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The new neutron guide laboratory ELLA at the Jülich research reactor started its full operation at the beginning of this year. The guide system supplies 10 instruments with cold neutrons from the rebuilt hydrogen cold source. We present a description of the technical layout of the guide system. In order to achieve a larger solid angle, the guides were covered with isotopically pure 68Ni. The obtained neutron fluxes will be quoted. In addition, special beam forming devices were installed, namely a neutron guide junction at the entrance of the guide system, a multislit-bender with a radius of curvature of only 57 m, which achieves a large beam separation, and conical focusing neutron guides with supermirror layers to increase the flux at the sample position. 1_ INTRODUCTIONA guide halls for cold neutrons has been built at the research reactor FRJ -2 of the Kernforschungsanlage (KFA) Jülich during 1983 to 1987 and taken into operation. The new hall replaces a former smaller laboratory2, which has been working since 1970. The FRJ -2 is a heavy water reactor (DIDO) with a power of 23 MW and a peak thermal neutron flux at the beam hole noses of about 1.5 1014 n/cm2s. Together with the guide hall and the neutron guide system, the old hydrogen cold source with a thermosyphon system was rebuilt.3 At the position of the hydrogen vessel of the cold source, the thermal flux is approximately 1.0 1014 n/cm2s.4 Between the cold source and the neutron guide system, a helium cooled bismuth filter was installed in order to reduce the background radiation of fast neutrons and gamma rays. The filter is necessary and has been maintained because it allows the installation of straight guides and the adaption of the time -of-flight spectrometer (TOF) inside the reactor hall FRJ -2.The neutron guide system6 starts inside the beam hole in the reactor shielding. The cold neutron flux close to the guide entrance was measured to be 2.0 109 n/cm2s. Altogether 10 neutron instruments6 are connected to the neutron guide system in the guide hall, 4 of them being at end positions.In the following we present the basic parameters for the layout together with details of the technical realization of the guide system as well as special neutron beam forming devices, for instance a neutron guide junction, a neutron guide with a high curvature (bender) and a conical focusing neutron guide for flux enhancement. ABSTRACTThe new neutron guide laboratory F.I J A at the Jiilich research reactor started its full operation at the beginning of this year. The guide system supplies 10 instruments with cold neutrons from the rebuilt hydrogen cold source. We present a description of the technical layout of the guide system. In order to achieve a larger solid angle, the guides were covered with isotopically pure 58Ni. The obtained neutron fluxes will be quoted. In addition, special beam forming devices were installed, namely a neutron guide junction at the entrance of the guide system, a multislit-bender with a radius of curvature of only 57 m, which achieves a large ...

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