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LINAC18 : 29th Linear Accelerator Conference : September 16-21, 2018, Friendship Hotel, Beijing, China / Pei, Guoxi , Geneva : JACoW Publishing, CERN, Jan 2019,; Geneva : JACoW Publishing, Geneva, Switzerland 982-987 (2019). doi:10.18429/JACOW-LINAC2018-FR1A05, The GSI UNILAC together with SIS18 will serve as injector for the future FAIR. A modified 1.4~MeV/u gas stripper setup has been developed, aiming at an increased yield into the particular desired charge state. The setup delivers short pulses of high gas density in synchronization with the beam pulse. This provides a higher gas density. Different gases as stripping targets were tested. Measurements with various isotopes and gas densities were conducted to investigate the stripping properties. High intensity beams of ²³⁸U⁴⁺ were successfully stripped using hydrogen as stripping gas. The stripping efficiency was significantly increased while the beam quality remained suitable. The new stripper setup and major results achieved during the development are presented. Problems with the fast valves arose while they were used for a longer duration. Another revision of the setup took place to exchange the valves. In parallel, the installation of the required infrastructure for regular operation of the gas stripper using hydrogen was planned., Published by JACoW Publishing, Geneva, Switzerland, Geneva

The UNIversal Linear ACcelerator (UNILAC) at GSI aims at provision of high brilliant ion beams, as it main purpose will be to serve as injector for the upcoming FAIR accelerator complex. The UNILAC injects into the subsequent synchrotron SIS18 applying horizontal multi-turn injection (MTI). Optimization of this process triggered intense theoretical and experimental studies of dynamics of transversely coupled beams. These activities comprise round-to-flat beam transformation, full 4d transverse beam diagnostics, optimization of the MTI parameters through generic algorithms, and extension of Busch's theorem to accelerated particle beams. Finally, recent advance in modeling time-transition-factors and its impact on improved linac performance will be presented as well as progress in the optimization of ion charge state stripping., Proceedings of the 61\textsuperscript{st} ICFA ABDW on High-Intensity and High-Brightness Hadron Beams, HB2018, Daejeon, Korea

The GSI UNILAC in combination with SIS18 will serve as a high-current, heavy-ion injector for the FAIR facility. It must meet high demands in terms of beam brilliance at a low duty factor. As part of an UNILAC upgrade program dedicated to FAIR, a new pulsed gas stripper cell was developed, aiming for increased beam intensities inside the post-stripper. The pulsed gas injection is synchronized with the beam pulse timing, enabling a highly-demanded, increased gas density. First tests using uranium beams on a hydrogen target showed a 60%-increased stripping efficiency into the desired 28+ charge state. In 2015, the setup was improved to be able to deliver increased target thicknesses and enhanced flexibility of the gas injection. In recent beam times, the pulsed gas cell was used with various ion-beam types, to test the capabilities for operation at the GSI UNILAC. The stripping of two ion beams in different gases at different gas densities was successfully tested in mixed-beam operation. Charge fractions, beam emittance, and energy-loss were systematically measured using uranium, bismuth, titanium, and argon beams on hydrogen, helium, and nitrogen targets. Selected results will be presented at the conference., Proceedings of the 28th Linear Accelerator Conf., LINAC2016, East Lansing, MI, USA

The GSI UNILAC in combination with SIS18 will serve as a high-current, heavy-ion injector for the future FAIR. It has to meet high demands in terms of beam brilliance at a low duty factor (100 mus beam pulse length, 2.7 Hz repetition rate). An advanced 1.4 MeV/u gas stripper setup has been developed, aiming at an enhanced yield into the required charge states. The setup delivers short, high-density gas pulses in synchronization with the beam pulse. This provides an increased gas density at a reduced gas load for the differential pumping system. In recent measurements, high-intensity, heavy-ion beams of U⁴⁺ were successfully stripped and separated for the desired charge state. The modified stripper setup, as well as major results, are presented, including a comparison to the present gas stripper based on a N₂ gas-jet. The stripping efficiency into the desired 28⁺ charge state was significantly increased by up to 60 % using a hydrogen stripper target while the beam quality remained similar., Proceedings of the 13th Heavy Ion Accelerator Technology Conference, HIAT2015, Yokohama, Japan

Proceedings of the 7th International Particle Accelerator Conference IPAC2016, IPAC2016, Busan, Korea, 8 May 2016 - 13 May 2016; Geneva : JACoW, 880-882 (2016). doi:10.18429/JACoW-IPAC2016-MOPOY017, In order to meet the requirements on beam parameters for the upcoming FAIR facility at GSI, the injector linac UNILAC will be upgraded. The activities comprise development of the sources for stable provision of intense uranium beams at a repetition rate of 2.7 Hz, a revision of the beam dynamics layout of the 120 keV/u RFQ, the replacement of the matching section to the 1.4 MeV/u pre-stripper DTL, and enhancement of the gaseous stripping section efficiency. This section shall also include a round-to-flat emittance adaptor to prepare the beam for injection into the synchrotron SIS18 which has a flat transverse injection acceptance. Finally, the upgrade includes the complete replacement of the 40 year old 11.4 MeV/u Alvarez-type post-stripper DTL with a new DTL, preferably using Alvarez-type cavities with improved beam focusing features, as well as its rf-power alimentations., Published by JACoW, Geneva

