[Triumf-seminars] TRIUMF ISAC Seminar today at 10:00

postmaster at admin.triumf.ca postmaster at admin.triumf.ca
Tue Jul 13 05:00:03 PDT 2010


Date/Time: Tue 2010-07-13 at 10:00

Location:  ISAC-II Video Rm 223

Speaker:   Philip Voss (NSCL, Michigan State University)

Title:     Recoil Distance Method Lifetime Measurements Via Gamma-Ray and Charged Particle Spectroscopy at NSCL

Abstract: At extreme isospin, exotic collective structures have been predicted to arise from the de-coupling of deformed proton and neutron distributions. Several years ago, the reported anomalously small reduced quadrupole transition strength, B(E2; 2+1-> 0+1 ), in 16C sparked interest in such decoupling phenomena in the neutron-rich carbon isotopic chain. Recoil Distance Method (RDM) lifetime measurements, from which the B(E2) is directly obtained, provide an important probe of the nuclear charge deformation and are complementary to hadron inelastic scattering probes for nuclear matter deformations. To shed light on the shape evolution in the even-even N = 10-14 carbon isotopes, RDM lifetime measurements were carried out at National Superconducting Cyclotron Laboratory (NSCL) through the coupling of the Segmented Germanium Array, the Digital Data Acquisition System, and the Köln/NSCL Plunger. By monitoring the Doppler shifted de-excitation gamma rays as a function of plunger target-degrader distance, the lifetimes of the the 2+1-> 0+1 transitions, and thus the B(E2) values, for 16,18,20C were extracted. The data, analysis, and results of the measurement for 18C will be presented in detail.

Additionally, the Köln/NSCL Plunger has been adapted for charged particle spectroscopy by replacing the velocity degrader with a silicon energy loss detector. This particle plunger provides a new fast beam probe for the study of exotic proton-decay isotopes with picosecond lifetimes along the proton drip line. Lifetime information in this region, especially near rp-process waiting point nuclei, is important for characterizing nucleosynthesis pathways. A recent proof of principle experiment at NSCL utilized this method in a lifetime study of the two-proton emitter 19Mg. The method and preliminary results for the commissioning particle plunger investigation will be discussed.



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