The setup took full advantage of the turn table installed in CASYMS.
Rotation around the beta axis and translation along the z axis was
used to move the setup into the field-of-view of the ion beam. The
theta table was mounted overhead and used to rotate the CODIF instrument
in order to select one of the several TOF entry slits (pixel). The
available pixels were of varying widths and sensitivity. The pixel
with the highest gain and the widest entry slit was selected for the
measurements. As the width of the pixels was considerably smaller
than the width of the exit aperture of the extraction lens, the lens
was mounted on a small translation table (x-translation) to allow
for scanning the whole exit aperture of the lens. This allowed the
verification of the energy resolution of the extraction lens (Figure
A flexible shielding was built around the extraction lens to make
sure that the lens was electrostatically completely shielded regardless
of the lens position. For the ion measurements a tunnel made out of
copper tape was built to provide a field free path to the grid replacing
the conversion surface (Figure 6.10). More
shielding was necessary for the neutral measurements because of the
conversion surface now being at high voltage. Figure 6.11
shows a view from the outside of the neutralizer and the lens shielding.
NICE setup with neutralizer and front
shielding removed. Neutral particles would travel from the neutralizer
along the line of sight to the conversion surface (CS). The x-translation
and theta rotation axis are shown in yellow. TOF, EBOX, and DPU are
submodules of CODIF. The shown part of the setup is approximately
70 cm in height.
Additional shielding for ion measurements.
Using the original setup (top left) it was impossible to guide low
energetic ions to the grid without an arbitrary deflection of the
beam. This problem was solved using better shielding (right). The
`tunnel' allowed for lens movements relative to the surrounding
shielding without opening gaps in the shield.
NICE setup inside the CASYMS chamber
prepared for neutral measurements. The neutral particle path to the
conversion surface is completely shielded to avoid attraction of background
ions to the conversion surface.
March 2001 - Martin Wieser, Physikalisches Institut, University of Berne, Switzerland