Acceleration Tubes

The NEC all metal and ceramic insulating assemblies are ideal for applications that require ultra high vacuum capability in regions of high voltage or where a complete insulating barrier is required.

All NEC acceleration tubes are insensitive to thermal shock and exhibit exceptional mechanical strength. They have been in use on a routine basis in very strenuous conditions for periods of over 20 years with no signs of degradation.

NEC offers two different syles of acceleration tubes based on application:

General Purpose Acceleration Tube: Designed for use in ambient air conditions

High Gradient Acceleration tube: Designed for use in 80 psig of SF6 insulating gas

NEC uses two types of metal/ceramic bonding processes:

  • Standard metal to ceramic braze: used for the NEC General Purpose Acceleration Tubes
  • Unique, NEC developed, metal diffusion bond: used for the NEC High Gradient Acceleration Tubes

General Purpose Acceleration Tube

The General Purpose (GP) Acceleration Tube section is designed for operation in clean, dry ambient air and is in use on all NEC open-air ion beam systems up to 500kV.

The all metal and ceramic general purpose acceleration tube section is a metal brazed assembly with no organic compounds in the vacuum volume.  This tube is fully bakeable for contaminant free and ultra high vacuum operation.

Each section is conservatively rated at 75kV.  Multiple sections can be combined to achieve higher voltage.  The exterior field is defined by demountable potential distribution rings.  Potential grading is provided by ten 150MOhm resistors in series.

A non-magnetic version of the General Purpose Acceleration Tube is also available for the acceleration of low energy electron beams that are adversely affected by proximity of ferromagnetic materials.

A GP tube assembly consisting of three (3) GP tube sections (left) as part of our 250kV open-air SSAMS (Safety cage removed)

High Gradient Acceleration Tube

The High Gradient Acceleration Tube section is designed for operation in high pressure SF6 gas.  These tubes have been used in Pelletron accelerators ranging from below 1MV to above 25MV terminal potentials.

Same as the General Purpose tube, the High Gradient tube is a metal bonded assembly with no organic compounds in the vacuum volume and fully bakeable for contaminant free and ultra high vacuum operation.

These tubes are offered in several standard lengths (varies by number of gaps).  Each gap of the standard High Gradient tube is rated at a conservative 30kV when used in Pelletron accelerators.  Typical tubes are 20 to 22 gaps long.  Multiple tubes can be combined to achieve higher voltage.  For use in Pelletron accelerators, potential grading is usually provided with a point to plane corona distribution system or resistor divider.

A large version of the High Gradient Acceleration Tube is also available.  This version has an I.D. of 5.63″ (compared to 4.0″ I.D. of standard)  and was originally designed to replace original tubes in the radiocarbon Dynamics, Inc. Dynamitrons.  Over the years, the use of these tubes has expanded and are part of many different accelerators around the world to handle larger diameter ion beams.  The large version has a conservative rating of 16kV per gap.

S-Series column with high gradient acceleration tube assembly surrounded by equipontential ringsS-Series column with high gradient acceleration tube assembly surrounded by equipontential rings


Related Documents
Accel Tubes v1