Using Ultracold Neutrons Research Articles

Homogeneous magnetic field for the neutron electric dipole moment (n-EDM) measurement using ultra-coldneutrons

Automatic compensation system for the environmental magnetic field has been developed for the neutron electric dipole moment (n-EDM) measurement using ultra-cold neutrons (UCN). In the test experiment, a magnetic field of ~ 40 μT including geomagnetism with the field gradient of ~ − 9 μT/m was successfully suppressed. The suppression factors were consistent with the feed-back gains. Our goal is to achieve a suppression by a factor of 103, necessary for the n-EDM measurement of the order of 10−27 ecm.

The PanEDM neutron electric dipole moment experiment at the ILL

The neutron's permanent electric dipole momentdnis constrained to below 3 × 10−26e cm (90% C.L.) [1, 2], by experiments using ultracold neutrons (UCN). We plan to improve this limit by an order of magnitude or more with PanEDM, the first experiment exploiting the ILL's new UCN source SuperSUN. SuperSUN is expected to provide a high density of UCN with energies below 80 neV, implying extended statistical reach with respect to existing sources, for experiments that rely on long storage or spin-precession times. Systematic errors in PanEDM are strongly suppressed by passive magnetic shielding, with magnetic field and gradient drifts at the single fT level. A holding-field homogeneity on the order of 10−4is achieved in low residual fields, via a high static damping factor and built-in coil system. No comagnetometer is needed for the first order-of-magnitude improvement indn, thanks to high magnetic stability and an assortment of sensors outside the UCN storage volumes. PanEDM will be commissioned and upgraded in parallel with SuperSUN, to take full advantage of the source's output in each phase. Commissioning is ongoing in 2019, and a new limit in the mid 10−27e cm range should be possible with two full reactor cycles of data in the commissioned apparatus.

New result for the neutron β -asymmetry parameter A0 from UCNA

The neutron $\beta$-decay asymmetry parameter $A_0$ defines the correlation between the spin of the neutron and the momentum of the emitted electron, which determines $\lambda=\frac{g_{A}}{g_{V}}$, the ratio of the axial-vector to vector weak coupling constants. The UCNA Experiment, located at the Ultracold Neutron facility at the Los Alamos Neutron Science Center, is the first to measure such a correlation coefficient using ultracold neutrons (UCN). Following improvements to the systematic uncertainties and increased statistics, we report the new result $A_0 = -0.12054(44)_{\mathrm{stat}}(68)_{\mathrm{syst}}$ which yields $\lambda\equiv \frac{g_{A}}{g_{V}}=-1.2783(22)$. Combination with the previous UCNA result and accounting for correlated systematic uncertainties produces $A_0=-0.12015(34)_{\mathrm{stat}}(63)_{\mathrm{syst}}$ and $\lambda\equiv \frac{g_{A}}{g_{V}}=-1.2772(20)$.

Cryogenic magnetic coil and superconducting magnetic shield for neutron electric dipole moment searches

A magnetic coil operated at cryogenic temperatures is used to produce spatial, relative field gradients below 6ppm/cm, stable for several hours. The apparatus is a prototype of the magnetic components for a neutron electric dipole moment (nEDM) search, which will take place at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory using ultra-cold neutrons (UCN). That search requires a uniform magnetic field to mitigate systematic effects and obtain long polarization lifetimes for neutron spin precession measurements. This paper details upgrades to a previously described apparatus [1], particularly the introduction of super-conducting magnetic shielding and the associated cryogenic apparatus. The magnetic gradients observed are sufficiently low for the nEDM search at SNS.

A prestorage method to measure neutron transmission of ultracold neutron guides

There are worldwide efforts to search for physics beyond the Standard Model of particle physics. Precision experiments using ultracold neutrons (UCN) require very high intensities of UCN. Efficient transport of UCN from the production volume to the experiment is therefore of great importance. We have developed a method using prestored UCN in order to quantify UCN transmission in tubular guides. This method simulates the final installation at the Paul Scherrer Institute׳s UCN source where neutrons are stored in an intermediate storage vessel serving three experimental ports. This method allowed us to qualify UCN guides for their intended use and compare their properties.

From ultracold antineutrons to neutron spin echo—The bootstrap offers significant gains in sensitivity

We describe a “bootstrap” method for amplifying the results of certain experiments and discuss its possible application to the search for n- n oscillations using ultracold neutrons (UCN) and to a high resolution neutron resonance spin echo spectrometer. In both these applications the particle “spin” is used to measure an angle defined by external conditions and in these circumstances the “bootstrap” can amplify the resulting effect.

A search for the electric dipole moment of the neutron using ultracold neutrons

The results of measurements of the electric dipole moment (EDM) of the neutron using ultra-cold neutrons (UCN) are presented. A description is given of the source of UCN devised, and of a magnetic resonance spectrometer confining UCN for ≈ 5 s. The use of a double-chamber spectrometer and a system for double analysis of polarization enabled us to eliminate most of the systematic errors possible. The measurements resulted in the EDM d=(4±7.5) × 10 −25 e · cm. From this it is inferred that ¦d¦ < 1.6 × 10 −24e · cm at the confidence level of 90%.