Beam analyzing system for a variable energy cyclotron

Hintz, R.E.; Selph, F.; Flood, W. S.; Harvey, Brian; Resmini, F.; McClatchie, E.A.

doi:10.1016/0029-554x(69)90266-3

Cited by 27 publications

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“…The total width r, and hence r a , is less than 1 MeV, which is at least a factor of 20 smaller than that cor re- sponding to an a-particle reduced width equal to the Wigner limit. Hence, unless some other parentages (e.g., 6 Li+d) are unexpectedly large, 9 the /-wave nucleon reduced widths for this state are not as small as suggested, 3 but the nucleon partial widths are small because of the small /-wave penetration factors. The broad 4 + resonance near E a = 51.3 MeV corresponds to a new level in 8 Be near 25.6 MeV excitation.…”

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confidence: 84%

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Observation of High-Lying Levels inBe8fromα−αElastic Scattering

et al. 1972

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The elastic scattering of a particles from 4 He has been measured in the energy range between 30 and 70 MeV. A phase-shift analysis was used to investigate the even-spin, positive-parity levels in 8 Be in the region between 15 and 35 MeV of excitation. New 0 + and 4 + levels have been located near 20.3 and 25.6 MeV, respectively. The positions of five 2 + levels and an additional 4 + level are compared with previous work and with theoretical predictions based on the intermediate-coupling shell model.Below an excitation energy of 16 MeV, the level structure of 8 Be is well understood 1,2 in terms of states predominantly of a two-a-particle configuration. Above 16 MeV the level structure rapidly becomes more complex as other configurations for these states (e.g., />+ 7 Li, «+ 7 Be, and d + 6 Li) become important. Those states of 8 Be which have both even spin and parity can decay into the 2a channel, and this selectivity is extremely useful in identifying levels of 8 Be that lie above the 7 Li+£ threshold. Although multilevel R-and S-matrix analyses of 7 Li(p, o?) 4 He 3 and 6 Li(tf, a) 4 He 4 data have provided some level assignments between excitation energies of 19 and 26 MeV in 8 Be, these assignments are not unique. However, any state with a significant aparticle width will appear as a resonance in a-a elastic scattering, which permits immediate assignment of spin and parity from a determination of the resonant partial wave. Earlier studies of the elastic scattering provided some information on 8 Be states above 16 MeV 5 ; however, it was clear that more detailed measurements were required in order to remove ambiguities in the phase-shift analysis. We report here new results which are already apparent from a phase-shift analysis of more extensive elastic scattering measurements.The present measurements were performed with a-particle beams from the Berkeley 88-in. cyclotron using a beam-analysis system 6 which provided a high-resolution beam (AE/E-0.02%) of accurately known 7 energy (±0.03%). Measurements were taken at about 100 energies between 30 and 70 MeV (spanning a region of excitation in 8 Be between 15 and 35 MeV). An array of seven detectors was used to obtain cross sections at 21 center-of-mass angles between 16° and 96°. The 4 He gas target with a thin (7500 A) nickel entrance foil was operated at a pressure of 0.1 atm. The relative errors are typically less than ±2%, while the absolute normalization of the cross section is accurate to better than 4%.A standard x 2 minimization search routine was employed to determine phase shifts including I = 8 at the higher energies. A small Z = 6 phase shift («2°) was required at the lowest energies. Continuity of the phase shifts as a function of energy was required for an acceptable solution. This criterion was particularly useful in regions where the level structure was most complex, e.g., near E a = 40MeV, where three resonances overlap. Numerous attempts to locate alternate solutions were unsuccessful. Phase shifts corresponding to the only acceptable soluti...

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confidence: 84%

“…Above 16 MeV the level structure rapidly becomes more complex as other configurations for these states (e.g., />+ 7 Li, «+ 7 Be, and d + 6 Li) become important. Those states of 8 Be which have both even spin and parity can decay into the 2a channel, and this selectivity is extremely useful in identifying levels of 8 Be that lie above the 7 Li+£ threshold.…”

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confidence: 98%

Observation of High-Lying Levels inBe8fromα−αElastic Scattering

et al. 1972

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“…An analysing slit selects a small part of the beam to be transmitted with the required energy spread. The system developed at the Berkeley 88 inch cyclotron by B G Harvey's group (Hintz et al 1969) is shown in figure 36. The beam from the cyclotron is defined first at an entrance slit of width 0.5-2 mm, depending on the resolution required.…”

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confidence: 99%

Accelerators for nuclear physics

Clark¹

1972

Rep. Prog. Phys.

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This article describes the principal charged particle accelerators being used today for research in nuclear physics in the energy range up to about 1000 MeV. The accelerators include Van de Graaffs, sector cyclotrons and linear accelerators for both positive ions and electrons. For each type of accelerator a brief treatment is given of the recent history, operating principles, some special techniques, a typical facility, and some examples of experimental data from that type of accelerator. Descriptions are also given of new types of machines under construction, such as Pelletrons, frequency modulated sector cyclotrons, separated sector cyclotrons, and superconducting linear accelerators. New ideas for the future are mentioned, including multi-stage tandem-cyclotrons, and the electron ring accelerator. The reader is assumed to have no experience in. accelerators or nuclear physics, and many references are given to more detailed treatments of the topics covered.

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General instrumentation

England¹

1974

Techniques in Nuclear Structure Physics

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Beam analyzing system for a variable energy cyclotron

Cited by 27 publications

References 3 publications

Observation of High-Lying Levels inBe8fromα−αElastic Scattering

Observation of High-Lying Levels inBe8fromα−αElastic Scattering

Accelerators for nuclear physics

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