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Rotating Target Neutron Source-II (RTNS-II) was a materials research facility for nuclear fusion constructed at the Lawrence Livermore National Laboratory in Livermore, California. From 1979 to 1987, its ability to generate high-intensity (14 MeV) neutrons was used by several countries to study the effects of neutron energy on various materials, especially those that could be used in fusion reactors. At the time of its operation, RTNS-II was the most intense source of continuous fast neutrons in the world.

History
Following the success of magnetically containing plasma in the early tokamaks of the Soviet Union and United States in the 1970s, more research was needed to study the effects of potential damage from the intense 14-megavolt neutron radiation produced by a sustained fusion reaction. Previously, LLNL had been experimenting with 14 MeV neutrons at its Insulating Core Transformer facility beginning in 1966 capable of emitting 2 x 1012 14-MeV neutrons per second, later upgraded in 1976 as the Rotating Target Neutron Source, or RTNS-I, to emit 6 x 1012 14-MeV neutrons per second. RTNS-II was built in 1979 to produce a higher flux of 4 x 1013 neutrons per second. In 1982, Japan's Ministry of Education, Culture and Science joined the U.S. Department of Energy as co-supporter of the facility and used it for their own experiments.

Over the facility's history, X-ray diffractometers, electron microscopes and mechanical testing instrumentation were added to further study the effects of neutron-irradiated material. RTNS-II initiated close to 500 irradiations in its history in experiments by nearly 40 laboratories and universities from multiple countries, irradiating tens of thousands of different samples. Although research for the fusion program was the main directive of the facility, many non-fusion related experiments on materials such as glass, electronics, strontium nitrate, and mice were run in tandem with fusion experiments in a "piggyback mode". In 1987, the program was ended and the facility was gradually shut down, cleaned and sealed. The experiments undergone at RTNS-II indicated that the effects experienced in potential fusion reactors were unique from typical fission reactors and allowed for more informed decisions in the future research of nuclear fusion.

Rotating Target Neutron Source-II (RTNS-II) is a national facility for fusion materials research. It contains two 14-MeV neutron sources. Deuterons are accelerated to ~400 keV and transported to a rotating titanium-tritide target. Present source strength is greater than 1 × 10 13 n/s and source diameter is 1 cm FWHM. Recent papers [1,2] describe the present status of the facility and the experiments [3] being conducted there.

Operation
The Rotating Target Neutron Source (RTNS-II) uses a 360-keV deuteron beam and the /sup 3/He(d,n)/sup 4/He reaction to generate 14-MeV neutrons. The neutrons are used for fusion materials damage studies. The tritium target consists of a band of titanium tritide on copper alloy substrates of 23- or 50-cm diameter. During operation, the substrates are internally cooled and rotated at approx. 4000 rpm to withstand beam intensities in excess of 100 mA. Neutron production data have been accumulated for fifty-eight 23-cm and five 50-cm targets. From these data, using a non-linear least-squares fitting procedure, target performance parameters have been obtained which permit a quantitative comparison of individual targets. Average parameters are obtained for the 23- and 50-cm targets.