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Two-dimensional position-sensitive 3He -neutron detector for reflectometry and high-resolution diffractometry
Physica B 276}278 (2000) 210}211
Two-dimensional position-sensitive He-neutron detector for re#ectometry and high-resolution di!ractometry M. Marmotti, M. Haese-Seiller, R. Kampmann* Institut fu( r Werkstoworschung, GKSS Forschungszentrum, Max Plank Strasse, 21502 Geesthacht, Germany
Abstract A two-dimensional position-sensitive neutron detector has been developed at the Geesthacht Neutron Facility (GeNF). The detector is a He and CF "lled multiwire proportional counter with delay line readout and has a sensitive area of 300 mm ;300 mm and a high detection e$ciency for wavelengths j'0.15 nm. It is an important component of the new di!ractometer ARES at GeNF which is dedicated to the analysis of residual stresses. The detector design to achieve excellent linearity, detection homogeneity and a spatial resolution of about 2 mm ;2 mm has been described. 2000 Elsevier Science B.V. All rights reserved. Keywords: Position-sensitive detectors; Re#ectometry; Residual stress
1. Introduction He and CF "lled multiwire proportional counters with delay line readout are widely used for the detection of thermal and cold neutrons, the basic design of such detectors is well known [1,2]. We have developed a two-dimensional position-sensitive neutron detector with an active area of 300 mm ;300 mm for the new di!ractometer ARES at GeNF which is dedicated to the analysis of residual stresses [3]. In this paper the design and test measurements of this detector are described. 2. ARES detector 2.1. Detector design Neutrons with wavelengths from about 0.1 to 0.3 nm may be used at ARES which is located at a thermal neutron guide with a characteristic wavelength of 0.1 nm [3].
* Corresponding author. Fax: #49-4152-87-1338. E-mail address: [email protected] (R. Kampmann)
The sensitive area of the ARES detector amounts to 300 mm ;300 mm. The anode is made of 8 lm thick tungsten wires arranged at a distance of 2 mm, pick-up and drift electrodes consist of 30 lm thick wires with a distance of 2 mm. The detector has a detection depth of 3 cm to achieve a high detection probability P at rather low He partial pressure (P+60% for j"0.15 nm and p "2.5 bar). & The anode is placed in the middle of the detection volume, which is limited by the drift electrodes located at a distance of 15 mm from the anode. The position of the neutron absorption is detected by means of the cathodes which are placed at a distance of only 5 mm from the anode. Thus, limiting the detection volume by drift electrodes and positioning the cathodes close to the anode lead to (i) a high detection sensitivity for short wavelength neutrons at rather low He pressure, (ii) rather strong cathode signals and (iii) these are concentrated on fewer wires as in case of a much larger distance between anode and cathode. 2.2. Test measurements At "rst the ARES detector was tested with a X-ray source for which the detector was "lled with a mixture of Ar and CO as detection gas and closed with a X-ray
0921-4526/00/$ - see front matter 2000 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 1 - 4 5 2 6 ( 9 9 ) 0 1 2 9 2 - 2
M. Marmotti et al. / Physica B 276}278 (2000) 210}211
Fig. 1. Test of the ARES detector with an X-ray source. Photons are absorbed by an Christmas angel placed in front of the detector.
transparent cover. Di!erent absorbers were put in front of the detector, and an excellent detection homogeneity as well as an impressive spatial resolution were found, Fig. 1. Then the pressure cover was mounted and the neutron detection gas consisting of 2.5 bar He and 2 bar CF was "lled in. Afterwards the detector was tested with a well-collimated cold neutron beam. A spatial resolution of about 2 mm;2 mm was found, Fig. 2.
211
Fig. 2. Test of the ARES detector with cold neutrons. The detector was moved perpendicular to the well collimated incident beam (diameter(0.5 mm) as indicated.
tested at the Geesthacht Neutron Facility (GeNF). Excellent linearity, detection homogeneity and a spatial resolution of about 2 mm;2 mm were found. Further detectors with improved resolution are being built for neutron re#ectometry and detection of high energetic synchrotron radiation.
References 3. Perspectives New electrodes are being developed for the ARES detector to improve its spatial resolution to about 1 mm. Further detectors of this type are being developed for neutron re#ectometry and detection of high energetic synchrotron radiation for which they may be "lled with Ar or Xe instead of He. A signi"cantly larger detector with a sensitive area of about 600 mm ;400 mm is being developed for the re#ectometer REFSANS to be built at the new research reactor FRM-II [4].
4. Summary A two-dimensional position-sensitive He multiwire neutron detector has successfully been developed and
[1] J. Fischer, V. Radeka, R.A. Boie, in: P. Convert, J.B. Forsyth (Eds.), Position-Sensitive Detection of Thermal Neutrons, Academic Press, New York, 1983, p. 129. [2] C.J. Boulin, R. Kempf, A. Gabriel, M.H.J. Koch, Nucl. Instr. and Meth. A 269 (1988) 312. [3] P. Staron, H.-U. Ruhnau, M. Marmotti, P. Mikula, R. Kampann, in these Proceedings (ECNS '99), Physica B 276}278 (2000). [4] R. Kampmann, V. Deriglazov, M. Haese-Seiller, M. Marmotti, M. Tristl, E. Sackmann, in these Proceedings (ECNS '99), Physica B 276}278 (2000).
