Speaker
Dr
Rattanaporn Norarat
(Faculty of Science and Agriculture, Rajamangala University of Technology Lanna Chiang Rai, 57120 Chiang Rai, Thailand)
Description
Scanning Transmission Ion Microscopy is a powerful technique that yields structural information in sub-cellular whole cell imaging [1,2]. Usually, a Si p-i-n diode is normally used in direct-STIM measurements as a detector. However, this is sensitive to radiation damage because when used to image deep sub–µm areas the ion fluence is high even for moderate numbers of ions per pixel. This leads to a shift in charge carrier collection efficiency which appears as an apparent degradation in energy resolution [3,4]. Gas ionisation detectors are intrinsically insensitive to radiation damage. Therefore, a compact gas ionization direct-STIM detector [4] is based on the Geiger-Muller geometry without a Frisch-grid is being developed for use in a MeV ion microscope based on a standard Oxford triplet lens and scanning system. In this work, the critical issues in designing the detector are a large the entrance window area to accept a scanned beam and obscuring as small a solid angle as possible to facilitate installation of proton induced fluorescence detector [2] while maintaining a small capacitance (10.2 pF) to achieve low noise. Tests with isobutane against a calibrated capacitor show that a resolution of about <~20 keV fwhm could be achieved which allowed imaging of Ren cells on a Si3N4 support and an effective ionisation energy of 21 eV at pressures above 600 mbar and bias voltage >600 V. The resolution is most probably limited by the charge sensitive amplifier resolution which is estimated to be ~180 e- rms in the current configuration.
References
[1] F. Watt, X. Chen, A.B.D. Vera, C. N. Udalagama, R. Minqin, J. A. van Kan, A.A. Bettiol, The Singapore high resolution single cell imaging facility, Nucl. Instr. and Meth. B 269 (2011) 2168.
[2] R. Norarat, V. Marjomäki, X. Chen, M. Zhaohong, R. Minqin, C. Chen, A.A. Bettiol, H.J. Whitlow and F. Watt, Ion-induced fluorescence imaging of endosomes, Nucl. Instr. and Meth. B 306 (2013) 113.
[3] R. Minqin, J.A. van Kan, A. A. Bettiol, L. Daina, C.Y. Gek, B.B. Huat, H.J. Whitlow, T. Osipowicz, and F. Watt, Nano-imaging of single cells and tissue using MeV ions, Nucl. Instr. and Meth. B 260 (2007) 124.
[4] A.M. Müller, A. Cassimi, M. Döbeli, M. Mallepell, I. Monnet, M.J. Simon, M. Suter, and H.-A. Synal, A new mini gas ionization chamber for IBA applications, Nucl. Instr. and Meth. B 269 (2011) 3037.
Primary author
Dr
Rattanaporn Norarat
(Faculty of Science and Agriculture, Rajamangala University of Technology Lanna Chiang Rai, 57120 Chiang Rai, Thailand)
Co-authors
Mr
Edouard Guibert
(University of Applied Sciences, Haute Ecole Arc Ingénierie, (HES-SO) Eplatures-Gris 17, CH-2300 La Chaux-de-Fonds, Switzerland)
Prof.
Harry James Whitlow
(University of Applied Sciences, Haute Ecole Arc Ingénierie, (HES-SO) Eplatures-Gris 17, CH-2300 La Chaux-de-Fonds, Switzerland)
Dr
Luc Stoppini
(inSTI, HEPIA, Rue de la Prairie 4, CH-1202 Genève, Switzerland.)
Dr
Patrick Jeanneret
(University of Applied Sciences, Haute Ecole Arc Ingénierie, (HES-SO) Eplatures-Gris 17, CH-2300 La Chaux-de-Fonds, Switzerland)
