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Downloading of data from the camera will be studied carefully. 
This is restricted by the need to use only existing wiring on the 
boom. The tight space envelop prevents the addition of 
additional wiring. The latest development of Leica's V-STARS 
system is expected to help overcome this difficulty as it 
incorporates a 486 chip in the camera which carries out partial 
processing of the data with the result that a single six-core 
network cable will handle all electrical interfaces to the camera. 
This can be accomodated within the boom's existing loom 
which caters for the addition of specialist tools. 
7. STEP AND GAP MEASUREMENTS 
After completion of the tile installation on the MKII Divertor 
structure the need to check the critical steps and gaps between 
certain tiles was identified. Convention mechanical means of 
carrying out this check were complicated by the fact that any 
contact with delicate tile edges would almost certainly damage 
them. A laser scanning survey was carried out using a tool 
originally developed for remote inspection of welding inside 
pipes. This non-contact tool scanned the gap between adjacent 
tiles (figure 10). The required dimensions could then be 
determined by selecting the appropriate points of the cross 
section with a cursor on a computer screen. Results of the 
survey allowed engineers to confirm that steps and gaps were 
within tolerance and that difficult and expensive remedial work 
was not necessary. Survey time to measure the step and gap at 
twelve locations was about twenty minutes with another twenty 
minutes required for interpretation of results. Accuracy 
achieved was of the order of 0.1mm. Superior accuracy can be 
achieved with a tool which scans in two orthogonal directions 
to take account of the complex surface geometry of the tiles. As 
steps between adjacent tiles are critical on most components, 
with gradual undulations being less critical, this system will be 
essential during a remote tile installation. It will be used to 
determine whether adjacent tile assemblies are fitted correctly 
and in the event that difficulties are encountered will be used to 
quantify the problem and allow a solution to be developed with 
certainty. The parameters for a scanner to be made for JET are 
being prepared. Remote handling of the scanner will be 
developed but again the major difficulty foreseen is that of the 
electrical interfaces with the articulated boom. 
Laser scanner 
  
Divertor tiles 
Figure 10. Illustration of laser scanner survey of tile step and 
gap 
8. CONCLUSION 
Plasma physics requirements have led to the need for improved 
installation and alignment accuracy. At JET this meant a 
transition from local jig based to non-contact optical techniques 
operated within a single coordinate datum system resulting in a 
tenfold improvement in alignment accuracy. Special survey 
methods and data handling techniques were developed to suit 
JET's particular geometry and difficult working conditions. 
Installation techniques developed are now being increasingly 
applied throughout manufacturing contracts. In-vessel survey 
techniques and equipment are now being used extensively ex- 
vessel for positioning equipment which has in-vessel interfaces 
and for providing ‘as-built’ information required for CAD 
configuration control models. 
The evolution of surveying will continue at JET with the 
planned remote application of targetless videogrammetry with 
the selective application of laser scanning techniques during the 
first full remote handling intervention at JET. 
9. REFERENCES 
Manufacturing and Installation of JET MKII Divertor Support 
Structure. G Celentano et al., 16th Symposium on Fusion 
Engineering, Champaign 1995. 
Alignment Systems for Pumped Divertor Installation at JET. B 
Macklin et al., 18th Symposium on Fusion Technology, 
Karlsruhe 1994. 
Application of ‘Best-Fit’ Survey Techniques Throughout 
Design, Manufacturing and Installation of the MKII Divertor at 
JET. B Macklin et al.,16th Symposium on Fusion Engineering, 
Champaign 1995 
Leica AG, Photogrammetry and Metrology, CH-5035, 
Unterendfelden, Switzerland. 
ESIC Reseau Eurisys, St. Quentin en Yvelines, France. 
335 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part BS. Vienna 1996