AVS 68 Session VT-MoM: Vacuum Measurement and Gas Analysis and Vacuum Technology for Quantum Applications

Quantum technology is currently experiencing a huge push towards commercialization. This means that basic experiments are more and more transferred into industrial applications. This means that enabling technologies must meet new quality criteria. In particular, the interplay between vacuum technology, mechanical and optical requirements must be taken into account. Vacua in the UHV/XHV range have to be achieved and several optical access ports for different optical tools have to be positioned in the range of a few µm to each other and.

In order to fulfill all this demands efficiently, aluminum CF components offer the possibility of providing customized solutions with high geometrical accuracy, reduced weight, outgassing rates of 1E–14 mbar*l/s/cm² as well as non-magnetic properties.

The talk covers the design of non-monolithic and monolithic CF vacuum chambers made from aluminum by using AluVaC®-technology. By discussing customized chamber designs, the talk shows that a monolithic design leads to a paradigm shift, since a monolithic chamber can be designed much more compactly, manufactured faster and without welding seams.

In combination with different optical components, the talk addresses the UHV compatibility of AluVaC®-viewports as well as VACOM made optical feedthroughs. Thorough different tests prove the UHV suitability with low outgassing rates shine light on product-relevant changes under extreme conditions.

We present a comparison of NIST’s cold atom primary vacuum standard and a dynamic expansion vacuum standard. The cold atom vacuum standard (CAVS) converts the background-gas-induced loss rate of atoms from a magnetic trap into vacuum pressure using atom-molecule collision cross-sections calculated from first-principles quantum scattering theory. An extreme-high-vacuum (XHV) flowmeter and dynamic expansion system generate low-uncertainty partial pressures within the CAVS atom trap. To validate the CAVS, we compare its measured pressure to the pressure set by the dynamic expansion vacuum standard. We will present comparisons using a variety of noble gases and common vacuum contaminant species colliding with two species of sensor atoms. Our results open the way to vacuum gauge calibrations in the XHV and deployable pressure sensors with embedded traceability.

We demonstrate the operation of the portable cold atom vacuum standard (pCAVS) by directly measuring the same vacuum with two independent devices. The pCAVS, designed as a replacement to the Bayard-Alpert ionization gauge, measures the loss rate of atoms from a magnetic trap, and converts that loss rate into a vacuum pressure using ab initio quantum-scattering calculations. Our pCAVS devices share the same laser system. Loss rate measurements are interlaced between the two, allowing for simultaneous readout. When initially assembled, the two pCAVS together detected a leak on the order of 10^-6 Pa L/s. After fixing the leak, the two pCAVS measured the same pressure of 41.8 nPa with approximately 2 % uncertainty. Operation of the pCAVS was found to cause some additional outgassing in the vacuum, raising the base pressure approximately 1 nPa. With improved thermal management and better modeling of other loss mechanisms, we expect that the uncertainty can be decreased sufficiently to allow primary pressure measurements in the extreme-high-vacuum range (< 10^-9 Pa).

In the framework of the EURAMET project 16NRM05 a novel ionization gauge was developed. The goal was to develop a stable gauge suitable as a reference standard in the high vacuum range. A robust design eliminates many of the weak points of present day Bayard-Alpert gauges. Results of performed measurements show sensitivity spread within an interval ± 1.5 % at 95 % confidence level. Due to its simple geometry, sensitivity values can in principle be computed for any gas with a known ionization cross section. Known and stable relative sensitivity factors are important properties for the calibration of mass spectrometers. We will present some aspects of the gauge design and performance in conjunction with an associated controller.

NIST with a collaboration research and development partnership with MKS Instruments has created a portable Fixed Length Optical Cavity (FLOC) pressure standard based on gas refractivity. The NIST team is now working to push the limits of pressure measurement into the UHV range. The goal for the new device would be to fill the gap in quantum-based traceability that currently exists between the FLOC and the Cold Atom Vacuum Standard, from 1 Pa to 10^-5 Pa. To achieve the measurement goals, several sources of noise and drift need to be studied and eliminated. The desired sensitivity requires a frequency measurement (heterodyne signal between two 194 THz cavities) to have noise on the order of 1 Hz. To achieve this, the portable FLOC must be redesigned with state-of-the-art lasers and cavity mirrors, vibration isolation, and improved thermal control. The current FLOC low pressure performance will be estimated and initial testing results along with our proposed pathway to ultra-high vacuum measurements will be presented.

With the goals of achieving quantum traceability over a broad pressure scale NIST is developing a Vacuum Fixed Length Optical Cavity (VFLOC) that will have a base pressure in the ultra-high vacuum range.The current FLOC operates in the 1 kPa to 150 kPa pressure range and the Cold Atom Vacuum Standard (CAVS) has an upper limit near 10^-5 Pa.The main limitation for pressure resolution and ultimate base pressure is the fractional frequency stability or frequency noise of dual cavity heterodyne signal.For operation at 1542 nm, hertz level frequency noise is required for achieving pressure noise floor on the order of 10^-6 Pa (10^-8 Torr).We will discuss current system status, design and recent results.