ACCELERATOR

MIC 2MV Tandetron accelerator

The HVEE Tandetron accelerator is highly reliable, compact and versatile tandem type accelerator designed to produce high energy ion beams for ion beam modification and analysis in a research environment. It has the capability of producing a large variety of highly stable ion beams with energies of a hundred keV up to several MeV.

Our Tandetron consists of the following main systems:

  • ion sources with analyzing magnet
  • accelerating tubes with high voltage power supply
  • high energy switching magnet
  • four operating beam lines with experimental stations

Ion Sources

Tandetron accelerator at Jožef Stefan Institute is equipped with two ion sources. The negative ion beam is formed in the sources, filtered by 90° analyzing magnet, focused and directed into acceleration tube.

The injector system consists of:

Duaplasmatron ion source model 358

This ion source is capable of producing beams of a light ions, such as H- and He+, which are extracted from plasma. For the conversion from He+ into He- ions, lithium exchange channel is used. Axial electron beam emitted from a heated cathode is used to ionize the gas admitted into the ion source.

Sputter ion source model 860 A

The sputter ion source is a heavy ion source that produces high intensity negative ion beams from a variety of elemental materials. The negative ions are produced by bombarding a target cathode of the desired beam material with positive cesium ions. An in-line gate valve allows simple replacement of target cathodes for quick changing of ion species and for servicing.



90° analyzing magnet

The 90° analyzing magnet is used to select the singly charged negative ion beam with proper mass and to direct the beam into acceleration tube. The magnet is water cooled and protected against overheating.

ion source injector magnet

Picture on left: Injector system: sputter ion source type 860 A (left) and duaplasmatron ion source type 358 (right)
Picture on right: 90° analyzing magnet




Acceleration

The Tandetron accelerator system is of the tandem type with both low and high energy ends of the machine at ground potential. It consists of:

  • Q-snout assembly
  • accelerator tubes
  • terminal with stripper and stripper gas recirculation system
  • equipotential rings that surround the entire acceleration tube assembly
  • generating voltmeter (GVM)
  • high voltage solid-state power supply
  • high voltage gas insulation and associated tank structure

The Q-snout assembly

The section between analyzing/injection magnet and accelerator is called Q-snout assembly and is provided with:

  • X-Y steerers
  • beam profile monitor (BMP)
  • mass defining aperture
  • Faraday cup
  • Q-snout electrode

Accelerator tubes

The Tandetron acceleration tubes are constructed by sandwich titanium electrodes between glass insulation rings. Several cutouts are made to improve the vacuum conductance of the assembled tube and small magnets are placed to suppress secondary electrons. This arrangement in combination with lead shield on the walls of accelerator tank assures low radiation levels around the accelerator.

Terminal with stripping channel

The high voltage terminal is located in the center of the pressure vessel between the low energy and high energy accelerator tube. The negative ions entering from the low energy accelerator tube lose electrons in the stripper and become positive so that they are accelerated a second time by the high energy acceleration tube. Gas stripping is used for good reliability and consists of a dilute gas target of nitrogen in a long thin tube. The stripper gas flow is controlled by a precision needle valve located inside the terminal. The gas supply enters through a fitting at the low energy end of the pressure vessel.

Generating voltmeter

The generating voltmeter (GVM) accurately measure voltages in the megavolt region. The GVM provides regulation of the terminal voltage and a digital readout of the terminal voltage for the operator.

High energy magnet

The high energy switching magnet is used to select the charge state of the high-energy ion beam and to steer it into the desired beamline. The vacuum chamber of the magnet is water-cooled so that high intensity beams, deflected onto the chamber, do not cause overheating. The magnet is water-cooled also and protected against overheating. The air-cooled magnet power supply is located in the magnet stand.



Last updated: 01/22/2014