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Hold time of the dewar

Shortly after installation, it was found out that the liquid He hold time was about one week, compared with more than two weeks in laboratory use. That difference is due to the fact that in the Grenoble laboratory, each CTI350 cold head is fed compressed He gas by a dedicated CTI1020 compressor, while at the 30-m telescope, each CTI1020 serves up to two cold heads; besides, the He lines at the 30-m are longer. Some improvement has been obtained by re-distributing the five receivers in operation over the available three compressors. More to the point, this is not a real problem, since the liquid He refilling of an Infrared Labs dewar takes only a few minutes.