Vacuum suitable cable

Vacuum suitable cableEvery electrical vacuum feedthrough needs to be connected and wired in order to operate. On the atmospheric side this is mostly trivial, due to the large variety of available connecting solutions.
On the vacuum side however, common cable insulation materials, such as  Polyethylene (PE) and Polyvinyl chloride (PVC), cannot be used, especially in high vacuum (HV), ultra high vacuum (UHV) and extreme high vacuum (XHV) applications. The outgassing of such materials would negatively affect the vacuum level and the processes therein.
The material Polyimide - also known as Kapton® from the company DuPont - has proved itself as a suitable cable insulation for vacuum applications.
Polyimide is an amber-coloured high-performance thermoplastic material showing outstanding mechanical, thermal, dielectric and chemical properties. The properties making Polyimide ideal specifically for vacuum application are listed below:

Vacuum-relevant properties of Polyimide:

  • High temperature resistance
    o Continuous use from -75 °C up to 200 °C or -269 °C up to 260 °C depending on insulation type
    o Short term bakeout temperature up to 250 °C or 350 °C depending on insulation type
  • High radiation resitance
    o Depending on insulation type, up to 107 Gy (= 109 Rad) ionisizing radiation
  • Outstanding dielectric strength
    o At least 25 kV/mm or 75 kV/mm depending on insulation type (even at elevated temperature)
  • Extremely low outgassing
    o Quick dissipation of adsorbed atmospheric gases during evacuation(*)
    o Total outgassing rates as low as 1e-8 mbar*l/s/cm2 without additional bakeout
    o Total outgassing rates < 1e-10 mbar*l/s/cm2 with additional "in-situ" bakeout(**) achievable (depending on bakeout temperature and duration)

Vacuum suitable single cables from VACOM are available in two basic types:

Enameled wire Film-wrapped solid/stranded wire
Solid copper wire, covered with Polyimide enamel Solid/Stranded silver-plated copper wire, wrapped with Polyimide insulating film
  • For no or little cable movement
  • For very high or low temperature
  • Suitable for high radiation exposure
  • Recommended for clamp connection
    (Solder/Crimp connection is not recommended)
  • Mechanical wire stripping recommended
  • For typical measurement and control applications
  • Stranded wires are highly flexible (even at low and high temperatures)
  • Suitable for solder, crimp and clamp connection

We offer the following vacuum suitable cable types:

  • Single solid and stranded wire (unshielded)
  • Flat ribbon cable (e.g. for Sub-D connections)
  • Coaxial cable
  • High voltage cable
  • Thermocouple wire
  • Custom cable

All cable types are shipped pre-conditioned for direct vacuum use and are sold by the meter, even in small quantities starting from 1 meter.

(*)   Compared to other insulation materials (e.g. PTFE), Polyimide has relatively high water absorption rates when exposed to ambient atmosphere. Values according to literature vary from 1% to 3% (depending on relative humidity)
(**)  "In-situ" bakeout refers to a bakeout procedure with a completely assembled hermetic chamber under vacuum.

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