Page 189 - Neutrons for Sciences and Society

This “ Second Wind ” led to the construction of four new instruments chosen in collaboration with the Scientific Council. As an example the triple axis spectrometer IN2 was replaced by the IN20 triple axis with much enhanced performance and allowing use of polarised neutrons.
Capital was available for new buildings; a new hall for the new computer, large enough to accommodate the biggest new system tendered, and the Biology group of the ILL joined that of the EMBL in a new laboratory building.
In April 1981 the first beam-tube nose replacement took
place. This was performed on one of the hot source beams. The exchange was necessary because a small crack had been detected. To avoid possible consequences of future cracks the beam-tubes, originally evacuated, were filled with helium under pressure which reduced the strains to which the nose was subjected.
The operation took place very smoothly and it was possible to envisage generalising these exchange operations which could
be achieved during a normal shutdown (about 10 days between reactor cycles). Study of the original nose-piece after removal has enabled assessment of how the strength of the aluminium
has been affected by the irradiation conditions in the reactor. Other beam-tube exchanges followed, taking place during normal shutdowns (one in 1982, and four in 1983).
A much longer shutdown of eleven months had to be planned between October 1984 and August 1985 to gather together more complex maintenance activities, including replacing the H1/H2 beam-tubes. These cold and thermal guides shared a combined nose assembly which was ageing. This time the aluminium
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Chapter 7 - Maturity