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At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

An Arbitrary Time Interval Generator Base on Vernier Clocks with 0.67 ps Adjustable Steps Implemented in FPGA

In TDC testing and timing system implementations, it is often necessary to generate signal pulses with finely adjustable time intervals. In delay cell–based schemes, the adjustment resolution is constrained by the propagation delay of the cells—typically 15–20 ps per step—and is sensitive to temperature and supply voltage variations. This document presents a fully digital approach that uses two vernier clocks, generated by two stages of cascaded phase-locked loops (PLLs) with a slight frequency difference, to achieve adjustable timing intervals through accumulated phase differences. The scheme was validated on two families of low-cost FPGA devices, achieving adjustable step sizes of 0.67 ps and 0.97 ps.

Wu, Jin-yuan [Fermilab] (ORCID:0000000344329521)↗
DOE OSTI2026

Enhancing quantum clocks and sensors with randomization and decoherence

This letter shows how incoherent dynamics can lead to metrological advantages in quantum sensing. The results rely on the fact that incoherent dynamics lead to an additive contribution to the quantum Fisher information about time. Such an additive contribution can reduce the error of optimal estimation protocols, as implied by the quantum Cramér–Rao bound. I characterize regimes in which the estimation of a time interval or a frequency is enhanced by decoherence, thereby identifying cases in which incoherent dynamics serve as a metrological resource. The decoherence processes that yield enhanced precision of quantum sensors can be engineered by randomized Hamiltonian dynamics. I illustrate the results with protocols that display improved sensing of time intervals or global fields by qubit and photonic sensors. Enhanced precision of time intervals is achieved with Hamiltonians that include randomized global parameters. Enhanced precision in field estimation is obtained by randomized sensing times.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2021

Clocking Auger electrons

Intense X-ray free-electron lasers (XFELs) can rapidly excite matter, leaving it in inherently unstable states that decay on femtosecond timescales. The relaxation occurs primarily via Auger emission, so excited-state observations are constrained by Auger decay. In situ measurement of this process is therefore crucial, yet it has thus far remained elusive in XFELs owing to inherent timing and phase jitter, which can be orders of magnitude larger than the timescale of Auger decay. Here we develop an approach termed ‘self-referenced attosecond streaking’ that provides subfemtosecond resolution in spite of jitter, enabling time-domain measurement of the delay between photoemission and Auger emission in atomic neon excited by intense, femtosecond pulses from an XFEL. FUrthermore, using a fully quantum-mechanical description that treats the ionization, core-hole formation and Auger emission as a single process, the observed delay yields an Auger decay lifetime of \(2.2_{ - 0.3}^{ + 0.2}\) fs for the KLL decay channel.

47 OTHER INSTRUMENTATION↗
DOE OSTI2022

Unsafe at Any Clock Speed: The Insecurity of Computer System Design, Implementation, and Operation

It appears that there are enormous differences of opinion as to the probability of a [system failure]. The higher figures come from the working engineers, and the very low figures from management. When playing Russian roulette the fact that the first shot got off safely is little comfort for the next. [T]here have been recent suggestions by management to curtail elaborate and expensive tests as being unnecessary. However, this must be resisted. The proper way to save money is to curtail the number of requested changes, not the quality of testing for each.

97 MATHEMATICS AND COMPUTING↗