design of the SFQ up/down counter for high-speed operation of the digital SQUID magnetometer.
Fine optimization of Josephson critical current in SQUID devices by thermal annealing
Authors: Vettoliere Antonio , Talamo Oliviero , Silvestrini Paolo , Valentino Massimo , Granata Carmine 
Published: June 2020

Abstract
In the present article an experimental study regarding optimization and fine-tuning and of Superconducting QUantum Interference Device (SQUID) parameters by a thermal annealing is presented. It allows to modify the parameters in order to meet a specific application or to adjust the device parameters to reduce the magnetic field noise preventing the work instability conditions due to a critical current value that exceed the expected one. In particular, we carried out the measurements of the critical current and the voltage swing as a functions of the annealing temperatures or time showing the effect of such procedures on the magnetic field spectral density of the SQUID magnetometers The experimental results demonstrate that it is possible to optimize the main device parameters reducing the SQUID noise to a suitable value improving the stability of working operations.
Investigation of NanoSQUIDs Fabricated with a Range of Focused Ion Beam Sources
Authors: Polychroniou E , Gallop J , Godfrey T , Cox D , Long G , Chen J , Romans E , Hao L 
Published: June 2020

Abstract
SQUIDs (Superconducting Quantum Interference Devices) are macroscopic quantum devices capable of detecting and measuring a wide variety of physical parameters with unprecedented sensitivity. SQUIDs based on nanobridge weak links have shown increasing promise for quantum information and quantum sensing applications such as single spin detection. Focussed ion beam etched nanobridges have properties which can enhance nanoSQUID device performance but are often limited in terms of their non-hysteretic operating temperature range. Here we describe measurements of FIB-milled nanobridges, as single weak links or in nanoSQUIDs, made using either Ga, Xe or Ne ion beam sources. Their properties as a function of temperature, bias current, magnetic field and microwave power are measured and modelled according to a range of superconductivity models, as a means for improved understanding of the associated nanobridge parameters. We further propose techniques to extend the non-hysteretic operating temperature range of the devices.
Dark counts double switching rates in NbTiN Superconducting Nanowire Single Photon Detectors
Authors: Salvoni D , Ejrnaes M , Parlato L , Yang X Y , You L X , Wang Z , Pepe G P , Cristiano R 
Published: June 2020

Abstract
In this work we present a study of the dark counts rate in a NbTiN Superconducting Nanowire Single Photon Detectors (SNSPD). We measure the distribution of the time intervals elapsed between two consecutive dark pulses at the fixed temperature of 4,2K. Due to the stochastic nature of the dark counts, the distribution is expected to have a Poisson shape but what we observe is a combination of two Poisson-like processes. A further analysis of the distributions dependence on the bias current highlights that the weight of the two process is not constant. In the scenario presented by Ejrnaes et al. [1], this result can confirm that, in this temperature regime, dark counts are generated mainly by multiple consecutive fluctuation events and the contribution to the dark counts rate coming from single fluctuations increases in the high bias current region.
Spectral filtering with diffractive reflection gratings for fast superconducting detectors in the THz frequency range
Authors: Schmid A , Kuzmin A , Wuensch S , Ilin K , Bruendermann E , Scherhaufer D , Mueller A-S , Siegel M 
Published: June 2020

Abstract
In this work we describe the design process of a grating spectrometer with fast superconducting THz detectors based on Niobiumnitride. The main application is the use as a diagnostic tool for accelerator-based sources of THz radiation like synchrotrons, where interactions of the electron bunches in storage ring lead to fluctuations in spectrum and intensity of the emitted radiation.
Guidelines for the design of the two main parts, grating and detector design, are given. Here, a blazed reflection grating for a frequency range of 1 THz to 5 THz has been developed and successfully fabricated in a high-precision milling process out of brass. Also three different planar antenna designs (double-slot, annular slot and log-per spiral) in combination with quasioptical bandpass filters for the THz range have been simulated and evaluated for best spectral resolution and power coupling.
Finally, we have verified grating performance for pulsed THz radiation of 1 THz in an experiment conducted at the synchrotron light source of the KIT. Excellent agreement of the grating performance to the simulations has been found.
Hard X-ray Fluorescence measurements with TESs at the Advanced Photon Source
Authors: Guruswamy Tejas , Gades Lisa M , Miceli Antonino , Patel Umeshkumar M , Weizeorick John T , Quaranta Orlando 
Published: June 2020

