#	Pagina
attuale pagina	/open-h2020/projects/200798/results.html

Report

Teaser, summary, work performed and final results

Periodic Reporting for period 2 - ASTRUm (Astrophysics with Stored Highy Charged Radionuclides)

Teaser

Summary

\"The ASTRUm project aims at performing experiments in laboratory which shall unveil still unknown details of the synthesis of chemical elements in stars.
Such nucleosynthesis processes involve exotic nuclei, that is radioactive nuclei that do normally not exist on Earth and have to be produced artificially.
One of the obvious thoughts is to try to store such exotic nuclei which are produced in tiny quantities only.
The main goal of ASTRUm is to employ stored and cooled radioactive ions for forefront nuclear astrophysics research.
Our experiments are based at the GSI Helmholtz Center for Heavy Ion Research in Darmstadt, Germany, where the worldwide unique combination of accelerator facilities is in operation.
The latter includes the heavy-ion cooler-storage ring ESR coupled to the radioactive-ion beam facility FRS.
By now we were focusing on three main goals.
Within our project we have developed a method to measure charge-particle capture reactions in inverse kinematics on secondary beams.
We have successfully measured the proton capture reaction on stable 124Xe in the center-of-mass energy range from 6 to 8 MeV/u.
The lowest energy is just at the upper end of the Gamow window of the p-process of stellar explosive nucleosynthesis.
This result is a significant step forward to achieve the first measurements on a radioactive beam directly in the Gamow window of the p-process.
The corresponding experiment proposal has been successfully defended at the Program Advisory pannel of GSI and received the highest grade \"\"A\"\" .
The second goal is to measure the bound-state beta decay of fully-stripped 205Tl.
205Tl is stable as neutral atom and is present on Earth.
However, if all bound electrons are removed, an exotic bound-state beta decay becomes energetically possible.
In an ordinary beta-minus decay one of the neutrons in the nucleus is transmuted to a proton with an emission of electron and electron antineutrino.
In the bound-state decay, the electron is not emitted to continuum but occupies one of the free atomic orbitals thus saving the binding energy.
By measuring the bound state beta decay of 205Tl, the constraints on the origin of the matter of our solar system will be made.
Furthermore, neutrino capture cross section on 205Tl to the first excited state in 205Pb will be deduced.
The corresponding experiment proposal has been successfully defended at the Program Advisory pannel of GSI and received the highest grade \"\"A\"\" .
The third goal relates to the development of highly sensitive non-destructive particle detectors for heavy-ion storage rings.
We have constructed the prototype detector and have installed it into the ESR storage ring.
The accelerator facilities of GSI are being presently re-commissioned and we are in stand-by mode waiting for our experiments to be performed.
\"

Work performed

\"From the beginning of the project we concentrated on three goals.
1) Charge-particle capture reactions for p-process nucleosynthesis.
We have measured for the first time the proton capture reaction 124Xe(p,g)125Cs.
The data analysis is finalized and the publication is being prepared.
In this measurement we could reach center-of-mass energy as low as 6 MeV/u which is at the upper end of the Gamow window.
We have prepared and defended a new experimental proposal.
In this new experiment we aim at the first measurements on a radioactive beam directly in the Gamow window of the p-process.
The Program Advisory pannel of GSI has recommended our experiment and ranked it with the highest grade \"\"A\"\" .
2) Bound state beta decay of 205Tl
We have prepared the experiment proposal to measure the bound state beta decay of 205Tl.
It has been recommended by the GSI Program Advisory pannel and received the highest grade \"\"A\"\" .
All necessary equipment for running the experiment has been prepared.
The enriched 206Pb source electrodes for ion sources were manufactured.
3) Highly sensitive non-destructive Schottky detectors
A dedicated work station has been used for thorough detector simulations.
The detector design has been finalized and a prototype detector has been built.
After characterization of the detector on the test bench and vacuum tests, the detector prototype has been installed into the ultra-high vacuum of the ESR storage ring at GSI.

The accelerator facilities of GSI are being presently re-commissioned and we are in stand-by mode waiting for the experiments to be performed.

\"

Final results

\"Within the Project we have measured for the first time the proton capture rate for 124Xe(p,g)125Cs reaction.
In this measurement we reached the center-of-mass energies as low as 6 MeV/u which is the lowest energy at which a nuclear reaction has ever been measured in a storage ring.
The results of this measurement has been compared to simulations thus enabling us to identify main sources of background.
In the planned experiment we shall be able to reach even lower energies.

In the remaining time of the project we aim at accomplishing the two \"\"A\"\" proposals, analyze the data, interpret the results and prepare the corresponding publications.
Dependent on the performance of the new non-destructive detector with real stored particles, we will prepare the new experiment proposal for the GSI Program Advisory panel aiming at mass and lifetime measurements of exotic neutron-rich nuclei.
\"