1 Lead analysis performed at CERN with EST division group S.Buontempo Lead cleaning procedure Surface analysis Ca-Lead Surface analysis of Lead in contact with emulsions Outlooks February 2004, Nagoya OPERA Collaboration Meeting

2 As-received samples Degreased : NGL SOLUTION: 17-40, 15g/l, T=60°C; 20 hours (~ 2 hours Ultrasond) RINSING : demineralized water, compressed air drying Degreased and etched samples: NGL SOLUTION: 17-40, 15g/l, T=60°C; 36 hours (~ 2 hours Ultrasond) RINSING : demineralized water, compressed air drying ETCHING H 2 SO 4 50% (Vol), room temperature, 10s RINSING : demineralized water, compressed air drying Lead cleaning procedure

3 Techniques used for surface analysis XPS: X-Ray irradiation of the sample – photo-emitted electron collection (electron emitted from the core levels) gives the number of collected electrons as a function of the binding energy surface analysis (a few nm depth) quantitative analysis (detection limit for Ca = 0.1 at. %) SIMS: sputtering of the sample surface with Ar ions – collection of the extracted ionic fragments with a mass spectrometer gives the number of ions detected as a function of their mass surface analysis (first layer) qualitative analysis high sensitivity for Ca J. Gavillet TS-MME-SC (CERN)

4 XPS detection limit Element “concentration” (at.%) Results of Surface analysis on Ca-Lead

5 Surface evolution within two weeks, after NGL cleaning: under ultra-high vacuum: increase of the surface Ca content (surface segregation) in air: no increase of the Ca content and increase of the Pb oxide thickness High contamination of the as-received sample surface, with: 80 at. % of C on the surface greases (silicone grease) Ca (> 2 at. %) Pb plates cleaning necessary Different cleaning solutions tested, best one: NGL good surface cleaning very low Ca content (  0.2 at. %) H 2 SO 4 surface etching: good surface cleaning no Ca detected on the surface strong pollution with S Results of Surface analysis on Ca-Lead (2)

6 Analyzed samples: 30ºC – 09/12/03 # 1.C.1: (Pb + Ca) NGL cleaned - vacuum packaging # 2.C.1: (Pb + Ca) NGL cleaned - mechanical pressure packaging # 1.B.1: (Pb + Ca) as-received – vacuum packaging # 2.B.1: (Pb + Ca) as-received – mechanical pressure packaging # 1.A.1: Pb pure (Cern) as-received – vacuum packaging # 2.A.1: Pb pure (Cern) as-received – pressure packaging both sides of the plates have been analyzed (side exposed to emulsion and back side) XPS and SIMS analyses before and after sputtering of the oxide layer partial sputtering of the carbonaceous layer followed by XPS and SIMS analyses J. Gavillet TS-MME-SC (CERN) Results of surface analysis of Lead in contact with emulsions

7 XPS results: side exposed to emulsion Strong surface pollution with F adsorbed on the surface (disappears as soon as the surface sputtering begins)

8 XPS results: back side No trace of F

9 These analyses don’t really support the hypothesis of the Ca as the origin of the emulsion deterioration. F pollution of the surface in contact with the emulsion The pollution is only superficial. As the back sides of the plates never show any trace of F, it probably arises from the emulsion surface. It doesn’t seem to be related to the fog production as F is present in all cases. No correlation between the content of Ca detected and the fog’s amount The Ca is almost never detected in XPS in both sides of the plates. It was only observed in the as-received plates (in the exposed side of the pressure package one and in the back side of the vacuum one). In these cases the amount of Ca detected stay lower than in the previous studies. Ca is however always detected in SIMS, implying a small Ca content present in every cases. No difference in the Pb state nor in the oxide thickness have been detected between the vacuum and pressure samples The fog observed in the emulsions can’t therefore be attributed to Pb surface state. Nothing noticeable has been observed in the pure Pb plates The F pollution is also present in the exposed side. Conclusions

10 Emulsion surface analysis Emulsion composition 1) emulsion (2 layers + base) weight 6.3 g with density of grains+gelatine = 2.6 g/cm3 2) the chemical composition is the following: % in weight density (g/cm3) I Ag =20 Br S O N C H ) the base is triacetate Preliminary results show on the emulsion surface a relevant amount of Flour, Calcium (!) and Lead….

11 XPS analysis of the emulsion (results in atomic %)

12 XPS analysis of the emulsion (zoom) (results in atomic %)

13 Outlooks Goslar has shipped lead-silver to CERN: delivery expected in next days We will pack Silver-lead with emulsions (vacuum and mechanical pressure) and store it at 20 and 30 degrees for about 40 days Development will be done in March We will measure emulsion fog and perform surface analysis both on emulsion and lead We need to perform same tests on refreshed emulsion too (maybe different behaviors?)