Cancellation of light-shifts in an N-resonance clock

We demonstrate that first-order light-shifts can be cancelled for an all-optical, three-photon-absorption resonance ("N-resonance") on the D1 transition of Rb87. This light-shift cancellation enables improved frequency stability for an N-resonance clock. For example, using a table-top apparatus designed for N-resonance spectroscopy, we measured a short-term fractional frequency stability (Allan deviation) 1.5e-11 tau^(-1/2) for observation times 1s< tau < 50s. Further improvements in frequency stability should be possible with an apparatus designed as a dedicated N-resonance clock.Comment: 4 pages, 4 figure

Comparison of 87Rb N-resonances for D1 and D2 transitions

We report an experimental comparison of three-photon-absorption resonances (known as "N-resonances") for the D_1 and D_2 optical transitions of thermal 87Rb vapor. We find that the D_2 N-resonance has better contrast, a broader linewidth, and a more symmetric lineshape than the D_1 N-resonance. Taken together, these factors imply superior performance for frequency standards operating on alkali D_2 N-resonances, in contrast to coherent population trapping (CPT) resonances for which the D_2 transition provides poorer frequency standard performance than the D_1 transition.Comment: 3 pages, 4 figure

A novel absorption resonance for all-optical atomic clocks

We report an experimental study of an all-optical three-photon-absorption resonance (known as a "N-resonance") and discuss its potential application as an alternative to atomic clocks based on coherent population trapping (CPT). We present measurements of the N-resonance contrast, width and light-shift for the D1 line of 87Rb with varying buffer gases, and find good agreement with an analytical model of this novel resonance. The results suggest that N-resonances are promising for atomic clock applications.Comment: 4 pages, 6 figure

Isolation of Peaks in TDS Spectra of Deuterium from Ion Irradiated Tungsten

AbstractInteraction of deuterium with radiation defects in tungsten was studied by means of thermal desorption spectroscopy. The displacement damage in a recrystallized tungsten foil was produced by irradiation with 10 keV/D ions to the fluences in the range of 3–8×1019 D/m2 at room temperature. The resulted thermal desorption spectra consisted of three wide overlapping peaks. It was shown that annealing of the damaged sample at 550 K and subsequent implantation with 0.67 keV/D ions allows to isolate the peak corresponding to deuterium release from vacancies

Detection of ultra-high resonance contrast in vapor cell atomic clocks

We propose and demonstrate a novel detection scheme of clock signals and obtain an ultra-high resonance contrast above 90%. The precision of the signal's detection and the signal-to-noise ratio (SNR) of atomic clock signal is improved remarkably. The frequency stability in terms of Allan deviation has been improved by an order for the new detection under the equivalent conditions. We also investigate density effect which produces the splitting of the transmission peak and consequently a narrower linewidth of Ramsey fringes.Comment: 5 pages, 4 figure

Effect of the surface temperature on surface morphology, deuterium retention and erosion of EUROFER steel exposed to low-energy, high-flux deuterium plasma

Samples of EUFROFER, a reduced activation ferritic martensitic steel, were exposed in the linear plasma device Pilot-PSI to a deuterium (D) plasma with incident ion energy of similar to 40 eV and incident D flux of 2-6 x10(23) D/m(2) s to fluences up to 10 27 D/m(2) at surface temperatures ranging from 400 K to 950 K. The main focus of the study lays on the surface morphology changes dependent on the surface temperature and the surface composition evolution, e.g., the enrichment in tungsten; but also the erosion and the D retention are studied. The created surface morphology varies strongly with surface temperature from needle-like to corral-like structures. The visible lateral length scale of the formed structures is in the range of tens of nanometres to above 1 mu m and exhibits two thermal activated regimes below and above similar to 770 K with activation energies of 0.2 eV and 1.3 eV, respectively. The lateral variation of the enrichment of heavy elements on the surface is correlated to this surface morphology at least in the high temperature regime, independent of the origin of the enrichment (intrinsic from the sample or deposited by the plasma). Also the erosion exhibits temperature dependence at least above similar to 770 K as well as a fluence dependence. The amount of deuterium retained in the top 500 nm is almost independent of the exposure temperature and is of the order of 10(18) D/m(2), which would correspond to a sub-monolayer D coverage on the surface. The retained D in the volume summing up over the complete samples exceeds the D retained close to the surface by one order of magnitude. (C) 2017 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license