Diamond membranes: applications for single ion detection using secondary electron emission

The assessment of mechanisms for radiation damage in both biological and semiconductor systems is much enhanced by ensuring that each cell or memory unit is hit by one and only one ion. Such "single ion" systems operate by detecting the passage of an ion and using the signal to deflect the beam upstream thus ensuring that only a single ion is injected to the system at a time. For biological investigations of the effects of single ion impact on living cells, the ion needs to be extracted from the vacuum of the accelerator through a thin window into the atmosphere. The requirements on such a window are: (a) that it be thin enough to allow the passage of the ion through it without excessive energy loss; (b) that it possess mechanical strength sufficient to survive the pressure differential; and (c) that upon passage of the ion through it, a sufficiently large signal is generated to ensure a 100% efficient detection of the passage of the ion. This set of demanding requirements can be met by a thin diamond window fabricated by CVD technique, taking advantage of the high secondary electron yield of B-doped diamond. In the present work, we report on the use of B-doped diamond membranes for this purpose. (C) 1998 Elsevier Science S.A.