Neutron to proton ratios of quasiprojectile and midrapidity emission in the 64^{64}Zn + 64^{64}Zn reaction at 45 MeV/nucleon

Simultaneous measurement of both neutrons and charged particles emitted in the reaction $^{64}$Zn + $^{64}$Zn at 45 MeV/nucleon allows comparison of the neutron to proton ratio at midrapidity with that at projectile rapidity. The evolution of N/Z in both rapidity regimes with increasing centrality is examined. For the completely re-constructed midrapidity material one finds that the neutron-to-proton ratio is above that of the overall $^{64}$Zn + $^{64}$Zn system. In contrast, the re-constructed ratio for the quasiprojectile is below that of the overall system. This difference provides the most complete evidence to date of neutron enrichment of midrapidity nuclear matter at the expense of the quasiprojectile

Resolving multiple particles in a highly segmented silicon array

The design, construction, and performance of a new highly segmented charged particle detector array, FIRST, are described. This forward angle annular array (2°≤θlab≤28°) has been developed to study peripheral and mid-central heavy-ion collisions at intermediate energies (E/A≈50MeV). FIRST consists of three individual telescopes that each utilize ion-passivated silicon detectors in either a Si(IP)-Si(IP)-CsI(Tl) stack or a Si(IP)-CsI(Tl) stack. This array provides elemental identification for 1≤Z≤50 with isotopic identification of lighter elements, Z≤13, over a wide dynamic range in energy. The high segmentation of each silicon detector provides good angular resolution in a compact geometry and allows deconvolution of multiple particles incident on a single telescope. The performance of the array in a commissioning experiment Zn64+Zn64,Bi209 at E/A=45MeV is shown. © 2005 Elsevier B.V