Startup of the high-intensity ultracold neutron source at the Paul Scherrer Institute

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 startu

Ultracold Neutrons

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

Fundamental measurements with muons - View from PSI

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

Startup of the High-Intensity Ultracold Neutron Source at the Paul Scherrer Institute

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 figure

Upgrade of the ultracold neutron source at the pulsed reactor TRIGA Mainz

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 figure

First measurements at the DAΦNE φ-factory with the DEAR experimental setup

The relevant background for the DEAR experiment } low-energy X rays and ionizing particles } present in the DEAR interaction region of the DA'NE e'e~ collider was investigated using the "rst-stage DEAR setup and CCD detectors. An extensive Monte Carlo simulation was performed for the present setup and beam conditions. Good quantitative agreement between measurements and simulation was achieved. This is a con"rmation that, with respect to the expected background, which gives an important contribution to the statistical precision of the experiment, the con"guration chosen to measure the strong interaction shift and width in kaonic hydrogen and kaonic deuterium can indeed reach the planned level of accuracy. ( 2000 Elsevier Science B.V. All rights reserved

PicoTesla absolute field readings with a hybrid 3He/87Rb magnetometer

We demonstrate the use of a hybrid 3He/87 magnetometer to measure absolute magnetic fields in the pT range. The measurements were undertaken by probing time-dependent 3He magnetisation using 87Rb 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 3He T2 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

Precision Measurement of PArity Violation in Polarized Cold Neutron Capture on the Proton: the NPDGamma Experiment

The NPDGamma experiment at the Los Alamos Neutron Science Center (LANSCE) is dedicated to measure with high precision the parity violating asymmetry in the $\gamma$ emission after capture of spin polarized cold neutrons in para-hydrogen. The measurement will determine unambiguously the weak pion-nucleon-nucleon ($\pi NN$) coupling constant {\it f$^1_{\pi}$}Comment: Proceedings of the PANIC'05 Conference, Santa Fe, NM, USA, October 24-28, 2005, 3 pages, 2 figure

Kaskade und Transfer von Myonen in Wasserstoff

In dieser Arbeit wird die Röntgenabregung von muonischen Wasserstoffatomen in reinem Wasserstoff (H), reinem Deuterium (D) und H-D Gemischen bei Dichten zwischen 0.1% und 100% Flüssigwassertoffdichte mittels CCD Technologie untersucht In reinem Wasserstoff erlaubt dies die Bestimmung der Strahlungsabregung waehrend der muonischen Kaskade. In einem HD Gemisch kann ein Muon nach Einfang am Wasserstoff zum Deuterium transferieren. In dieser Arbeit wird fuer verschiedene Gemische die Wahrscheinlichkeit (q1s) des Eintreffens des Muons am Grundzustand (1s) beim leichteren Isotop bestimmt. Bei der Untersuchung der muon-katalysierten Kernfusion ist diese Problematik unter dem "q1s Puzzle" bekannt und wird seit vielen Jahren diskutiert. Neben dem prinzipiellen Interesse an muonischen Atome ist dieser Prozess fuer muon-katalysierte Kernfusion von Bedeutung, da die Zeit bis zur Fusion vom Ausgangspunkt des Prozesses abhängt, das heisst bei welchem Atom das Muon den Grundzustand erreicht. Die Kenntnis des Wertes von q1s und seine Dichte- und Konzentrationsabhängigkeit erlaubt die Optimierung der Effizienz der Fusionsausbeute. Die Messungen in dieser Arbeit werden mit einem einfachen Kaskadenmodell interpretiert und danach mit theoretischen Simulationen verglichen.This work experimentally investigates the x-ray deexcitation of muonic hydrogen atoms formed in pure hydrogen (H), in pure deuterium (D) and in isotopic mixtures of H and D at densities between 0.1 % and 100 % of liquid hydrogen density using CCD technology. In pure hydrogens this allows to determine the radiative deexcitation in the muonic atom during the muonic cascade. In an H/D-mixture muons initially captured by a hydrogen atom transfer to the deuteron during the cascade. This work determines for different mixtures the probability of arrival in one of the ground states. In the investigation of muon-catalyzed fusion, this problem has been known as the q1s – puzzle, debated for over a decade. Beyond the fundamental understanding of muonic atoms, this process is also important for muon-catalyzed fusion ad the time needed by different processes to catalyze fusion in hydrogen mixtures depends strongly on the starting point, i.e. on which atom the muon reaches the ground (1s) state. The knowledge of the quantity q1s and its dependence on density and isotopic concentration therefore allows to optimize the efficiency of the muon-catalyzed fusion. The measurements in this work are interpreted using a simple cascade model developed for this analysis and are compared to detailed theory calculations