56 research outputs found
A highly stable atomic vector magnetometer based on free spin precession
We present a magnetometer based on optically pumped Cs atoms that measures
the magnitude and direction of a 1 T magnetic field. Multiple circularly
polarized laser beams were used to probe the free spin precession of the Cs
atoms. The design was optimized for long-time stability and achieves a scalar
resolution better than 300 fT for integration times ranging from 80 ms to 1000
s. The best scalar resolution of less than 80 fT was reached with integration
times of 1.6 to 6 s. We were able to measure the magnetic field direction with
a resolution better than 10 rad for integration times from 10 s up to 2000
s
A 16 Parts per Trillion Comparison of the Antiproton-to-Proton q/m Ratios
The Standard Model (SM) of particle physics is both incredibly successful and
glaringly incomplete. Among the questions left open is the striking imbalance
of matter and antimatter in the observable universe which inspires experiments
to compare the fundamental properties of matter/antimatter conjugates with high
precision. Our experiments deal with direct investigations of the fundamental
properties of protons and antiprotons, performing spectroscopy in advanced
cryogenic Penning-trap systems. For instance, we compared the proton/antiproton
magnetic moments with 1.5 ppb fractional precision, which improved upon
previous best measurements by a factor of >3000. Here we report on a new
comparison of the proton/antiproton charge-to-mass ratios with a fractional
uncertainty of 16ppt. Our result is based on the combination of four
independent long term studies, recorded in a total time span of 1.5 years. We
use different measurement methods and experimental setups incorporating
different systematic effects. The final result,
= ,
is consistent with the fundamental charge-parity-time (CPT) reversal
invariance, and improves the precision of our previous best measurement by a
factor of 4.3. The measurement tests the SM at an energy scale of
GeV (CL 0.68), and improves 10 coefficients of the
Standard Model Extension (SME). Our cyclotron-clock-study also constrains
hypothetical interactions mediating violations of the clock weak equivalence
principle (WEP) for antimatter to a level of , and enables the first differential test of the WEP
using antiprotons \cite{hughes1991constraints}. From this interpretation we
constrain the differential WEP-violating coefficient to
Revised experimental upper limit on the electric dipole moment of the neutron
We present for the first time a detailed and comprehensive analysis of the experimental results that set the current world sensitivity limit on the magnitude of the electric dipole moment (EDM) of the neutron. We have extended and enhanced our earlier analysis to include recent developments in the understanding of the effects of gravity in depolarizing ultracold neutrons; an improved calculation of the spectrum of the neutrons; and conservative estimates of other possible systematic errors, which are also shown to be consistent with more recent measurements undertaken with the apparatus. We obtain a net result of dn=−0.21±1.82×10−26 e cm, which may be interpreted as a slightly revised upper limit on the magnitude of the EDM of 3.0×10−26 e cm (90% C.L.) or 3.6×10−26 e cm (95% C.L.)
Ultra thin polymer foil cryogenic window for antiproton deceleration and storage
We present the design and characterisation of a cryogenic window based on an
ultra-thin aluminised PET foil at T < 10K, which can withstand a pressure
difference larger than 1bar at a leak rate < mbar l/s.
