Initial performance of sealed straw modules for large area neutron science detectors

Alternative neutron detection technologies must be considered, to overcome limitations imposed by a depleting ³He supply. We have developed a detector technology based on close-packed arrays of boron-coated straws (BCS) in two configurations: (1) each is 4 mm in diameter and 1 m long, and are packaged in groups of 7 that fit inside a single sealed aluminum tube (1.27 cm in diameter, 1 m long); (2) each is 7.5 mm in diameter and 2 m long, and are packaged in groups of 7 that fit inside a single sealed aluminum tube (2.54 cm in diameter, 2 m long). It thus allows operation of the straw detectors in sealed mode, for indefinite periods of time, and in vacuum environments, as required in neutron scattering instruments. The sealed detector modules form a large area (e.g., 1×1 m², 2×1 m²) neutron imager. Initial testing of the sealed straw detector bundles showed promising results in straw decoding, detector life time, longitudinal resolution, and gas gain stability. The 3D resolution is expected to be 4 mm × 4 mm × 4 mm in configuration #1 and 2.5 cm × 2.5 cm × 2.5 cm in configuration #2, throughout the entire imaging area. Negligible gas gain change was seen over the long test period, in different sealed straw detectors. In addition to facilitating operation in vacuum, another advantageous aspects of the sealed straw detector bundle technique are high portability and structural versatility. Detector modules are easy to transport and detector arrays can be easily installed and tailored to a multitude of different scattering experimental setups. The depth of the detector array can be easily tailored to the desired neutron wavelength and the size and configuration of panels varied of a wide range while utilizing the same elemental modules.