The CENBG microbeam line. The beam is focused down to a few micrometers on the target using magnetic lenses. In single ion mode, the particles are extracted in air through a transmission detector. The signal generated in the detector triggers a logic counter. When the required number of particles has been detected, the beam is deflected by applying a high voltage on the deflection plates.
The two transmission detectors developed at CENBG. (a) The scintillation detector. A thin scintillating foil (BC400®, ) is coupled to two photomultiplier tubes using a light guide. This foil is mounted on the support using optical paste and is used as an exit window. The beam is passing through the guide in a hole of in diameter. (b) The gas detector. The particles enter the gas chamber through a diameter collimator and pass into air through a -thick window. The volume containing isobutane is delimited by the dashed lines.
Vertical cross section of the irradiation stage (left) and perspective view of the same setup (right). The UV lamp is clearly visible on the foreground. The high resolution CCD camera (background) is used to acquire fluorescence images of the sample. The entire microscope is fixed on a massive translation stage to achieve a micron precision.
The different coordinate frames of the irradiation setup. On this figure represents the microscope image frame, the cell dish motion frame and the beam scanning frame.
Assessment of the targeting accuracy by CR39 etching. An array of circles ( in diameter) was first etched under vacuum. This pattern was then used as target reference to deliver 50 alpha particles halfway between two adjacent circles. The 15 unexpected large tracks are due to slit scattering during the first irradiation step under vacuum. Since they were etched twice, these alpha tracks, together with those constituting the circle pits, are larger. A few alpha particle tracks presumably due to scattering in the gas detector are clearly visible close to the main pits. Their proportion is at a level of a few percent as a function of the gas pressure within the detector. The distance between two adjacent circles is .
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