Browsing by Author "Smith, D"

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    Digital coincidence counting - initial results
    (Elsevier, 2000-08-01) Butcher, KSA; Watt, GC; Alexiev, D; van der Gaast, H; Davies, JB; Mo, L; Wyllie, HA; Keightley, JD; Smith, D; Woods, MJ
    Digital Coincidence Counting (DCC) is a new technique in radiation metrology, based on the older method of analogue coincidence counting. It has been developed by the Australian Nuclear Science and Technology Organisation (ANSTO), in collaboration with the National Physical Laboratory (NPL) of the United Kingdom, as a faster more reliable means of determining the activity of ionising radiation samples. The technique employs a dual channel analogue-to-digital converter acquisition system for collecting pulse information from a 4π beta detector and an NaI(Tl) gamma detector. The digitised pulse information is stored on a high-speed hard disk and timing information for both channels is also stored. The data may subsequently be recalled and analysed using software-based algorithms. In this letter we describe some recent results obtained with the new acquistion hardware being tested at ANSTO. The system is fully operational and is now in routine use. Results for 60Co and 22Na radiation activity calibrations are presented, initial results with 153Sm are also briefly mentioned. © 2000, Elsevier Ltd.
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    Investigation and optimization of reactive ion etching of Si3N4 and polyphthalaldehyde for two-step gray scale fabrication of diffractive optics
    (AIP, 2019-11-18) Aminzadeh, A; Bose, M; Smith, D; Uddin, MH; Peele, AG; van Riessen, GA
    Nanofabrication of x-ray diffractive optics using electron beam lithography requires a complex process of electron exposure optimization and resist development. Thermal scanning probe lithography (TSPL) offers a high resolution, maskless, gray scale patterning method with reduced complexity. Thin diffractive optics with high efficiency for the extreme ultraviolet (EUV) and soft x-ray (SXR) photon range could be fabricated by combining TSPL with a single etching step if the TSPL resist, polyphthalaldehyde (PPA), can be used as an etch mask to direct-etch the pattern into a substrate using reactive ion etching. This condition critically depends on high etch selectivity between the substrate and the PPA, because TSPL resolution deteriorates as the PPA patterning depth increases beyond tens of nanometers. In this work, the authors have evaluated the etch selectivity for PPA and Si3N4 using SF6/C4F8 gases and the influence of process parameters, including gas flow rate, vacuum pressure, radio frequency bias power, and inductively coupled plasma power. The experimental results indicate that an etch selectivity of 7 (Si3N4:PPA) is achievable, and the authors demonstrate that diffractive optics for EUV/SXR can be fabricated in only two steps. © 2023 AIP
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    Three-dimensional phase imaging with near infrared synchrotron beam using phase-retrieval algorithm
    (Society of Photo-Optical Instrumentation Engineers (SPIE), 2023-03-08) Han, M; Smith, D; Ng, SH; Katkus, TA; Simon, A; Rajeswary, JF; Praveen, PA; Tobin, MJ; Vongsvivut, JP; Juodkazis, S; Anand, V
    The near infrared (NIR) part of the infrared synchrotron beam is usually dumped to improve the signal to noise ratio of spectral imaging. In this study, this NIR synchrotron beam has been extracted and used for three-dimensional (3D) phase imaging. A pinhole was inserted in the path of the fork shaped NIR synchrotron beam and the Airy diffraction pattern was aligned with biochemical samples and the diffracted intensity distribution was captured using an image sensor sensitive to NIR. A phase retrieval algorithm was used to estimate the 3D phase distribution at the object plane from the recorded intensity distribution. © (2023) Society of Photo-Optical Instrumentation Engineers (SPIE)