https://link.springer.com/content/pdf/10.1016%2FS1044-0305%2802%2900384-7.pdf

A two-dimensional quadrupole ion trap mass spectrometer.

Atomic clocks have been instrumental in science and technology, leading to innovations such as global positioning, advanced communications, and tests of fundamental constant variation. Timekeeping precision at 1 part in 10 18 enables new timing applications in relativistic geodesy, enhanced Earth- and space-based navigation and telescopy, and new tests of physics beyond the standard model. Here, we describe the development and operation of two optical lattice clocks, both using spin-polarized, ultracold atomic ytterbium. A measurement comparing these systems demonstrates an unprecedented atomic clock instability of 1.6 × 10 –18 after only 7 hours of averaging.

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An atomic clock with $10^{-18}$ instability

Micromotion of ions in Paul traps has several adverse effects, including alterations of atomic transition line shapes, significant second-order Doppler shifts in high-accuracy studies, and limited confinement time in the absence of cooling. The ac electric field that causes the micromotion may also induce significant Stark shifts in atomic transitions. We describe three methods of detecting micromotion. The first relies on the change of the average ion position as the trap potentials are changed. The second monitors the amplitude of the sidebands of a narrow atomic transition, caused by the first-order Doppler shift due to the micromotion. The last technique detects the Doppler shift induced modulation of the fluorescence rate of a broad atomic transition. We discuss the detection sensitivity of each method to Doppler and Stark shifts, and show experimental results using the last technique.

Minimization of ion micromotion in a Paul trap

▪ Abstract Laser ablation of in situ metals has recently made it possible to immerse a large number of different metal atoms and ions and small clusters of metal atoms in liquid helium (He) and thus study their absorption and emission spectra in the visible region. Atoms and molecules are readily picked up by large ( ≥ 103 atoms) He droplets, and their spectra are sensitively detected through the use of either beam depletion following absorption or laser-induced fluorescence. Within the past three years, a wide variety of molecules, ranging from OCS to large organic molecules such as amino acids and a number of van der Waals complexes and even large metal clusters, have been embedded in He droplets and studied either in infrared or in the visible region. These results are discussed here in detail, and the evidence for the effect of superfluidity on the spectral features is reviewed.

Spectroscopy of atoms and molecules in liquid helium

Characteristics of mass selective axial ion ejection from a linear quadrupole ion trap in the presence of an auxiliary quadrupole field are described. Ion ejection is shown to occur through coupling of radial and axial motion in the exit fringing fields of the linear ion trap. The coupling is efficient and can result in extraction of as much as 20% of the trapped ions. This, together with the very high trapping efficiencies, can yield high sensitivity mass spectral responses. The experimental apparatus is based on the ion path of a triple quadrupole mass spectrometer allowing either the q2 collision cell or the final mass analysis quadrupole to be used as the linear trap. Space charge induced distortions of the mass resolved features while using the pressurized q2 linear ion trap occur at approximately the same ion density as reported for conventional three-dimensional ion traps. These distortions are, however, much reduced for the lower pressure linear trap possibly owing to the proposed axial ejection mechanism that leads to ion ejection only for ions of considerable radial amplitude. RF heating due to the high ejection q-value and the low collision frequency may also contribute. Two hybrid RF/DC quadrupole-linear ion trap instruments are described that provide high sensitivity product ion scanning while operated in the linear ion trap mode while also retaining all conventional triple quadrupole scan modes such as precursor ion and neutral loss scan modes. Copyright © 2002 John Wiley & Sons, Ltd.

A new linear ion trap mass spectrometer

We present the design for a phase-modulated opto electronic oscillator (OEO) that incorporates asymmetric Mach-Zehnder (AMZ) interferometers as phase demodulators together with PM modulation suppression. The new design promises to obtain in the electro-optical domain the low-noise advantages previously achieved in RF and microwave oscillators by the use of carrier suppression but which have been achieved only to a limited extent in OEO's

A New OEO Design Using Optical Phase Modulation and Modulation Suppression

This paper discusses the demonstrated accuracy and utility of a 2-D finite element methodology for whispering gallery mode sapphire resonators. The mode solutions obtained by the software compared with experimental results for a wheel-shaped sapphire resonator give an error in mode frequency of less than 0.55%. We also show parts per million agreement with analytical solutions for simple geometries such as an empty coaxial resonator. The CYRES 2D FEM software package developed at The University of Texas at El Paso has proven invaluable for the analysis and identification of modes and mode families for resonators of various geometries. The software also shows promise as a tool for optimization of new resonator designs. Current uses include design of optimum sized dielectric resonators for minimized wall losses, and new resonator geometries for temperature compensated resonators. The operational characteristics of the software and the general methodology for use of the software as a laboratory and design tool are discussed. >

Experimental test and application of a 2-D finite element calculation for whispering gallery sapphire resonators

The authors combined a superconducting cavity maser oscillator (SCMO) and a hydrogen maser to form a standard which shows the medium-term performance of the hydrogen maser together with improved short-term performance available only from cryogenic oscillators. A double-loop receiver combines the two sources with a 100-MHz quartz crystal oscillator. Fractional frequency stability of 2*10/sup -14/ was obtained for a measuring time of tau =1 s, and 1*10/sup -15/ at tau =1000 s. The 1-s value is almost as low as the floor (1*10/sup -14/) for the measurement system, while the 1000-s value is identical to hydrogen maser performance. The design is based on models of hydrogen maser and SCMO phase noise for offset frequencies down to 1*10/sup -6/ Hz. >

Combined stability of hydrogen maser and superconducting cavity maser oscillator

Doppler Sideband Spectra for Hg Ions in a Linear Ion Trap

We show that the frequency bias caused by distributed cavity phase has a strong dependence on microwave power. We also show that frequency biases associated with microwave leakage have distinct signatures in their dependence on microwave power and the physical location of the leakage interaction with the atom.

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Frequency Biases Associated with Distributed Cavity Phase and Microwave Leakage in the Atomic Fountian Primary Frequency Standards IEN-CSF1 and NIST-F1

G.J. Dick

Papers

A New OEO Design Using Optical Phase Modulation and Modulation Suppression

Experimental test and application of a 2-D finite element calculation for whispering gallery sapphire resonators

Combined stability of hydrogen maser and superconducting cavity maser oscillator

Doppler Sideband Spectra for Hg Ions in a Linear Ion Trap

Frequency Biases Associated with Distributed Cavity Phase and Microwave Leakage in the Atomic Fountian Primary Frequency Standards IEN-CSF1 and NIST-F1