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The tiniest details – maximum requirements

Power supply for the MERLIN scanning electron microscope (SEM) by ZEISS.

Optical technology is considered one of the key technologies of the future. Its field of application, in particular in scientific terms, is to increasingly penetrate daily life. It paves the way for a multitude of innovation, i.e. in information technology, telecommunications, the car industry and in medical technology. Alongside this, artificial intelligence and the convergence of technology are further megatrends that will shape our lives and future products.

DC-unit used in scanning electron microscope Merlin
DC-unit used in scanning electron microscope Merlin

As an example, the company ZEISS was developed by combining its expertise in optics and the precision engineering of modern problem solving. An example of this is correlative microscopy, which has made it possible to combine information from light microscopy with the resolving power of electron microscopy. This not only permits dynamic processes to be examined down to nanometre range, but it also allows rare events in cells or organisms to be precisely located.

Light microscopy has the advantage that it can present a large field of view and provides functional information through fluorescent marks in living or fixed samples. Combined with electron microscopy, this information can also be displayed as detailed images with a resolution in the nanometre range and compared to one another. Two different techniques are therefore combined into a single system that provides new and valuable information for the medical sector.

As the world’s only provider that develops, produces and sells light microscopes, electron microscopes and X-ray microscopes, it is natural for ZEISS to provide solutions for correlative microscopy. Today, several technical solutions are available for various applications in this area. ZEISS has therefore succeeded in bridging the gap between electron and light microscopy. A pioneering instrument is now available to researchers and scientists to promote a better understanding of life processes and diseases.

Scanning electron microscope MERLIN
Scanning electron microscope MERLIN

The ultra-modern ZEISS MERLIN SEMs can form part of the necessary technology platform in this interplay of microscopy. These distinguish themselves in particular by an ultra-fast analysis capability in the sub-nanometre range, combined with flexible configuration options. The innovative technical specification makes it possible to adjust voltage or current probes seamlessly to use and samples, regardless of magnification level, without any readjustment being necessary. With the modular chamber structure, which has 15 adaptations for other modules, ZEISS MERLIN can be individually adapted to different applications – from the SEM to a complete Nanotechnology Characterisation Laboratory.

Maximum requirements

For the development of this ultra-modern SEM, particularly high demands were placed on the power supply system to be integrated in addition to the innovative solutions in the field of optics and precision
engineering, as flexibility means that many different DC and AC outputs will have to be available. The overall system has to guarantee an extremely high level of reliability, so that return on investment can be achieved quickly and safely for the operator. To meet these challenges, there has been intensive cooperation between the development departments of the companies ZEISS and BENNING since 2010.

BENNING has been known for over three decades for tailor-made and reliable power supplies or power supply units used for medical applications – for anaesthesia, intensive ventilation, dialysis systems, heart-lung machines, dental applications (e.g. dental chairs) and magnetic resonance imaging, among other things.

BENNING in-house EMC laboratory, Factory 2, Bocholt, Germany / AC unit used in scanning electron microscope Merlin
BENNING in-house EMC laboratory, Factory 2, Bocholt, Germany / AC unit used in scanning electron microscope Merlin

Vibration-free and reliable

Even the smallest mechanical vibrations or shocks in screen shots in the nanometre range (10-9 m) can result in blurring and distorted recordings. The objective of the development and construction contract was therefore to be able to rely on a network device that caused no mechanical oscillations in the LF range in future. In this respect, only one power supply unit with a high overall efficiency for convection cooling could be taken into consideration.

Another challenge in the development of the power supply was to generate a ripple of < 2mV on the DC output, so that this does not interfere with the SEM cathode ray.

Flexible and sharp

The power supply unit has 18 AC outputs, of which 6 can be regulated – and 26 DC-outputs are adjustable. To optimise the operating points of the linear amplifier, it must be possible to adjust and save the DC voltages or DC outputs in a tolerance range of +/- 20% via Management software (based on CAN-Bus). Using special designs for the winding materials, we have managed to realise the smallest coupling capacitances in order to keep the SEM useful signal free of ripple pickups.

Development and Quality Assurance

The development of such sophisticated, individual power supply units is the result of permanent communication between the development departments of the companies involved. BENNING initially developed and manufactured some evaluation models based on predetermined specifications by ZEISS. The theoretically calculated printed circuit boards (PCBs) could then be tested in detail and optimised by two development departments under practical conditions. Simultaneously, the first electromagnetic compatibility (EMC) tests were carried out at the BENNING in-house EMC laboratory (see fig. below).

All results were put together, evaluated accordingly and adopted in the redesign.  The new prototypes (pre-series) had already been manufactured under real manufacturing conditions in order to meet the requirements of subsequent series production. While ZEISS tested the pre-series unit further in the system and made some Earlybirds available for a field test for selected institutes, BENNING began with the approval process, in accordance with UL and CB report standards, among others. At the same time, the results of the field tests were used for this purpose, in order to optimise the overall system for final series production.

Expectations exceeded

The developed BENNING solution shows a lot of good and positive characteristics, so ZEISS has already implemented this solution concept in other applications.
Today, all ZEISS MERLIN SEMs are fitted with BENNING power supplies.

Further information

contact: Dirk Petrich
telephone: +49 (0) 2871 / 93 - 401

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