Monoenergetic positrons and correlated electrons from superheavy nuclear collisions

Thesis/Dissertation · Fri Jan 01 04:00:00 EST 1988

OSTI ID:6092706

Cowan, T E

The origin of the narrow peaks in the energy distribution of positrons produced in superheavy ion-atom collisions has been experimentally investigated using the EPOS spectrometer at GSI Darmstadt. The author systematically studied the dependence of monoenergetic positron emission on the combined charge of the colliding nuclei Z{sub u}, and measured the velocity of the system emitting the peaks by their laboratory Doppler broadening. Motivated by the results of these studies, additional experiments designed to search for monoenergetic electrons emitted in coincidence with the positron peaks were performed. In the first series of measurements, narrow positron peaks between 300 and 400 keV were detected in each of five supercritical (U + Cm, Th + Cm, U + U, Th + U, and Th + Th) and one subcritical (Th + Ta) collision systems studied. The structures were produced with similar cross section ({approximately}10 {mu} b/sr) in quasi-elastic collisions which differed slightly from Rutherford scattering. They cannot be attributed to nuclear conversion processes. The positron peak widths (each {approximately}75 keV) indicate that the emitting source lives for {ge}10{sup {minus}20}s, and has a mean laboratory velocity of {approximately}0.05c, consistent with the center-of-mass velocity. Spontaneous positron emission from the decay of the QED vacuum is unable to explain the independence of the peak energies on Z{sub u}.

• Research Organization: Yale Univ., New Haven, CT (USA)
• OSTI ID: 6092706
• Country of Publication: United States
• Language: English

Related Subjects

652020* -- Nuclear Properties & Reactions
A=220 & above
Experimental
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
ACTINIDES
ATOM COLLISIONS
CHARGED PARTICLE DETECTION
COLLISIONS
CROSS SECTIONS
CURIUM
DETECTION
DOPPLER BROADENING
ELEMENTS
ENERGY RANGE
ION COLLISIONS
ION-ATOM COLLISIONS
KEV RANGE
KEV RANGE 100-1000
LINE BROADENING
MEASURING METHODS
METALS
POSITRON DETECTION
RADIATION DETECTION
THORIUM
TRANSPLUTONIUM ELEMENTS
TRANSURANIUM ELEMENTS
URANIUM