Advertising feature Physics World  April 2017

Positioning in a vacuum

Vibrational stability in beamline optics continues to evolve to comply with the improved brilliance of low-emittance storage rings around the world. This requires the vibrational performance of the beamline to be characterized, monitored and often compensated for during operation to nanometre levels of performance.

Vacuum versions of Queensgate’s nanopositioning and nanosensing products are used to providing active damping to reduce vibration and to measure vibration to 0.1 nm. We also produce custom designs and variants where an off-the-shelf solution is not available.

Material selection for UHV-prepared products

Providing products to operate at UHV, frequently at cryogenic temperatures and potentially needing to be rad-hard, requires that we select materials carefully. The higher the vacuum the more important it is to source materials that have low outgassing. This often means that we avoid materials such as brass, zinc, lead, etc, as not suitable for UHV. Polymers must also have low outgassing, so our standard PVC wiring is replaced with Kapton-insulated wires, and all bonding agents are selected using the NASA outgassing database.

Vacuum preparation

The preparation of materials and components is also important because the manufacturing process can introduce problems under vacuum conditions. Parts are therefore ultrasonically cleaned to remove oils and carbon residue from any metalwork. Prior to installation, we recommend a bake-out to remove any solvent residues.

Sensors

The NanoSensor® is a non-contact position measuring system based on the principle of capacitance micrometry. The sensors are non-self-heating and maintain their zero position when powered down. Resolutions as small as 7 picometres (RMS) can be achieved. Measurement ranges from 20 µm up to 11 mm are available as standard, with frequency responses up to 5 KHz and linearity down to 0.02 %.

The NX NanoSensor® is a series of high-resolution capacitive sensors, constructed of either super invar where temperature coefficient is critical or lower-cost aluminium. They are available in a number of shapes and sizes to operate over different ranges and with a UHV variant, which can be used to 10–9 Torr.

The NC NanoSensor® is a new series of high-resolution capacitive sensors developed specifically for UHV to 10–10 Torr. Their ceramic gold construction has removed all adhesive bonding agents and the construction also means that they can be baked out at higher temperatures and be used in high-radiation environments.

Closed-loop actuators

The preparation of materials and components is also important because the manufacturing process can introduce problems under vacuum conditions. Parts are therefore ultrasonically cleaned to remove oils and carbon residue from any metalwork. Prior to installation, we recommend a bake-out to remove any solvent residues.

Opem-loop actuators

The MTP range of actuators offer an open-loop alternative with up to 105 µm displacement. They have a rugged stainless-steel construction and are internally pre-loaded to provide high pulling forces. The MTP actuators can be used with a Queensgate NanoSensor® to provide a sub-nanometre precision closed-loop system, and allows the sensor to be mounted in the most appropriate position for system accuracy. There is a comprehensive range of accessories available for both the MTP and DPT ranges of actuators.

Stages

Vacuum-compatible versions of Queensgate flexure-guided piezo-actuated stages are available and assembled using Kapton wiring. The stages can be used to position optics with sub-nanometre precision.

As part of a vacuum nanopositioning/nanosensing system, a feedthrough and airside cable is required. Suitable feedthroughs can be provided by Queensgate or sent to be calibrated as part of a complete system calibration.

Queensgate specialise in offering product solutions with the highest stability, performance and reliability, to meet individual customer requirements. Our engineers, scientists and manufacturing experts provide the best solution for challenging problems. We can advise on the best use of standard products and are specialists in delivering custom systems. Products are engineered to last, with many systems in continuous operation in excess of 20 years. Queensgate offers a number of products, including flexure-guided stages, closed-loop actuators and nanoposition sensors, as well as high-quality control electronics.

If you have a positioning application where you require a nanopositioning solution, please contact us.