About Weapons Neutron Research Facility at LANSCE
Neutron and Nuclear Science
The Weapons Neutron Research (WNR) Facility consists of a high-energy "white" neutron source (Target 4) with six flight paths, three low-energy nuclear science flight paths at the Lujan Center (Target 1), and a proton reaction area (Target 2). The neutron beams produced at the WNR Target 4 complement those produced at the Lujan Center because they are of much higher energy and have shorter pulse widths. The neutron sources are driven by the 800-MeV proton beam of the LANSCE linear accelerator (or LINAC).
Neutron beams with energies ranging from approximately 0.1 MeV to greater than 600 MeV are produced in Target 4. The neutron production target at Target 4 is a bare unmoderated tungsten cylinder that is bombarded by the 800-MeV pulsed proton beam from the LANSCE linear accelerator and produces neutrons via spallation reactions. Because the proton beam is pulsed, the energy of the neutrons can be determined by time-of-flight (TOF) techniques. The time structure of the proton beam can be easily changed to optimize a particular experiment. Presently, Target 4 operates with a proton beam current of approximately 1.5 μA, 1.8 sec between pulses and approximately 14,000 pulses/sec. Target 4 is the most intense high-energy neutron source in the world and has six flight paths instrumented for a variety of measurements.With the completion of planned accelerator radio-frequency generator upgrades, the beam current to Target 4 will be increased by a factor of 2.5 to provide beam currents up to 5 μA.
In the Target 2 area (Blue Room) samples can be exposed to the 800-MeV proton beam directly from the linac, or beam that has been compressed in time from the Proton Storage Ring (PSR). Although the total beam current is limited by the shielding in Target 2, the PSR beam provides significantly more peak intensity than the direct beam from the accelerator. Target 2 is used for proton irradiations and hosts the high-flux Lead Slowing-Down Spectrometer (LSDS). For lower energy proton experiments, proton beams with energies as low as 200 MeV have been transported to Target 2.
At present there are four flight paths at the Lujan Center that are devoted to nuclear science research. Three flight paths are devoted to materials science and are supported by the NNSA. These flight paths view a moderated target and have neutron energies that range from sub-thermal to approximately 500 keV.
With these facilities, LANSCE is able to deliver neutrons with energies ranging from small fractions of an electron volt to several hundreds of MeV as well as a proton beam with a wide range of time and intensity characteristics.