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Neutrons for Science
continue to reflect at up to four times the critical angle, hence
the name supermirror. If only twice the critical angle of nickel
is taken as the acceptable limit then the efficiency rises to 92%. This has led to a programme of gradual replacement of the nickel mirrors in the neutron guides by supermirrors. All this implied
a huge task of research and development, especially to improve the quality of the deposited films. By using a magnetic material for one of the layers the supermirrors can be used to produce polarised neutrons. Otto Schärpf led even more research work to find the best materials an techniques95.
However the most important event for the ILL with Mössbauer as director was the arrival of the British as an equal third partner. This was the result of lengthy negotiations which had started in the time of Maier-Leibnitz.
6.3 The arrival of the British
Negotiating96 with the British for their accession to the ILL was totally different in nature from that which led to the establishment of the Institut. Negotiation between French and Germans was intended to build a reactor that had yet to be precisely defined. I have indicated above the many decisions which had to be taken. Negotiation with the British took even more time despite the fact that there were only a few technical points to discuss since the reactor was already operational, with instruments ready, or nearly
95 O. Schärpf, I.S. Anderson (1994) Physica B 198, 203-212, DOI 10.1016/0921-4526(94)90161-9
96 I wrote this chapter using copies of the original documents (letters, minutes of meetings, memoranda) which I possess.
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