Abstract
To meet the Facility for Antiproton and Ion Research science requirements higher beam intensity has to be achieved in the present GSI-accelerator complex. For this an advanced upgrade program for the UNILAC is ongoing. Stripping is a key technology for all heavy ion accelerators. For this an extensive research and development program was carried out to optimize for high brilliance heavy ion operation. After upgrade of the supersonic ${\mathrm{N}}_{2}$-gas jet (2007), implementation of high current foil stripping (2011) and preliminary investigation of ${\mathrm{H}}_{2}$-gas jet operation (2012), recently (2014) a new ${\mathrm{H}}_{2}$-gas cell using a pulsed gas regime synchronized with arrival of the beam pulse has been developed. An obviously enhanced stripper gas density as well as a simultaneously reduced gas load for the pumping system result in an increased stripping efficiency, while the beam emittance remains the same. A new record intensity (7.8 emA) for ${^{238}\mathrm{U}}^{28+}$ beams at $1.4\text{ }\text{ }\mathrm{MeV}/\mathrm{u}$ has been achieved applying the pulsed high density ${\mathrm{H}}_{2}$ stripper target to a high intensity ${^{238}\mathrm{U}}^{4+}$ beam from the VARIS ion source with a newly developed extraction system. The experimental results are presented in detail.
Highlights
Stripping is a key technology for all heavy ion accelerators. For this an extensive research and development program was carried out to optimize for high brilliance heavy ion operation
Meeting the science requirements of the Facility for Antiproton and Ion Research (FAIR) [1] higher beam intensities has to be achieved in the present GSI-accelerator complex, through faster cycling and, for heavy ions, lower charge state which enters quadratically into the space charge limit (SCL)
The gas stripper section [4] provides for a higher charge state; during standard operation an U28þ beam is matched to the Alvarez DTL
Summary
Meeting the science requirements of the Facility for Antiproton and Ion Research (FAIR) [1] higher beam intensities has to be achieved in the present GSI-accelerator complex, through faster cycling and, for heavy ions, lower charge state which enters quadratically into the space charge limit (SCL). The desired energy of up to 1.5 GeV=u for radioactive beam production will be delivered by the synchrotron SIS100. GSI put effort in increasing the uranium beam intensities delivered to the SIS18. For uranium (FAIR reference ion) the UNILAC has to deliver 3.3 × 1011 U28þ particles per 100 μs (see Table I) [2]. Transfer line (TK) to the SIS18 provides optionally for foil stripping and another charge separating system
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