M. L. Stelts

A versatile data acquisition system and the ISOL facility TRISTAN

Abstract The on-line mass separator, TRISTAN, is located at Brookhavens High Flux Beam Reactor. A Nielsen-type ion source, which can contain up to 8g of 235 U in an external beam with a flux of ∼2 × 10 9 n/cm 2 /s is used to generate short-lived fission products. Experiments have been constructed on two of the five available beam lines to measure β-γ and γ-γ coincidences, γ-γ angular correlations and delayed neutron emissions. A Users Group has been formed to coordinate research between University groups and BNL. Developments planned for TRISTAN include FEBIAD, surface ionization and negative-surface ionization-type ion sources, and a He-jet system as well as construction of new experimental facilities. An off-line separator, ISTU, is available for the development program. We have constructed a versatile, modular data acquisition system to service experiments on TRISTAN and other nuclear research facilities at the HFBR using CAMAC interfacing. Standard, commercially-available electronic instruments and computer programs, such as FORTRAN and system routines, are used throughout. Simple interfaces have been built to adapt non-CAMAC equipment to CAMAC input registers. Up to eight different experiments can be multiplexed on the branch highway by a fast microprogrammed branch driver with a 4096 word memory. The branch driver delivers pre-processed data to a bus which links devices such as a central processor, 1 megaword core memory, tape drives, discs, display processor and terminal. The following features are offered: two 8192 channel pulse height analyzers, a 3-parameter coincidence unit, 4 multiscalers, a timed sequence of delayed γ-ray spectra (33 spectra of 4096 channels each), a 2-parameter (pulse height versus time-of-flight) analyzer, 16 scalers and 24 experimental interlocks. Up to 100 different spectra are available to users for display during an experiment. Event mode recording on magnetic tape and direct sorting into the 1 megaword array are used as appropriate. A master program, almost entirely written in FORTRAN, allows users to control and monitor each experiment with simple mnemonic codes. Analysis of the data is carried out on a companion computer devoted to data processing, allowing rapid sorting, plotting, listing and analysis of data.

A Four-detector System For γ - γ Angular Correlation Studies

Abstract A multiple detector system for γ - γ coincidence and angular correlation measurements is described. The system consists of four large coaxial Ge detectors set at fixed positions, enabling the measurement of γ - γ coincidences between any pair. Thus, six distinct angles are measured simultaneously. The performance of the system was studied with a 152 Eu source. An application for γ - γ correlation studies in 146 Ce is described. Systematic errors, if present, are shown to be less than 0.03 and 0.05 for A 2 and A 4 , respectively. The extension of this system to more than four detectors is straightforward.

Rotational-vibrational band structure in 155Sm

Abstract The nuclear structure of 155Sm has been studied via primary and secondary γ-rays and by internal conversion electrons following thermal neutron capture. Furthermore average resonance neutron capture spectra for various neutron energy ranges were recorded. A detailed level scheme with a complete set of levels with spin 7 2 has been well established up to 1400 keV excitation energy. The neutron binding energy has been determined to be 5807.2(3) keV. The scheme is interpreted in a basis of Coriolis and ΔN = 2 coupled Nilsson states and compared with the less deformed Sm isotopes. A possible additional band coupling via the octupole vibrational mode is discussed.

Multiple-User Data Acquisition and Analysis System

The nuclear physics program at the Brookhaven National Laboratory High Flux Beam Reactor (HFBR) employs a pair of PDP-11 computers for the dual functions of data acquisition and analysis. The data acquisition is accomplished through CAMAC and features a microprogrammed branch driver to accommodate various experimental inputs. The acquisition computer performs the functions of multi-channel analyzers, multiscaling and time-sequenced multichannel analyzers and gamma-ray coincidence analyzers. The data analysis computer is available for rapid processing of data tapes written by the acquisition computer. The ability to accommodate many users is facilitated by separating the data acquisition and analysis functions, and allowing each user to tailor the analysis to the specific requirements of his own experiment. The system is to be upgraded soon by the introduction of a dual port disk to allow a data base to be available to each computer.

Capture of 2 and 24 keV Neutrons by the Zirconium Isotopes

The Zr isotopes were studied with the capture of 2- and 24-keV neutrons from the Brookhaven High Flux Reactor tailored beam facility. The binding energies of /sup 91/, /sup 92/ /sup 94/Zr were measured. The intensities of the primary ..gamma..-ray intensities for /sup 91/ /sup 92/ /sup 94/Zr are given and compared with previous experimental evidence. 9 references.