Search

Ultracold neutrons provide a unique tool for the study of neutron properties. An overview is given of the ultracold neutron (UCN) source at PSI, which produces the highest UCN intensities to fundamental physics experiments by exploiting the high intensity proton beam in combination with the high UCN yield in solid deuterium at a temperature of 5K. We briefly list important fundamental physics results based on measurements with neutrons at PSI., Comment: Submission to SciPost, special issue: PSI Particle Physics

Ultracold neutrons (UCN) are free neutrons that can be stored in experimental setups for several minutes. Some of the most important properties of the neutron, such as its tiny permanent electric dipole moment and its beta decay lifetime, are best measured with UCN. Also searches for well motivated but yet unknown, hypothetical additional interactions are being pursued with UCN. Such measurements in the field of low-energy, precision physics may have far reaching implications from particle physics to cosmology. Most experiments are statistics limited and need high-intensity UCN sources. The UCN source at PSI is at the forefront of the field and home to the international nEDM collaboration and its world-leading search for the neutron electric dipole moment. This article aims at giving an overview of the fascinating research using ultracold neutrons emphasizing on activities at PSI including various physics side-analyses which were pioneered by the nEDM collaboration., Comment: 20 pages, 10 figures; invited article in 'Swiss Neutron News', the journal of the Swiss Neutron Science Society https://sgn.web.psi.ch/

We demonstrate the use of a hybrid $^{3}$He / $^{87}$Rb magnetometer to measure absolute magnetic fields in the pT range. The measurements were undertaken by probing time-dependent $^3$He magnetisation using $^{87}$Rb zero-field magnetometers. Measurements were taken to demonstrate the use of the magnetometer in cancelling residual fields within a magnetic shield. It was shown that the absolute field could be reduced to the 10 pT level by using field readings from the magnetometer. Furthermore, the hybrid magnetometer was shown to be applicable for the reduction of gradient fields by optimising the effective $^3$He $T_2$ time. This procedure represents a convenient and consistent way to provide a near zero magnetic field environment which can be potentially used as a base for generating desired magnetic field configurations for use in precision measurements.

The performance of the upgraded solid deuterium ultracold neutron source at the pulsed reactor TRIGA Mainz is described. The current configuration stage comprises the installation of a He liquefier to run UCN experiments over long-term periods, the use of stainless steel neutron guides with improved transmission as well as sputter-coated non-magnetic $^{58}$NiMo alloy at the inside walls of the thermal bridge and the converter cup. The UCN yield was measured in a `standard' UCN storage bottle (stainless steel) with a volume of 32 litres outside the biological shield at the experimental area yielding UCN densities of 8.5 /cm$^3$; an increase by a factor of 3.5 compared to the former setup. The measured UCN storage curve is in good agreement with the predictions from a Monte Carlo simulation developed to model the source. The growth and formation of the solid deuterium converter during freeze-out are affected by the ortho/para ratio of the H$_2$ premoderator., Comment: 12 pages, 7 figures

A $^{6}$Li glass based scintillation detector developed for the TRIUMF neutron electric dipole moment experiment was characterized using the ultra-cold neutron source at the Paul Scherrer Institute (PSI). The data acquisition system for this detector was demonstrated to perform well at rejecting backgrounds. An estimate of the absolute efficiency of background rejection of $99.7\pm0.1$% is made. For variable ultra-cold neutron rate (varying from $<$1 kHz to approx. 100 kHz per channel) and background rate seen at the Paul Scherrer Institute, we estimate that the absolute detector efficiency is $89.7^{+1.3}_{-1.9}$%. Finally a comparison with a commercial Cascade detector was performed for a specific setup at the West-2 beamline of the ultra-cold neutron source at PSI., Comment: 15 pages, 17 figures, submitted to EPJ A

Ultracold neutrons (UCN) can be stored in suitable bottles and observed for several hundreds of seconds. Therefore UCN can be used to study in detail the fundamental properties of the neutron. A new user facility providing ultracold neutrons for fundamental physics research has been constructed at the Paul Scherrer Institute, the PSI UCN source. Assembly of the facility finished in December 2010 with the first production of ultracold neutrons. Operation approval was received in June 2011. We give an overview of the source and the status at startup., Comment: Proceedings of the International Conference on Exotic Atoms and Related Topics - EXA2011 September 5-9, 2011 Austrian Academy of Sciences, Theatersaal, Sonnenfelsgasse 19, 1010 Wien, Austria 6 pages, 3 figures

Commissioning of the new high-intensity ultracold neutron (UCN) source at the Paul Scherrer Institut (PSI) has started in 2009. The design goal of this new generation high intensity UCN source is to surpass by a factor of ~100 the current ultracold neutron densities available for fundamental physics research, with the greatest thrust coming from the search for a neutron electric dipole moment. The PSI UCN source is based on neutron production via proton induced lead spallation, followed by neutron thermalization in heavy water and neutron cooling in a solid deuterium crystal to cold and ultracold energies. A successful beam test with up to 2 mA proton beam on the spallation target was conducted recently. Most source components are installed, others being finally mounted. The installation is on the track for the first cool-down and UCN production in 2010., Comment: Proceedings of the International Nuclear Physics Conference - INPC-2010, July 4 - 9, 2010, Vancouver, Canada; 6 pages, 7 figures

Muons can serve as probes to precisely determine fundamental parameters of the Standard Model or search for `new physics'. The high intensity muon beams at the Paul Scherrer Institut (PSI) allow for precision measurements and searches for rare or forbidden processes. Both types of experiments challenge the Standard Model in a way complementary to high energy physics. We give a short overview of recent results and ongoing experiments at PSI, and of ideas for the future., Comment: 7 pages, 4 Figures Proceedings of the PANIC'08 Conference, Eilat, Israel, (invited talk)

We discuss two precision experiments which will measure fundamental weak interaction parameters: MuLAN's goal is the measurement of the positive muon lifetime to 1 ppm, which will in turn determine the Fermi coupling constant G_F to 0.5 ppm precision. MuCAP is the first experiment which will unambiguously determine the induced pseudoscalar form factor of the proton, g_p. While contradictory experimental results for g_p are under discussion, firm theoretical calculations on the percent level within the framework of Chiral Perturbation Theory are now challenging the measurements. We will describe our experimental efforts and latest achievements., Comment: Proceedings of the Intern. Conference on Exotic Atoms, EXA'05, Feb. 21 - 25, 2005, Vienna, Austria, to be published by the Austrian Academy of Sciences Press. 10 pages, 11 figures