Dust particle analysis with electron microscopy Josep Busom

Dust particle analysis with electron microscopy Josep Busom and Anité Pérez Aim of dust particle analysis: The combination of morphological and chemical data on a particle by particle basis enables the deepest understanding of their nature and their role in the processes being studied. 9/6/2021 1

Current procedure: Sample preparation Dust collection on carbon stickers On paper filters No coating required Coating required A. T. Perez Fontenla EDMS: 1710881 9/6/2021 A. T. Perez Fontenla EDMS: 1335772 2

Current procedure: Chemical study Manual mode analyst uses their experience and skill to: • • • Detect particles by using As. B detector on a Scanning Electron Microscope (SEM) Place the electron beam on the particle Collect a qualitative spectrum by EDX The substrate or matrix will ideally be of a dissimilar chemistry from the features of interest Summary of the most representative spectra/ main elements per specimen 9/6/2021 Document reference 3

Current procedure: Particles counting Automatic mode The procedure has been recently optimized by replacing the manual counting for an automatic process (performed with “Axio Vision SE 64” ZEISS software) To effectively automate the process: • • the particles have different grayscale level compared to the substrate (As. B detector) the particles should be dispersed (they are not touching each other) Results using manual and automated counting procedures have been compared on the EDMS 1335772 and the values (very close) are shown in the table Original SEM image after particle analysis 9/6/2021 Manual counting Automatic counting Av. ≈ 155 ≈ 154 Total 8. 7 106 ± 8. 4 105 8. 5 106 ± 7. 1 105 The measurement are done on five SEM pictures taken at 500 x and extrapolated to the filter complete area Document reference 4

Current procedure: Limitations Samples preparation: • Metallic coatings might be required depending on the substrate EDX: • No precise for organic compounds (similar to the substrate) or light elements (Z <11) • Beam spatial resolution ≈ 1 μm • Detection limits 0. 1 wt% • Not 100% of the particles are analysed • Manual analysis is potentially accurate but depends on the skill of the analyst and is relatively laborious and time consuming Counting: • Total value is calculated based in few SEM images Report: • Summary of the most representative spectra/ main elements 9/6/2021 Document reference 5

Alternative: Automated Particles Analysis (APA) Some necessary requirements of both the sample and of the SEM/EDS hardware and software not available at CERN Any sample that is suitable for SEM-EDX can be analysed using APA, but proper sample preparation is essential to obtaining the best results • After the initial setup, all of the steps are done without operator intervention and all data are saved automatically done as overnight and as over-theweekend collections • 100 % of the particles (above a defined size) are analysed by EDX; • The software is able to differentiate between size and shape (fibre - non fibre) ü A close collaboration with an external company has been started in order to check the technique feasibility for CERN studies e. g. UFO particles or recurrent cleanliness and contamination analyses in the different projects ü A initial study performed on Swagelok 15 micron filter used in ATLAS project will be received in the following weeks ü If you have specific samples/questions don’t hesitate to contact us to design an investigation suitable for your specimens and application 9/6/2021 6

Summary of analysis performed on May 2016 By Josep Busom and Laura K. Grob • 6 samples were under study • More than 50 particles were analysed by Electron Dispersive X-ray spectroscopy (EDX) • Most of the analysed particles were stainless steel chips (Fe, Cr, Mn) • Also important presence of metallic chips (Cu, Zn, Al and punctually Ti and Ag) • In addition, inorganic compounds rich in C and O were also observed 9/6/2021 Document reference 7

Si, Al, K rich particles Al and Ca particles 9/6/2021 Document reference 8

Metallic chips 9/6/2021 Document reference 9

Metallic chips 9/6/2021 Document reference 10

Metallic chips 9/6/2021 Document reference 11