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Project List » Slow positrons from magnetic bottle

Slow positrons from magnetic bottle
www.eli-np.ro/projects/9-projects.html


Acronym: POSBOT
Contracting Authority: Institutul de Fizica Atomica (IFA)
Number / Date of the contract: 05 / 2020-10-01
PN-III-P5/Subprogramul 5.1
Project Manager: Dr. Nikolay Djourelov
Partners: ICPE-CA
Starting date / finishing date: 2020-10-01 / 2023-09-30
Project value: 999442 RON
Abstract: Compton scattering of laser-light off a high-energy electron beam is a process that will be used within the ELI-NP project for the Gamma Beam System (GBS) to produce low and high energy gamma-beam. Using the gamma beam, it is planned to create fast e+ and moderate them in a converter/moderator assembly (CMA) made of tungsten or platinum. The users who would like to perform experiments using the CMA for production of slow positrons have to compete for beam time of the GBS with other users willing to conduct nuclear physics experiments with the gamma beam. In order to ensure the round year operation of the positron laboratory, it is foreseen to feed the beam lines with e+ obtained from a commercial 22Na source after moderation with solid neon. The project aims at the realization of a functional high-efficiency positron moderation setup and will lead to the establishment a procedure for the production of high activity 48V isotope and for its integration into the magnetic bottle setup. Having this alternative slow positron source with high intensity, users will be able to perform material study experiments with slow positrons on the sample end-stations equipped with CDBS, PALS, and PAES.
The reason for the low efficiency of the standard moderation setups is that those fast positrons which are not thermalized within the moderation layer are wasted. So, if fast positrons can be trapped, they will have the chance to interact with the moderator material more than once to enhance moderation efficiency. The idea to use a thin degrader foil as an energy reducer of fast particles prior to trapping or already confined in a trap is not new. The energy decrease will lead to smaller orbitals inside the trap. These positrons which are moderated and have momentum directed in a narrow cone will escape the trap. The idea has been successfully applied in a cyclotron trap for positrons [Gerchow et al., Instruments 2 (2018) 10, Patent WO2018/069147]. An optimization of the device against the magnetic field, foil thicknesses, geometry, etc. may result in even higher moderation efficiency.
The main objective is to put in operation a source of slow positrons based on high-efficiency moderation in the magnetic bottle setup. In order to achieve this objective, the physical processes like positron confinement in the magnetic field of the trap, the interaction of the fast positrons with the positron source foil and the moderation foil will be simulated. Optimization against obtaining high efficiency of the moderation process of the geometric parameters (chamber sizes, foils size and thickness, etc.) of the setup will be performed as well as evaluation of the necessary radiation protection shield, simulation of the heat generation in the coils for the magnetic shield, and evaluation of the possibility to use high-Tc superconductor for the coils. Weak and strong 48V positron sources will be produced by proton irradiation of 48Ti foil at TR-19. The device will be integrated to the positron beam lines at ELI-NP.

Objectives:
  • The main objective is to build and put in operation a source of slow positrons based on high-efficiency moderation in a magnetic bottle setup
  • The first objective is to simulate the positron confinement in the magnetic field of the trap, the interaction of the fast positrons with the positron source foil and the moderation foil. Optimization against obtaining high efficiency of the moderation process of the geometric parameters (chamber sizes, foils size and thickness, etc.) of the setup. Evaluation of the necessary radiation protection shield. Simulation of the heat generation in the coils for the magnetic shield. Evaluation of the possibility to use high-Tc superconductor for the coils
  • The second objective is to build the magnetic bottle setup. The list includes a vacuum chamber, coils, lead shield, power supplies, and detectors
  • The third objective is to produce 48V positron sources (weak and strong) by proton irradiation of 48Ti foil at TR-19. Obtaining permissions and licenses for its utilization from the Romanian authorities (CNCAN)
  • The last objective is to demonstrate and perform full functional tests of the setup. The setup to be integrated to the positron beam lines at ELI-NP


  • THE STAGES OF THE PROJECT AND DELIVERY DATES
    1. Optimization of the positron moderation device (I)  (2020-12-30)
    2. Optimization of the positron moderation device (II). Manufacture of the positron moderation device (2021-12-31)
    3. Preparatory work and tests with a weak positron source (2022-12-31)
    4. Commissioning of the positron moderation device (2023-09-13)

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