International Society for Neutron Radiology (ISNR)

The Workshop for Energy depended Neutron Imaging studies was held in Sapporo, Japan, during June 6th and 9th, 2010.

Scientists from 6 major countries, specialized in neutron imaging, met in Sapporo, Japan, between June 6th and 9th 2010, to discuss the progress and future development in the very promising field of neutron energy selective imaging. This aspect in neutron research gained more relevance in the past years with the inauguration of new neutron sources, which are spallation based and provide pulsed neutron beam lines. A suitable energy selection can be obtained by the time-of-flight measurement techniques. The neutron imaging aspect at these sources was one of the main issues of the NEUWAVE-3 meeting.

For the moment, there are facilities started running in USA (SNS), Japan (J-PARC) and UK (ISIS-TS2) which are top in their performance in respect to pulse peak power with the potential of further improvement and upgrade. Europe has decided about its spallation neutron source project ESS, allocated to be installed in Lund (Sweden).

Among the potential users of these sources the neutron imaging community plays still a minor role. However, there are indications for important new options in neutron research when imaging capabilities will be introduced and used properly. A direct link to neutron scattering techniques and its information becomes clearly visible. So, phase bases techniques, as well as the use of polarized neutrons become more and more important for both neutron scattering and imaging due to complementary information about the physical system (sample). The development of new detector systems enriches the field of neutron scattering in a same manner.

This approach was one major aspect during NEUWAVE-3, which was triggered by the decision at ISIS to build the IMAT facility at target station 2 and to prepare the beam port 22 at J-PARC for a dedicated neutron imaging installation. In USA, there is the VENUS project in its preparative phase and looks for funding after its approval by the scientific council at SNS in 2009.

The series of NEUWAVE meetings was initialized at the Technische Universität München two years ago in order to invite prominent representatives of the neutron imaging community dealing with advanced methods at their facilities to exchange their knowledge and experience in a relaxed manner and open-minded atmosphere. Therefore, the days of topical presentations were surpassed by an introductory walk to a mountain on the Sunday in advance to the scientific event. This physical activity has enabled to familiarize between all participants in an easy manner.

The second meeting (NEUWAVE-2) was held in 2009 near to ISIS in Abingdon (UK) and focused more onto the pulsed beam option for neutron imaging than before. It was clarified that the study of textures, strain and phase effects might bridge between neutron scattering and imaging in a best possible way by the future installations at pulsed sources.

During NEUWAVE-3, hosted by the Hokkaido University, Sapporo, Japan, a broad range of topics was discussed within the 30 oral presentations during the three days of scientific interaction. First of all, the experiences about the options in the energy selective mode were reported in respect to the visualization of stress-strain performance, crystalline grain size distribution and Bragg edge contrast enhancement. Secondly, the approach towards new detection system for time-dependent studies keeping the spatial resolution high was discussed and some new concepts were described with first obtained results. Here, the Japanese contribution was the most important one, which is based on the usage of the test beam line NOBORU (BL10) at the J-PARC facility. The third topic was the beam line layout and a comparison was made between the proposed projects at the above mentioned facilities.

From the application point of view and not less important was the discussion of running new features in neutron imaging: usage of polarized neutrons for the study of magnetic phenomena and phase contrast phenomena for enhancing the contrast near edges within non-visible structures. These contributions indicated that both the scientific and the applied usage of the future beam lines at the new sources have to be taken into account adequately.

The meeting in Sapporo took profit from the excellent preparation by the team around Prof. Y. Kyjanagy (Sapporo University), the exited interaction between the participants and the challenge for new scientific options with the methods in energy selective neutron imaging. It was started with a similar mountain walk than near Munich two years before, but now onto the top of the volcano Mt. Tarumae. The visit of the accelerator installation at the Hokkaido University for neutron research convinced the participants about the competence of the Japanese scientists dealing with specific preparative studies for the J-PARC facilities.

The workshop presentations will be made available on the home page of the Hokkaido University in the next few weeks.

All participants agreed to continue this kind of meetings in a tight sequence of one year in order to keep valid the access to the new neutron sources in the most pragmatic and best possible scientific way. It was decided to hand over the responsibility for NEUWAVE-4 to USA, probably to be held in Tennessee next to the SNS facility.

Eberhard Lehmann

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