Projectile fragmentation of radioactive beams of ${}^{68}\mathrm{Ni}$, ${}^{69}\mathrm{Cu}$, and ${}^{72}\mathrm{Zn}$

The fragment production cross sections of secondary neutron-rich beams of ${}^{68}\mathrm{Ni}$, ${}^{69}\mathrm{Cu}$, and ${}^{72}\mathrm{Zn}$ isotopes at energies of about $95A$ MeV have been measured. We compare the measured cross sections to EPAX, an empirical parametrization of fragmentation cross sections. A reasonable agreement of the experimental data and EPAX predictions suggests that an EPAX parametrization used for stable beams seems to be valid for unstable neutron-rich ion beams. EPAX tends to overestimate the yields of neutron-rich isotopes. This problem is amplified when neutron-rich radioactive beams are employed, leading to overly optimistic estimates of the production of neutron-rich isotopes.

Figure 1

Schematic of the A1900 [12] and S800 [13] spectrometers.

Figure 2

(Top) Secondary beam particle identification from the two-dimensional spectrum of energy loss in a plastic detector versus $\mathit{ToF}$. (Bottom) Projection onto the $\mathit{ToF}$ axis.

Figure 3

Particle identification spectrum obtained in the ${}^{72}\mathrm{Zn}+{}^9\mathrm{Be}$ reaction. In this representation, the $\Delta E$ and $\mathit{ToF}$ signals have been calibrated and converted to $Z$ and $N-Z$.

Figure 4

Momentum distributions for fragments ${}^{47}\mathrm{Ca}$, ${}^{54}\mathrm{V}$, and ${}^{62}\mathrm{Co}$ produced in fragmentation of ${}^{72}\mathrm{Zn}$ on a ${}^9\mathrm{Be}$ target. The solid curves represent Gaussian fits.

Figure 5

Dispersive angular distributions at the target position for ${}^{44}\mathrm{Ca}$ and ${}^{59}\mathrm{Co}$ fragments from the ${}^{64}\mathrm{Ni}+{}^9\mathrm{Be}$ reactions at $93.7A$ MeV, measured at the S800 spectrograph using an inverse map calculation (see text).

Figure 6

Cross sections plotted as a function of neutron excess, $N-Z$, for the fragmentation reaction of ${}^{64}\mathrm{Ni}$ at $93.7A$ MeV, on a beryllium target (solid circles) in comparison with data from ${}^{64}\mathrm{Ni}+{}^9\mathrm{Be}$ reactions at $140A$ MeV (open circles) [5].

Figure 7

Isotope distributions for Ca–Ni elements detected in reaction with a ${}^{68}\mathrm{Ni}$ beam at $94.3A$ MeV. Experimental fragmentation data are shown as filled squares (complete momentum distribution measurement) and open squares (incomplete momentum distribution measurement). EPAX predictions are shown as solid lines.

Figure 8

Isotope distributions for Ar–Cu elements detected in reaction with a ${}^{69}\mathrm{Cu}$ beam at $98.1A$ MeV. We use the same symbol conventions as in Fig. 7.

Figure 9

Isotope distributions for K–Zn elements detected in reaction with a ${}^{72}\mathrm{Zn}$ beam at 95.4 $A$ MeV. We use the same symbol conventions as in Fig. 7.

Figure 10

Isotope distributions from the fragmentation of $140\text{−}A$ MeV ${}^{58,64}\mathrm{Ni}$ [5, 7] (solid and open squares) and $94.3\text{−}A$ MeV ${}^{68}\mathrm{Ni}$ (solid circles) with a beryllium target. Lines are drawn to guide the eye.