P. P. J. Delheij

First Penning-trap mass measurement of the exotic halo nucleus 11Li.

M. Smith, M. Brodeur, T. Brunner, S. Ettenauer, A Lapierre, R. Ringle, V. L. Ryjkov, F. Ames, P. Bricault, G. W. F. Drake, P. Delheij, D Lunney, and J. Dilling TRIUMF, 4004 Wesbrook Mall, Vancouver, British Columbia, Canada Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver BC, Canada Technische Universität München, E12, James Franck Strasse, Garching, Germany Department of Physics, University of Windsor, Windsor, Ontario, Canada and CSNSM/CNRS/IN2P3, Universite de Paris-Sud, F-91405, Orsay, France (Dated: July 21, 2008)

The HERA polarimeter and the first observation of electron spin polarization at HERA

Abstract Electron spin polarizations of about 8% were observed at HERA in November 1991. In runs during 1992, utilizing special orbit corrections, polarization values close to 60% have been achieved. In this paper the polarimeter, the machine conditions, the data analysis, the first results and plans for future measurements are described.

First direct mass measurement of the two-neutron halo nucleus 6He and improved mass for the four-neutron halo 8He.

The first direct mass measurement of {6}He has been performed with the TITAN Penning trap mass spectrometer at the ISAC facility. In addition, the mass of {8}He was determined with improved precision over our previous measurement. The obtained masses are m({6}He)=6.018 885 883(57)  u and m({8}He)=8.033 934 44(11)  u. The {6}He value shows a deviation from the literature of 4σ. With these new mass values and the previously measured atomic isotope shifts we obtain charge radii of 2.060(8) and 1.959(16) fm for {6}He and {8}He, respectively. We present a detailed comparison to nuclear theory for {6}He, including new hyperspherical harmonics results. A correlation plot of the point-proton radius with the two-neutron separation energy demonstrates clearly the importance of three-nucleon forces.

Verifying the accuracy of the TITAN Penning-trap mass spectrometer

Abstract TITAN (TRIUMFs Ion Traps for Atomic and Nuclear science) is an online facility designed to carry out high-precision mass measurements on singly and highly charged radioactive ions. The TITAN Penning trap has been built and optimized in order to perform such measurements with an accuracy in the sub ppb-range. A detailed characterization of the TITAN Penning trap is presented and a new compensation method is derived and demonstrated, verifying the performance in the range of sub-ppb.

A measurement of the absolute neutron beam polarization produced by an optically pumped 3He neutron spin filter

Abstract The capability of performing accurate absolute measurements of neutron beam polarization opens a number of exciting opportunities in fundamental neutron physics and in neutron scattering. At the LANSCE pulsed neutron source we have measured the neutron beam polarization with an absolute accuracy of 0.3% in the neutron energy range from 40 meV to 10 eV using an optically pumped polarized 3 He spin filter and a relative transmission measurement technique. 3 He was polarized using the Rb spin-exchange method. We describe the measurement technique, present our results, and discuss some of the systematic effects associated with the method.

Ion chamber system for neutron flux measurements

Abstract A helium-filled ion chamber detector for intensity measurements of high-intensity epithermal neutron bursts with instantaneous rates as high as 10 11 Hz is presented. This system consists of an ion chamber to detect a portion of the neutron beam, a current-to-frequency converter and CAMAC scalers to readout the chamber. The chambers and readout electronics have a small temperature sensitivity and have high noise immunity. The statistical precision of the system is measured to be 10 −3 for each neutron beam pulse.

An apparatus and techniques of tests for fundamental symmetries in compound-nucleus scattering with epithermal polarized neutron beams

Abstract The epithermal polarized-neutron beam facility used for tests of fundamental symmetries is described. The initial unpolarized beam is obtained from the spallation source at the Los Alamos Neutron Scattering Center. Characteristics of the polarized and unpolarized beams are described, as well as design and performance of a fast-spin reversal system, neutron flux monitor and target cooler. Experimental results for polarized-neutron transmission experiments are given to illustrate the overall quality of the system.

Charge breeding rare isotopes for high precision mass measurements: challenges and opportunities

Ion charge breeding for Penning-trap mass spectrometry has been established as providing a precision increase that scales linearly with the charge state of the ion. Fast and efficient charge breeding is a precondition for the application of this approach to rare isotopes. However, in view of low yields and short half-lives the precision boost is partly compromised by unavoidable ion losses inherent to the charge breeding process. The mass spectrometer TRIUMFs ion trap for atomic and nuclear science is pioneering this field by coupling a Penning trap and an electron beam ion trap to the rare-isotope beam facility ISAC at TRIUMF. Here we present simulations that calculate and maximize the effective precision gain of time-of-flight ion-cyclotron-resonance measurements with highly charged ions of short-lived nuclides. In addition we compare the characteristics of measurements with singly and highly charged ions, and we summarize recent results that explored benefits of charge breeding that go beyond the precision increase.

Proton-induced nucleon knockout from polarized 3He at 290 MeV

Abstract A novel polarized 3 He gas target has been used to measure spin observables for ( p ,2 p ) and ( p , pn ) nucleon knockout in quasielastic kinematics at 290 MeV. Comparisons with PWIA calculations show the importance of rescattering corrections, especially for neutron knockout and the target-related asymmetry A 0 n . The A nn ( p ,2 p ) results agree with the PWIA and qualitatively indicate the effects of spin momentum distributions of protons in 3 He as predicted by Faddeev calculations.

NMR measurements on the triumf polarized deuterium target

Abstract The NMR system and the polarization measurements of the TRIUMF polarized deuterium target are described. The NMR tuned circuit is kept resonant at all frequencies to allow for a high gain in the rf amplifiers and to permit the measurement of the real part of the NMR signal. A Starburst (J-11) and an LSI-11 are used to process the NMR signal at a high sample rate. A synthesizer under the control of an 8085 based microprocessor (TRIMAC) provides the rf sweep. Vector polarizations between −0.33 and −0.40 were routinely achieved during a four week run in the TRIUMF M11 pion beamline with a statistical uncertainty of 3.4% and a systematic uncertainty of 5%.