Matt Kern

Hope College

Dr. DeYoung and Dr. Peaslee (Nuclear Group)

Supported by the NSF

In this experiment we wished to study the emission of pre-equilibrium light charged particles (LCPs) from a highly fissile system. The system that was used was a krypton beam, both at 35 MeV/A and 60 MeV/A, with both gold and thorium targets. With these masses and their corresponding energies, the fissile system was at the point where binary fission becomes less frequent and multi-fragmentation starts to take over. At this point, there is an issue regarding the energy required to multi-fragment, and where it goes when only binary fission occures. We proposed that the energy is released in the emission of LCPs before equilibrium is attained. A study of fission fragments in coincidence with LCPs would give us an idea of whether or not this is true. In order to study this, a sophisticated array of detectors was required. We used the 4pi Ball at Michigan State Universitys National Superconducting Cyclotron Laboratory to gain the desired information. The 4pi Ball consists of 30 "ball detectors" covering nearly all of 4pi space, and a set of 45 smaller, more condensed detectors nearly in line with the beam and target, known as the forward array. Over the course of a few days, the data was collected and stored on tapes. Using a data analysis program called Lisa, we could manipulate the data to obtain the information that was desired. When large fission fragments coinciding with LCPs were detected in a ball detector, corresponding fragments were "searched for" on the opposite side of the ball. These two points and the collision point itself defined the plane of the reaction. We then looked at LCPs in the forward array, both in the plane and out of the plane. Analyses of these spectra would give an indication of whether or not these LCPs were truly pre-equilibrium. If significantly more energy was deposited in-plane than out of plane, we could then conclude that the excess energy was emitted through these pre-equilibrium LCPs. For further proof of our results, we would employ the use of modeling programs such as Modgan.