Electromagnetic dissociation of ²³⁸U in heavy-ion collisions at 120 MeV/A

Thesis/Dissertation · Mon Apr 01 00:00:00 EST 1991

DOI:https://doi.org/10.2172/10124791· OSTI ID:10124791

Justice, Marvin Lealon ^[1]

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1. Univ. of California, Berkeley, CA (United States)

This thesis describes a measurement of the heavy-ion induced electromagnetic dissociation of a 120 MeV/A ²³⁸U beam incident on five targets: ⁹Be, ²⁷Al, ^natCu, ^natAg, and ^natU. Electromagnetic dissociation at this beam energy is essentially a two step process involving the excitation of a giant resonance followed by particle decay. At 120 MeV/A there is predicted to be a significant contribution of the giant quadrupole resonance to the EMD cross sections. The specific exit channel which was looked at was projectile fission. The two fission fragments were detected in coincidence by an array of solid-state ΔE-E detectors, allowing the changes of the fragments to be determined to within ± .5 units. The events were sorted on the basis of the sums of the fragments` charges, acceptance corrections were applied, and total cross sections for the most peripheral events were determined. Electromagnetic fission at the beam energy of this experiment always leads to a true charge sum of 92. Due to the imperfect resolution of the detectors, charge sums of 91 and 93 were included in order to account for all of the electromagnetic fission events. The experimentally observed cross sections are due to nuclear interaction processes as well as electromagnetic processes. Under the conditions of this experiment, the cross sections for the beryllium target are almost entirely due to nuclear processes. The nuclear cross sections for the other four targets were determined by extrapolation from the beryllium data using a geometrical scaling model. After subtraction of the nuclear cross sections, the resulting electromagnetic cross sections are compared to theoretical calculations based on the equivalent photon approximation. Systematic uncertainties are discussed and suggestions for improving the experiment are given.

• Research Organization: Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), High Energy Physics (HEP)
• DOE Contract Number: AC03-76SF00098
• OSTI ID: 10124791
• Report Number(s): LBL-31704; ON: DE92008313
• Resource Relation: Other Information: TH: Thesis (Ph.D.); PBD: Apr 1991
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
URANIUM 238 REACTIONS
ELECTROMAGNETIC INTERACTIONS
BERYLLIUM 9 TARGET
ALUMINIUM 27 TARGET
COPPER
SILVER
URANIUM
DISSOCIATION
CROSS SECTIONS
CALIBRATION
MONTE CARLO METHOD
PLASTIC SCINTILLATION DETECTORS
663450
663520
663530
663590
663560
663550
HEAVY-ION-INDUCED REACTIONS AND SCATTERING
A = 6-19
A = 20-38
A = 220 AND ABOVE
A = 90-149
A = 59-89