122 research outputs found
Mobility of thorium ions in liquid xenon
We present a measurement of the Th ion mobility in LXe at 163.0 K and
0.9 bar. The result obtained, 0.2400.011 (stat) 0.011 (syst)
cm/(kV-s), is compared with a popular model of ion transport.Comment: 6.5 pages,
Observation of single collisionally cooled trapped ions in a buffer gas
Individual Ba ions are trapped in a gas-filled linear ion trap and observed
with a high signal-to-noise ratio by resonance fluorescence. Single-ion storage
times of ~5 min (~1 min) are achieved using He (Ar) as a buffer gas at
pressures in the range 8e-5 - 4e-3 torr. Trap dynamics in buffer gases are
experimentally studied in the simple case of single ions. In particular, the
cooling effects of light gases such as He and Ar and the destabilizing
properties of heavier gases such as Xe are studied. A simple model is offered
to explain the observed phenomenology.Comment: 5 pages, 4 figures, accepted for publication in Phys. Rev. A. Minor
text and figure change
A magnetically-driven piston pump for ultra-clean applications
A magnetically driven piston pump for xenon gas recirculation is presented.
The pump is designed to satisfy extreme purity and containment requirements, as
is appropriate for the recirculation of isotopically enriched xenon through the
purification system and large liquid xenon TPC of EXO-200. The pump, using
sprung polymer gaskets, is capable of pumping more than 16 standard liters per
minute (SLPM) of xenon gas with 750 torr differential pressure.Comment: 6 pages, 5 figure
A liquid xenon ionization chamber in an all-fluoropolymer vessel
A novel technique has been developed to build vessels for liquid xenon
ionization detectors entirely out of ultra-clean fluoropolymer. We describe the
advantages in terms of low radioactivity contamination, provide some details of
the construction techniques, and show the energy resolution achieved with a
prototype all-fluoropolymer ionization detector.Comment: 12 pages, 9 figure
Systematic study of trace radioactive impurities in candidate construction materials for EXO-200
The Enriched Xenon Observatory (EXO) will search for double beta decays of
136Xe. We report the results of a systematic study of trace concentrations of
radioactive impurities in a wide range of raw materials and finished parts
considered for use in the construction of EXO-200, the first stage of the EXO
experimental program. Analysis techniques employed, and described here, include
direct gamma counting, alpha counting, neutron activation analysis, and
high-sensitivity mass spectrometry.Comment: 32 pages, 6 figures. Expanded introduction, added missing table
entry. Accepted for publication in Nucl. Instrum. Meth.
Borrelia burgdorferi sensu lato in Ixodes ricinus ticks collected from migratory birds in Southern Norway
<p>Abstract</p> <p>Background</p> <p><it>Borrelia burgdorferi </it>sensu lato (s.l.) are the causative agent for Lyme borreliosis (LB), the most common tick-borne disease in the northern hemisphere. Birds are considered important in the global dispersal of ticks and tick-borne pathogens through their migration. The present study is the first description of <it>B. burgdorferi </it>prevalence and genotypes in <it>Ixodes ricinus </it>ticks feeding on birds during spring and autumn migration in Norway.</p> <p>Methods</p> <p>6538 migratory birds were captured and examined for ticks at Lista Bird Observatory during the spring and the autumn migration in 2008. 822 immature <it>I. ricinus </it>ticks were collected from 215 infested birds. Ticks were investigated for infection with <it>B. burgdorferi </it>s.l. by real-time PCR amplification of the 16S rRNA gene, and <it>B. burgdorferi </it>s.l. were thereafter genotyped by melting curve analysis after real-time PCR amplification of the <it>hbb </it>gene, or by direct sequencing of the PCR amplicon generated from the <it>rrs </it>(16S)-<it>rrl </it>(23S) intergenetic spacer.</p> <p>Results</p> <p><it>B. burgdorferi </it>s.l. were detected in 4.4% of the ticks. The most prevalent <it>B. burgdorferi </it>genospecies identified were <it>B. garinii </it>(77.8%), followed by <it>B.valaisiana </it>(11.1%), <it>B. afzelii </it>(8.3%) and <it>B. burgdorferi </it>sensu stricto (2.8%).</p> <p>Conclusion</p> <p>Infection rate in ticks and genospecies composition were similar in spring and autumn migration, however, the prevalence of ticks on birds was higher during spring migration. The study supports the notion that birds are important in the dispersal of ticks, and that they may be partly responsible for the heterogeneous distribution of <it>B. burgdorferi </it>s.l. in Europe.</p
Identification of Radiopure Titanium for the LZ Dark Matter Experiment and Future Rare Event Searches
The LUX-ZEPLIN (LZ) experiment will search for dark matter particle
interactions with a detector containing a total of 10 tonnes of liquid xenon
within a double-vessel cryostat. The large mass and proximity of the cryostat
to the active detector volume demand the use of material with extremely low
intrinsic radioactivity. We report on the radioassay campaign conducted to
identify suitable metals, the determination of factors limiting radiopure
production, and the selection of titanium for construction of the LZ cryostat
and other detector components. This titanium has been measured with activities
of U~1.6~mBq/kg, U~0.09~mBq/kg,
Th~~mBq/kg, Th~~mBq/kg, K~0.54~mBq/kg, and Co~0.02~mBq/kg (68\% CL).
Such low intrinsic activities, which are some of the lowest ever reported for
titanium, enable its use for future dark matter and other rare event searches.
Monte Carlo simulations have been performed to assess the expected background
contribution from the LZ cryostat with this radioactivity. In 1,000 days of
WIMP search exposure of a 5.6-tonne fiducial mass, the cryostat will contribute
only a mean background of (stat)(sys) counts.Comment: 13 pages, 3 figures, accepted for publication in Astroparticle
Physic
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