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Project List » Laser-plasma triggered release of the 2.4 MeV isomer in 93mMo using the 1 PW system at ELI-NP

Laser-plasma triggered release of the 2.4 MeV isomer in 93mMo using the 1 PW system at ELI-NP

Acronym: LTR93Mo
Contracting Authority: Institutul de Fizica Atomica (IFA)
Number / Date of the contract: ELI-12 / 2020-10-01
PN-III-P5/Subprogramul 5.1
Project Manager: Dr. Klaus Michael Spohr
Partners: University of Bucharest
Starting date / finishing date: 2020-10-01 / 2023-09-30
Project value: 1000000 RON
Abstract: We propose the use of the 1 PW laser beam-line to investigate the PRODUCTION and TRIGGERED release of the long-lived (T(1/2)=6.85 h) nuclear isomer 93m-Mo at the high energy of 2.425 MeV to investigate a pathway for storage of energy densities in the nuclear regime with isomers (Nuclear Battery). The isomer is the ideal candidate for this investigation, as its triggered decay via the short-lived (T(1/2)=3.52 ns) state situated only 4.85 keV (2.430 MeV) above 93m-Mo resulting in a 500-fold energy amplification has already been observed by Chiara et al. ([1]=[Nature 554.7691, 216 (2018)]) and assigned to the NEEC process (Nuclear Excitations by Electron Capture). The production of the isomer will proceed with laser-induced MeV protons pulses (2 MeV < E(p) < 15 MeV), facilitating the reaction 93-Nb(p,n)93m-Mo. In this first experiment (Tier A) the production irradiation will last up to 6 hrs to maximize the total number of proton shots and hence the isomer's yield Y(93m-Mo). To achieve a triggered release of 93m-Mo via the intermediate state at 2.430 MeV, the in-situ produced isomers will be subsequently exposed for ~3 hrs to high fluxes of keV X-rays (photon-induced de-excitation, 'Tier B' ) or keV electrons for testing NEEC induced de-excitation ('Tier C'). To benchmark Y(93m-Mo), a 'spy' reaction 45-Sc(p,n)-45Ti, resulting in β+ decaying 45-Ti, is used. Its yield, Y(45-Ti), is not influenced by resonant X-ray absorption nor NEEC. After irradiation, the mixed 93-Nb/45-Sc target will be measured off-line with a high-resolution gamma detector, allowing the comparison between Y(93m-Mo) and Y(45-Sc) by measuring the intensities of the associated decay radiation, represented by a characteristic gamma cascade for 93m-Mo (263-685-1478 keV) and the 511 keV annihilation line related to the decay of 45-Sc. Our proposal is supported by the theory work of the Max Planck Institute of Theoretical Nuclear Physics in Heidelberg, who already performed some theoretical groundwork. The scientific discussion about the interpretation in the framework of the NEEC mechanism is ongoing ([2]=[Wu et al., PRL 122.21 (2019)]). The proof of controlled production and decay, resulting in a 500-fold energy amplification, will significantly impact further research into the 'Nuclear Battery' concept. Moreover, confirmation of the NEEC will establish ELI-NP as an innovative acceleration system the 'triple' interface of nuclear, laser plasma, and atomic physics.




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