Grant Johnson - IonCCD (TM) for Direct Position-Sensitive Charged-Particle Detection: from Electrons and keV Ions to Hyperthermal Biomolecular Ions

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  Publication Details (including relevant citation   information):


  Volume:   22

    Issue: 4

    Pages: 612-623


Published: APR 2011


    A novel, low-cost, pixel-based detector array (described   elsewhere Sinha and Wadsworth (76(2), 1) is examined using   different charged particles, from electrons to hyperthermal (<   100 eV) large biomolecular positive and negative ions, including   keV small atomic and molecular ions. With this in mind, it is   used in instrumentation design (beam profiling), mass   spectrometry, and electron spectroscopy. The array detector is a   modified light-sensitive charge-coupled device (CCD) that was   engineered for direct charged-particle detection by replacing the   semiconductor part of the CCD pixel with a conductor Sinha and   Wadsworth (76(2), 1). The device is referred to as the IonCCD.   For the first time, we show the direct detection of 250-eV   electrons, providing linearity response of the IonCCD to the   electron beam current. We demonstrate that the IonCCD detection   efficiency is virtually independent from the particle energy (250   eV, 1250 eV), impact angle (45(o), 90(o)) and flux. By combining   the IonCCD with a double-focusing sector field mass spectrometer   (MS) of Mattauch-Herzog geometry (MH-MS), we demonstrate fast   data acquisition. Detection of hyperthermal biomolecular ions   produced using an electrospray ionization source (ESI) is also   presented. In addition, the IonCCD was used as a beam profiler to   characterize the beam shape and intensity of 15 eV protonated and   deprotonated biomolecular ions at the exit of an rf-only   collisional quadrupole. This demonstrates an ion-beam profiling   application for instrument design. Finally, we present   simultaneous detection of 140 eV doubly protonated biomolecular   ions when the IonCCD is combined with the MH-MS. This   demonstrates the possibility of simultaneous separation and   micro-array deposition of biological material using a miniature   MH-MS.

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