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Research Highlight

First Science Result from the JENSA gas jet target

JENSA gas jet target system and first science result
The target chamber of the JENSA gas jet target system is shown in the inset, where the 20Ne gas flows from the nozzle to the receiver, and proton beam particles (green) undergo a nuclear reaction with the 20Ne nuclei in the gas to form deutrons (yellow) which are detected in the silicon strip detectors (SSD) and heavier 19Ne nuclei (blue) which are measured in another detector. The energy spectrum of the deuterons is shown in the bottom plot, and the critical level is shown highlighted in red. An angular distribution of those deuterons from the critical level are shown in the inset, experimentally determining the properties of this level.

Measuring the yield of radioactive decays of 18F nuclei that are produced in nova explosions and ejected into space can help diagnose the mechanism of these violent outbursts, making this a priority of billion-dollar gamma-ray astronomy observatories.  A possible excited quantum mechanical level in the nucleus 19Ne  below the threshold of the 18F + p --> 15O + alpha reaction has contributed a large uncertainty in the total amount of 18F synthesized in a nova. The new Jet Experiments in Nuclear Structure and Astrophysics (JENSA) gas jet target system enabled an unambiguous confirmation of this subthreshold resonance and determined its properties via a measurement of the 20Ne + p --> 19Ne + d reaction. The success of the measurement is due to the high density (equivalent to some solid targets), small width (few mm), and ultra-high purity of the target. This measurement resulted in a reduction of the uncertainty of the thermonuclear rate of the 18F + p --> 15O + alpha reaction by factor of approximately 3 at nova temperatures. This gives a corresponding factor of 2 reduction in uncertainty of nova 18F production in novae, and a corresponding factor of 2.8 decrease in the uncertainty of nova 18F detection probability by satellite observatories. For more details, see the publication in Physics Letters B: The first science result with the JENSA gas-jet target: Confirmation and study of a strong subthreshold 18F(p,帢)15O resonance