Rudi's major achievements

Neutron physics
Radiation and metrology
Mass-spectrometric gas analysis
Vacuum and surface technology
International relations and congress organization

Vacuum and surface technology

Application of the radioactive tracer technique in vacuum research

Rudi's main field of interest in this area for almost fifty(!) years: Tritium-Tracer-Technique (TTT) for studies of adsorption and migration phenomena of hydrogen-bearing molecules in vacuum and atmosphere. Other isotopes used in Rudi's vacuum tasks: 41Ar and 133Xe (both for adsorption studies on charcoal and zeolite), 31Si, and colloidal suspensions of 198Au (the latter two for labelling diffusion pump oil).

Labelling of diffusion-pump oil with tritium

Study of oil migration phenomena in vacuum by means of the radioactive tracer technique - industrial contract of great interest in times when uhv was produced mainly by diffusion pumps.

500 ml DC 704 silicone oil with 68 mCi/ml (2,5 GBq/ml) specific T-activity have been produced by exposure of the vaporized oil to 100 Ci (= 3,7 TBq) gaseous tritium at 300°C, resulting in a 34% exchange yield (i.e., a record-yield for a Wilzbach-type reaction!). Results of oil-migration measurements in baffles and other parts of vacuum systems can be found, e.g., in: R. Dobrozemsky, W.K. Huber, and F.P. Viehböck, Z. Naturforschg. 22a (1967) 549. Detection limits between 10-2 and 10-3 "monolayers" have been achieved for oil coverages on technical surfaces.

Residence times of water molecules on surfaces

For the study of adsorbed water on technical surfaces in atmosphere and vacuum, Tritium-Tracer-Technique (TTT) has been introduced to surface physics. The measurements are carried out by exposing samples to HTO vapor (tritiated water) and evaluating the adsorbed quantities by liquid scintillation counting techniqu, see e.g. R. Dobrozemsky, Vacuum 46 (1995) 789 and R. Dobrozemsky, S. Menhart, and K. Buchtela, J.Vac.Sci.Technol.  A 25, 551 (2007). This way, precise measurements of adsorbed water quantities down to one percent of a "monolayer" are possible on almost any kind of surface.

Water coverages on aluminum, stainless steel, copper, gold, various polymers, and Si02- and TiN-covered stainless steel have been investigated. It was found that water adsorption capacities depend - to a great extend - on the cleanliness of the surfaces, that water sojourn times in vacuum are - contrary to the general opinion - much longer than in atmosphere, and that reproducible results can be achieved even from tiny samples with dimensions of about 1 cm². Furthermore, it could be shown that the water coverage and its time behaviour agree rather well with the outgassing rates obtained by conventional methods. Thus, the HTO-method as outlined here allows an estimation of outgassing rates by means of just tiny (cm²-size) samples.

Novel cryosorption pump (CSP):
High speed from 1 to 10-10 bar

Patent specification, design and construction of cryosorption pumps for oil-free evacuation from atmosphere down to 10-7 mbar with low LN2-consumption, allowing up to three days between refills (Japan. J.  Appl. Physics Suppl. 2 (1974) 97. Several copies of two models, exhibiting pumping speeds of 50 l/s and 150 l/s, respectively, have been produced (essentially as "working horses" for evacuation of the neutron-decay experiment) and utilized for various applications over a period of about three decades without the need for maintenance.

Vacuum Tweezers

Invention, patent specification, design, and construction of several models of tweezers manipulators (termed "vacuum chopsticks" by Japanese visitors). Field of application: Handling of sensible objects in uhv (see, e.g., Proc. 8th Internat. Vac. Congr., Cannes 1980, p. 90). More than three decades permanent use during gas-analysis measurements, e.g., when small specimens had to be moved into and out of the oven area.

Low outgassing rates after 100°C bakeout:
Aluminum, copper, and stainless steel

First proof of low outgassing rates of aluminum and copper, and of the usefulness of "low" bakeout temperatures between 100°C and 150°C for these metals and for stainless steel ( Japan J. Appl. Physics Suppl. 2 (1974) 261) - thus allowing reliable uhv-operation of the 7.5 meter long beam tube of the neutron-decay experiment (essentially aluminum and copper), see R. Dobrozemsky, Nucl. Instrum. Methods 118 (1974) 1-37.

Electrical surface charges on metals

The changes of the electrical potential on metal surfaces due to bombardment by low-energy electrons have been measured by observing the deflection of a narrow low-energy ion beam guided just above the surface to be investigated. Various metal surfaces with and without coatings have been tested with potential changes between fractions of 1 mV up to 10 V observed even for very low electron current densities of about 1 pA/cm2 (see e.g. Nederlands Tijdschrift voor Vacuümtechniek 8 (1970) 133-138.

Surface contamination on Si-wafers

Adaptation of a clean room uhv system for measurements of BHT-contamination on Si-wafer surfaces. Work was performed within the frame of a short-term employment at the Center for Microcontamination Control at University of Arizona (Tucson) in cooperation with J. O'Hanlon, H.G. "Skip" Parks, and students.

Production of metal-tritides and study of T2- and 3He-release

Ta- and Ti-samples have been loaded with T2, and the release of T2 and 3He has been studied over a period of 3 years by means of the mass-spectrometric method. Due to a tricky gas-accumulation procedure, a sensitivity limit of about 10-16 mbar.l/s for the T2- and 3He-release could be obtained.

Magnetic water treatment:
Long-term tests of high significance

Study of possible effects of magnetic fields on scale and stain in house-water systems. High significance of results due to continuous measurements on 27 test objects in parallel during a several-years' double-blind study with careful statistical data evaluation. Actual tests have also been performed on commercially available magnetic water treatment devices (industrial contract, unpublished).

Rudi's other major achievements
Neutron physics
Radiation and metrology
Mass-spectrometric gas analysis
International relations and congress organization

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