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POWTEX (under construction)
High-intensity time-of-flight diffractometer
The high-intensity TOF diffractometer POWTEX is designed and built by RWTH Aachen University and Forschungszentrum Jülich. The University of Göttingen cooperates by developing the texture analysis and by providing additional sample environments. Both projects have been granted by the German Federal Ministry of Education and Research (BMBF). POWTEX will be part of the JCNS instrumentation pool.
POWTEX is an acronym for POWder and TEXture because the instrument will fulfill the needs of the solid-state chemistry, the geoscience as well as the materials science communities with regard to powder and texture diffraction. The instrument design combines several new concepts. The neutron guide system consists of two double-elliptic parts with a common focal point of
In order to produce sharp pulses of 10 µs, the pulse chopper uses two counter-rotating discs at 200 Hz and at a short distance of only 0.5 cm. A variation of the chopper settings allows a flexible time structure to change the wavelength band or the pulse frequency (pulse-overlap mode like at POLDI, PSI yields a ten times higher intensity).
Because of the 3He shortage, two new detector developments were initiated (6LiF-WSF and 10B-Jalousie). While both prototypes successfully passed a test beam time, the 10B-Jalousie detector was chosen as the future POWTEX detector concept. The detector design will cover a huge solid angle (10 sr) and its dimensions will allow large sample environments (e.g. in situ experiments). The high detector coverage is of particular importance for texture measurements because it avoids the need for tilting the sample. Furthermore, it allows texture measurements without sample rotation (without sample environment) and it reduces the number of sample rotations with sample environment. It allows simultaneous strain/stress/texture measurements and recrystallization analysis. For powder diffraction the covered solid angle relates directly to the efficiency/measurement time. With the three-dimensional (2θ, TOF, intensity) diffractograms and an adapted data treatment, POWTEX will simultaneously benefit from the higher resolution in back-scattering and the high intensity at lower angles.
 A. Houben, W. Schweika, Th. Brückel, R. Dronskowski, Nucl. Instr. and Meth. A, 2012, 680, 124–133.
The high intensity will allow comparatively short measurement times and a high sample throughput.
A tailored set of sample environment is inevitable to avoid shadowing the detector. To benefit from the short measurement times a cryo-furnace with a temperature range from 10 K to 700 K including a sample changer is planned. Our colleagues at the University of Göttingen and the FRM II design a mirror oven for temperatures up to 2000 °C which can be operated with inert or reactive gases. Göttingen University also designs sample environments for specific geoscience applications, e.g., a unique uniaxial and triaxial deformation apparatus.
*Expected design values
Dr. Werner Schweika (JCNS)
Phone: +49 (0)2461 61-6650
Dr. Jens Walter (GZ Göttingen)
Phone: +49 (0)551 39-33196
Find the latest publications regarding POWTEX in our publication database iMPULSE: