I. HIGHLIGHTS OF THE YEARRIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Development of inspection system for bus extender cable ofRHIC-sPHENIX INTT detector
H. Imai,∗1,∗6 Y. Akiba,∗1 D. Cacace,∗2 K. Cheng,∗3 H. En’yo,∗1 T. Hachiya,∗1,∗4 S. Hasegawa,∗1,∗5 M. Hata,∗4T. Kondo,∗7 C. Kuo,∗3 H. -S. Li,∗8 R. -S. Lu,∗9 E. Mannel,∗2 C. Miraval,∗2 M. Morita,∗1,∗4 I. Nakagawa,∗1Y. Nakamura,∗1,∗6 G. Nakano,∗1,∗6 Y. Namimoto,∗1,∗4 R. Nouicer,∗2 G. Nukazuka,∗1 R. Pisani,∗2 M. Shibata,∗1,∗4C. Shih,∗3 M. Shimomura,∗4 M. Stojanovic,∗8 Y. Sugiyama,∗4 R. Takahama,∗1,∗4 W. -C. Tang,∗3 M. Watanabe,∗4
and X. Wei∗8
The sPHNEIX experiment is scheduled to begin
at Brookhaven National Laboratory (BNL) in 2023,
study quark-gluon plasma (QGP) by using a heavyion accelerator.1) We have developed a long, highsignal-line-density, ﬂexible substrate cable to transmit
data from one of the tracking detectors, INTermediate
Tracker (INTT), to a downstream data-processing circuit board. The cable is called Bus Extender (BEX),
which is 111 cm long and comprises 124 signal lines
separated by a space of 130 μm.
After ﬁve years of research and development, the cable is meets the speciﬁcations required by sPHENIX in
terms of both mechanical and electrical performances.
However, there is one remaining technical issue, namely,
a poor yield rate (30–50%) in mass production mainly
due to dust contamination during signal-line patterning. The contaminated dust causes abnormal patterns
in the signal lines, which tends to result in either shortor broken signal lines. The anomaly used to be manually inspected using a magnifying glass during the prototyping stage of the cable, which is not practical formass production because of the large area (a patternsheet accommodates four BEXs and the size is about
120 cm × 25 cm) to be inspected for 120 BEXs in total. The motivation of this study was to establish asemi-automated process for pattern inspection.
For this purpose, we developed an inspection ﬁxture,
which consists of a high-resolution microscope camera
on a moving aluminum frame, as shown in Fig. 1. The
aluminum base frame is set along the BEX signal line,
and the camera moves along the base frame, as shownwith the red arrow. A pattern image taken by the camera is then analyzed using a pattern-recognition software developed by us. The algorithm for anomaly detection from the image is as follows. First, the color
image is converted to black and white. Next, the number of pixels for each line and space in a direction perpendicular to the signal lines is counted for both black
and white zones and ﬁll number of pixel histograms,
∗1
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∗4
∗5
∗6
∗7
∗8
∗9RIKEN Nishina Center
Physics Department, Brookhaven National Laboratory
Department of Physics, National Central University
Department of Mathematical and Physical Sciences, Nara
Women’s University
Japan Atomic Energy Agency
Department of Physics, Rikkyo University
Tokyo Metropolitan Industrial Technology Research InstituteDepartment of Physics and Astronomy, Purdue University
Department of Physics, National Taiwan University

Fig. 1. Inspection ﬁxture and camera for the signal-line pattern of BEX.

respectively, to evaluate the mean and standard deviations of the number of pixels as references. Finally, thealgorithm detects anomaly spots on the image, wherethe pattern deviates by more than 5σ from the reference. The process described above is repeated to scanthrough the 111-cm-long signal lines. One of the abnormal patterns detected with this algorithm is indicatedusing the red circle in Fig. 2. This technique facilitatedinspections in mass production, which would have been
impossible otherwise.

Fig. 2. Example of anomaly spot and histogram of signalline pattern detected by the algorithm.

Reference1) I. Nakagawa et al., in this report.

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