'ONDITIONS 
ham in the U.K. 
n is to prove the 
lar modifications 
has deteriorated 
cs has led to a 
nt methods used 
2 ultimate aim is 
1 vessel in which 
magnetic field 
plasma and the 
al components of 
roduced due to 
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suspended within 
shell is mounted 
he plasma forms 
cal shell and the 
roidal field coils. 
rom inconel, has 
with an internal 
)m?, weighs 108 
m of 10? mbar. 
Ise of up to one 
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winding of the 
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asma acts as the 
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1] D-shaped coils. 
re but within the 
sloidal field coils 
e plasma. 
96 
  
2.2 In-vessel Installation 
A key requirement of in-vessel installations is usually 
alignment. There are a number of reasons for this ranging from 
the need to have components carefully aligned with respect to 
the magnetic field to ensure uniform thermal loading, to 
knowing where diagnostic sensors are to allow interpretation of 
data which is often used to control plasma parameters. During 
future shutdowns at JET, radiation levels due to neutron 
activation will restrict durations of manned in-vessel access to 
the point where work would no longer be possible. In fact, all 
installation work is planned to be carried out remotely using 
JET's remote articulated boom (figure 2). 
Precision surveys will also have to be carried out remotely. 
This has been the subject of research at JET for some time, 
with many different systems being investigated, e.g. optical, 
photogrammetry, laser scanning. Videogrammetry was used at 
the end of the recently completed major shutdown to provide 
an 'as-built' record of major in-vessel components and a datum 
base for dimensional integration into the future. Suitability of 
videogrammetry for use in remote handling shutdowns is 
being assessed. Targetting of components is a major problem, 
but at present a targetless form of videogrammetry is being 
considered for collecting ‘as-built’ information to an accuracy 
of +1-2mm, with laser scanning techniques for more accurate 
local measurements, e.g. steps and gaps between tiles. The 
techniques developed at JET over the last three years are 
described along with steps to ensure that similar control will 
be exercised in the future when installation work is carried out 
remotely. 
  
PX 
Figure 2. JET's Remote Handling Articulated Boom being 
used to install tiles inside the vacuum vessel. 
3. THE PUMPED DIVERTOR PROGRAMME 
JET's scientific programme for the future is largely based on a 
series of Pumped Divertors with a campaign of experiments 
planned to study control impurities in the plasma. The first or 
MKI Divertor was installed in 1992, the MKII during 1995/96 
With the fully remote installation of MKIIGB (Gasbox) planned 
for 1997. The MKII Divertor concept is based on two major 
components - a fully machined and very precise support 
Structure on which different configurations of plasma facing 
liles can be mounted. Future changes such as the MKIIGB 
International Archives of Photogrammetry and 
configuration will be implemented by changing only the tile 
assemblies remotely. 
3.1 The MKI Divertor Installation 
In 1992 a major rebuild of the JET machine was carried out in 
order to install the MKI Pumped Divertor. Due to the high 
thermal loads envisaged during operation, accurate positioning 
of the plasma facing components to the magnetic centre of the 
machine was a major requirement. Typically alignment to 
better than £2mm was required with steps between tiles on a 
component being controlled to £0.25mm. In some cases a set 
of components was required to be concentric while also lying 
within a narrow band defined by the position of some other 
components. Clearly, a measuring system accurate to better 
than £0.5mm was required. 
Prior to 1992 component surveys and alignment checks at JET 
depended on some combination of conventional metrology 
equipment and jigs, usually based on a precise survey ring. For 
the installation of the MKI Divertor (Macklin, 1994) a 
sophisticated survey ring system was designed and built. This 
was used successfully for the installation of the lower vessel 
components. However, it soon became apparent that to achieve 
the required accuracy for the upper vessel components would 
require a system so complex and cumbersome that it would not 
be compatible with other installation tasks, therefore having a 
serious adverse effect on the shutdown schedule which was 
critical. 
3.2 Computer Aided Theodolite Systems 
Various alternative systems were investigated resulting in the 
purchase of Leica’s ECDS3, an optical 3-D non-contact 
measuring system now known at JET as the CAT (Computer 
Aided Theodolite) system. 
theodolites to measure the horizontal and vertical angles to a 
network of targets and a calibrated scale bar. The resulting set 
of simultaneous equations is solved using a mathematical 
technique known as bundling. 
  
  
  
  
  
  
  
| x. 
| FE] 
Lert RERO 770m Hate i [ 
| gE 
| 
ig 
3 
be 
I= 
| o 
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E 
15 : 
I= In-vessel master 
reference 
| targets 
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i 
| 
| 
i 
  
JG96.158/3c 
Laser zenith 
plummet 
2-way micrometer 
table 
777 
Figure 3. Transferring ex-vessel refence to establish in-vessel 
datum system. 
  
3.3 In-vessel Datum System 
331 
Remote Sensing. Vol. XXXI, Part B5. Vienna 1996 
ECDS3 uses two electronic