Figure 1

Particle spectra recorded in the focal plane detector for: (a) all events from the low-gain spectra anti-coincident with the MWPC and punch-through detectors; (b) all $\alpha$-like events initiating a beam shutoff; (c) all $\alpha$-like events occurring during the beam off and correlated within $3\sigma$ and 240 s to the $\alpha$-like event initiating shutoff; (d) all $\alpha$-like events occurring during the beam off that were not correlated within $3\sigma$ and 240 s to the $\alpha$-like event initiating beam shutoff. The peaks at 7.4 and 6.7 MeV are due to ${}^{250}\mathrm{Fm}$ and ${}^{246}\mathrm{Cf}$ $\alpha$-particles that are correlated to earlier beam shutoff events. The peak at 8.1 is due to ${}^{254}\mathrm{No}$ $\alpha$-decays that are preceded by ${}^{258}\mathrm{Db}$ $\alpha$-decays in which the $\alpha$-particle escaped the front of the detector and imparted only a portion of its energy, thus not triggering a beam shutoff. These decays are long-lived enough to be recorded in subsequent beam shutoffs due to the high rate of Db-like events.Reuse & Permissions

Figure 2

$1n$ and $2n$ excitation functions for the ${}^{208}\mathrm{Pb}({}^{51}\mathrm{V},\mathit{xn}){}^{259\text{−}x}\mathrm{Db}$ reactions. Horizontal error bars represent the range of beam energies inside the target. Vertical error bars are uncertainties due to counting statistics. Downward arrows are upper limit cross sections calculated at the $1\sigma$ level. The lines are fits to the data using the procedure described in Sec. 3d and [22, 23].Reuse & Permissions

Figure 3

Excitation functions for the ${}^{209}\mathrm{Bi}({}^{50}\mathrm{Ti},n){}^{258}\mathrm{Db}$ reaction as measured by LBNL (this work) and GSI [12, 25]. A partial excitation function measured at LBNL for the $2n$ exit channel is also included. Horizontal error bars represent the range of beam energies inside the target. Vertical error bars are uncertainties due to counting statistics. Downward pointing arrows are upper limit cross sections calculated at the $1\sigma$ level. The lines are a Gaussian smoothly joined up to an exponential on the high energy side best fitting the 1n data using the procedure described in Sec. 3d and [22, 23].Reuse & Permissions

Figure 4

Comparison of the $1n$ excitation functions for the ${}^{208}\mathrm{Pb}({}^{51}\mathrm{V},n)$ and ${}^{209}\mathrm{Bi}({}^{50}\mathrm{Ti},n)$ reactions. Horizontal error bars represent the range of beam energies inside the target. Vertical error bars are uncertainties due to counting statistics. Downward pointing arrows are upper limit cross sections calculated at the $1\sigma$ level. The solid lines are Gaussians smoothly joined to exponentials on the high energy side using the procedure described in Sec. 3d and [22, 23]. The lines are ${\sigma }_{\mathrm{cap}}\times {10}^{-4}$ for the ${}^{208}\mathrm{Pb}({}^{51}\mathrm{V},n)$ (dashed) and ${}^{209}\mathrm{Bi}({}^{50}\mathrm{Ti},n)$ (dotted) reactions.Reuse & Permissions

Figure 5

Comparison of the $2n$ excitation functions for the ${}^{208}\mathrm{Pb}$(${}^{51}\mathrm{V}$,2$n)$ (this work) and ${}^{209}\mathrm{Bi}({}^{50}\mathrm{Ti},2n)$ [12, 25] reactions. Horizontal error bars represent the range of beam energies inside the target. Vertical error bars are uncertainties due to counting statistics. Downward pointing arrows are upper limit cross sections calculated at the 1$\sigma$ level. The solid lines are fits to the data using the procedure described in Sec. 3d and [22, 23]. The broken lines are ${\sigma }_{\mathrm{cap}}\times {10}^{-4}$ for the ${}^{208}\mathrm{Pb}({}^{51}\mathrm{V},n)$ (dashed) and ${}^{209}\mathrm{Bi}({}^{50}\mathrm{Ti},n)$ (dotted) reactions.Reuse & Permissions