NeuLAND - FAIR

Executive Summary
The R 3 B (Reactions with Relativistic Radioactive Beams) experiment at FAIR will be
the only facility worldwide providing the capability for kinematically complete measurements
of reactions with relativistic heavy-ion beams of short-lived nuclei up to about
1 AGeV. These measurements require a high resolution to allow for a comprehensive experimental
investigation of fundamental science questions related to nuclear structure,
astrophysics, and reactions with neutron-proton asymmetric nuclei. The experimental
setup has been designed and will be built by the R 3 B collaboration on the basis of more
than 20 years of experience with the reaction setup LAND at GSI. The newly designed
instrumentation thereby overcomes major limitations of the present setup. The main
design goals emerging from the physics cases are the applicability of the experimental
approach to energetic beams maintaining the high resolution, as well as the extension
of the physics program, i.e., the capability to measure a large variety of reaction types.
The beams provided by Super-FRS at FAIR will be more neutron-rich than presently
available, up to uranium. Consequently, high beam energies are needed in order to ensure
fully-stripped ions for heavy beams. At the same time, the capability to detect
multi-neutron events is required due to the low thresholds of neutron-rich nuclei.
NeuLAND (new Large-Area Neutron Detector) is the next-generation neutron detector
designed for R 3 B which meets all requirements defined by the ambitious physics program
proposed for the R 3 B facility. NeuLAND features a high detection efficiency, a high
resolution, and a large multi-neutron-hit resolving power. This is achieved by a highly
granular design of plastic scintillators, avoiding insensitive converter material. The detector
will consist of 3000 individual submodules with a size of 5×5×250 cm 3 , arranged
in 30 double planes with 100 submodules providing an active face size of 250×250 cm 2
and a total depth of 3 m. NeuLAND can be divided into two detectors for special applications
and will be placed at different distances from the target, in order to meet specific
experimental demands.
The neutron detector NeuLAND is an integral part of the R 3 B experiment, and is
the key instrument for a major part of the physics program. The main design goals
comprise a one-neutron detection efficiency above 95% in a wide energy range and a full
acceptance corresponding to an angular coverage of ±80 mrad. The desired resolutions
for momenta and thus the excitation energies, as described in detail in chapter 2, lead to
the required spatial resolutions of σx,y,z ≤ 1.5 cm and to a time resolution of σt ≤ 150 ps
for the standard distance between detector and target of 15.5 m. When placed at a
distance of 35 m, an excitation-energy resolution of less than 20 keV(!) will be reached
for an excitation energy of 100 keV above threshold for a beam energy of 600 AMeV.
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