Its thickness of approximately 1.7 m makes it transparent to various types
of particles over a broad energy range. To optimise the transfer of 100keV
antiprotons through the window, we tested the degrading properties of different
aluminium coated PET foils of thicknesses between 900nm and 2160nm, concluding
that 1760nm foil decelerates antiprotons to an average energy of 5 keV. We have
also explicitly studied the permeation as a function of coating thickness and
temperature, and have performed extensive thermal and mechanical endurance and
stress tests. Our final design integrated into the experiment has an effective
open surface consisting of 7 holes with 1 mm diameter and will transmit up to
2.5% of the injected 100keV antiproton beam delivered by the AD/ELENA-facility
of CERN
BASE-STEP: A transportable antiproton reservoir for fundamental interaction studies
Currently, the only worldwide source of low-energy antiprotons is the
AD/ELENA facility located at CERN. To date, all precision measurements on
single antiprotons have been conducted at this facility and provide stringent
tests of the fundamental interactions and their symmetries. However, the
magnetic field fluctuations from the facility operation limit the precision of
upcoming measurements. To overcome this limitation, we have designed the
transportable antiproton trap system BASE-STEP to relocate antiprotons to
laboratories with a calm magnetic environment. We anticipate that the
transportable antiproton trap will facilitate enhanced tests of CPT invariance
with antiprotons, and provide new experimental possibilities of using
transported antiprotons and other accelerator-produced exotic ions. We present
here the technical design of the transportable trap system. This includes the
transportable superconducting magnet, the cryogenic inlay consisting of the
trap stack and the detection systems, and the differential pumping section to
suppress the residual gas flow into the cryogenic trap chamber.Comment: To be submitted to Rev. Sci. Instrument
Search for ultralight axion dark matter in a side-band analysis of a 199Hg free-spin precession signal
Ultra-low-mass axions are a viable dark matter candidate and may form a
coherently oscillating classical field. Nuclear spins in experiments on Earth
might couple to this oscillating axion dark-matter field, when propagating on
Earth's trajectory through our Galaxy. This spin coupling resembles an
oscillating pseudo-magnetic field which modulates the spin precession of
nuclear spins. Here we report on the null result of a demonstration experiment
searching for a frequency modulation of the free spin-precession signal of
\magHg in a \SI{1}{\micro\tesla} magnetic field. Our search covers the axion
mass range
and achieves a peak sensitivity to the axion-nucleon coupling of .Comment: 18 pages, 4 images, submitted to SciPost Physic
The n2EDM experiment at the Paul Scherrer Institute
We present the new spectrometer for the neutron electric dipole moment (nEDM) search at the Paul Scherrer Institute (PSI), called n2EDM. The setup is at room temperature in vacuum using ultracold neutrons. n2EDM features a large UCN double storage chamber design with neutron transport adapted to the PSI UCN source. The design builds on experience gained from the previous apparatus operated at PSI until 2017. An order of magnitude increase in sensitivity is calculated for the new baseline setup based on scalable results from the previous apparatus, and the UCN source performance achieved in 2016
Revised experimental upper limit on the electric dipole moment of the neutron
We present for the first time a detailed and comprehensive analysis of the experimental results that set the current world sensitivity limit on the magnitude of the electric dipole moment (EDM) of the neutron. We have extended and enhanced our earlier analysis to include recent developments in the understanding of the effects of gravity in depolarizing ultracold neutrons; an improved calculation of the spectrum of the neutrons; and conservative estimates of other possible systematic errors, which are also shown to be consistent with more recent measurements undertaken with the apparatus. We obtain a net result of dn=−0.21±1.82×10−26 e cm, which may be interpreted as a slightly revised upper limit on the magnitude of the EDM of 3.0×10−26 e cm (90% C.L.) or 3.6×10−26 e cm (95% C.L.)
Search for an interaction mediated by axion-like particles with ultracold neutrons at the PSI
We report on a search for a new, short-range, spin-dependent interaction
using a modified version of the experimental apparatus used to measure the
permanent neutron electric dipole moment at the Paul Scherrer Institute. This
interaction, which could be mediated by axion-like particles, concerned the
unpolarized nucleons (protons and neutrons) near the material surfaces of the
apparatus and polarized ultracold neutrons stored in vacuum. The dominant
systematic uncertainty resulting from magnetic-field gradients was controlled
to an unprecedented level of approximately 4 pT/cm using an array of
optically-pumped cesium vapor magnetometers and magnetic-field maps
independently recorded using a dedicated measurement device. No signature of a
theoretically predicted new interaction was found, and we set a new limit on
the product of the scalar and the pseudoscalar couplings (95% C.L.) in a range of for the monopole-dipole interaction. This new result confirms
and improves our previous limit by a factor of 2.7 and provides the current
tightest limit obtained with free neutrons
Observation of gravitationally induced vertical striation of polarized ultracold neutrons by spin-echo spectroscopy
We describe a spin-echo method for ultracold neutrons (UCNs) confined in a precession chamber and exposed to a |B 0 |=1 μT magnetic field. We have demonstrated that the analysis of UCN spin-echo resonance signals in combination with knowledge of the ambient magnetic field provides an excellent method by which to reconstruct the energy spectrum of a confined ensemble of neutrons. The method takes advantage of the relative dephasing of spins arising from a gravitationally induced striation of stored UCNs of different energies, and also permits an improved determination of the vertical magnetic-field gradient with an exceptional accuracy of 1.1 pT/cm . This novel combination of a well-known nuclear resonance method and gravitationally induced vertical striation is unique in the realm of nuclear and particle physics and should prove to be invaluable for the assessment of systematic effects in precision experiments such as searches for an electric dipole moment of the neutron or the measurement of the neutron lifetime
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