Ⅱ-9. Instrumentation

RIKEN Accel. Prog. Rep. 53

Performance evaluation of a sensor module for INTT at sPHENIX
A. Suzuki,∗1 Y. Akiba,∗2 D. Cacace,∗3 K. Cheng,∗4 E. Desmond,∗3 T. Hachiya,∗2,∗1 S. Hasegawa,∗5 T. Kondo,∗6C. Kuo,∗4 M. Lenz,∗3 E. Mannel,∗3 C. Miraval,∗3 M. Morita,∗1 I. Nakagawa,∗2 R. Nouicer,∗3 R. Pisani,∗3
M. Shibata,∗1 C. Shih,∗4 T. Todoroki,∗2 X. Wei,∗7 and R. Xiao∗7
The intermediate silicon strip tracker (INTT) is oneof the tracking detectors of sPHENIX.1) An INTT sensor module consists of a silicon strip sensor, a readout chip called FPHX and a high-density interconnect(HDI).2) The size of the silicon strip sensor is 232.2 ×22.5 × 0.32 mm3 . FPHX is a read-out LSI chip usedfor PHENIX.1) One FPHX reads out 128 channels. 26
FPHXs correspond to 128 × 26 read-out channels. Eachchannel is equipped with a shaping ampliﬁer and 3-bit
ADC. HDI is a ﬂexible PC board.
We performed a beam test using a 120 GeV proton
beam in June, 2019 at Fermilab and analyzed the data
to evaluate the performance of the INTT sensor module.
Figure 1 shows the setup of three sensor modules and twotrigger scintillators. We call the layers from the front of
the beam direction L0, L1 and L2. Two scintillators arearranged to sandwich the sensor modules.
We deﬁne the eﬃciency of L0 by Eq. (1) and describe
how to calculate the eﬃciency. (1) Figure 2 shows thehit channel distributions for 26 FPHXs in a layer. Thebeam spot was observed at chip 6, 7, 19 and 20, respectively. L1 and L2 required a single strip hit at chip 6
and ADC > 3 to reduce noise. An L0 hit can be multistrip hits among several chips around the beam spot. (2)We calculate the channel diﬀerence between L1 and L2
to choose the coincident hit from the track. Figure 3(a)shows the hit correlation between L1 and L2 so thatevents of channels with a diﬀerence <±5 are selected foras shown in Fig. 3(b). (3) We calculate the hit expectation of L0 using L1 and L2 hits by using Eq. (2) to searchfor the most probable hit at L0. (4) We search for a corresponding hit at L0 to choose the one closest to the hitexpectation. L0 channels are numbered from 0 to 256
by combining two FPHX chips to cover the whole widthFig. 2. Hit channel distribution of L0. X-axis: entries, Yaxis: channel number.

Fig. 3. (a) Hit correlation between L1 and L2. X-axis: L1channel, Y-axis: L2 channel. (b) Diﬀerence (L1 channel L2 channel). (c) Hit correlation between L0 and expectation. X-axis: L0 channel, Y-axis: expected channel. (d)Diﬀerence (L0 channel - expected channel).

of the sensor. Figure 3(c) shows the hit correlation ofL0 with the expectation so that events of the closest hitof channels with a diﬀerence <±5 are selected as shown
Fig. 3(d). (5) The events of (2) as the denominator and(4) as the numerator for Eq. (1) are counted. The detection eﬃciency is evaluated as 96.0±0.5%, which is within
the error margins of the value of 96.4 ± 1.0% obtained in
the previous experiment conducted in 2018.
L0 Eﬃciency =N(L0hit ∩ L1hit ∩ L2hit ).
N(L1hit ∩ L2hit )L0exp = L1chan × 3 − L2chan × 2.

Fig. 1. Setup of ladders and scintillators in the beam test.
The orange arrow indicates the beam direction.
∗1
∗2
∗3
∗4
∗5
∗6
∗7

Nara Women’s University
RIKEN Nishina Center
Brookhaven National Laboratory
National Central University
Japan Atomic Energy Agency
Tokyo Metropolitan Industrial Technology Research InstitutePurdue University

(1)
(2)

In summary, we analyzed the beam test data to evaluate the eﬃciency of the INTT sensor module. The eﬃciency of L0 is 96.0 ± 0.6%. This result is consistent withthe 2018 result.
References

1) I. Nakagawa et al., in this report.
2) C. Aidata et al., Nucl. Instrum. Methods Phys. Res. A
755, 44–61 (2014).

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