Topic（题目）：IsoDAR: A Neutrino Experiment that Radically Advances Cyclotron Technology
Speaker（报告人）：Dr. Jose R. Alonso
Laboratory for Nuclear Science, MIT
Date（时间）：2019年8月30号（周五）上午9:00
Place（地点）：北京大学加速器楼202室
Contact Person（联系人）：彭士香（sxpeng@pku.edu.cn）
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Abstract（摘要）：
IsoDAR (Isotope Decay-At-Rest) is a highly-sensitive search for sterile neutrinos. Seemingly anomalous results from several neutrino experiments (eg. LSND, MiniBooNE) can be reconciled by the existence of a fourth (or more) neutrino(s) with a Delta m^2 in the range of 1-10 eV^2 above the three Standard Model (SM) neutrinos. Oscillation between such states and the SM states gives a signal that oscillates with a wavelength of a few meters [1]. Placing an electron antineutrino source close to a large (hydrogen-containing) detector allows detection (via inverse-beta-decay) of several oscillation periods as a function of depth in the medium, virtually eliminating systematic errors from the measurements. The isoDAR experiment delivers 10 mA of 60 MeV protons to a beryllium target, producing neutrons that flood a sleeve surrounding the target of a highly-enriched Li-7 and beryllium powder mixture. The neutron capture of Li-7 produces Li-8 which decays in less than 1 second releasing a high-energy electron anti-neutrino (13.5 MeV end-point energy). This neutrino source will be placed about 4 meters from the surface of the KamLAND detector (1 kiloton liquid scintillator) in the Kamioka Observatory in Japan [2].
The 10 mA of protons are generated by a compact cyclotron accelerating H2+ (5 mA) to 60 MeV/amu. This current, a factor of 10 higher than existing (H-) cyclotrons, is enabled by the choice of ion, and by a novel injection scheme using an RFQ as a buncher. This talk will explore the techniques that will be employed to achieve this extracted current level. Though septum extraction is the principal means of extracting the beam, stripping foils can be used to better advantage than with H- ions. [3]
We have observed that this cyclotron can offer huge advantages for medical isotope production, particularly for long-lived isotopes (e.g. the Ge^68/Ga^68 generator — parent halflife 270 days), or for low cross section isotopes such as producing Ac^225 from natural thorium. An additional intriguing possibility is that this q/A = 0.5 cyclotron can easily accelerate He++ or C6+ ions, opening up interesting new avenues for isotope production.
[1] A Bungau et al “Proposal for an Electron Antineutrino Disappearance Search Using High-Rate Li^8 Production and Decay” arXiv:1205.4419; Phys. Rev. Lett. 109, 141802 (2012).
[2] M Abs et al, “IsoDAR@KamLAND: A Conceptual Design Report for the Technical Facility”, arXiv:1511.05130 (2015).
[3] JR Alonso, R Barlow, JM Conrad, LH Waites, “Isotope Production from the IsoDAR Cyclotron” arXiv:1807.06627 (2019); Nature Reviews/Physics 10.1038/s42254-019-0095-6 (August-2019).
Biography（个人简介）：
- MIT,
PhD Nuclear Physics, 1967
- Lawrence Berkeley National Laboratory
Co-discoverer of Element 106 (Sg), 1974
Director of Bevalac 1982-1989
First relativistic heavy ion beams
First cancer patient treatments with ion beams
- Oak Ridge National Laboratory
Senior Management team for construction of SNS 1995-1999
- Sanford Underground Laboratory, Lead, South Dakota
Laboratory Director 2007-2009
- MIT
Conrad neutrino group 2010-present
