  We report on the development of the HEC2 (High Energy Compression and
Current) charge breeder, a possible high performance successor to REXEBIS at
ISOLDE. The new breeder would match the performance of the HIE-ISOLDE linac
upgrade and make full use of the possible installation of a storage ring at
ISOLDE (the TSR@ISOLDE initiative [1]). Dictated by ion beam acceptance and
capacity requirements, the breeder features a 2-3.5 A electron beam. In many
cases very high charge states, including bare ions up to Z=70 and Li/Na-like up
to Z=92 could be requested for experiments in the storage ring, therefore,
electron beam energies up to 150 keV are required. The electron-beam current
density needed for producing ions with such high charge states at an injection
rate into TSR of 0.5-1 Hz is between 10 and 20 kA/cm2, which agrees with the
current density needed to produce A/q<4.5 ions for the HIE-ISOLDE linac with a
maximum repetition rate of 100 Hz. The first operation of a prototype electron
gun with a pulsed electron beam of 1.5 A and 30 keV was demonstrated in a joint
experiment with BNL [2]. In addition, we report on further development aiming
to achieve CW operation of an electron beam having a geometrical transverse
ion-acceptance matching the injection of 1+ ions (11.5 {\mu}m), and an
emittance/energy spread of the extracted ion beam matching the downstream mass
separator and RFQ (0.08 {\mu}m normalized / +/- 1% ).
