129 research outputs found
Precision high voltage divider for the KATRIN experiment
The Karlsruhe Tritium Neutrino Experiment (KATRIN) aims to determine the
absolute mass of the electron antineutrino from a precise measurement of the
tritium beta-spectrum near its endpoint at 18.6 keV with a sensitivity of 0.2
eV. KATRIN uses an electrostatic retardation spectrometer of MAC-E filter type
for which it is crucial to monitor high voltages of up to 35 kV with a
precision and long-term stability at the ppm level. Since devices capable of
this precision are not commercially available, a new high voltage divider for
direct voltages of up to 35 kV has been designed, following the new concept of
the standard divider for direct voltages of up to 100 kV developed at the
Physikalisch-Technische Bundesanstalt (PTB). The electrical and mechanical
design of the divider, the screening procedure for the selection of the
precision resistors, and the results of the investigation and calibration at
PTB are reported here. During the latter, uncertainties at the low ppm level
have been deduced for the new divider, thus qualifying it for the precision
measurements of the KATRIN experiment.Comment: 22 pages, 12 figure
The KATRIN Experiment
The KArlsruhe TRitium Neutrino mass experiment, KATRIN, aims to search for
the mass of the electron neutrino with a sensitivity of 0.2 eV/c^2 (90% C.L.)
and a detection limit of 0.35 eV/c^2 (5 sigma). Both a positive or a negative
result will have far reaching implications for cosmology and the standard model
of particle physics and will give new input for astroparticle physics and
cosmology. The major components of KATRIN are being set up at the Karlsruhe
Institut of Technology in Karlsruhe, Germany, and test measurements of the
individual components have started. Data taking with tritium is scheduled to
start in 2012.Comment: 3 pages, 1 figure, proceedings of the TAUP 2009 International
Conference on Topics in Astroparticle and Underground Physics, to be
published in Journal of Physics, Conference Serie
Final Results from phase II of the Mainz Neutrino Mass Search in Tritium Decay
The paper reports on the improved Mainz experiment on tritum
spectroscopy which yields a 10 times' higher signal to background ratio than
before. The main experimental effects and systematic uncertainties have been
investigated in side experiments and possible error sources have been
eliminated. Extensive data taking took place in the years 1997 to 2001. A
residual analysis of the data sets yields for the square of the electron
antineutrino mass the final result of eV/c. We derive an upper limit of
eV/c at 95% confidence level for the mass itself.Comment: 22 pages, 22 figures submitted to EPJ
Final State Interaction Effects in pol 3He(pol e,e'p)
Asymmetries in quasi-elastic pol 3He(pol e,e'p) have been measured at a
momentum transfer of 0.67 (GeV/c)^2 and are compared to a calculation which
takes into account relativistic kinematics in the final state and a
relativistic one-body current operator. With an exact solution of the Faddeev
equation for the 3He-ground state and an approximate treatment of final state
interactions in the continuum good agreement is found with the experimental
data.Comment: 11 pages, 6 figures, submitted to Phys. Lett. B, revised version,
sensitivity study to relativity and NN-potential adde
Isotope shift in the dielectronic recombination of three-electron ^{A}Nd^{57+}
Isotope shifts in dielectronic recombination spectra were studied for Li-like
^{A}Nd^{57+} ions with A=142 and A=150. From the displacement of resonance
positions energy shifts \delta E^{142,150}(2s-2p_1/2)= 40.2(3)(6) meV
(stat)(sys)) and \delta E^{142,150}(2s-2p_3/2) = 42.3(12)(20) meV of 2s-2p_j
transitions were deduced. An evaluation of these values within a full QED
treatment yields a change in the mean-square charge radius of ^{142,150}\delta
= -1.36(1)(3) fm^2. The approach is conceptually new and combines the
advantage of a simple atomic structure with high sensitivity to nuclear size.Comment: 10 pages, 3 figures, accepted for publication in Physical Review
Letter
Isotope Shift Measurements of Stable and Short-Lived Lithium Isotopes for Nuclear Charge Radii Determination
Changes in the mean-square nuclear charge radii along the lithium isotopic
chain were determined using a combination of precise isotope shift measurements
and theoretical atomic structure calculations. Nuclear charge radii of light
elements are of high interest due to the appearance of the nuclear halo
phenomenon in this region of the nuclear chart. During the past years we have
developed a new laser spectroscopic approach to determine the charge radii of
lithium isotopes which combines high sensitivity, speed, and accuracy to
measure the extremely small field shift of an 8 ms lifetime isotope with
production rates on the order of only 10,000 atoms/s. The method was applied to
all bound isotopes of lithium including the two-neutron halo isotope Li-11 at
the on-line isotope separators at GSI, Darmstadt, Germany and at TRIUMF,
Vancouver, Canada. We describe the laser spectroscopic method in detail,
present updated and improved values from theory and experiment, and discuss the
results.Comment: 34 pages, 24 figures, 14 table
The KATRIN Pre-Spectrometer at reduced Filter Energy
The KArlsruhe TRItium Neutrino experiment, KATRIN, will determine the mass of
the electron neutrino with a sensitivity of 0.2 eV (90% C.L.) via a measurement
of the beta-spectrum of gaseous tritium near its endpoint of E_0 =18.57 keV. An
ultra-low background of about b = 10 mHz is among the requirements to reach
this sensitivity. In the KATRIN main beam-line two spectrometers of MAC-E
filter type are used in a tandem configuration. This setup, however, produces a
Penning trap which could lead to increased background. We have performed test
measurements showing that the filter energy of the pre-spectrometer can be
reduced by several keV in order to diminish this trap. These measurements were
analyzed with the help of a complex computer simulation, modeling multiple
electron reflections both from the detector and the photoelectric electron
source used in our test setup.Comment: 22 pages, 12 figure
Do non-relativistic neutrinos constitute the dark matter?
