  A low-energy, compact and superconducting electron beam ion trap (the
Shanghai-Wuhan EBIT or SW-EBIT) for extraction of highly charged ions is
presented. The magnetic field in the central drift tube of the SW-EBIT is
approximately 0.21 T produced by a pair of high-temperature superconducting
coils. The electron-beam energy of the SW-EBIT is in the range of 30-4000 eV,
and the maximum electron-beam current is up to 9 mA. Acting as a source of
highly charged ions, the ion-beam optics for extraction is integrated,
including an ion extractor and an einzel lens. A Wien filter is then used to
measure the charge-state distribution of the extracted ions. In this work, the
tungsten ions below the charge state of 15 have been produced, extracted, and
analyzed. The charge-state distributions and spectra in the range of 530-580 nm
of tungsten ions have been measured simultaneously with the electron-beam
energy of 279 eV and 300 eV, which preliminarily indicates that the 549.9 nm
line comes from $W^{14+}$.
