EXPERIMENTAL FACILITIES AT THE 5 MV TANDEM
HYDRA (HYDrogen Resonance depth profiling Analysis)The experimental setup HYDRA has been developed for hydrogen depth profiling utilizing nuclear resonance reactions like 1H(15N, ag) 12C or 1H(19F, ag )16O.
A specially shaped UHV scattering chamber enables a low 30 mm target distance of the 4" NaJ -Detector, placed under 0° to the beam.
Complementary equipment like residual gas analyser, sputter cleaning, RBS - and PIXE detectors can be easily attached to the scattering chamber. A variety of multiple or single sample holders, introduced via a load lock system with integrated translational stage, provides features like sample cooling to LN2 temperature or heating up to 1000 ° C, or high voltage biasing, respectively.
External beamOne of the beamlines is dedicated to materials analysis with an external beam of light ions. The beam penetrates a thin Havar foil dividing off the vacuum of the accelerator from the atmosphere, and is directed to the object to be investigated.
This irradiation in normal atmosphere is absolutely necessary for the analysis of very delicate art objects , but is as well as useful for studying materials incompatible with high vacuum. Detectors for PIXE, PIGE and RBS, resp., are installed.
High energy ion implantationTwo beamlines with beam scanning systems are installed at the Tandem accelerator for high energy ion implantation.
One beamline is particularly designed for semi-industrial applications of high energy ion implanation. It is equipped with a scanning system for homogeneous large area implantations up to 125 mm (5") diameter. The wafer chamber admits up to 13 wafers for one vacuum cycle.
High level and in-situ experimentsThree different versatile end stations for in-situ ion beam analysis during low energy ion beam implantation or plasma processing of surfaces are installed at other beamlines.
All scattering or processing chambers, resp., are designed in UHV - technique and equipped with precision manipulators for a variety of sample holders including LN2 cooling and PBN heaters. Besides of RBS mainly ERD analysis is widely used. A large number of free ports offers the possibility for an easy completion with various additional components.
BISSIEAt one station a simple 20 kV implanter for gaseous ions, consisting of a microwave ion source, the acceleration optics and a 90° analysing magnet, is connected to the scattering chamber, where the low energy ions hit the sample perpendicular to the accelerator beam. A load lock system enables the transfer of various sample holders to the head of a precision, computer controlled manipulator without breaking the vacuum. Sample heating or cooling stages can be used.
Various spectrometers with particle identification, necessary for heavy ion ERDA, are available for recoil spectrometry. The simultaneous usage of a Bragg ionization chamber detector or a time-of-flight heavy ion spectrometer with a solid state detector telescope for hydrogen and helium recoils enables the depth profiling of all light elements. Additionally an RBS detector is mounted at a backward angle of 150°. A very schematic layout is given here :
LIONS (Low energy Implantation Of Nitrogen and other Species)The second chamber is equipped with an internal Kaufmann ion source for in situ investigations of materials modification by low energy ion implantation.
Due to the necessarily high operating gas pressure
during the ion beam processing of the samples the chamber is coupled to
the beam line via a differential pumping station enabling simultaneous
ion beam analysis.
PLASMAThe third end station is a process chamber as well, but mainly designed for plasma surface processing. Here an ECR plasma source (ASTeX) is mounted at a port 75° to the tandem beam. The RF biased sample holder provides a very accurate translational and angular alignement of the sample. This allows the in situ characterization of the surface layers by ERDA and simultaneously by an attached ellipsometer . The gas supply system enables the safe handling of even toxic gases like boron trifluoride.
For the recoil spectroscopy of ERDA in the latter two experiments a two-dimensional position sensitive ionisation chamber telescope is employed. Like with the Bragg IC the identification of light heavy ions ranges up to about Z=15 (phosphorus). The data acquisition offers an on line correction for the position information.
Magnetic spectrometer " Little John"This QQDS spectrometer has been developed and used at FZ Karlsruhe by H.-J. Gils and coworkers. It is now being under reconstruction at Rossendorf, equipped with a new UHV scattering chamber.
A detailed description you´ll find here soon !