AVS2016 Session VT-WeM: Vacuum Technology – History and Innovation (8:20-10:00 am)/Transfer and Manipulation (11:00 am-12:20 pm)

A number of key scientific demonstrations from the 18^th century to the present were enabled by the essential task of obtaining a low enough level of vacuum. This talk explores a number of well-known events in the history of science and technology that depended on achieving a remarkable level of high vacuum for the era contemporary to the demonstration. We start with Franklin’s lyceum experiments where he applied static voltages across glass cylinders where pressures were lowered below ambient conditions with crude air pumps. This work presaged subsequent work on gas discharges and modern accelerator cavities. A century later, J. J. Thomson was the first to make an electron beam by lowering vacuum levels sufficiently to prevent ionized residual gas ions from shielding the negative particle beam. Fast-forward to the early 1960’s where G.K. O’Neill invented the now standard configuration for contemporary particle physics experiments- the high intensity storage ring. This configuration demanded and achieved true ultrahigh vacuum levels on an industrial scale. The story concludes with this year’s remarkable detection of gravity waves using LIGO - the kilometer-scale laser interferometers that required extreme high vacuum levels for all residual gas components.

Development of innovative sensors and standards that—through improvements in cost, size, speed, and durability—will enable new manufacturing processes, tools and products of tomorrow. The NIST vision is that these innovations will improve the dissemination of standards to the point where routine exchange of artifacts for measurement quality assurance is no longer needed. Quantum and photonic based rugged small-scale vacuum sensors open new horizons in measurement science and represent a paradigm shift in how metrology is done. Networks of small and precise sensors embedded within structures and composite materials could improve their performance and reliability. These sensors draw upon a range of technologies not previously exploited for these applications, such as nanofabrication, photonics, and atomic physics. Photonic and quantum-based vacuum sensors will allow both the absolute sensing of vacuum and the realization of the SI at the user site and will allow the user to calibrate other sensors or directly measure process vacuum levels for critical applications. Several related research programs at NIST are geared towards realizing the vision of small or chip sized absolute sensors for practical applications. NIST is building a sensor program, with the goal to establish a set of chip-scale tools that enable real-world use. An example is the chip-scale cold-atom technology requires maintaining UHV conditions throughout the operating lifetime of the device, posing practical technical challenges to the vacuum engineering. Our program to replace primary mercury manometers with photonic-based primary standard relies on lasers and Fabry–Pérot optical cavities that are stable from several atmospheres of pressure down to high-vacuum. These cavities will be field-deployable absolute sensors requiring no calibration. Other quantum and photonic based sensors include dynamic pressure measurements and thermometry. These programs will be discussed in terms of the larger programmatic view of how quantum-based, chip scale technologies will disrupt vacuum technology, primary standards, and pressure, vacuum and temperature measurement.

In 2018 the unit of the kilogram will be redefined. Instead of being based on the physical artifact known as the International Prototype Kilogram (IPK), the kilogram will be defined by fixing the value of a fundamental physical constant, Plancks constant. It will now be realized using watt balance or x-ray crystal density (Avogadro) experiments. This will enable any research group throughout the world to realize the unit of mass if they have sufficient technical expertise and equipment. Both of these experimental methods are optimally designed to operate in vacuum. As a result, mass metrology must now deal with the issues of maintaining, manipulating and moving masses under vacuum.

At the National Institute of Standards (NIST), at least five different experimental systems operating in vacuum will be used for the realization and dissemination of the kilogram. First, the kilogram will be realized using the NIST-4 watt balance. Second, NIST is developing a unique apparatus called the magnetic suspension mass comparator (MSMC) to transfer the unit of mass in vacuum to a mass in air. Third, a commercial vacuum comparator will be used to directly compare different masses in vacuum and for sorption studies. Fourth, a new plasma cleaning station is being developed to use a downstream hydrogen plasma source to clean a mass. And finally, there will be a vacuum mass storage facility where multiple calibrated masses can be kept for later mass comparisons.

In order to transport a mass under vacuum between the different apparatus, a custom built mass transport vehicle (MTV) has been constructed. It is essentially a mobile vacuum chamber made out of a 4 way cross and gate valve. It has a wide range pressure gauge and a battery powered getter pump. The vacuum chamber is supported by an aluminum frame mounted on castors. The MTV can maintain a vacuum below 1.3x10^-3 Pa for 30 minutes without pumping which is sufficient time to transport a mass between the different rooms housing the experimental apparatuses. The MTV can be attached to a load lock on each apparatus which can extract the mass and transfer it inside while maintaining the mass in vacuum. The complete transfer process of a mass from one machine to another with the MTV takes on the order of an hour. Most of this time is due to the evacuation time of the load lock after the MTV has been attached.

Handling, Transfer, Storage, and Shipping of Commercial Thin Film Hydride

Disk Target Samples

James L. Provo^*

Consultant, J. L. Provo Consulting, Trinity, FL 34655-7179

Thin film hydride targets are important for many applications including,

accelerator research, various neutron devices, contraband detection, etc.

They are very sensitive to air-oxidation and easily contaminated by improper

handling . Air-exposure, which oxidizes Group IIIB, IVB, and rare earth film

materials, affects their operating properties. This paper will discuss the

development of handling techniques, and special transfer and shipping

containers for hydride target samples from post processing to transfer and

shipment to a customer. Studies were performed to determine the best physical

handling devices, procedures for reducing particulate contamination, and for

reducing air-exposure and moisture from samples before actual use. Initially, as

an example, samples in an air-exposure hydriding system, were backfilled with

an inert gas just before opening into an environmentally controlled clean room,

quickly moved to an inert gas glove box, and then placed in special vacuum

transfer or shipping containers, as quickly as possible, and then pumped down

to a vacuum of ~ 1 x 10 ^{- 7} Torr( 1.33 x 10 ^-5 Pa) or less. For optimum handling

conditions, a system was developed with the major components being a hydride

loading system in a double-sided stainless steel glove box contained in an

environmentally controlled room. This glove box contained a loader vacuum

chamber, a video microscope, a HEPA filter/ fan module and a hydriding gas

manifold. The glove box had an inert Ar or N₂ atmosphere, achieved by circulating

the gas through a commercially made purifier which striped oxygen and water

vapor. The glove box atmosphere was monitored by an oxygen monitor, and a

water vapor analyzer. When loaded samples are removed from the chamber

of such a system, samples are automatically in a pristine environment,with very

low particulate contamination, and a minimum amount of water vapor.

On the other side of the glove box, samples are placed into transfer and/or

shipping containers, which are then pumped down to high vacuum conditions for

shipment. Examples of sample handling clips, and sample containers are given.

Results have shown, that by using such methods and techniques, hydride target

disk samples can be successfully processed, handled, transferred and shipped in a

condition very close to that as processed out of a loader.

* Formerly, Principle Member of the Technical Staff at Sandia National Laboratories,

Albuquerque, New Mexico 87185 (Retired); electronic mail: jlprovo@verizon.net