Measurement of thin oil layers by PIXE-α P. Brisset, D. Chambellan and J. de Sanoit CEA-LIST Département des technologies du Capteur et du Signal 91191 Gif-sur-Yvette Cedex, France International conference on Recent dvelopments and applications of nuclear technologies 15-17 september 28, Bialowieza, Poland 1 Principle of the PIXE -αmethod détecteur X source alpha X α α 2 PIXE analysis of the silver coating of a Roman coin (III century BC) 3 1
25 2 15 5 25 2 15 5 Si Al Si Ar K K Ca Vernice Falsa 1 2 3 4 5 6 7 8 9 1 Energia (kev) Ceramica Attica 1 2 3 4 5 6 7 8 9 1 Energia (kev) Fe Fe Characterisation of the blue pigments of Madonna del Roseto (Luca della Robbia, XV+ century Florence, Italy) 4 Analysis of the black pigment Conteggi Body >>> false Conteggi Basis >>> authentified 5 General advantages of the method Non destructive analysis Analysis of light elements ( Z < 26 ) Surface analysis (some mm) samples analysis with dimensionnal or administrative constraints Field equipment 6 2
PIXE -αadaptation to thin layer thickness measurement principle Source Detector Excitation by α Emission of X-ray Oil Studied material Metallic plate CEA EU patent 7 Radioactive source specifications Pure α emission ( >>>> 21 Po ) High activity (37MBq) Annular geometry Source : sealed but thin Resistance to radiolysis 8 21 Po desintegration scheme T = 138,4 jours 21 Po 83,1 a1 a2 = 5.3 MeV (99,99%) γ (.1%) 26 Pb 9 3
21 Po radiological and chemical safety -Chemical safety : -very low level of the toxicity limit 4. 1-11 mg/m 3 -Polonium compounds are very volatile - Radiological safety (annual incorporation limit) - Workers: 2. 1 4 Bq - Public : 2. 1 3 Bq From Journal Officiel des Communautés Européennes (JOCE, 198) 1 Chemical reaction for source preparation Spontaneous electrochemical replacement (Haïssinsky, 1937) Po 2+ + 2 e Po ( Ag Ag + + e ) x2 Po 2+ + 2 Ag 2 Ag + + Po 11 Electrodeposition cells Annular truncated concave source Annular source 12 4
Sources socket MYLAR / Silver (,2 mm) Annular truncated concave source Annular source Confinement barrier Layer of aromatic epoxy resin (e <,5 µm) KAPTON window (e < 2 µm) NYLON grid (mechanical protection) 13 21 Po Source preparation deposition kinetics Po deposition yield (%) 8 6 4 2 21 Po deposition yield vs contact time 4 ml of aqueous HCl or HCl/N 2 H 4, 2 HCL containing.8 MBq of carrier free polonium silver electrode area = 1.77 cm 2 Stirring 2 rpm [HCl] = 2 M [HCl] = 2 M; [N 2 H 4, 2 HCl] = 1 M,,5 1, 1,5 2, time (hours) 14 21 Po Source ready to use 15 5
21 Po source experimental arrangement Common EU patent CEA + IN FN Technology transfer from CEA to INFN 16 Experimental device Detail of the PIXE -αhead Area of measurement NaI(Tl) detector 17 Experimental program Objectives : Influence of the thickness of demoulding oils on the aesthetic quality of concrete facings Studies on the influence of oils deposition method on film thickness Materials: 2 types of concrete 2 types of oils Oil deposition methods Spraying with conic nozzle at 2 cm from surface spread after spraying with a rubber scraper 18 6
Studied materials Concrete composition Constituents Silex 5/15 Aggregate 4/8 Sand /4 Cement CEM I 52,5 Filler Water E/L* Quantities (kg/m 3 ) 761 281 826 258 86 167.49 Oils characteristics Properties Vegetable-based oil (V) Mineral-based oil (M) Nature Color Flash point ( C) Density (g/cm 3 ) Viscosity at 2 C (mpa.s) Liquid Straw-coloured > 9 C.93 177.7 Liquid yellow > 8 C.85 2.4 Contact angle ( ) 32 19 19 Measured spectra Metallic Mylar surface (steel) Metallic surface Infinite (steel) Mylar 2 Calibration with mylar disks Mylar Discs Disc # 1 Disc # 2 Disc # 3 Mass (mg) 14.2 12.4 14. Thickness (µm) 3.61 3.16 3.56 The calculation of each equivalent thickness is done according to the following equation: density of the mylar Equivalent thickness = Thickness of the disc density of the studied oil 21 7
Calibration curves Impulsion (c/s) Transmission (%) Equivalent thickness (µm) Mineral Vegetable Steel 29.54 Steel + Disc # 1 13.96 45.4 5.9 5.4 Steel + Disc # 2 8.18 25.2 11.7 1.12 Steel + Disc # 2 4.85 13.5 16.89 15.44 Steel + infinite Mylar.99 3. 3. an approximate equation of these curves is of the form : y = a + bx 3 + c.lnx By fitting on the results we obtain the equations coefficients, thus : For the mineral oil: For the vegetable oil: -6 3 y = 4.59 + 1.33.1 x - 9.12 ln x -6 3 y = 36.93 + 1.17.1 x - 8.28 ln x 22 Calibration curves Transmission (%) 9 8 7 6 Gauging of mineral-based oils 5 4 3 2 1 5 1 15 2 25 3 35 4 Thickness of the oil film (µm) 9 8 7 6 5 Gauging of vegetable-based oils. 4 3 2 1 5 1 15 2 25 3 35 4 Thickness of the oil film (µm) 23 Measurement uncertainties σ = - x R x t e x x with R : counting rate with no oil t : measurement time x : thickness of the measured oil x : characteristic constant of the oil absorption x (µm) σ x (µm) σ x / x (%) 1.19.2-2.1 5 1.26.35 5.2 3.5 15 2.48.66 3.2 3.3 Standard deviation on the thickness measure 24 8
Comparison between gauging and weighting results Oil Thickness (µm) Sprayed film Scraped film after spraying Mineral oil Between 3 to 5 1. Vegetable oil Between 2 to 3 1.6 25 Conclusion -PIXE method really adapted for this kind of measurement -Range of measurement : 1 to 1 µm -Film thicknesses are between 1 to 2 µm after scraping sprayed film -A film of 1 to 2 µm is enough to obtain a high quality facing allowing minimization of oil quantities -the studied vegetable oil allows obtaining a facing with a better aesthetical quality than the mineral oil -Many other applications are possible and some have been tested (teflon for ex.) - Evolution to Curium 244 source (half life,.) 26 Thank you for your attention 27 9