A simple method of coil design Rawlik, M.; Eggenberger, A.; Krempel, J. ...
American journal of physics,
08/2018, Letnik:
86, Številka:
8
Journal Article
Recenzirano
Odprti dostop
In this article, we present a method to design a coil producing an arbitrarily shaped magnetic field by restricting the path of the coil's wires to a regular grid. The solution is then found by a ...simple least squares minimum. We discuss practical applications, in particular, in the active magnetic field stabilization system of the neutron electric dipole moment experiment at the Paul Scherrer Institute in Villigen, Switzerland. We also publish the software implementation of the method.
We present a magnetometer based on optically pumped Cs atoms that measures the magnitude and direction of a 1 μT 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 μrad for integration times from 10 s up to 2000 s.
We report a new limit on a possible short range spin-dependent interaction from the precise measurement of the ratio of Larmor precession frequencies of stored ultracold neutrons and Hg199 atoms ...confined in the same volume. The measurement was performed in a ∼1μT vertical magnetic holding field with the apparatus searching for a permanent electric dipole moment of the neutron at the Paul Scherrer Institute. A possible coupling between freely precessing polarized neutron spins and unpolarized nucleons of the wall material can be investigated by searching for a tiny change of the precession frequencies of neutron and mercury spins. Such a frequency change can be interpreted as a consequence of a short range spin-dependent interaction that could possibly be mediated by axions or axion-like particles. The interaction strength is proportional to the CP violating product of scalar and pseudoscalar coupling constants gSgP. Our result confirms limits from complementary experiments with spin-polarized nuclei in a model-independent way. Limits from other neutron experiments are improved by up to two orders of magnitude in the interaction range of 10−6<λ<10−4m.
.
Solid deuterium (sD
2
is used as an efficient converter to produce ultracold neutrons (UCN). It is known that the sD
2
must be sufficiently cold, of high purity and mostly in its ortho-state in ...order to guarantee long lifetimes of UCN in the solid from which they are extracted into vacuum. Also the UCN transparency of the bulk sD
2
material must be high because crystal inhomogeneities limit the mean free path for elastic scattering and reduce the extraction efficiency. Observations at the UCN sources at Paul Scherrer Institute and at Los Alamos National Laboratory consistently show a decrease of the UCN yield with time of operation after initial preparation or later treatment (“conditioning”) of the sD
2
. We show that, in addition to the quality of the bulk sD
2
, the quality of its surface is essential. Our observations and simulations support the view that the surface is deteriorating due to a build-up of D
2
frost-layers under pulsed operation which leads to strong albedo reflections of UCN and subsequent loss. We report results of UCN yield measurements, temperature and pressure behavior of deuterium during source operation and conditioning, and UCN transport simulations. This, together with optical observations of sD
2
frost formation on initially transparent sD
2
in offline studies with pulsed heat input at the North Carolina State University UCN source, results in a consistent description of the UCN yield decrease.
The leak rate of helium gas through thin Kapton HN foils was measured for various temperatures between 310 and 150K and gas pressures ranging from 10 to 300mbar. From these measurements the ...permeability constant P(T) and its temperature dependence were determined. At room temperature the permeability constant for Kapton HN is P(T=296K)=(2.56±0.31) barrer. The temperature dependence of P(T) was verified to drop exponentially with decreasing temperature, causing a change in the permeability by more than two orders of magnitude in the range between 310 and 150K.
We report the first observation of the annihilation of positronium from the 2S state. Positronium (Ps) is excited with a two-photon transition from the 1S to the 2S state where its lifetime is ...increased by a factor of eight compared to the ground state due to the decrease in the overlap of the positron electron wave-function. The yield of delayed annihilation photons detected as a function of laser frequency is used as a new method of detecting laser-excited Ps in the 2S state. This can be considered the first step towards a new high precision measurement of the 1S–2S Ps line.
PDF