The dark matter of the Abell 1689 galaxy cluster is modeled by thermal,
non-relativistic gravitating fermions and its galaxies and X-ray gas by
isothermal distributions. A fit yields a mass of 1.445 eV. A dark matter fraction
occurs for degrees
of freedom, i. e., for 3 families of left plus right handed neutrinos with
masses . Given a temperature of 0.045 K and a de
Broglie length of 0.20 mm, they establish a quantum structure of several
million light years across, the largest known in the Universe. The virial
-particle temperature of keV coincides with the
average one of X-rays. The results are compatible with neutrino genesis,
nucleosynthesis and free streaming. The neutrinos condense on the cluster at
redshift , thereby causing reionization of the intracluster gas
without assistance of heavy stars. The baryons are poor tracers of the dark
matter density.Comment: Extended published version, 6.1 pages, 2 figure
Effect of a sweeping conductive wire on electrons stored in the Penning trap between the KATRIN spectrometers
The KATRIN experiment is going to search for the mass of the electron
antineutrino down to 0.2 eV/c^2. In order to reach this sensitivity the
background rate has to be understood and minimised to 0.01 counts per second.
One of the background sources is the unavoidable Penning trap for electrons due
to the combination of the electric and magnetic fields between the pre- and the
main spectrometer at KATRIN. In this article we will show that by sweeping a
conducting wire periodically through such a particle trap stored particles can
be removed, an ongoing discharge in the trap can be stopped, and the count rate
measured with a detector looking at the trap is reduced.Comment: Final version published in EPJ A, 14 pages, 19 figures (21 files
Final height in girls with turner syndrome after long-term growth hormone treatment in three dosages and low dose estrogens
Although GH treatment for short stature in Turner syndrome is an accepted
treatment in many countries, which GH dosage to use and which age to start
puberty induction are issues of debate. This study shows final height (FH)
in 60 girls with Turner syndrome treated in a randomized dose-response
trial, combining GH treatment with low dose estrogens at a relatively
young age. Girls were randomly assigned to group A (4 IU/m(2).d;
approximately 0.045 mg/kg/d), group B (first year, 4 IU/m(2).d; thereafter
6 IU/m(2).d), or group C (first year, 4 IU/m(2).d; second year, 6
IU/m(2).d; thereafter, 8 IU/m(2).d). After a minimum of 4 yr of GH
treatment, at a mean age of 12.7 +/- 0.7 yr, low dose micronized
17beta-estradiol was given orally. After a mean duration of GH treatment
of 8.6 +/- 1.9 yr, FH was reached at a mean age of 15.8 +/- 0.9 yr. FH,
expressed in centimeters or SD score, was 157.6 +/- 6.5 or -1.6 +/- 1.0 in
group A, 162.9 +/- 6.1 or -0.7 +/- 1.0 in group B, and 163.6 +/- 6.0 or
-0.6 +/- 1.0 in group C. The difference in FH in centimeters, corrected
for height SD score and age at start of treatment, was significant between
groups A and B [regression coefficient, 4.1; 95% confidence interval (CI),
1.4, 6.9; P < 0.01], and groups A and C (coefficient, 5.0; 95% CI, 2.3,
7.7; P < 0.001), but not between groups B and C (coefficient, 0.9; 95% CI,
-1.8, 3.6). Fifty of the 60 girls (83%) had reached a normal FH (FH SD
score, more than -2). After starting estrogen treatment, the decrease in
height velocity (HV) changed significantly to a stable HV, without
affecting bone maturation (change in bone age/change in chronological
age). The following variables contributed significantly to predicting FH
SD score: GH dose, height SD score (ref. normal girls), chronological age
at start of treatment, and HV in the first year of GH treatment. GH
treatment was well tolerated. In conclusion, GH treatment leads to a
normalization of FH in most girls, even when puberty is induced at a
normal pubertal age. The optimal GH dosage depends on height and age at
the start of treatment and first year HV
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