[en] Periodic beam-transport systems have several advantages including insensitivity to errors, minimum magnet apertures, and use of standardized components. A simple procedure is given for the design of modules, with and without bending magnets, that have the same matched beam properties. These modules can be combined in certain ways to produce systems that are achromatic and require a minimum number of matching elements

[en] PATH is a group of computer programs for simulating charged-particle beam-transport systems. It was developed for evaluating the effects of some aberrations without a time-consuming integration of trajectories through the system. The beam-transport portion of PATH is derived from the well-known program, DECAY TURTLE. PATH contains all features available in DECAY TURTLE (including the input format) plus additional features such as a more flexible random-ray generator, longitudinal phase space, some additional beamline elements, and space-charge routines. One of the programs also provides a simulation of an Alvarez linear accelerator. The programs, originally written for a CDC 7600 computer system, also are available on a VAX-VMS system. All of the programs are interactive with input prompting for ease of use

[en] A review of major achievements in the White Horse Program is provided. Most efforts in FY 82 involved completion of the 2-MeV accelerator test stand culminating in installation of the RFQ, on-line in September 1982. Numerous experiments were conducted, resulting in a significant understanding of beam dynamics and rf structures

[en] The present trend in ion-linac design is to begin with a radio-frequency quadrupole (RFQ) linac followed by one or more drift-tube linac (DTL) tanks in which permanent-magnet quadrupoles are used for transverse focusing. The lack of adjustable elements (knobs) strongly suggests that one should seek linac designs with intertank matching solutions that are insensitive to beam currents and emittances, which can be accomplished if there are no sharp discontinuities in the focusing properties along the entire linac. Guidelines are presented for linac design and describe techniques for longitudinal as well as transverse matching between tanks. For a wide range of beam currents and emittances, a beam matched at the entrance to the RFQ should remain well matched throughout the entire linac

[en] We have designed a linear accelerator to accelerate negative hydrogen ions to 50 MeV with an instantaneous output current of 100 mA and a normalized rms emittance in both transverse planes of 0.02 π cm mrad. The design and results obtained to date with a 2-MeV prototype are presented

[en] The High-Energy Beam Transport (HEBT) system for the Fusion Materials Irradiation Test (FMIT) Facility is to be installed at the Hanford Engineering Development Laboratory (HEDL) at Richland, Washington. The linear accelerator must transport a large emittance, high-current, high-power, continuous-duty deuteron beam with a large energy spread either to a lithium target or a beam stop. A periodic quadrupole and bending-magnet system provides the beam transport and focusing on target with small beam aberrations. A special rf cavity distributes the energy in the beam so that the Bragg Peak is distributed within the lithium target. Operation of the rf control system, the Energy Dispersion Cavity (EDC), and the beam transport magnets is tested on the beam stop during accelerator turn-on. Characterizing the beam will require extensions of beam diagnostic techniques and noninterceptive sensors. Provisions are being made in the facility for suspending the transport system from overhead supports using a cluster system to simplify maintenance and alignment techniques

[en] The authors have designed a linear accelerator to accelerate negative hydrogen ions to 50 MeV with an instantaneous output current of 100 mA and a normalized rms emittance in both transverse planes of 0.02π cm X mrad. The design and results obtained to date with a 2-MeV prototype are presented

[en] The fission cross-section of ²³²U has been measured from a neutron energy of 65 eV to 6 keV with a resolution of approximately 12 ns/m using an underground nuclear explosion as a pulsed neutron source. ²³²U is the only even-even target nucleus with an appreciable low energy fission cross-section and therefore furnishes an opportunity to study the resonance parameters of a fissionable nucleus without the complications introduced by the presence of two spin states. The data have been fitted with a multilevel cross-section formula from 65 to 220 eV. It was necessary to assume the existence of two 1/2⁺ fission channels to fit adequately the valleys between resonances. The average fission width of the 14 resonances between 80 and 150 eV is only 1/4 of the average fission width of the next 14 resonances between 150 and 220 eV. The interference between each of the resonances between 80 and 150 eV was found to be destructive in the dominant fission channel and mostly constructive in the second. Since the interference would be expected to be random, this suggests the presence of one or more resonances with small neutron widths and very large fission widths of 30 eV or more in this region. Such a resonance, which would be nearly invisible in the fission cross-section but would interfere strongly with the neighbouring resonances, can be interpreted as due to a state in the second minimum of the fission potential barrier where the excitation energy is near the second maximum and the coupling between states in the two wells is relatively weak. To test this hypothesis, several sets of mock data were generated assuming a single fission channel and a very wide resonance with a negligible neutron width. It was possible to fit the mock data without including a wide resonance if a second fission channel was introduced. The resulting parameters display interference properties and small apparent widths similar to those obtained from the ²³²U analysis. Based on these results, we interpret the small fission widths, two fission channels, and apparent correlation in interference between resonances obtained in the ²³²U fit as probably spurious, being due to the fact that one or more wide levels have been missed. (author)

[en] PATH is a group of computer programs for simulating charged-particle beam-transport systems. It was developed for evaluating the effects of some aberrations without a time-consuming integration of trajectories through the system. The beam-transport portion of PATH is derived from the well-known program, DECAY TURTLE. PATH contains all features available in DECAY TURTLE (including the input format) plus additional features such as a more flexible random-ray generator, longitudinal phase space, some additional beamline elements, and space-charge routines. One of the programs also provides a simulation of an Alvarez linear accelerator. The programs, originally written for a CDC 7600 computer system, also are available on a VAX-VMS system. All of the programs are interactive with input prompting for ease of use

[en] Analysis of four small-scale photographs of Comet West taken on 5--8 March 1976 offers evidence of five discrete bursts of dust from the comet's nucleus between 19 and 28 February, i.e., from six days before perihelion to three days after it. The images of the comet on the photographs were computer-enhanced to increase the contrast of the fine structure. The timing of two of the bursts suggests very strongly that they accompanied the two breakup events that gave birth to the companion nuclei D and B. The primary breakup, on 19 February, also coincides with a 2-magnitude surge in the comet's brightness. Some of the other dust bursts might be correlated with less conspicous flare-ups observed in both the visual brightness and the thermal emission of the comet. A distinct intensity discontinuity makes up the trailing boundary of the main body of the dust tail. When the observed position of the discontinuity is corrected for an effect of particle-expulsion velocity, it is found to correspond to dust expelled from the comet exactly at perihelion. It is suggested that because of its timing, the intensity discontinuity could be a product of particle evaporation sharply peaked at perihelion