12 2020.26
Nuclear Astrophysics JUNA inauguration
<p>Inauguration and development of the Jinping Underground Laboratory for Nuclear Astrophysics (JUNA) in year 2020 is summarized. </p> <p>The centerpiece of the JUNA project is an accelerator capable of delivering a 10mA H and He beams at 50-800 keV. The combination of high current and a deep underground location maximizes the signal/background ratio, enabling measurements at low energy where counting rates are severely suppressed by Coulomb barriers. Ideally nuclear reactions important to astrophysics should be measured in the Gamow peak, the window of energies relevant to nucleosynthesis in stars. Although reactions can in principle be measured at higher energies and extrapolated to threshold, the theoretical uncertainties associated with such extrapolations can be both large and difficult to quantify.</p> <p>JUNA has the potential to be a world-leading facility. JUNA’s current will exceed by about an order of magnitude that available with the present 400 kV LUNA accelerator. JUNA’s accelerator is developed and tested above ground. The collaboration finished to move the accelerator underground in Oct. 2020. The coordination with Jinping laboratory development is potentially quite attractive, as hall developments can continue over the next year while development and testing finished by 1st quarter of 2021. In Dec. 26, 2020, JUNA accelerator delivered proton beam with intensity of 2.1 mA with beam energy of 270 keV. Underground experiments started from Dec. 27 and the commissioning of JUNA NSFC program scheduled in the end of 2021.</p> <p>JUNA team followed the CJPL management to support this plan, providing required space, services (cooling/power, etc.) and safety rules. The collaboration is working in parallel on other important tasks, including the measurement and continued monitoring of backgrounds within CJPL, developing detector and laboratory shielding designs (with particular attention to mitigating neutrons induced by the accelerator), developing an array of gamma ray, and neutron detectors, and developing a target design capable of dissipating the power from a 10 mA beam.</p> <img src="/static/img/news/20201226-2.jpg"></img> <img src="/static/img/news/20201226-3.jpg"></img> <p>The collaboration’s experimental program, including above-ground measurements of the 19F(p,α)16O reaction recently obtained from the JUNA 400kV platform as well as the 320kV platform In Lanzhou, all those calibrate and test the JUNA setup well. JUNA goals include studies of 12C(α,γ)16O, which controls the carbon- and oxygen-shell structure of supernova progenitors; 13C(α,n)16O, an important neutron source for s-process nucleosynthesis; 25Mg(p, γ)26Al, with the daughter isotope an important galactic gamma-ray source that traces recent nucleosynthesis; and 19F(p, γ)16O, important in understanding the nucleosynthetic origin of 19F.</p> <p>The JUNA Collaboration has an outstanding International Advisory Committee, chaired by Michael Wiescher and including leading experimentalists from Japan, the US, and Europe. The Collaboration includes a few leading theorists who can evaluate the impact of new measurements through state-of-the-art stellar evolution simulations, another example of the group’s foresight.</p> <p>Status updates in Nov. 2020: accelerator vacuum tested, detector start to test on site, the de-humidifier is being installed, beam test will started from end of Nov. 2020. </p> <p>For increasing JUNA’s visibility would be to host a workshop in 2021, near the end of NIC conference, when JUNA underground program get first batch of experimental result. JUNA plan is now very timely in 2020, given JUNA’s schedule, taking into account the CJPL-II construction, but progress is under control, by the end of 2020 accelerator underground tuning was successful , an on site beam on ceremony is finished in December 26, 2020. Fig. 1 shows the current status of JUNA in hall A1 in Nov. 2020, CJPL-II. Fig. 2 shows the high energy ground level test results by using JUNA setup in early 2020. Fig. 3 shows the the moment of beam on during the inauguration ceremony in CPJL-II A1 hall, where on the screen the light from 2.1 mA proton beam can be clearly seen. </p> <img src="/static/img/news/20201226-4.jpg"></img>
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