Precise quantum measurement of vacuum with cold atoms.

We describe the cold-atom vacuum standards (CAVS) under development at the National Institute of Standards and Technology (NIST). The CAVS measures pressure in the ultra-high and extreme-high vacuum regimes by measuring the loss rate of sub-millikelvin sensor atoms from a magnetic trap. Ab initio quantum scattering calculations of cross sections and rate coefficients relate the density of background gas molecules or atoms to the loss rate of ultra-cold sensor atoms.

Λ-enhanced gray molasses in a tetrahedral laser beam geometry.

We report the observation of sub-Doppler cooling of lithium using an irregular-tetrahedral laser beam arrangement, which is produced by a nanofabricated diffraction grating. We are able to capture 11(2)% of the lithium atoms from a grating magneto-optical trap into Λ-enhanced D gray molasses. The molasses cools the captured atoms to a radial temperature of 60(9) μK and an axial temperature of 23(3) μK.

A Bitter-type electromagnet for complex atomic trapping and manipulation.

We create a pair of symmetric Bitter-type electromagnet assemblies capable of producing multiple field configurations including uniform magnetic fields, spherical quadruple traps, or Ioffe-Pritchard magnetic bottles. Unlike other designs, our coil allows both radial and azimuthal cooling water flows by incorporating an innovative 3D-printed water distribution manifold. Combined with a double-coil geometry, such orthogonal flows permit stacking of non-concentric Bitter coils.

Collisions of room-temperature helium with ultracold lithium and the van der Waals bound state of HeLi.

We have computed the thermally averaged total, elastic rate coefficient for the collision of a room-temperature helium atom with an ultracold lithium atom. This rate coefficient has been computed as part of the characterization of a cold-atom vacuum sensor based on laser-cooled Li or Li atoms that will operate in the ultrahigh-vacuum ( < 10 Pa) and extreme-high-vacuum ( < 10 Pa) regimes. The analysis involves computing the Σ HeLi Born-Oppenheimer potential followed by the numerical solution of the relevant radial Schrodinger equation.

A radiofrequency voltage-controlled current source for quantum spin manipulation.

We present a wide-bandwidth, voltage-controlled current source that is easily integrated with radiofrequency magnetic field coils. Our design uses current feedback to compensate for the frequency-dependent impedance of a radiofrequency antenna. We are able to deliver peak currents greater than 100 mA over a 300 kHz to 54 MHz frequency span.

Elastic rate coefficients for Li+H collisions in the calibration of a cold-atom vacuum standard.

Ongoing efforts at the National Institute of Standards and Technology in creating a cold-atom vacuum standard device have prompted theoretical investigations of atom-molecule collision processes that characterize its operation. Such a device will operate as a primary standard for the ultrahigh-vacuum and extreme-high-vacuum regimes. This device operates by relating loss of ultracold lithium atoms from a conservative trap by collisions with ambient atoms and molecules to the background density and thus pressure through the ideal gas law.

Light-induced atomic desorption of lithium.

We demonstrate loading of a Li magneto-optical trap using light-induced atomic desorption. The magnetooptical trap confines up to approximately 4 × 10 Li atoms with loading rates up to approximately 4 × 10 atoms per second. We study the Li desorption rate as a function of the desorption wavelength and power.

Single-beam Zeeman slower and magneto-optical trap using a nanofabricated grating.

We demonstrate a compact (0.25 L) system for laser cooling and trapping atoms from a heated dispenser source. Our system uses a nanofabricated diffraction grating to generate a magnetooptical trap (MOT) using a single input laser beam.

Vacuum Furnace for Degassing Stainless-Steel Vacuum Components.

Ultra-high vacuum systems must often be constructed of materials with ultra-low outgassing rates to achieve pressure of 10 Pa and below. Any component placed into the ultra-high vacuum system must also be constructed of materials with ultra-low outgassing rates. Baking stainless steel vacuum components to a temperature range of 400 °C to 450 °C while under vacuum is an effective method to reduce the outgassing rate of vacuum components for use in ultra-high vacuum systems.

Note: A 3D-printed alkali metal dispenser.

We demonstrate and characterize a source of Li atoms made from direct metal laser sintered titanium. The source's outgassing rate is measured to be 5(2) × 10 Pa L s at a temperature T = 330 °C, which optimizes the number of atoms loaded into a magneto-optical trap. The source loads ≈10Li atoms in the trap in ≈1 s.

Toward 3D Printed Hydrogen Storage Materials Made with ABS-MOF Composites.

The push to advance efficient, renewable, and clean energy sources has brought with it an effort to generate materials that are capable of storing hydrogen. Metal-organic framework materials (MOFs) have been the focus of many such studies as they are categorized for their large internal surface areas. We have addressed one of the major shortcomings of MOFs (their processibility) by creating and 3D printing a composite of acrylonitrile butadiene styrene (ABS) and MOF-5, a prototypical MOF, which is often used to benchmark H uptake capacity of other MOFs.

