U28+-intensity record applying aH2

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 N 2 -gas jet (2007), implementation of high current foil stripping (2011) and preliminary investigation of H 2 -gas jet operation (2012), recently (2014) a new 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 U 28þ beams at 1.4 MeV=u has been achieved applying the pulsed high density H 2 stripper target to a high intensity 238 U 4þ beam from the VARIS ion source with a newly developed extraction system. The experimental results are presented in detail.

Strong asymmetry of the electron-loss-to-continuum cusp of multielectronU28+projectiles in near-relativistic collisions with gaseous targets

“…(iv) The relatively large change in the mass-to-charge ratio when ionizing to U 29+ or recombining to U 27+ made it impossible to detect the charge-exchanged projectiles by the available particle detectors installed in the dispersive sections of the ESR, such that no coincidence measurement of the ionized projectile with the emitted electron was possible in the applied experimental configuration. (v) Due to the low projectile velocity and the low charge state, the signal induced in the beam current transformer is relatively weak, such that only a significant increase of the beam intensity for U 28+ ions provided by the UNILAC [42] and SIS18 within the last few years enabled a reliable determination of the ion beam intensity in the ESR.…”

Measurements of charge state distributions of 0.74 and 1.4 MeV/u heavy ions passing through dilute gases

“…However, the behavior of the beam emittance for ion beams passing the pulsed gas stripper cell is not discussed here. Previous works have already reported on this [16,19].…”

“…1) in horizontal (left) and vertical (right) plane. The desired charge peak is selected by adjusting the width of the slit, as indicated in panel (a) [16].…”

“…Their use was strongly limited before due to the high gas load of the jet-based gas injection [15]. In recent measurement campaigns applying the new setup, charge state distributions of 238 U, 209 Bi, 50 Ti, and 40 Ar ion beams after passing through different gas targets, including H 2 and He, were measured at two different beam energies (0.74 MeV=u and 1.4 MeV=u) [15][16][17][18][19].…”

High brilliance uranium beams for the GSI FAIR

“…The U 4þ -beam current and brilliance was improved by applying a multiaperture extraction system [6] at the VARIS ion source [2]. VARIS is a new generation of vacuum arctype ion source.…”