The upgraded external-beam PIXE/PIGE set-up at LABEC for very fast measurements on aerosol samples F. Lucarelli ⇑ , G. Calzolai, M. Chiari, M. Giannoni, D. Mochi, S. Nava, L. Carraresi Department of Physics and Astronomy, University of Florence and INFN, Florence, Italy article info Article history: Received 15 March 2013 Received in revised form 6 May 2013 Accepted 27 May 2013 Available online 22 July 2013 Keywords: PIXE Atmospheric aerosol External beam Silicon drift detector abstract At the 3 MV Tandetron accelerator of the LABEC laboratory of INFN in Florence, an external beam facility is fully dedicated to measurements of elemental composition of atmospheric aerosol. The experimental set-up hitherto used for this kind of applications has been upgraded with the replacement of a traditional Si(Li) detector for the detection of medium–high Z elements with a silicon drift detector (SDD) with a big active area (80 mm 2 ) and 450 lm thickness, with the aim of obtaining better minimum detection limits (MDL) and reduce measuring times. The Upilex extraction window has been replaced by a more resistant one (Si 3 N 4 ). A comparison between the old Si(Li) and the new SDD for aerosol samples collected on dif- ferent substrata like Teflon, Kapton and Nuclepore evidenced the better performances of the SDD. It allows obtaining better results (higher counting statistics, lower MDLs) even in shorter measuring times, thus allowing very fast analysis of both daily and hourly samples. Ó 2013 Elsevier B.V. All rights reserved. 1. Introduction Many trace elements are emitted into the atmosphere both by human activity and as natural background. Beside their potential for adverse health effects, the typical element patterns can be used for the apportionment of the ambient aerosol to specific sources [1,2]. Standard aerosol sampling campaigns produce huge amounts of daily samples (from hundreds to thousands of samples). Most particulate emissions as well as their atmospheric dilution pro- cesses change within a few hours. Daily samples are however not capable of tracking these rapid changes. Furthermore, source apportionment receptor models need a series of samples contain- ing material from the same set of sources in differing proportions. Increasing the time resolution of the measurements typically pro- vides samples that have greater between-sample variability in the source contributions than samples integrated over longer time periods. The time-resolved measurement requires a suitable tech- nique both for particle sampling and analysis. For time-resolved sampling there exist a variety of samplers with automated move- ment of the individual impactor stages, for example the streaker sampler [3,4] with two size ranges or the DRUM sampler with 3 or 8 stages [5,6]. The resolution in time and size leads to even a lar- ger number of collected samples to be analysed. PIXE technique is a powerful tool to investigate environmental problems and it has been widely used since its birth for the study of the aerosol composition [7,8]. However, it has now to compete with other techniques, like Inductively Coupled Plasma and detec- tion by Atomic Emission Spectroscopy (ICP-AES) or Mass Spec- trometry (ICP-MS) or Syncrotron Radiation XRF (SR-XRF). To remain competitive, a proper experimental set-up is important to fully exploit PIXE capabilities. In the past ten years our group has been increasingly involved in extensive programs aiming at the characterizations of particu- late matter in urban areas [9,10], industrial districts [11,12] or re- mote sites [13,14]. To be able to analyze the huge number of samples collected both with daily and hourly time resolution, we have decided to upgrade the external-beam PIXE-PIGE set-up at LABEC for very fast measurements on aerosol samples, aiming not only at reducing the measurement time, but also at improving the minimum detection limits (MDLs) of the technique. The aim of this paper is thus to give a description of the current status of the new set-up and to present some tests we have performed; a special emphasis will be given to the improvement obtained in the analy- sis of Teflon filters which are the most widely used substrata for aerosol studies and which, commonly, are not easily analyzed by PIXE. 2. Experimental set-up At LABEC, an external beam line is fully dedicated to PIXE-PIGE measurements of atmospheric aerosols [15]. Recently silicon drift detectors (SDD) have been introduced for X-ray detection thanks to their better resolution with respect to Si(Li) detectors, even at moderate cooling (10 /40 °C, achievable with Peltier cells), 0168-583X/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.nimb.2013.05.099 ⇑ Corresponding author. Address: Via Sansone 1, I-50019 Sesto Fiorentino (Firenze), Italy. Tel.: +39 055 4572274; fax: +39 055 4572641. E-mail address: lucarelli@fi.infn.it (F. Lucarelli). Nuclear Instruments and Methods in Physics Research B 318 (2014) 55–59 Contents lists available at SciVerse ScienceDirect Nuclear Instruments and Methods in Physics Research B journal homepage: www.elsevier.com/locate/nimb