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

Solid deuterium surface degradation at ultracold neutron sources

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.Comment: 15 pages, 22 figures, accepted by EPJ-

‘Kamikaze’ heritage tourism in Japan: A pathway to peace and understanding?

Reflecting the wider belief that international tourism offers the opportunity to encourage peace and understanding amongst peoples and nations, one objective of Japan’s recent tourism development policy is the enhancement of mutual understanding and the promotion of international peace. The purpose of this paper is to consider the extent to which this objective is achievable, particularly in the context of continuing controversy surrounding the country’s confrontation of its twentieth century military heritage in general and its role in the Pacific War in particular. Based on research at two ‘difficult’ heritage sites, Chiran Peace Museum in Kagoshima Prefecture and Yūshūkan War Museum in Tokyo, it explores specifically how the kamikaze phenomenon is commemorated and interpreted for international visitors, in so doing revealing a significant degree of dissonance at both sites. Not only is a selective narrative of heroic sacrifice presented within a wider revisionist history of the Pacific War but also no attempt is made to acknowledge the prevailing cultural context that might underpin a more nuanced understanding of the kamikaze. Hence, the paper concludes that a meaningful opportunity to enhance international understanding has been missed

Validation of Monte-Carlo simulations with measurements at the ICON beam-line at SINQ

ICON is the new cold neutron imaging facility at the neutron spallation source SINQ. The ICON facility is placed at beam-line S52 with direct view to the cold liquid D-2 moderator. The beam-line includes a 4.4 m long collimation section followed by a 1 I m long flight path to the imaging system. The essential part of the collimation section is composed of six revolving drums and a variable aperture wheel. Depending on the investigated object, different apertures are used. Measurements have shown that each setup has a different spatial neutron flux distribution and specific beam profiles. Measured beam profiles have been used to validate results of simulations coupling the Monte-Carlo program MCNPX with the neutron ray-tracing program McStas. In a first step, MCNPX was used to calculate neutron spectra closed to the SINQ target, at the entrance of the collimation section. These results served as an input for Mcstas where the beam-line itself was simulated. In the present paper, experimental and theoretical results will be compared and discussed. (c) 2008 Elsevier B.V. All rights reserved

Vol. 43 - The Energy Efficiency of Proton Driver Accelerators

High power proton driver accelerators are used to generate secondary particles at high intensities, such as pions, muons, neutrons and ultracold neutrons or neutrinos. The applications of these facilities have a broad spectrum in the fields of particle physics and condensed matter physics. Another industrial application under discussion is transmutation with accelerator driven systems. On the other hand, the production of megawatt-class proton beams implies the consumption of electrical power on a large scale. New projects and operating facilities must focus on improving the energy efficiency with a higher priority. This is especially true for linacs suggested for ADS-type applications, which may have to deliver >10 MW beams. With this workshop we are aiming to support such developments towards higher efficiency. The goal of this workshop is to consider the whole power conversion chain from grid to the secondary radiation needed at the experiments. In addition, important auxiliary systems of proton drivers are covered, such as cryogenic facilities. In the first session the motivation for energy efficienct accelerator technology was summarized. Then the major applications of proton drivers were reviewed – accelerator driven systems, particle physics research at the intensity frontier and neutron sources for condensed matter physics. In four sessions the energy efficiency topics beam targets, RF generation, accelerator concepts and auxiliary systems were discussed