Production and Installation of the Top Counters

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At he same time as the module frames were installed the production ofveto modules continued in R12. The counters for the roof of the bunker were not assembled together in frames but produced as single modules. Those were packed into wooden boxes and transported to R55.

The pictures below illustrate the production of the veto top counters and their installation at the bunker. Before one could start with the installation of the top counters the walls of the bunker and parts of the roof had to be reinstalled first.

	The top counters were produced at the same tables as the module frames for the side walls. Two counters were finished together per production cycle.		The counters at the side walls had to have special clamps to fix the photomultipliers because they were installed vertically. This was easier in the case of the top counters. There one only had to prevent the photomultipliers from rolling away.
	A complete top counter just before wrapping. This counters are protected against thermal neutons by boron polyethylen sheets at the top and bottom side in the same way as the side counters.		The production table positioned vertically for glueing the photomultipliers to the scintillator bars.
	The same procedure as for the side counters: glueing of the photomultipliers.		Wrapping of the counters with light tight, black ployethylen foil.
	Welding of the foil. This is one of the last production steps.		The boxes used to deliver the plastic scintillators from USA were reused to transport the modules to R55.
	A specially constructed lifting device was used to bring the counters up to the roof of the bunker.		This device was necessary because of the limited space available for lifting the counters. The first counter is laid down at the side of the bunker towards the target.
	The next counter is laid down. To cover the whole width of the roof two counters each with a lenth of 3.75 m were necessary.		In order to minimize the gaps between the counters they had to be positioned very carefully.
	And this was the view before the first roof slabs were reinstalled. A total of 30 counters cover the roof completely.

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