Quantum-based vacuum metrology at NIST.

The measurement science in realizing and disseminating the unit for pressure in the International System of Units (SI), the pascal (Pa), has been the subject of much interest at NIST. Modern optical-based techniques for pascal metrology have been investigated, including multi-photon ionization and cavity ringdown spectroscopy. Work is ongoing to recast the pascal in terms of quantum properties and fundamental constants and in so doing, make vacuum metrology consistent with the global trend toward quantum-based metrology.

Recommended practice for calibrating vacuum gauges of the ionization type.

This article represents a recommended practice for the calibration of ionization gauges using the comparison method. In this method, ionization gauges are compared to a working standard that has an SI traceable calibration. The ionization gauge is either of the hot-cathode ionization type or the cold-cathode ionization type.

Challenges to miniaturizing cold atom technology for deployable vacuum metrology.

Cold atoms are excellent metrological tools; they currently realize SI time and, soon, SI pressure in the ultra-high (UHV) and extreme high vacuum (XHV) regimes. The development of primary, vacuum metrology based on cold atoms currently falls under the purview of national metrology institutes. Under the emerging paradigm of the "quantum-SI", these technologies become deployable (relatively easy-to-use sensors that integrate with other vacuum chambers), providing a primary realization of the pascal in the UHV and XHV for the end-user.

Development of a new UHV/XHV pressure standard (Cold Atom Vacuum Standard).

The National Institute of Standards and Technology has recently begun a program to develop a primary pressure standard that is based on ultra-cold atoms, covering a pressure range of 1 × 10 Pa to 1 × 10 Pa and possibly lower. These pressures correspond to the entire ultra-high vacuum (UHV) range and extend into the extreme-high vacuum (XHV). This cold-atom vacuum standard (CAVS) is both a primary standard and absolute sensor of vacuum.

Investigations of medium-temperature heat treatments to achieve low outgassing rates in stainless steel ultrahigh vacuum chambers.

The authors investigated the outgassing rates and fluxes of vacuum chambers constructed from common 304L stainless steel vacuum components and subjected to heat treatments. Our goal was to obtain H outgassing flux on the order of 10 Pa l scm or better from standard stainless steel vacuum components readily available from a variety of manufacturers. The authors found that a medium-temperature bake in the range of 400 to 450°C, performed with the interior of the chamber under vacuum, was sufficient to produce the desired outgassing flux.

Gas Uptake of 3-D Printed Acrylonitrile Butadiene Styrene (ABS) Using a Vacuum Apparatus Designed for Absorption and Desorption Studies.

We describe a vacuum apparatus for determining the outgassing rate into vacuum, the diffusion coefficient, and the amount of gas absorbed for various materials. The diffusion coefficient is determined from a model applied to time-dependent desorption data taken using a throughput method. We used this method to determine the diffusion coefficient, , for HO in 3-D printed acrylonitrile butadiene styrene (ABS).

Final report on the key comparison, CCM.P-K15 in the pressure range from 1.0 × 10 Pa to 1.0 Pa.

The comparison CCM.P-K15 is a key comparison in pressure involving six laboratories in three regional metrological organizations (RMO). The measurand of the comparison is the accommodation coefficient of two spinning rotating gauge characterized in nitrogen from 0.

How to Build a Vacuum Spring-transport Package for Spinning Rotor Gauges.

The spinning rotor gauge (SRG) is a high-vacuum gauge often used as a secondary or transfer standard for vacuum pressures in the range of 1.0 x 10(-4) Pa to 1.0 Pa.

Intercomparison of the LBIR Absolute Cryogenic Radiometers to the NIST Optical Power Measurement Standard.

The Low Background Infrared calibration (LBIR) facility at the National Institute of Standards and Technology (NIST) presently maintains four absolute cryogenic radiometers (ACRs) which serve as standard reference detectors for infrared calibrations performed by the facility. The primary standard for optical power measurements at NIST-Gaithersburg has been the High Accuracy Cryogenic Radiometer (HACR). Recently, an improved radiometer, the Primary Optical Watt Radiometer (POWR), has replaced the HACR as the primary standard.

Evidence for a three-nucleon-force effect in proton-deuteron elastic scattering.

Developments in spin-polarized internal targets for storage rings have permitted measurements of 197 MeV polarized protons scattering from vector polarized deuterons. This work presents measurements of the polarization observables A(y), iT11, and C(y,y) in proton-deuteron elastic scattering. When compared to calculations with and without three-nucleon forces, the measurements provide further evidence that three-nucleon forces make a contribution to the observables.