We review the status of the proton charge radius puzzle. Emphasis is given to the various experiments initiated to resolve the conflict between the muonic hydrogen results and the results from ...scattering and regular hydrogen spectroscopy.
An analytic solution to the magnetostatic inverse problem in the framework of vector spherical harmonic basis functions is presented. This formalism is used for the design of a spherical magnetic ...field compensation system and its performance is compared with an already existing rectangular coil system. The proposed set of spherical coils with 15 degrees of freedom achieves a shielding factor of 1000 or better in a large part of the volume enclosed by the coils for a dipolar type external perturbation.
We have produced hydrogen-free diamond-like carbon (DLC) films by vacuum arc deposition for use as wall coating material in ultracold neutron (UCN) applications. The sp
3 fraction, the main quality ...factor for DLC used in UCN applications, was varied from 0.4 to 0.9, the coating thickness between 10 nm and 120 nm. The samples were characterized by using X-ray Absorption Near-Edge Spectroscopy (XANES), X-ray induced Photoelectron Spectroscopy (XPS), Laser induced surface Acoustic Waves (LAwave), cold neutron reflectometry and Raman spectroscopy at visible excitation wavelength. We observe reasonable agreement between the different results for film thicknesses below 20 nm. For larger thickness, we find that the surface-sensitive methods XPS and XANES yield smaller sp
3 fractions (by up to 20%) than the bulk-sensitive LAwave, being consistent with the assumption of a lower-density surface layer on a nominal-density bulk layer.
Ultra-cold neutrons (UCN), neutrons with energies low enough to be confined by the Fermi potential in material bottles, are playing an increasing role in measurements of fundamental properties of the ...neutron. The ability to manipulate UCN with material guides and bottles, magnetic fields, and gravity can lead to experiments with lower systematic errors than have been obtained in experiments with cold neutron beams. The UCN densities provided by existing reactor sources limit these experiments. The promise of much higher densities from solid deuterium sources has led to proposed facilities coupled to both reactor and spallation neutron sources. In this Letter we report on the performance of a prototype spallation neutron-driven solid deuterium source. This source produced bottled UCN densities of 145±7 UCN/cm3, about three times greater than the largest bottled UCN densities previously reported. These results indicate that a production UCN source with substantially higher densities should be possible.
We report a measurement of the reflection of ultracold neutrons from flat, large-area plates of different Fermi potential materials with low surface roughness. The results were used to test two ...diffuse reflection models, the well-known Lambert model and the micro-roughness model which is based on wave scattering. The Lambert model fails to reproduce the diffuse reflection data. The surface roughness
b
and correlation length
w
, obtained by fitting the micro-roughness model to the data are in the range 1
b
3 nm and 10
w
120 nm, in qualitative agreement with independent measurements using atomic force microscopy.
We have used copper-coated carbon fiber reinforced plastic (CuCFRP) for the construction of high and ultra-high vacuum chambers. The vacuum performance is found to be comparable to typical stainless ...steel used for this purpose. In test chambers we have reached pressures of 2 × 10−8 mbar and measured a desorption rate of 1 × 10−11 mbar l/s m2; no degradation over time (2 years) has been found. Suitability for baking has been found to depend on the CFRP production process, presumably on the temperature of the autoclave curing. Together with other unique properties of CuCFRP such as low weight and being nearly non-magnetic, this makes it an ideal material for many high-end vacuum applications.
•Copper coated carbon reinforced fiber was tested for vacuum properties.•Test chambers have shown a desorption rate of less then 1E-11 mbar l/s/cm2.•Lowest pressures measured (2E-8 mbar) were limited by fluoroelastomer gaskets.•Baking of high grade CuCFRP improved vacuum performance.•Low grade CuCFRP showed delamination after heat cycling.
The simulation of ultracold neutron experiments using GEANT4 Atchison, F.; Bryś, T.; Daum, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
11/2005, Letnik:
552, Številka:
3
Journal Article
Recenzirano
The GEANT4 code has been adapted to include the influence of gravity and inhomogeneous, slowly time-varying magnetic fields on neutrons. Ultracold neutrons (UCN) are introduced as a new class of ...particles. All relevant processes for the interactions at material boundaries and inside materials are implemented. The GEANT4 environment allows for an effective handling of complicated geometries.
PDF
