2008 IEEE Nuclear Science Symposium Conference Record N26-6 Characterization of the High-Efficiency Neutron Detector Array (HENDA) P. Ugorowski, Member, IEEE, S Bellinger, Member, IEEE, L. Crow, C. Henderson, W.L. Dunn, W.J. McNeil, Member, IEEE, R.D. Taylor and D. S. McGregor, Member, IEEE Fig. 1 Planar device layout [McNeil, 2007]. and connects them to a 125 Jlm square bonding pad [1]. The aluminum trace has an added effect of lowering the resistance along each channel, allowing the charges produced by the 6Li(n,aiH reaction to travel to the bonding pads with minimal loss. 4 Single pixel p-typc n-typc \ 6JjI" As shown in Fig. 1, the bonding pads were arranged for every other channel which easily matches the PATARA I chip's pitch [2], and required two sets of bond pads for the detector. The bond pads were placed on the top and bottom of the detector, which was organized in odd and even channels. A uniform 10 11m layer of neutron-sensitive 6LiF was placed over the channels. A diagram of the layer structure of the planar device is shown in Fig. 2. Abstract-Two new pixellated neutron detectors developed at the Semiconductor Materials and Radiological Technologies Laboratory (SMART Lab) at Kansas State University, for eventual use at Oak Ridge National Laboratory Spallation Neutron Source, were tested for resolution, count rate and efficiency. II. PROTOTYPE DESIGN Each prototype consists of 32 channels, and uses 6LiF as the neutron-sensitive material and a Si photodiode p-n junction as the base for the detector. Neutrons react with the 6LiF, producing electron-hole pairs that cause current to flow within the biased semiconductor. Each channel has 100 Jlm pitch with a 10 11m border on each side and is 4 cm long. The 10 11m border serves to prevent channels from shorting out one another, and prevents channel cross-talk. The planar device consisted of 32 individual channels that utilized a p-type diffuse region within the 100 11m pitch. As seen in Fig 1, an aluminum metal contact lines the perimeter of each channel I. INTRODUCTION T hree new High-Efficiency Neutron Detector Arrays (HENDA) were developed, fabricated and characterized at the Semiconductor Materials and Radiological Technologies Laboratory (SMART Lab) at Kansas State University for the Spallation Neutron Source (SNS) located at Oak Ridge National Laboratory (ORNL). The proposed uses of a this semiconductor-based neutron detector are neutron diffraction measurements on materials, conducted at Neutron Power Diffractometer and the Neutron Residual Stress Mapping Facility at the High Flux Isotope Reactor (HFIR), and the proposed VULCAN Engineering Diffractometer (VED) and High Pressure Diffractometer (HPD), all at ORNL. The small pixel size should provide angular resolution without the need for long neutron path lengths. Two detectors based on the general designs described below were tested: a planar device, and a trenched device with 100 J.1m deep trenches. Manuscript received November 14, 2008. Project funded by the National Science Foundation under grant no. 0412208. P. Ugorowski, S. Bellinger, C. Henderson, W.L. Dunn, W.J. McNeil, R.D. Taylor and D. S. McGregor are with Kansas State University, Manhattan, KS 66506 USA (phone: 785-532-2382; fax: 785-532-7057; e-mail: pugo@ksu.edu, slb3888@ksu.edu, cmhender@kstl.edu, dunn@ksu.edu, wjm444@ksu.edu , rdtaylor@ksu.edu, mcgregor@ksll.edu). L. Crow is with Oak Ridge National Laboratory, Oak Ridge, TN 37831-6459, (phone: (865)241-0096 Fax: (865)241-6739, email:crowlmjr@ornl.gov) Fig. 2 Planar device cross-section. The trenched device used the basic design of the planar device with the exception that each 100 J.1m p-type diffused region contains a 4 cm long 30 Jlm wide straight trench through the middle of each channel, as seen in Fig. 3. 978-1-4244-2715-4/08/$25.00 ©2008 IEEE 1901 Authorized licensed use limited to: Kansas State University. Downloaded on September 8, 2009 at 14:37 from IEEE Xplore. Restrictions apply.