J. M. Wouters

Sudbury neutrino observatory neutral current detector acquisition software overview

The Sudbury Neutrino Observatory begins a new phase of operation in the autumn of 2003 with the installation of the neutral current detectors (NCDs). This paper focuses mainly on the object-oriented real-time control and acquisition (ORCA) software that is the framework for the data acquisition system of the NCD array. Particular emphasis is given to the general purpose nature of ORCA and the manner in which it provides generic object-oriented software modules that can be configured and connected together at run-time to build general-purpose data acquisition applications. ORCA is the main graphical user interface for the NCD experiment and is used for hardware initialization, run control, data readout, and data shipping.

Direct mass measurements of the neutron-rich isotopes of fluorine through chlorine

Abstract The masses of 34 neutron-rich isotopes of fluorine through chlorine are reported. These measurements more fully delineate the mass surface in the region of deformed nuclei centered around 31 Na and, in addition, provide the first mass values of several silicon through sulfur nuclei. We compare our data to recent shell model and mass model calculations

Optical design of the TOFI (time-of-flight isochronous)spectrometer for mass measurements of exotic nuclei

Abstract The design of a novel recoil time-of-flight isochronous spectrometer for systematic mass measurements of nuclei which lie far from the valley of β-stability is described. Using a four identical cell approach, optical aberrations of the spectrometer are minimized resulting in a calculated flight-time mass resolving power of m Δm = 2000 . With the spectrometer designed for a solid angle acceptance of μ = 2.8 msr and a momentum over charge acceptance of ( Δp ze )/( p ze ) = ± 2% , use of the high intensity proton beam at LAMPF will facilitate good statistics experiments yielding new direct mass measurements with uncertainties of 30 keV to 1 MeV (depending on production rates) for nuclei with A

An array of low-background 3He proportional counters for the Sudbury Neutrino Observatory

An array of Neutral-Current Detectors (NCDs) has been built in order to make a unique measurement of the total active ux of solar neutrinos in the Sudbury Neutrino Observatory (SNO). Data in the third phase of the SNO experiment were collected between November 2004 and November 2006, after the NCD array was added to improve the neutral-current sensitivity of the SNO detector. This array consisted of 36 strings of proportional counters lled with a mixture of 3He and CF4 gas capable of detecting the neutrons liberated by the neutrino-deuteron neutral current reaction in the D2O, and four strings lled with a mixture of 4He and CF4 gas for background measurements. The proportional counter diameter is 5 cm. The total deployed array length was 398 m. The SNO NCD array is the lowest-radioactivity large array of proportional counters ever produced. This article describes the design, construction, deployment, and characterization of the NCD array, discusses the electronics and data acquisition system, and considers event signatures and backgrounds.

Background identification and suppression for the measurement of (n,γ) reactions with the DANCE array at LANSCE

Abstract In the commissioning phase of the DANCE project (Detector for Advanced Neutron Capture Experiments) measurements have been performed with special emphasis on the identification and suppression of possible backgrounds for the planned (n,γ) experiments. This report describes several background sources, observed in the experiment or anticipated from simulations, which will need to be suppressed in this and in similar detectors that are planned at other facilities. First successes are documented in the suppression of background from scattered neutrons captured in the detector as well as from the internal radiation. Experimental results and simulations using the GEANT code are compared.

The Time-of-Flight Isochronous (TOFI) spectrometer for direct mass measurements of exotic light nuclei

Abstract A new type of time-of-flight recoil spectrometer designed to measure the masses of neutron-rich light nuclei has recently been completed at LAMPF. The spectrometer relies on an isochronous design that directly correlates an ions time-of-flight through the spectrometer with its mass-to-charge ratio. Additional measurements of the ions velocity and energy enable the charge state of the recoil to be uniquely defined and thus permit precision mass measurements given sufficient statistics. The performance of the spectrometer has been investigated in both off-line (using alpha sources) and on-line tests. The design resolution of ΔM/M = 1 2000 (fwhm) has been achieved. Initial performance results of the spectrometer are described with emphasis placed on the techniques used to achieve the overall high mass resolution and large solid angle/momentum acceptance.

Large-area fast-timing detectors developed for the TOFI spectrometer

Large-area fast-timing detectors have been developed for use in the TOFI spectrometer. A gridless detector was constructed in which secondary electrons emitted from a thin ( ∼ 80 μg/cm2 ) target foil were transported isochronously to microchannel plate electron multipliers by crossed electric and magnetic fields. A novel convex anode was designed to reduce the time dispersion caused by the position at which the secondary electrons were collected. Timing performance for aluminium oxide target foils was found to be superiors to that of carbon foils. Intrinsic timing resolutions of 68 and 109 ps fwhm have been measured for 5.4 MeV alpha particles from a thin 241Am source for two different detectors with active areas of 270 and 1000 mm2, respectively. Detection efficiencies in excess of 75% for alpha particles were measured.

Acquisition-analysis system for the DANCE (detector for advanced neutron capture experiments) BaF/sub 2/ gamma-ray calorimeter

The DANCE detector is a segmented 4/spl pi/ gamma-ray calorimeter for measuring (n, /spl gamma/) and (n,fission) cross-sections of stable and long-lived radioactive isotopes. DANCE uses waveform digitization to acquire the basic gamma-ray data, which maximizes the information available for event reconstruction, but has necessitated the development of several techniques for handling the resulting high data rates. This paper describes the basic experimental requirements for acquisition and analysis and how we have satisfied these requirements primarily by extending existing acquisition and analysis frameworks.

Mass measurement of neutron-rich isotopes from51Ca to72Ni

The ground state masses of thirty-nine neutronrich nuclei from51Ca to72Ni have been measured using the Time-of-Flight Isochronous (TOFI) spectrometer. Eight of these masses have been measured for the first time and thirty-one are remeasurements of neutron-rich nuclei previously reported. Good agreement between these results and a previous TOFI experiment was observed except for the most neutron-rich isotopes of vanadium through iron with the present results being more bound and in better agreement with theory. The low binding energy of68Ni, as indicated by an unreasonably low two-neutron separation energy, suggests the presence of a high-lying, long-lived isomeric state in this nucleus.

The MAJORANA DEMONSTRATOR: An R&D project towards a tonne-scale germanium neutrinoless double-beta decay search

The MAJORANA collaboration is pursuing the development of the so‐called MAJORANA DEMONSTRATOR. The DEMONSTRATOR is intended to perform research and development towards a tonne‐scale germanium‐based experiment to search for the neutrinoless double‐beta decay of 76Ge. The DEMONSTRATOR can also perform a competitive direct dark matter search for light WIMPs in the 1–10 GeV/c2 mass range. It will consist of approximately 60 kg of germanium detectors in an ultra‐low background shield located deep underground at the Sanford Underground Laboratory in Lead, SD. The DEMONSTRATOR will also perform background and technology studies, and half of the detector mass will be enriched germanium. This talk will review the motivation, design, technology and status of the Demonstrator.