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

Technical Report · Mon Apr 01 04:00:00 EST 1991

DOI:https://doi.org/10.2172/5592089· OSTI ID:5592089

Justice, M L

This thesis describes a measurement of the heavy-ion induced electromagnetic dissociation of a 120 MeV/A {sup 238}U beam incident on five targets: {sup 9}Be, {sup 27}Al, {sup nat}Cu, {sup nat}Ag, and {sup nat}U. 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 {Delta}E-E detectors, allowing the changes of the fragments to be determined to within {plus minus} .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 Lab., CA (United States)
• Sponsoring Organization: DOE; USDOE, Washington, DC (United States)
• DOE Contract Number: AC03-76SF00098
• OSTI ID: 5592089
• Report Number(s): LBL-31704; ON: DE92008313
• Country of Publication: United States
• Language: English

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73 NUCLEAR PHYSICS AND RADIATION PHYSICS
ACTINIDES
ALUMINIUM 27 TARGET
BASIC INTERACTIONS
BERYLLIUM 9 TARGET
CALIBRATION
CHARGED-PARTICLE REACTIONS
COPPER
CROSS SECTIONS
DISSOCIATION
ELECTROMAGNETIC INTERACTIONS
ELEMENTS
HEAVY ION REACTIONS
INTERACTIONS
MEASURING INSTRUMENTS
METALS
MONTE CARLO METHOD
NUCLEAR REACTIONS
PLASTIC SCINTILLATION DETECTORS
RADIATION DETECTORS
SCINTILLATION COUNTERS
SILVER
SOLID SCINTILLATION DETECTORS
TARGETS
TRANSITION ELEMENTS
URANIUM
URANIUM 238 REACTIONS