Weapons Neutron Research Facility Research Articles

Magnetic moments of low-energy neutron resonances in 161Dy

A low-energy neutron beam and polarized 161Dy target at the Weapons Neutron Research Facility in Los Alamos have been used to determine magnetic moments of 7 neutron resonances. The ferromagnetic dyspromium metal was cooled by a 3He– 4He dilution refrigerator to 35 mK. With a time-of-flight setup the total cross section was measured at temperatures of 4 K and 35 mK. The magnetic moments are derived from the shift of the resonance energy. Results obtained with a random orientation of the ferromagnetic domains agree well with a previous experiment. The target was also magnetized in a field of 6 T. In this case, the degree of nuclear polarization could be derived from the change of the resonance shape.

The WNR/PSR facility - neutron physics capabilities from sub-thermal to 800 mev

The Weapons Neutron Research facility (WNR) is a versatile pulsed neutron source used in a variety of research programs ranging from fundamental neutron properties with ultra cold neutrons to medium energy charge exchange reaction studies. Here we describe the WNR facility and the improvements presently in progress as the Proton Storage Ring (PSR) becomes operational. 14 refs., 11 figs.

Los Alamos Neutron Source Meets First Test

26 April was a day for celebrating at the Los Alamos National Laboratory as jubilant researchers stored a beam in the Proton Storage Ring (PSR) on the very first attempt. The PSR is a $22-million addition to the Weapons Neutron Research (WNR) facility whose effect will be to convert the WNR into a world-class pulsed source for neutron scattering on a par with the British Spallation Neutron Source that recently entered the commissioning phase at the Rutherford Appleton Laboratory (l). The combined WNR/PSR facility will be dedicated this August as the Los Alamos Neutron Scattering Center (LANSCE). However, two important provisos to be satisfied before researchers can tap the intense neutron beam the WNR/PSR will provide are the construction of an experimental hall sufficiently large to house research instrumentation and the development of the instrumentation itself. Now set at $17.5 million, funding for this purpose has never made it into the presidential budget.

Dynamic Data Structures and Concurrency in a Real-Time Data Acquisition System

We report on our efforts in developing an innovative real-time data acquisition system that makes extensive use of dynamic data structures, concurrency and state machine features. The Data Acquisition Command Language developed at the Los Alamos Weapons Neutron Research (WNR) Facility is a Pascal-based system that incorporates these features to maximize system performance, reliability and adaptability while supporting a consistent, familiar and comfortable user interface. The details and benefits of the implementation philosophy and underlying structures are discussed.

A Development Methodology for Scientific Software

We present the details of a software development methodology that addresses all phases of the software life cycle, yet is well suited for application by small projects with limited resources. The methodology has been developed at the Los Alamos Weapons Neutron Research (WNR) Facility and was utilized during the recent development of the WNR Data Acquisition Command Language. The methodology emphasizes the development and maintenance of comprehensive documentation for all software components. The impact of the methodology upon software quality and programmer productivity is assessed.

FASTBUS Data Acquisition System for Neutron Time-of-Flight Measurements

The design of a new data acquisition system for the Weapons Neutron Research Facility is based on the FASTBUS system hosted by DEC computers. System and FASTBUS configurations are discussed. Modules unique to pulsed time-of-fliqht measurements are presented.

Configuration for the WNR Data Acquisition System for Neutron Measurements

The configuration for a new data acquisition system for the Weapons Neutron Research Facility at the Los Alamos National Laboratory is introduced. The system utilizes a FASTBUS front-end for real-time data collection and DEC computers for the experiment control and analysis. A local area network is used extensively within the overall system.

A Data Acquisition Command Interface Using VAX/VMS DCL

The user interface to a data acquisition system is being developed at the Los Alamos Weapons Neutron Research Facility using the VAX/VMS command language interface DCL. Commands are being implemented which provide for system initialization and control functions and FASTBUS diagnostics. The data acquisition system incorporates the concept of a data acquisition "state" (running, halted, etc.) where a certain subset of input commands is allowed.

Multiple-Independent Detector System

The Weapons Neutron Research (WNR) facility has several neutron diffraction and scattering instruments which use arrays of 3He-filled proportional counters to detect thermal and epithermal neutrons and to measure time of flight. A Multiple-Independent Detector System (MIDS) has been developed with emphasis on high speed, low cost, modularity, and simplicity. Dead time for one detector channel is 400 ns, and system throughput may be 6 MHz. Cost is $200 per detector, including amplifiers, multiplexers, and time analysis. Modules include individual shaping preamps for each detector, a 32-channel discriminator/multiplexer, a family of second-level multiplexers incorporating line drivers, an 8-bit optoisolated latch, and a time-of-flight clock which concatenates time and detector information and interfaces through CAMAC to a data-acquisition system. Four systems are now in operation, with 25 to 100 detectors each.