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Register a new userA new method of alpha ray measurement using a Quadrupole Mass Spectrometer
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We propose a new method of alpha($alpha$)-ray measurement that detects helium atoms with a Quadrupole Mass Spectrometer(QMS). A demonstration is undertaken with a plastic-covered $^{241}$Am $alpha$-emitting source to detect $alpha$-rays stopped in the capsule. We successfully detect helium atoms that diffuse out of the capsule by accumulating them for one to 20 hours in a closed chamber. The detected amount is found to be proportional to the accumulation time. Our method is applicable to probe $alpha$-emitting radioactivity in bulk material.
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The atomic masses of the isotopes 206,207Ra have been measured via decay-correlated mass spectroscopy using a multi-reflection time-of-flight mass spectrograph equipped with an {alpha}-TOF detector. The Ra isotopes were produced as fusion-evaporation products in the 51V+159Tb reaction system and delivered by the gas-filled recoil ion separator GARIS-II at RIKEN. The {alpha}-TOF detector provides for high-accuracy mass measurements by correlating time-of-flight signals with subsequent {alpha}-decay events. The masses of 207gRa and 207mRa were directly measured using a multi-reflection time-of-flight mass spectrograph equipped with an {alpha}-TOF detector. A mass excess of ME = 3538(15) keV/c2 and an excitation energy of Eex = 552(42) keV were determined. The {alpha}-decay branching ratio of 207mRa, b{alpha} = 0.26(20), was directly determined from decay-correlated time-of- flight signals, and the reduced alpha width of 207mRa was calculated to be {delta}2 = 50+62-41 keV from the branching ratio. The spin-parity of 207mRa was confirmed to be J{pi} = 13/2 from decay correlated mass measurement results.
Elastic and inelastic alpha scatterings on $^{10}$C were measured using a 68-MeV/u radioactive $^{10}$C beam incident on the recently developed MAIKo active target system. The phenomenological effective $alpha$-$N$ interaction and the point-nucleon density distribution in the ground state were determined from the elastic scattering data. The cross sections of the inelastic alpha scattering were calculated using this interaction and density distribution and were compared with the experiment to determine the neutron quadrupole transition matrix element $M_{n}$ between the ground state and the $2_{1}^{+}$ state at $E_{x} = 3.35$ MeV in $^{10}$C. The deduced neutron transition matrix element is $M_{n} = 6.9, pm0.7, mathrm{(fit)}, pm1.2, mathrm{(sys)}$ fm$^{2}$. The ratio of the neutron transition strength to proton transition strength was determined as $M_{n}/M_{p} = 1.05, pm0.11, mathrm{(fit)}, pm0.17, mathrm{(sys)}$, which indicates that the quadrupole transition between the ground state and the $2_{1}^{+}$ state in $^{10}$C is less neutron dominant compared to that in $^{16}$C.
We report the first direct measurement of differential transfer cross sections using a Recoil Mass Spectrometer. Absolute differential $1p$ and $2p$-stripping cross sections at $theta_mathrm{c.m.}=180^circ$ have been determined for the system $^{16}$O+$^{142}$Ce by detecting the heavier target-like ions at the focal plane of the Heavy Ion Reaction Analyzer. Focal plane spectra have been compared with the results of a semi-microscopic Monte-Carlo simulation to unambiguously identify the transfer channels. Transmission efficiency of the target-like ions through the spectrometer has also been estimated using the simulation. The methodology adopted in this work can be applied to other recoil separators. The measured excitation functions for the reactions $^{142}mathrm{Ce(}^{16}mathrm{O,}^{15}mathrm{N)}^{143}mathrm{Pr}$ and $^{142}mathrm{Ce(}^{16}mathrm{O,}^{14}mathrm{C)}^{144}mathrm{Nd}$ have been compared with coupled reaction channel calculations. An excellent matching between measurement and theory has been obtained. For $1p$-stripping, major contribution to the cross section has been found to be the transfer of a proton from $^{16}mathrm{O}$ to the $2d_{frac{5}{2}}$ excited state of $^{143}mathrm{Pr}$, leaving behind $^{15}mathrm{N}$ in the $1p_{frac{1}{2}}$ ground state. Transfer of a cluster of two protons from $^{16}mathrm{O}$ to the $2^{+}$ excited state of $^{144}mathrm{Nd}$, resulting in $^{14}mathrm{C}$ in the $0^{+}$ ground state, appears to be the most probable cause for $2p$-stripping. Measured transfer probabilities for $1p$ and $2p$ channels have been compared with Time-Dependent Hartree-Fock calculations. Proton stripping channels are found to be more favourable compared to neutron pick-up channels. However, the theory overpredicts measurement hinting at the need for extended approaches with explicit treatment of pairing correlations in the calculations.
We describe an electron spectrometer designed for a precision measurement of the neutron $beta$-asymmetry with spin-polarized ultracold neutrons. The spectrometer consists of a 1.0-Tesla solenoidal field with two identical multiwire proportional chamber and plastic scintillator electron detector packages situated within 0.6-Tesla field-expansion regions. Select results from performance studies of the spectrometer with calibration sources are reported.
The $bar{K}N$ system at threshold is a sensitive testing ground for low energy QCD, especially for the explicit chiral symmetry breaking. Therefore, we have measured the $K$-series x rays of kaonic hydrogen atoms at the DA$Phi$NE electron-positron collider of Laboratori Nazionali di Frascati, and have determined the most precise values of the strong-interaction energy-level shift and width of the $1s$ atomic state. As x-ray detectors, we used large-area silicon drift detectors having excellent energy and timing resolution, which were developed especially for the SIDDHARTA experiment. The shift and width were determined to be $epsilon_{1s} = -283 pm 36 pm 6 {(syst)}$ eV and $Gamma_{1s} = 541 pm 89 {(stat)} pm 22 {(syst)}$ eV, respectively. The new values will provide vital constraints on the theoretical description of the low-energy $bar{K}N$ interaction.
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