Abstract
Transition Edge Sensor (TES) spectrometers for hard X-ray beamline science will enable improved X-ray emission and absorption spectroscopy in the information-rich 2 to 20 keV energy range. We are building a TES-based instrument for the Advanced Photon Source (APS) synchrotron, to be made available to beamline users. 24-pixel prototype arrays have recently been fabricated and tested. The first spectroscopy measurements using these arrays are promising, with a best single-pixel energy resolution of 11.2 eV and saturation energy > 20 keV. We present a series of recent X-ray Fluorescence measurements involving transition metal elements and multi-element samples with closely spaced emission lines, in particular a Cu-Ni-Co thin film and a foil of Cu and Hf. The TES-measured spectra are directly compared to spectra measured with silicon drift detectors at an APS beamline, demonstrating the improved X-ray science made possible by TES spectrometers.
Multiphysics simulation of a superconducting bolometer working in a portable cryostat
Authors: Napolitano Andrea , Ferracin Samuele , Gerbaldo Roberto , Ghigo Gianluca , Gozzelino Laura , Torsello Daniele , Laviano Francesco 
Published: June 2020

Abstract
We present the characterization and the numerical simulation of a high-temperature superconducting bolometer based on an YBa2Cu3O7-x (YBCO) film, which is patterned in serpentine elements and selectively modified by means of micro-collimated high-energy heavy-ion irradiation. The local irradiation of YBCO yields to a controlled reduction of the critical temperature and of the critical current, but the resistance versus temperature slope is preserved near Tc. In this way, only the irradiated part of the YBCO films is used for detecting infrared radiation, while the pristine one serves for electro-thermal feedback. The bolometer has been engineered in a portable cryostat, which is equipped with an optical window for suitably filtering the spectrum of the incoming electromagnetic radiation. The optimization of the cryostat has been performed with modelling by finite element method of the whole apparatus, along with simulations of the bolometer response.
Development of a Josephson junction based single photon microwave detector for axion detection experiments
Authors: Alesini D , Babusci D , Barone C , Buonomo B , Beretta M M , Bianchini L , Castellano G , Chiarello F , Di Gioacchino D , Falferi P , Felici G , Filatrella G , Foggetta L G , Gallo A , Gatti C , Giazotto F , Lamanna G , Ligabue F , Ligato N , Ligi C , Maccarrone G , Margesin B , Mattioli F , Monticone E , Oberto L , Pagano S , Paolucci F , Rajteri M , Rettaroli A , Rolandi L , Spagnolo P , Toncelli A , Torrioli G 
Published: June 2020

Abstract
Josephson junctions, in appropriate configurations, can be excellent candidates for detection of single photons in the microwave frequency band. Such possibility has been recently addressed in the framework of galactic axion detection. Here are reported recent developments in the modelling and simulation of dynamic behaviour of a Josephson junction single microwave photon detector. For a Josephson junction to be enough sensitive, small critical currents and operating temperatures of the order of ten of mK are necessary. Thermal and quantum tunnelling out of the zero-voltage state can also mask the detection process. Axion detection would require dark count rates in the order of 0.001 Hz. It is, therefore, is of paramount importance to identify proper device fabrication parameters and junction operation point.
Superconducting heterostructure with barrier with strong spin-orbit interaction
Authors: Constantinian K Y , Petrzhik A M , Ovsyannikov G A , Shadrin A V , Kislinskii Yu V , Cristiani G , Logvenov G 
Published: June 2020

Abstract
We report on observation of superconducting current and AC Josephson effect in mesa-heterostructures with spin-singlet superconducting electrodes, interlayered by a barrier material with strong spin-orbit interaction. The mesa-heterostructures were Nb/Au/Sr2IrO4/YBa2Cu3Ox with d=5 nm and 7 nm thick interlayer of strontium iridate Sr2IrO4, which is known as a canted antiferromagnetic insulator with a weak magnetic moment from Ir atoms and with spin-orbit interaction energy ESO
~0.4 eV. The superconducting critical current density was jC
≈0.3 A/cm2 at T=4.2 K for mesa-heterostructures with d=7 nm and a few times higher for d=5 nm. The zero-bias conductance peak has been observed due to low energy states originated at Sr2IrO4/YBa2Cu3Ox interface. Under influence of weak magnetic field the critical current IC
(H) dependences showed Fraunhofer-like pattern indicating absence of pinholes, supported also by oscillating with microwave power Shapiro steps. Fiske resonance steps with voltage positions deviated from the ordinary ones were registered for mesas with d=5 nm.
Occurrence of Flux Jumps in MgB2 Bulk Magnets during Pulse-Field Magnetization
Authors: Sakai N , Oka T , Yamanaka K , Dadiel L , Oki H , Ogawa J , Fukui S , Scheiter J , Häßler W , Yokoyama K , Noudem J , Miryala M , Murakami M 
Published: June 2020

