High brilliance beam investigations at the universal linear accelerator

The more than 45-year-old GSI-UNILAC (universal linear accelerator) as well as the heavy ion synchrotron SIS18 will serve as a high-current heavy ion injector for the new Facility for Antiproton and Ion Research (FAIR) synchrotron SIS100. UNILAC will serve together with the SIS18 as FAIR injector for short intense pulse operation; the newly developed heavy ion linac Helmholtz linear accelerator shall deliver cw beams, still required for the comprehensive research program at GSI. In the context of an advanced machine investigation program in combination with the ongoing UNILAC upgrade program, a dedicated beam investigation campaign has been carried out in order to characterize front-to-end high-current medium and heavy ion beam behavior at GSI-UNILAC. A very high beam brilliance at the end of transfer line from UNILAC to SIS18 was achieved recently for medium heavy ion beams in a machine experiment campaign. This is an important step paving the way to fulfill the FAIR heavy ion high-intensity beam requirements. Results of high-current uranium beam measurements applying the novel technique of pulsed hydrogen gas stripping (at $1.4\mathrm{MeV}/\mathrm{u}$) will be presented as well.

Figure 1

GSI-UNILAC; the slit-grid-emittance measuring devices are shown in blue. 1, LEBT/UH1; 2, gas stripper section or US4; 3, poststripper or UA4; 4, transfer line or TK5; 5, transfer line or TK8.

Figure 2

Uranium beam intensities along the HSI from 2014 to 2021.

Figure 3

Measured normalized beam transmission at HSI for Xe, Ta, and Ar beams as a function of norm. RFQ voltage, RFQ working point is set to norm. $\text{RFQ voltage}=1$.

Figure 4

Beam brilliance analysis for a ${{}^{238}\mathrm{U}}^{28+}$ beam on a ${\mathrm{N}}_2$- or a ${\mathrm{H}}_2$-stripper target.

Figure 5

Beam emittance measurements behind carbon foil stripping and charge separation of high-intensity U beam at $11.4\mathrm{MeV}/\mathrm{u}$ in the transfer line to SIS18.

Figure 6

High-intensity ${}^{209}\mathrm{Bi}$-beam emittance and current measurement along UNILAC and transfer line to SIS18.

Figure 7

Evaluation of high-intensity ${}^{209}\mathrm{Bi}$-beam emittance measurements corresponding to Fig. 6.

Figure 8

High-intensity uranium-beam emittance and current measurement along UNILAC.

Figure 9

Evaluation of measured high-intensity uranium-beam emittance corresponding to Fig. 8.

Figure 10

High-intensity ${}^{40}\mathrm{Ar}$-beam emittance and current measurements along UNILAC and TK.

Figure 11

Evaluation of high-intensity ${}^{40}\mathrm{Ar}$-beam emittance measurements corresponding to Fig. 10.

Figure 12

${\mathrm{Ar}}^{10+}$- (fractional) beam brilliance analysis based on beam emittance and corresponding beam intensity measurements at the end of the transfer line (TK8) to the SIS18; FAIR requirement ($\mathrm{A}/\mathrm{Z}=4$; $\mathrm{I}=7\mathrm{emA}$, horizontal $\text{emittance}=1\mathrm{mm}\times \mathrm{mrad}$).