Ⅱ-9. Instrumentation

RIKEN Accel. Prog. Rep. 48 (2015)

Quality assurance test of pixel detector ladders for VTX
T. Sumita,∗1 Y. Akiba,∗1 H. Asano,∗1,∗2 T. Hachiya,∗1 M. Kurosawa,∗1 T. Moon,∗1,∗3 H. Nakagomi,∗1,∗4C. Pancake,∗5 H. Sako,∗1 S. Sato,∗1 A. Taketani,∗1 and the PHENIX VTX group
A silicon vertex tracker (VTX) was installed in thePHENIX detector at the Relativistic Heavy Ion Collider. The VTX detector consists of two inner layersof silicon pixel detectors and two outer layers of silicon strip detectors. A pixel ladder is composed of amechanical stave, four hybrid sensors1) , and two readout buses. A hybrid sensor is an assembly consistingof a silicon pixel sensor and four readout chips (ALICE1LHCb2) ) bump-bonded to the sensor. One ladderhas 16 readout chips and one readout chip has 8,192
pixels, with a pixel size of 425 µm × 50 µm, organizedin 32 columns and 256 rows.
We fabricated new spare silicon pixel ladders. Inorder to ensure correct operation before the assemblyof the VTX detector, quality assurance (QA) test ofthe ladders need to be performed. This report presents
the results of the QA test for the ladders.
The QA test system consists of Silicon PIxel ReadOut (SPIRO) modules, Front-End Module (FEM), andNOVEC HFE-7200.3) The SPIRO modules provide allelectricity, control the readout chip of the sensor module and read out pixel data The FEM is an interface
between the SPIRO modules and the data acquisition
system. NOVEC HFE-7200 was used to cool the readout chips. The following tests are performed for eachladder.
(1) Current consumption:
The current consumption of the analog and digital circuits of the readout chips are measured.
(2) JTAG functionality:
It is conﬁrmed whether the conﬁguration settings in the chip can be controlled by using Joint
Test Action Group (JTAG4) ) protocol.
(3) Minimum threshold:For all chips, the minimum threshold in all pixels
are determined.
(4) Pulse test:
Pulse test is to check for dead chips and connections. The test pulse from the pulsar inside thechip is transmitted to each pixel cell.
(5) Test using a β-ray source (90 Sr):
Faulty bump bonds and the maximum eﬃciency
are evaluated by β-source measurements
The ladder is biased at 10 V during the measurement.
A total of 7 ladders were tested, and correct operation of all the ladders was conﬁrmed except for one lad∗1∗2∗3∗4∗5Fig. 1. Typical result of a readout chip in the source test.
The horizontal and vertical axes represent pixel position
along the column and row directions, respectively. Low
gray-levels represents a low number of hits.

der. Four chips (one hybrid sensor) of the incorrectly
working ladder did not respond to the tests because ofa short circuit in the readout bus. A typical result ofa readout chip in the source test is shown in Fig. 1.
The ineﬃcient area at the bottom of columns 1, 9, 17,
and 25 is attributed to the presence of the test pulse
signal generator on the readout chips, which aﬀected
the readout circuit.
In summary, QA tests for the seven new assembled
pixel ladders were performed. The results conﬁrmedthat six ladders are working properly and that a part ofone ladder is not functional. One of functional ladders
will be used in the 2015 run.
References
1) T. Sumita et al.: RIKEN Accel. Prog. Rep. 47 230(2013).
2) W. Snoeys et al.: Nucl. Instr. Meth. A 466, 366 (2001).
3) M. Kurosawa et al.: RIKEN Accel. Prog. Rep. 43 208(2010).
4) IEEE std 1149.1.

RIKEN Nishina Center
Department of Physics, Kyoto University
Department of Physics, Yonsei University
Department of Physics, University of Tsukuba
Department of Physics, Stony Brook University- 245 -

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