Atomic Interactions in Supercritical Field: Contribution to the GPAC E129 Experiment at ESR / (SPARC-RO)

Project duration


Nov 2020- Oct 2023 (36 months)

Project description


Prior to this project, our group has been involved in the preparation and implementation of experiments of G-PAC Proposal E129: Photoionization of C+ ions at CRYRING, scheduled for September-October 2019 in collaboration with colleagues from the Helmholtz- Institute Jena & Institute of Applied Physics (HI Jena) and GSI. The new XUV light source (J. Rothhardt et al, PRL 112,233002(2014) will become fulcrum of the new experimental program at CRYRING@ESR (J Rothhardt et. al. Phys. Scr. T166: 014030, 2015). Extreme ultraviolet (XUV) laser sources based on high harmonic generation are a table-top alternative to Synchrotrons and Free-Electron-Lasers. We have contributed to theoretical and experimental preparation of E129 proposal on the following issues: a) the optimization and development of the theoretical and computational methods to study the atomic structure and the interaction of atoms with laser pulses; b) test experiments on a dedicated vacuum coupling unit; c) preparation and implementation of the G-PAC Proposal E129: Photoionization of C+ ions at CRYRING. We believe that our previous achievements are a substantial contribution to the FAIR instrumentation.

With the present project we intend to express our continued interest in the preparation and implementation of the next proposal of experiments "Probing of the ultra-short-lived states in Be-like C at the ESR" submitted for the call on 10th June 2020. The group with INFLPR aims to contribute on the following major objectives:

Objective 1. Ab initio calculation of the lifetime of fine-structure levels of Be-like Carbon ions. Specific activities are focused on: a) ab initio calculation of the fine structure levels in CIII,
b) the autoionization levels and their life time as function of the laser field properties.
In addition, for comparison purposes, two separate relativistic configuration-interaction approaches will be used. We will use Multi-Configuration Dirac Fock approach with and without QED in the General Purpose Relativistic Atomic Structure Package and Multi-Configuration Dirac Hartree-Fock implemented in the framework of GRASP2K code which has been significantly revised and improved in the last decade.

Objective 2. Assisting the preparation and implementation of the proposed experiment at GSI. During the experiment on " Photoionization of C+ ions at CRYRING" last October 2019 a vacuum incident caused the shutdown of CRYRING, thus leading to an early abruption. The open aperture of the differential pumping unit (DPU) guarantees lossless transportation of the generated XUV photons to the interaction region. In the same time the Ar-partial pressure was reduced over 8 orders of magnitude down to the low 10-11 mbar regime. Except for the actual detection of photoionized C2+ the majority of tasks were achieved (M. Tschernajew et al. including A. Stancalie, "Differential pumping unit for windowless coupling of laser beams to ultra high vacuum," Vacuum 178, 109443 (2020). The XUV source and the DPUwill be moved to ESR before the beam time of the proposed experiment. This preparation phase includes tests of the vacuum system and the XUV laser source control system.
Activity 2.1. Preparation and implementation of the setup at ESR. Assisting the test experiments on UHV unit at ESR.
Activity 2.2. Preparation and implementation of the UHV unit plus XUV laser setup at ESR. Assisting the proposed experiments.

Objective 3. Complementary on-line diagnostics including fiber sensors in radiation field. FAIR will host large number of frontier experiments with focusing on providing the infrastructure such as highest intensities of relativistic beams of both stable and unstable heavy nuclei in combination with the strong electromagnetic fields generated by high-power lasers. Working with or near ionizing radiation in such large infrastructure comes as almost a normal condition. We propose to develop as complementary-research, on-line diagnostics in such environment based on fiber sensors. The objective aims to demonstrate the feasibility of monitoring an area, subjected to ionizing radiation field, in such way that the information on how radiation is spatially distributed with respect of the source, is directly available or deduced.
Activity.3.1. Designing fiber sensors based optical system for energy distribution measurements within a charged particle beam.