1. Microscopy inspection on various LINAC 2 cathodes
EN Division-Metallurgy and Metrology
Domaine / Field:
LINAC2
Date:
N° EDMS / EDMS Nr.:
On-going
Requérant / Customer:
R. Scrivens
Liste de distribution / Distribution list:
C. Mastrostefano
Microscopy inspection on various LINAC 2 cathodes
Ana Teresa Pérez EN-MME-MM
Equipment:
Scanning Electron Microscope (SEM), field emission gun FEG Sigma (ZEISS) with InLens (Secondary Electron), Evan-Thornley Secondary Electron (SE2), and back-scattered electron (AsB) detectors for imaging.
50 mm2 X Max EDS detector (Oxford), INCA software.
Digital microscope KEYENCE VHX 1000
Summary: Various specimens were under study but some of the questions remain unanswered.
Key words: SEM, OM, LINAC2, ICP-EOS
EN Division-Materials and Metrology
CERN/EN/MME-MM

2. Broken source cathode (#1) March 2015 Optical microscopy
Samples
Received on
Performed analysis
Broken source cathode (#1)
March 2015
Optical microscopy
Scanning Electron Microscopy (SEM)
Chemical analysis by Energy Dispersive Spectroscopy (EDX)
Broken source cathode (#2)
July 2015
Reference mesh and mesh on cathode from 1971 (#3)
Cathode in operation from March – Sep. 16 (#4) Not broken!
Sept. 2016

3. MESH STRUCTURE
The mesh structure presented in all cases nickel (Ni), manganese (Mn), iron (Fe), carbon (C) and oxygen (O). However, a correct identification of some elements, especially Ti is problematic due to EDX artefacts
Why Ti?  In the “PROCEDE DE FORMATION DE LA CATHODE A OXYDE DE LA SOURCE DUOPLASMATRON DU LINAC” July 1973, was included a X-ray diffractogram where Ti was present. Ti was not confirmed in used electrodes via EDX due to the Ti (Kα: 4.508) and Ba (Lα: 4.465) peak’s overlapping that might hinder a realistic analysis  External analysis was proposed: Elementary analysis by Inductively Coupled Plasma Optical Emission Spectrometry (ICP-EOS). Company: EAG (FR)
SOI-1
SOI-2
SOI-1
SOI-2

4. PAINTING
The painting was analysed and main components were Ni, barium (Ba) and strontium (Sr) corresponding with the expected elements of the mixture (15% BaCo3, 15% SrCo3 and 70% Ni in dust).
Nevertheless, these elements seems to be heterogeneously distributed in the cathode surface:

5. CATHODE IN OPERATION FROM MARCH TO SEPT. 2016 (#4)
Cathode analysis, but not dismounting from the support  The cathode will be remounted on a test bench for further heating

6. SOI-1
SOI-2
SOI-3
SOI-4
SOI-5

7. SEM observation AsB detector (Sigma)
Grey region

8. SEM observation AsB detector (Sigma)
Dark region

9. SUMMARY
Various specimens were under study but some of the questions remain unanswered
The mesh composition still not confirmed due to the EDX artefacts  ICP-EOS
It seams that the mesh was melt in the cathode areas that appeared dark or broken
Painting composition seems to be heterogeneous Study before installation (?)
Study of the last electrode (in operation from March to September 2016):
No major morphology variations were evident. The chemical analysis was not possible due to the sample size.
Nevertheless, different SOI were localized and the images can be compared with future images/studies on the same cathode after heating.