Abstract
The magnetic flux capturing of MgB2 bulk magnets made by spark plasma sintering process has been precisely investigated to clarify the mechanism of flux motions during the pulse-field magnetization processes. The field trapping ratio B
T/B
P was evaluated as a key parameter of field trapping ability which strongly relates to the heat generation due to the rapid flux motion in the samples. The time dependence of magnetic flux density revealed the actual flux motion which penetrated the samples. The trapped fields B
T and field trapping ratios B
T/B
P of various samples were classified into three regions of ‘no flux flow’, ‘fast flux flow’ and ‘flux jump’ according to the generation of heat and its propagation. A flux jump was observed late at 280 ms from the beginning of PFM process, while the field penetration B
P showed its peak at 10 ms. Considering the heat propagation speed, the long-delayed flux jump should be attributed to the macroscopic barriers against the heat propagation to the surface centre of bulk magnet.
Performance and Microstructure of Bi-2212 Wire under Different OverPressures Heat-treatment
Authors: Yang Dongsheng , Yu Min , Jin Huan , Liu Fang , Qin Jinggang 
Published: June 2020

Abstract
Bi2Sr2CaCu2Ox is a potential material for the superconducting magnets of the next generation of Fusion-reactors. A R & D activity based on Bi-2212 wire is running at Institute of Plasma Physics Chinese Academy of Sciences (ASIPP) for the feasibility demonstration of Cable In Conduit Conductor (CICC). The Bi-2212 round wires were heat-treated by the tube furnace at a pressure of 30 atm and 50 atm. Wire diameter, critical current performance, and n value were studied. The surface morphology and grain size distribution of Bi-2212 superconductor after heat treatment analyzed by Electron Backscattering Diffraction (EBSD). The performance difference of Bi-2212 at 30atm and 50atm is small, and the grain size and distribution are similar. The performance difference of Bi-2212 samples with 30atm and 50atm over-pressure heat-treatment is small. 30atm requires less equipment and can obtain a longer constant temperature zone, which is suitable for exploring the heat treatment process of a long conductor.
Simulation of mechanical stresses in reinforced REBaCuO ring bulks during pulsed-field magnetization
Authors: Hirano T. , Fujishiro H. , Naito T. , Ainslie M. D. 
Published: June 2020

Abstract
We have performed numerical simulations of the electromagnetic, thermal and mechanical properties of a REBaCuO ring-shaped bulk with various reinforcement structures during pulsed-field magnetization (PFM). Compressive and tensile electromagnetic stresses,

σ
θ

mag

, are developed in the ring-shaped bulk during the ascending and descending stages of PFM, respectively. These stresses increase at lower operating temperatures and for higher applied pulsed fields. In order to reduce these stresses, the ring-shaped bulk was fully encapsulated by outer and inner ring with upper and lower plates made by Al alloy. In particular, this reinforcement structure can achieve the lowest electromagnetic compressive stress, which corresponds to about 54% of that for a conventional ring reinforcement structure, and the electromagnetic tensile stress was also reduced. We also compared the simulation results of the electromagnetic stresses for the ring-shaped bulk to those for a disk-shaped bulk.
Simulation of mechanical stresses in reinforced REBaCuO disk bulks during pulsed-field magnetization
Authors: Shimoyashiki F. , Fujishiro H. , Hirano T. , Naito T. , Ainslie M. D. 
Published: June 2020

Abstract
We have performed numerical simulations of the electromagnetic hoop stress, σθ
, in a REBaCuO disk bulk reinforced by a metal ring during pulsed-field magnetization (PFM) using a solenoid coil, in which the superconducting characteristics of the bulk material were assumed to have realistic J
c-B-T ones. The compressive and tensile σθ
stresses were applied in the bulk during the ascending and descending stages of PFM, respectively. The time and position dependences of the mechanical stresses were estimated. The possibility of mechanical fracture due to these hoop stresses and the effect of the metal ring reinforcement were discussed.
Numerical optimisation of mechanical ring reinforcement for bulk high-temperature superconductors
Authors: Barthlott D , Huang K Y , Durrell J H , Cardwell D A , Holzapfel B , Ainslie M D 
Published: June 2020

Abstract
The finite element method has been used extensively in recent years to solve various problems related to applied superconductivity and provides a useful tool for analysing and predicting experimental results. Based on a recently-developed modelling framework, implemented in the finite element software package COMSOL Multiphysics, investigations on the minimum ring reinforcement required to prevent mechanical failure in bulk high-temperature superconducting magnets have been carried out. Assuming homogeneous Jc
(B,T) across the bulk sample irrespective of its dimensions, the maximum magnetic stresses experienced, and the minimum ring thickness required to prevent the hoop and radial stresses from exceeding the tensile strength of the bulk superconductor have been determined for varying values of the Young’s modulus, radius, height and temperature of a representative single-grain Ag-containing Gd-Ba-Cu-O bulk sample. This comprehensive analysis details the influence each of these key parameters has on the magnetic stress and hence their impact on the necessary ring thickness to prevent mechanical failure in any given system, i.e., for any combination of material properties and sample dimensions.