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This document outlines plans for fully utilizing low-energy beams from CARIBU for mass measurements, laser spectroscopy, and decay experiments. It includes proposed experiments, equipment layouts, and future goals to enhance experimental capabilities and data reliability.
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Fundamental InteractionsPhysics & InstrumentationConclusions Conveners: P. Mueller, J. ClarkG. Savard, N. Scielzo
Short Term • Fully utilize low energy beams from CARIBU for mass measurements, laser spectroscopic studies and decay experiments. Ideally, the space available for low energy experiments at CARIBU should be expanded to fully exploit these possibilities (NA6).
Initial focus of measurements with the CPT at CARIBU • First measurements: • 132Sn and neighbors • 130Cd and neighbors • Future measurements: • go as neutron-rich as possible
Moving the CPT to CARIBU CARIBU
AC Laser Enclosure (~ 6’ x 10’) HEPA Laser Table (~ 3’ x 7’) Tape Station Ion Trap Collinear Beamline Laser Lab Layout @ CARIBU Cf-252 source 80 mCi -> 1Ci Gas catcher High-resolution mass separator dm/m > 1/20000 RF Cooler & Buncher … starting in fall 2010
Beta-delayed neutron emission Novel approach: determine neutron energies and branching ratios by detecting beta particles and recoil ions that emerge from ion trap Provide reliable data for: r-process nucleosynthesis, nuclear structure, nuclear reactor performance, modeling of environments where fission fragments are produced 95Rb 95Sr* + b- + n 94Sr* + n Example Q = 4.9 MeV t1/2 = 0.378 sec Pn ≈ 9% MCP ion detector n 94Sr Plastic scintillator 95Rb+ • 1-mm3 trapped-ion sample and 1-ns timing resolution of detectors determines neutron momentum/energy to ~1% from time-of-flight of recoiling daughter ion • intrinsic efficiency for MCP detectors can be ~100% • many fission fragments available from the newly-developed CARIBU facility (an intense source of fission-fragment beams) at ANL b n Plastic scintillator
Short Term • Utilize ATLAS intensity upgrade (Phase I) for improved beta decay correlation experiments and weak interaction studies by increased production rate of light isotopes close to stability (e.g. 6He, 8Li, 14O, 18Ne ) (FI4). Phase II upgrade, in particular the recoil separator, would significantly improve production and separation of these isotopes.
Beta-neutrino correlation in 8Li Beta-neutrino correlation measurement takes advantage of 1 mm3 trapped ion sample and position and energy resolution of double-sided silicon strip detectors to precisely reconstruct momentum vectors of all emitted particles (including neutrino!) 8Li 8Be* + b- + n a + a Plastic scintillator DSSD Neutrino momentum/energy can be determined from b- and recoiling 8Be momentum/energy b- momentum/energy measured from DSSD and plastic scintillator detector 8Be momentum/energy determined from a particle break-up… with no recoil, a particles would have same energy and would be back-to-back. With recoil, energy difference can be up to 730 keV and the angle can deviate by as much as ±70 n a 8Li+ b a Low mass of 8Li and Q ≈ 13 MeV lead to large recoil energies of 12 keV which makes the correlation easier to measure. Other b-n correlation measurements have had to deal with recoil energies of only 0.2-1.4 keV.
Simulated time-of-flight signal New Physics Standard Model Beta-Decay Study with Laser Trapped 6He • 6He trapping rate: 1104 s-1, • 2105 coincidence events in 15 min: da = ± 0.008 • 1 week: da/a = 0.1% • 6He yields: • ATLAS: 1107 s-1 • CENPA: ~1109 s-1 • SARAF / SPIRAL2: ~11012 s-1
Medium Term • Improve isotope separation and overall transmission of the ion transfer line after the gas catcher into the triangle room. This would enable mass measurements closer to the proton drip line (65As) once the CPT is moved back to its previous location (NA2). This upgrade also would improve correlation studies and decay experiments possible at that location (FI4).
Moving the CPT to CARIBU CARIBU
Long Term • Add gas catcher and low-energy beam-line behind recoil separator for studies of very proton rich isotopes (e.g. around 100Sn, requires Phase II). Provide experimental area to accommodate low-energy beam experiments, e.g., in the ATSCAT area. • Support high precision measurements of basic nuclear properties of isotopes close to stability (on the proton rich side) to enable future high precision measurement far off stability at FRIB, e.g., measurements of T=2 superallowed beta decays.
Moving the CPT to CARIBU CARIBU RecoilSeparator
T=2 nuclei present an alternative way to check Isospin breaking corrections Bhattacharya et al., PRC 77, 065503 (2008)
Long Term • Find a stronger source for 225Ra for improved EDM experiment that will be truly statistics limited (FI9).
Oven: 225Ra (+Ba) Transverse cooling Zeeman Slower EDM probe Optical dipole trap Search for EDM of 225Ra • Advantages: • Large enhancement: • EDM(Ra) / EDM(Hg) ~ 200 – 2000 • Efficient use of 225Ra atoms • High electric field (> 100 kV/cm) • Long coherence times (~ 100 s) • Negligible “v x E” systematic effect