Andelkovic, Z.

Fedotova, S.

Herfurth, F.

Kotovskiy, N.

Maaß, B.

Steinmann, J.

Vorobjev, G.

GSI Repository

Development of the HITRAP experimental facilityZ. Andelkovic1, S. Fedotova1, F. Herfurth1, N. Kotovskiy1, B. Maaß2, J. Steinmann3, and G. Vorobjev11GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt; 2TU Darmstadt; 3Hochschule DarmstadtHeavy few-electron ions are relatively simple systems interms of electron structure which offer unique opportuni-ties to conduct experiments under extremely large electro-magnetic fields that exist around their cores. This makesthem perfectly suited for various experiments including,but not limited to, tests of quantum electrodynamics at thestrong field limit, multiple electron transfer or interactionof highly charged ions (HCI) with surfaces. In the recentdecades the theory has advanced enough to be able to cal-culate quantities such as the g-factor of bound electrons orelectron energy levels with high precision. Thus, the majorchallenge for such kind of experiments has remained thepreparation of such highly charged ions.As an extension of the existing GSI accelerator facility,the heavy ion trap (HITRAP) facility was conceived as thefinal deceleration stage for HCI. It is designed to providecold bunches of up to 105 ions with charge states as highas bare uranium. The HITRAP decelerator consists of sev-eral stages designed to bring the energy of HCI from theinitial 4 MeV per nucleon stepwise down into the sub-eVrange. After the successful offline tests of the modifiedradio-frequency quadrupole (RFQ) - the second decelera-tion stage - it was installed back into the main beamlineand equipped with diaphragms at the ion input and output.They will ensure ion beam injection on axis of the 4-rodstructure, which was found to be crucial for the decelera-tion efficiency during the offline tests.The final deceleration stage - the cooling trap - has seensome modifications for better high voltage stability andsuppression of unwanted electron emission processes. Af-ter successful trapping of HCI from the EBIT in the yearbefore, the ongoing work at the moment is to prepare thetrap for the ions at 6 keV/u decelerated from the RFQ. Adetailed simulation study of the resistive cooling processis carried out at the same time [1]. Together with elec-tron cooling, this method will reduce the ion energy to thesub-eV level and prepare a cold bunch of heavy HCI fordistribution to different experiments.The HITRAP facility on the experimental platform in-cluded so far a Dresden EBIT and a transfer beamline con-necting it to the cooling trap. In 2013 the branch connectingthe EBIT and the HITRAP decelerator with various exper-iments has been completed, thus extending the low-energybeamline by some 15 m, as shown in the figure below. Thenew section includes nine quadrupole doublets, two 90◦deflectors, four diagnostics chambers and an appropriatenumber of UHV pumps for reaching a residual gas pressureof 10−10 mbar. Ion bunches, including highly charged O,Xe and Ar ions have been successfully transported alongthe full beamline length. This result enables the plannedlaser spectroscopy experiments in the SpecTrap Penningtrap [2], and also paves the way for other experiments asso-ciated with HITRAP, like the measurements of the bound-electron g-factor [3] and study of multiple electron transferin cold atom-HCI collisions [4].As an addition to the Dresden EBIT, plans and prepara-tions were made for an installation of the high-energy S-EBIT [5]. Consigned to GSI as a loan from the HelmholtzInstitut Jena, it currently being installed on the HITRAPexperimental platform and connected with the existing in-frastructure. This accelerator-independent source of heavy,highly charged ions will help bridge the shutdown timeof the GSI accelerator complex during the preparation forFAIR and supply heavy HCI to the experimental stations.References[1] J. Steinmann, J. Groß, F. Herfurth, G. Zwicknagel, GSI Sci-entific Report 2013[2] T. Murböck, et al. GSI Scientific Report 2013[3] D. von Lindenfels, et al.: Phys. Rev. A 87, 023412 (2013)[4] S. Götz, et al.: Rev. Sci. Instrum. 83, 073112 (2012)[5] S. Trotsenko, et al. GSI Scientific Report 2013GSI SCIENTIFIC REPORT 2013 PNI-AP-18doi:10.15120/GR-2014-1-PNI-AP-18 FAIR@GSI 175

Development of the HITRAP experimental facility

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Development of the HITRAP experimental facility

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