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.
One meter square high rate neutron imaging panel based on boron straws
In order to fully realize the enhanced potential of the powerful neutron scattering technique provided by high intensity facilities like SNS, large area high rate detectors must be developed that do not depend upon the dwindling stock of 3He. We have developed a neutron detector that offers a large sensitive area (1 m2), 3D spatial resolution, high sensitivity and high count rate capability, and it is economical and practical to produce. The detector technology is based on 10B thin film conversion of neutrons in long straw-like gas detectors, as a novel and superior replacement of 3He detectors. Twenty-two detector modules, each consisting of 50 straws (1 m long, 4 mm in diameter, natural boron carbide coated), have been constructed and mounted into a robust housing to form a square meter panel detector. Readout electronics including preamplifiers, signal conditioning modules and digitization modules have been designed and tested to meet the required count rate in a 1 m2 detector. We have successfully tested the panel detector, by imaging objects of different materials and different shapes. Additionally, one enriched detector module has been fabricated. The enriched module was integrated into the panel and produced a factor of four enhanced sensitivity in agreement with modeling predictions based on five fold higher 10B content. The neutron imaging detector has achieved the required performance for SNS applications and substantially increases performance compared with 3He while utilizing a cheap and inexhaustible conversion medium.
On the Role of Professional Sports in the National Economy Under the Market Economy Conditions
Through the research of the present situations of the professional sports at home and abroad and its influence on economy, this paper points out the opportunities, challenges and the exist- ing main problems that the professional sports faces in the transitional peried-from plan economy to market economy, then elucidates that the professional sports can becompletely developed and improved and play an important role in the national economy under the market economy conditions.