IsoDAR (Isotope Decay-At-Rest) is a novel experiment designed to measure neutrino oscillations through ν̄(e) disappearance, thus providing a definitive search for sterile neutrinos. In order to generate the necessary anti-neutrino flux, a high intensity primary proton beam is needed. In IsoDAR, H2(+) is accelerated and is stripped into protons just before the target, to overcome space charge issues at injection. As part of the design, we have refined an old proposal to use a RFQ to axially inject bunched H2(+) ions into the driver cyclotron. This method has several advantages over a classical low energy beam transport (LEBT) design: (1) The bunching efficiency is higher than for the previously considered two-gap buncher and thus the overall injection efficiency is higher. This relaxes the constraints on the H2(+) current required from the ion source. (2) The overall length of the LEBT can be reduced. (3) The RFQ can also accelerate the ions. This enables the ion source platform high voltage to be reduced from 70 kV to 15 kV, making underground installation easier. We are presenting the preliminary RFQ design parameters and first beam dynamics simulations from the ion source to the spiral inflector entrance.
Photoejection of both electrons from the H" ion by a single incident photon has been observed with use of a crossed-relativistic-beam technique. The dipole selection rules for a single photon pick out the i P° final state. The relative cross section was measured over a 0.30-eV range of photon energies near threshold in steps of 0.007 eV with a resolution of 0.007 eV full width at half maximum. The energy dependence of the cross section in this region was consistent with a Wannier threshold law.
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