Texas A&M International University, Laredo, Texas
Dr. DeYoung and Dr. Peaslee (Nuclear Group)
Supported by the NSF-REU
I. PREFACE In 1992, an experiment was conducted by Hope College researchers, in which 84Krypton was reacted with 197Gold at 35 MeV per nucleon, 55 MeV/A, 70 MeV/A at Michigan State University. The experiment consisted of several runs but RUN 38 is currently being investigated for measuring nuclear temperatures from exploding nuclei. As the Krypton ion beam was reacted with the stationary gold film, light-charged fragmented particles were detected using the Miniball and Miniwall detector system. The light-charged particles identified were protons, deuterons, tritons, 3helium, and 4helium. The size of the Miniball is roughly four(4) feet in diameter. The purpose of detecting all the possible fragmented particles is to analyze the energy of the system. The multiplicity(number of particles detected) tells us how much energy is created in each collision between target and projectiles. The magnitude of energy that is produced from the collision gives us an idea of the kinds of temperatures that exist in the system. Some reactions will give out a higher multiplicity, thus having higher energy, therefore a higher temperature, and vice versa. The temperature can also vary by the type of collision the nuclei underwent. Central/head-on collisions (which are rare) call for higher temperatures than peripheral/off-center collisions (common type of collisions). Collisions that are off-center only fragment a portion of the nucleus. The purpose of conducing these kinds of studies (nuclear temperatures) is to observe whether the Caloric Curve (similar to Van der Waals Curve) is a credible prediction of the nuclear transition phases from solid, to liquid, to gas.
II. LAST YEAR - Summer '97 The Miniball is made up of a series of rings of detectors from which was choosen the ring that could be best analyzed. A ring holds a certain number of detectors at one angle (theta) with respect to the beam. The goal for the summer of 1997 was to measure temperature at one theta only. Data had to be sorted to probe a temperature in that ring. Ring 3' was chosen, which consisted of 28 detectors; and a temperature was measured at that angle (27°), in which the ring is located with respect to the beam, using an isotopic yield temperature equation.
III. NEW GOAL - Summer '98 The goal for this summer (1998) was to calculate two (2) more measurements of nuclear temperatures in exploding nuclei. We wanted to know if nuclear temperature is distributed equally or if more energy exists in certain parts of the system. We would like to prove the validity in equal i.m.f. (intermediate mass fragments) distribution that other scientists have claimed in past experiments. This will help us get a clear understanding of the direction of the majority of particles are being emitted with respect to the beam. Since one ring, Ring 3', had already been analyzed , two (2) different other rings were chosen. Again, the rings that were chosen were those with particles well defined in the spectra. The rings selected were: Miniball Ring 5 (from detectors 73-96), and Miniwall Ring 5 (from detectors 225-247). Programs were created: to identify the particles emitted, to get a multiplicity, and to define gates around every particle. Then, another batch of programs were created to join all the programs together. A set of about eight programs were created for every detector in every ring. Programs and data from Ring 3' were edited to increase accuracy. Using our isotopic yield temperature equation, two magnitudes of temperatures were measured.
IV. CONCLUSION The conclusion for Summer '97 was that a measurement for nuclear temperatures can be probed using isotopic yield ratios of the particles emitted. The multiplicity of the four l.c.p.s (4he, 3he, deuterons, and tritons) were fitted into an isotopic yield temperature equation for the measurement of the temperature in that ring. The measurement of the temperature was 5.5 MeV. Yet the uncertainty remained as to whether that temperature was universal in the system (meaning if the same number of particles were detected in all the other detectors) or if the temperature differs in certain areas of the system. One conclusion that was derived was that we can use the MINIBALL experiments to measure nuclear temperatures. At these bombarding energies (70 MeV/A), there may be a temperature dependence on detection angle. This year the temperature measured in Miniball Ring 5 was 6.6 MeV and 5.1 in Miniwall Ring 5. If there is a dependence on detection angle, the interpretation of the caloric curve will have to be modified for nuclear matter.