Two-dimensional position-sensitive He-neutron detector for re#ectometry and high-resolution di!ractometry M. Marmotti, M. Haese-Seiller, R. Kampmann* Institut fu( r Werkstoworschung, GKSS Forschungszentrum, Max Plank Strasse, 21502 Geesthacht, Germany
Abstract A two-dimensional position-sensitive neutron detector has been developed at the Geesthacht Neutron Facility (GeNF). The detector is a He and CF "lled multiwire proportional counter with delay line readout and has a sensitive area of 300 mm ;300 mm and a high detection e$ciency for wavelengths j'0.15 nm. It is an important component of the new di!ractometer ARES at GeNF which is dedicated to the analysis of residual stresses. The detector design to achieve excellent linearity, detection homogeneity and a spatial resolution of about 2 mm ;2 mm has been described. 2000 Elsevier Science B.V. All rights reserved. Keywords: Position-sensitive detectors; Re#ectometry; Residual stress
1. Introduction He and CF "lled multiwire proportional counters with delay line readout are widely used for the detection of thermal and cold neutrons, the basic design of such detectors is well known [1,2]. We have developed a two-dimensional position-sensitive neutron detector with an active area of 300 mm ;300 mm for the new di!ractometer ARES at GeNF which is dedicated to the analysis of residual stresses [3]. In this paper the design and test measurements of this detector are described. 2. ARES detector 2.1. Detector design Neutrons with wavelengths from about 0.1 to 0.3 nm may be used at ARES which is located at a thermal neutron guide with a characteristic wavelength of 0.1 nm [3].
* Corresponding author. Fax: #49-4152-87-1338. E-mail address: [email protected] (R. Kampmann)
The sensitive area of the ARES detector amounts to 300 mm ;300 mm. The anode is made of 8 lm thick tungsten wires arranged at a distance of 2 mm, pick-up and drift electrodes consist of 30 lm thick wires with a distance of 2 mm. The detector has a detection depth of 3 cm to achieve a high detection probability P at rather low He partial pressure (P+60% for j"0.15 nm and p "2.5 bar). & The anode is placed in the middle of the detection volume, which is limited by the drift electrodes located at a distance of 15 mm from the anode. The position of the neutron absorption is detected by means of the cathodes which are placed at a distance of only 5 mm from the anode. Thus, limiting the detection volume by drift electrodes and positioning the cathodes close to the anode lead to (i) a high detection sensitivity for short wavelength neutrons at rather low He pressure, (ii) rather strong cathode signals and (iii) these are concentrated on fewer wires as in case of a much larger distance between anode and cathode. 2.2. Test measurements At "rst the ARES detector was tested with a X-ray source for which the detector was "lled with a mixture of Ar and CO as detection gas and closed with a X-ray
0921-4526/00/$ - see front matter 2000 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 1 - 4 5 2 6 ( 9 9 ) 0 1 2 9 2 - 2
M. Marmotti et al. / Physica B 276}278 (2000) 210}211
Fig. 1. Test of the ARES detector with an X-ray source. Photons are absorbed by an Christmas angel placed in front of the detector.
transparent cover. Di!erent absorbers were put in front of the detector, and an excellent detection homogeneity as well as an impressive spatial resolution were found, Fig. 1. Then the pressure cover was mounted and the neutron detection gas consisting of 2.5 bar He and 2 bar CF was "lled in. Afterwards the detector was tested with a well-collimated cold neutron beam. A spatial resolution of about 2 mm;2 mm was found, Fig. 2.
211
Fig. 2. Test of the ARES detector with cold neutrons. The detector was moved perpendicular to the well collimated incident beam (diameter(0.5 mm) as indicated.
tested at the Geesthacht Neutron Facility (GeNF). Excellent linearity, detection homogeneity and a spatial resolution of about 2 mm;2 mm were found. Further detectors with improved resolution are being built for neutron re#ectometry and detection of high energetic synchrotron radiation.
References 3. Perspectives New electrodes are being developed for the ARES detector to improve its spatial resolution to about 1 mm. Further detectors of this type are being developed for neutron re#ectometry and detection of high energetic synchrotron radiation for which they may be "lled with Ar or Xe instead of He. A signi"cantly larger detector with a sensitive area of about 600 mm ;400 mm is being developed for the re#ectometer REFSANS to be built at the new research reactor FRM-II [4].
4. Summary A two-dimensional position-sensitive He multiwire neutron detector has successfully been developed and
[1] J. Fischer, V. Radeka, R.A. Boie, in: P. Convert, J.B. Forsyth (Eds.), Position-Sensitive Detection of Thermal Neutrons, Academic Press, New York, 1983, p. 129. [2] C.J. Boulin, R. Kempf, A. Gabriel, M.H.J. Koch, Nucl. Instr. and Meth. A 269 (1988) 312. [3] P. Staron, H.-U. Ruhnau, M. Marmotti, P. Mikula, R. Kampann, in these Proceedings (ECNS '99), Physica B 276}278 (2000). [4] R. Kampmann, V. Deriglazov, M. Haese-Seiller, M. Marmotti, M. Tristl, E. Sackmann, in these Proceedings (ECNS '99), Physica B 276}278 (2000).