The nuclear physics experimental program at the Area A, high-intensity experimental area, was completely shut down in 1996. A few radiation damage experiments were conducted in Area A following the end of the nuclear physics experiments as part of the Accelerator Production of Tritium project (APT) until 1999. Since that time, Area A has been closed to experimental work.
The demise of the intermediate-energy physics experimental program led to lean funding in the early to middle nineties. New leadership at LAMPF changed the mission and direction of the facility. Thus, the accelerator facility was renamed the Los Alamos Neutron Science Center, and the focus was changed from nuclear physics to neutron scattering experimental work.
In 1996, LANSCE began proton and neutron radiography experiments as part of the stockpile stewardship program. Initial experiments involved fixed objects, but these experiments rapidly transitioned into taking multiple pictures of exploding materials and full hydrodynamic experiments with material thickness greater than 200 gm/cm^2. This methodology is now part of stockpile stewardship weapons verification and will soon become a DOE user program. There is a proposal to build a 50-GeV synchrotron either at LANSCE or the Nevada Test Site to take pictures of dynamic experiments with higher energy, more penetrating, protons. If the new synchrotron facility is built at LANSCE, it will utilize the LANSCE accelerator as the injector to the synchrotron. The methodology for proton radiography was developed over 25 years ago, but was perfected at LANSCE and the Alternating Gradient Synchrotron (AGS) at Brookhaven. LANSCE is currently approved for doing dynamic experiments with up to 10 pounds of high explosives. (Spherical steel vessels are used to contain the explosions.) Dynamic neutron radiography experiments are also completed annually at the Weapons Neutron Research (WNR) Center. The development of the proton and neutron radiography programs prompted DOE's DP division to take over funding most of the LANSCE operation, while DOE ER still funds the Manuel Lujan Jr. Neutron Scattering Center.
LANSCE began developing an ultracold neutron experimental program in the early to middle nineties. The program was successful from the beginning and has continued to provide quality experiments. In 2000, LANSCE set a record for the flux of contained ultracold neutrons. The experiments have been so successful that LANSCE is now designing and building a 10-microamp ultracold neutron target and user facility in the old Line B experimental area. The ultracold neutrons are so slow (<25 m/s) that they are affected by gravity and don't have enough energy to pass over the top of an 8-ft shield wall.
Materials research is also a major part of the current LANSCE mission. LANSCE has completed work to enhance the beam current and intensity at the Manuel Lujan Jr. Neutron Scattering Center. The proton storage ring was reconfigured in 1998 along with the addition of a new buncher cavity. The new configuration, along with the recognition that dark current was responsible for many of the beam instability problems in the proton storage ring, has significantly increased the transmission of beam to the 1 Left (1L) target and, as a result, the neutron beam to the Manuel Lujan Jr. Neutron Scattering Center. The 1L target was also replaced with a new modular target, which can easily be installed and removed as a unit. This target was designed as a two-piece tungsten spallation target. Lead reflectors were located above and below the target, water moderation is located around the target at the top and bottom on three sides, and liquid hydrogen moderation is located beside the top and bottom targets on one side. This configuration has allowed the 1L target to operate with a constant beam current of 100 microamps and is designed to operate at 200 microamps. LANSCE plans to increase the beam current to 200 microamps in coming years. Last year (2001), the 1L target decoupled from the lead reflector and had to be replaced (this year) with a new target utilizing beryllium reflectors.
The Manuel Lujan Jr. Neutron Scattering Center has completed the installation of several new beam lines in the last two years. They are as follows.
This year the Lujan Center will operate 14 different flight paths.
The WNR Center has been very successful at completing a wide range of experiments at a minimal cost. This facility is the only spallation facility in the U.S. that provides unmoderated, high-energy neutrons for experimentation.
In the mid-nineties, a spare Little Boy bomb casing was used as a target at WNR flight path 30 degrees left. The neutron transmission through the casing was measured and used to calculate the neutron source term from the atomic bomb used at Hiroshima. This measurement was then used to calculate field dose measurements to the Hiroshima survivors. This measurement was a factor in the acceptance of the latest estimate of the dosimetry to Japanese atomic bomb survivors.
Also in the mid-nineties, the WNR Center installed the Genie detector on flight path 60 degrees right. Genie has been used to determine the high-energy neutron interaction cross-sections for many different elements and is largely responsible for the data in the new 150-MeV cross-section tables in MCNPX.
Last year, the WNR Center completed the addition of a new experimental area called the Ice House on flight path 30 degrees left. It is designed for use by the electronics industry. Circuit boards and circuit board components are tested for singe-event upsets by a wide variety of electronics circuit board manufacturers each year.
A series of experiments have been completed at the WNR Center 2 right target (Blue Room) to verify the design of the new mercury target for the Spallation Neutron Source (SNS).
Last year, WNR Center completed the first experiments in the U.S. with a eutectic lead/bismuth target in the Blue Room. The WNR Center was also successful in completing experiments to measure the response to beam loss in cryogenic niobium accelerating cavities designed for the APT accelerator and completed a whole series of experimental measurements used to design the APT target.
The Los Alamos National Lab's isotope production group has nearly completed the installation of a new isotope production facility at LANSCE. The new facility is located in a new beam tunnel just downstream of the 100-MeV drift tube linear accelerator (Alvarez Tanks). The facility will use the H+ source to produce 200 microamps of protons. The protons will produce neutrons in a water bath. These will interact with up to three targets and produce medical research isotopes. A hot cell was built above the target area to allow the retrieval of the targets and shipment to another lab facility for processing.
The LANSCE facility successfully designed and operated the 6.7-MeV Low-Energy Demonstration Accelerator (LEDA) for three years. The accelerator consisted of a high-current, 35-keV injector and a 6.35-MeV radiofrequency quadrapole. This accelerator was designed as part of the APT project. The accelerator operates at 100 milliamps and is not only the highest current proton accelerator in the world but is also the only CW proton accelerator. This accelerator is currently on cold standby waiting for additional funding.