Showing scientific research new ways with the help of new analysis methods - this is the noble goal of the Swiss company TOFWERK. To this end, TOFWERK engineers develop, manufacture and optimize high-performance mass spectrometers that can record up to 100,000 complete mass spectra per second. This allows ultra-fast processes in a wide range of research areas to be reliably tracked and analyzed in detail, for example for ambient air mobile monitoring or aroma analysis in alcoholic beverages.
In view of the current climate debate, the former is becoming increasingly important. The air around us contains a diverse mixture of volatile organic compounds (VOCs), and some of these compounds - such as the highly flammable toluene, which is contained in gasoline, among other things, and is released in comparatively large quantities in motor vehicle traffic - can cause damage to health above certain concentrations (in the case of toluene, damage to the nervous system is one of the risks).
Accordingly, there is an urgent need for uncomplicated mobile VOC measurement methods to precisely determine the prevailing VOC composition of the ambient air. For example, municipalities could use vehicles equipped with VOC measurement instruments to analyze the air at a wide variety of locations on a daily basis and quickly sound the alarm in the event that VOC limits are exceeded. Due to their small size, low energy requirements and fast operation, TOFWERK's high-precision ion mobility mass spectrometers are ideal for such mobile VOC measurements.
The company name TOFWERK says it all, because technically the spectrometers are time-of-flight mass spectrometers, also called time-of-flight or TOF spectrometers for short. In TOF mass spectrometers, the mass-to-charge ratio of ions is commonly determined. For this purpose, the ions to be investigated are accelerated in an electric field, after which the mass-to-charge ratio of the ions can be determined from the absorbed kinetic energy. This means that the weight of individual atoms or small molecules can be reliably calculated.
But the TOFWERK devices can do even more, as another important field of application called FIB-SIMS impressively demonstrates. Lex Pillatsch, product manager for fibTOF instruments, explains the process as follows: "FIB-SIMS is a method from surface physics, for example to analyze the chemical composition of material surfaces, or to detect contaminations in thin film coatings or nanostructures. For this purpose, our TOF mass spectrometer is coupled with a Focused Ion Beam (FIB) microscope, whose high-energy primary ion beam dislodges atoms from the surface of the sample. Using the secondary ion mass spectrometry (SIMS) technique we developed, we can thus analyze the chemical composition of the sample surface with high precision - from the mass of the extracted atoms to the position of their occurrence on the sample in question."
The high-tech equipment TOFWERK has developed to implement the FIB-SIMS process can be used in a wide variety of applications, from the semiconductor industry to life science applications where high spatial resolution is required. "In the development of the entire fibTOF instrumentation, we have worked closely with the three well-known microscope manufacturers: Zeiss, Tescan and Thermo Fisher, so our products are compatible with all current FIB microscopes," Lex Pillatsch is pleased to report.
However, the flange-mounting of the FIB microscopes presented the TOFWERK developers with a vacuum-related problem. This is because the TOF spectrometer must be continuously under vacuum while the microscope chamber is regularly opened, for example to insert new samples. "At the delicate interface between the microscope and TOF spectrometer - i.e. in the middle of the ion beam optics - we therefore needed a clever vacuum valve solution that would reliably protect the existing spectrometer vacuum while ventilating and re-evacuating the area around the microscope," says Lex Pillatsch, describing the technical issue with which he and his TOFWERK colleagues asked VAT to help with.
Due to the prevailing pressures - in the spectrometer up to a maximum of 10-7 mbar, on the microscope side in the low 10-6 mbar range, depending on the design and outgassing of the FIB microscope used - it quickly became clear that a mini UHV slide valve from the VAT 01.0 series could be a sensible basis for the valve solution. "Thanks to the special MONOVAT sealing technology, the leakage rate of this valve is in the range of up to 10-9 mbar, so there is sufficient buffer," says Andreas Dostmann, the VAT Sales Manager responsible for this project, explaining the choice.
But this is where the work really began. This is because the highly complex focusing process of the ion beam requires that the valve be positioned exactly between two lenses of the ion beam optics - and these two lenses are just 5 mm apart! It also quickly became clear that the approximately 2 cm wide lenses would require a valve diameter of at least 40 mm, even though the ion beam's passage area is only a few millimeters wide. Andreas Dostmann aptly summarizes the dilemma: "Normally, DN40 valves have a width of 5 cm in the passage area, flange and all. And now TOFWERK wanted a solution with the same disc diameter but only a tenth of the width!"
Fortunately, the broad VAT standard portfolio is deliberately designed to be very modular, so that all products can be adapted quite flexibly to a wide variety of customer requirements. Andreas Dostmann describes the individual solution that brought TOFWERK to the target as follows: "From the mini UHV gate valve, the valve insert is used - that is, the drive and the closing disc mechanism - and integrated into the process chamber in such a way that the closing disc seat is part of the chamber. This direct integration of the valve function into the chamber eliminates the need for the valve housing and flanges, which then results in the desired streamlined solution."
While VAT also offers its customers such integrated solutions in their entirety (valve functions + chamber), for this project, it was decided to provide TOFWERK with appropriate instructions for producing the exact valve seat contour as part of the chamber. With the MONOVAT sealing technology developed by VAT and used in the 1.0 series, this is achievable.
Lex Pillatsch is very impressed with the result: "The VAT valve inserts have been in use since the beginning of the project in 2013, and they have always performed reliably since then. The fact that the valve seat integrated into the chamber holds so wonderfully tightly is due in no small part to the VAT colleagues who provided us with advice and support during the development phase!" One of these pieces of advice was, for example, not to implement the static seal on the head flange with the help of an elastomer O-ring as is usually the case, but instead to use a special VATSEAL seal - that is, a hard-on-hard-sealing metal seal.
"In this application, an elastomer is too permeable to be able to maintain the required pressures without the permanent use of a vacuum pump," explains Andreas Dostmann. "With the VATSEAL solution, on the other hand, TOFWERK is on the absolutely safe side; with it, even pressures down to 10-13 mbar would be possible!"
It was also enormously important to Lex Pillatsch and his TOFWERK colleagues that the valve used would be self-locking - that is, that it maintain the selected valve position, e.g., the closed position, in the event of a failure of both the electrics and the pneumatics. Recalling the discussions during the development phase he says, "It's hard to imagine what would happen if the valve suddenly opened in such a case as soon as the customer ventilated the microscope!"
Lex Pillatsch summarizes his all-around good experience with VAT as follows: "I have always found the cooperation with VAT to be very constructive and enriching. The VAT valves themselves are wonderfully reliable and of excellent quality". Further joint projects are being planned or are close to technical completion.