HV and UHV Positioning Systems

  • Vacuum classes from 10-3 to 10-10 hPa
  • Careful selection of components and materials
  • In-house developed drives such as piezo actuators and piezomotors, or suitable electric motors
  • Painstaking design taking outgassing behavior into account
  • Careful handling, adequate premises: Equipped for the qualification of materials, components and final products – also in combination with other difficult environments: Nonmagnetic, cryo, extreme ultraviolet (EUV)
  • Longstanding experience

Classification of Vacuum Stages at PI

To determine the required vacuum class, it is necessary to know the application as well as possible. Crystallography or optical coating, for example, have different requirements not only with regard to the pressure range but also with regard to allowed residual materials in the vacuum chamber.

Frequently, the partial pressure of carbon hydrides is decisive. They are part of lubricants and plastics, are released when pumping out the vacuum chamber, and can contaminate surfaces. Laser applications in the UV range are particularly sensible because carbon hydrides are split up and precipitate on the optical system.

Further modifications of products suitable for UHV:

  • Extremely high vacuum up to 10-11 hPa
  • Lubricant-free design
  • Suitable for operation in a cryogenic environment at -269 to 40 °C
  • Suitable for operation in magnetic fields, radiation resistance (particle and X-ray radiation, EUV)

High vacuum (HV)

1 × 10-3 hPa to 1 × 10-6 hPa  

 

Ultrahigh vacuum (UHV)

1 × 10-7 hPa to 1 × 10-9 hPa  

 

Units

1 hPa = 1 mbar


Drive Types for Vacuum Environments

Next to the drive, the selection of suitable materials and additional components is crucial for the vacuum compatibility of a positioning system. Piezo stages employ technologies which are exceptionally well suited for vacuum use as a matter of principle:

Piezo actuatorscapacitive positioning sensors, and flexure joint guides.

In addition, they do not require any lubricants and grease for operation.

The PICMA® piezo actuators in all PI nanopositioning systems are manufactured without polymers and have particularly low gas emissions as a consequence. They can be baked out at up to 150 °C. PICMA® piezo actuators are exceptionally well suited for use in very strong magnetic fields. Piezo positioning systems can be manufactured without ferromagnetic materials.

Piezo actuators show displacements well into the cryogenic range. Special models of PICMA® actuators can be used down to -271°C but with a considerably reduced travel range.

Regardless of the drive principle, all >> Piezomotors can be used in a vacuum environment. Piezomotors can also be used in magnetic fields, because they do not generate magnetic fields nor are they affected by them. Piezomotors are the drive of choice, especially when radiation resistance and travel ranges in the millimeter range are required.

Motorized stages employ special 2-phase stepper motors which operate reliably up to 10-9 hPa. Bakeable limit switches and suitable measuring systems round off the choice. In general, vacuum stages offer lower velocities and a shorter service life than variants for indoor air.


Materials and Design

The requirements for a vacuum-compatible material include:

  • no particle emission
  • no outgassing
  • bakeable and temperature resistant

Preferred Materials
Stainless steel, aluminum, titanium, 
bronze, FKM (e.g., Viton), 
ceramics, sapphire, 
PTFE (e.g., Teflon), PEEK, 
polyimide (e.g., Kapton), 
glass ceramics (e.g., Macor)

The materials used for vacuum positioning stages are aluminum alloys, stainless steels, or titanium. Surface treatment is adapted to the vacuum class, for example, the surfaces of the higher vacuum classes are not coated but electro polished.

For a use in HV and UHV, special vacuum lubricants are used. On request, the lubricant may be defined when placing the order. Vacuum cable insulation is made of PTFE or FEP (Teflon), on request also of polyimide (Kapton) or PEEK. The use of plastics and adhesives is reduced as far as possible.

Painstaking Design for Highly Sensitive Environments

Stages specifically developed for vacuum operation must meet a number of criteria. Vacuum chambers only offer limited space and therefore require a compact design.

Air pockets, i.e., under mountings, must be avoided as they considerably delay or even make generating a stable vacuum impossible.

The selection of suitable components, especially the drive systems, is very important. In particular, it is very important to take heat generation during operation into account, as heat can only be dissipated with great difficulty under vacuum. Knowledge of the planned working cycles is therefore useful for selection. This allows advance testing of the outgassing behavior of the selected individual parts.

Assembly and Test Equipment

Vacuum stages are mounted under cleanroom conditions. All components are cleaned in ultrasound. They are shipped in an antistatic packaging free from particles. Outgassing tests with a mass spectogram to evaluate residual gas composition are available upon request.

 

  • Clean room manufacturing
  • Ultrasonic cleaning
  • Vacuum chambers up to 10-10 hPa
  • Measurement with mass spectrometer and supplied with measuring protocol upon request

 

 


Applications

Vacuum environments can be found in many sensitive high-tehnology fields such as:

 

  • Semiconductor technology
  • Beamline Instrumentation
  • Aviation and aerospace
  • Materials Research
  • Research

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Products

PI offers UHV versions as catalog products for a number of positioning stage series. Almost all stages can be modified for use in different classes of vacuum. Design and manufacture for ranges beyond these limits are offered on request. Complete solutions for several axes are also possible. The vacuum feedthroughs are not included in the scope of delivery and may be ordered separately, if required. Unless agreed otherwise or described for the individual product, the bakeout temperature is max. 80 °C.

Controllers, Amplifiers, and Other Electronic Devices

In general, the control electronics is not suitable for being operated in the vacuum chamber. It has to be mounted outside of the chamber.

Downloads

pdf
pdf

Brochure: Positioning in Vacuum (英語)

High-Precision Solutions to 10-10 hPa
BRO30
BRO30
pdf
pdf

Catalog: PI Piezo Nano Positioning 2014/2015 (英語)

CAT130
CAT130
pdf

Whitepaper: Motion Control and Precision Positioning in Vacuum Environments (英語)

WP4005
English