The experimental program of the future facility for Antiproton and Ion Research (FAIR) project requires a high number of cooled anti-protons per hour. The FAIR proton injector linac has to deliver a 70 MeV, 35 mA pulsed proton beam at a repetition rate of 4 Hz. During recent machine investigations at the GSI a high current proton beam was achieved in the Universal Lineral Accelerator (UNILAC). In preparation for this the ion source was equipped with a newly developed 7-hole extraction system and optimized for single charged hydrocarbon beam (isobutane gas) operation. This beam was accelerated to 1.4 MeV/u and cracked in a new pulsed gas stripper into protons and charged carbon. The new stripper setup injects high density gas pulses synchronous with the transit of the beam pulse close to the beam trajectory. With this setup a proton (up to 4.3 mA) as well a carbon beam (up to 9.5 mA) intensity record at beam energy of 1.4 MeV was achieved. The proton beam was accelerated up to 3.6 MeV/u inside the first Alvarez-section with full transmission. The paper will present beam measurement in comparison to the former beam investigations using a 2 mA proton beam in the entire UNILAC., Proceedings of the 7th Int. Particle Accelerator Conf., IPAC2016, Busan, Korea

The GSI UNILAC will serve as part of an injector system for the future FAIR facility, currently under construction in Darmstadt, Germany. For this, it has to deliver short-pulsed, high-current, heavy-ion beams with highest beam quality. An upgrade for the 1.4 MeV/u gas stripper is ongoing to increase the yield of uranium ions in the desired charge state. The new setup features a pulsed gas injection synchronized with the beam pulse transit to increase the effective density of the stripper target while keeping the gas load for the differential pumping system low. Systematic measurements of charge state distributions and energy-loss were conducted with 238U-ion beams and different stripper gases, including H2 and He. By using H2 as a stripper gas, the yield into the most populated charge state was increased by over 50%, compared to the current stripper. Furthermore, the high gas density, enabled by the pulsed injection, results in increased mean charge states., Proceedings of the 7th Int. Particle Accelerator Conf., IPAC2016, Busan, Korea

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^{28+} beams at 1.4 MeV/u has been achieved applying the pulsed high density H_{2} stripper target to a high intensity ^{238}U^{4+} beam from the VARIS ion source with a newly developed extraction system. The experimental results are presented in detail.

As part of an injector system for FAIR, the GSI UNILAC has to meet high demands in terms of beam brilliance at a low duty factor. To accomplish this goal an extensive upgrade program has started. To increase the beam intensity behind the UNILAC, it is aimed to increase the efficiency of the 1.4 MeV/u gas stripper. A modification of the stripper setup was developed to replace the N2-jet with a pulsed gas injection, synchronized with the transit of the beam pulse. The pulsed gas injection lowers the gas load for the differential pumping system, rendering possible the use of other promising gas targets. In recent measurements the performance of the modified setup was tested using an 238U-beam with various stripper media, including H2, He, and N2. The data provide a systematic basis for an improved understanding of slow heavy ions passing through gaseous media. The stripping performance of the current N2-jet was excelled by using H2 at increased gas densities, enabled by the new pulsed gas cell., Proceedings of the 6th Int. Particle Accelerator Conf., IPAC2015, Richmond, VA, USA

Online gas-solid adsorption studies with single atom quantities of Hg, Tl, and Pb on SiO$_{2}$ and Au surfaces were carried out using short-lived radioisotopes with half-lives in the range of 4-49 s. This is a model study to measure adsorption enthalpies of superheavy elements Cn, Nh, and Fl. The short-lived isotopes were produced and separated by the gas-filled recoil separator TASCA at GSI. The products were stopped in He gas, and flushed into gas chromatography columns made of Si detectors whose surfaces were covered by SiO$_{2}$ or Au. The short-lived Tl and Pb were successfully measured by the Si detectors with the SiO$_{2}$ surface at room temperature. On the other hand, the Hg did not adsorb on the SiO$_{2}$ surface, but adsorbed on the Au surface. The results demonstrated that the adsorption properties of short-lived Hg, Tl, and Pb could be studied with this setup, and that this method is applicable to the experiment for Cn, Nh, and Fl., 半減期4$\sim$49秒の短寿命同位体を用いて、水銀(Hg), タリウム(Tl), 鉛(Pb)の単一原子レベルでのSiO$_{2}$及びAu表面への固体吸着挙動をオンライン気相実験により調べた。超重元素Cn, Nh, Flの吸着エンタルピー測定のためのモデル実験として実施した。短寿命同位体はドイツ重イオン研究所の反跳核分離装置TASCAを用いて生成・分離した。生成核はヘリウムガス中に捕集された後、SiO$_{2}$あるいはAuで表面を覆われたSi検出器で作製されたガスクロマトグラフィーカラムへと導入した。短寿命Tl及びPb同位体は室温においてSiO$_{2}$表面に吸着し、Si検出器で測定することに成功した。一方、HgはSiO$_{2}$表面には吸着せず、Au表面に吸着した。この結果より、本実験のセットアップを用いることで短寿命Hg, Tl, Pb同位体の吸着特性を調べることができると証明され、この手法がCn, Nh, Flの実験にも適用できることが確認された。