The response to 150 GeV/nuc primary lead (^(208)Pb) and fragmented (A/Z=2.4, 2.2, 2.0) beams measured a silicon strip detector, designed for use in the Heavy Nuclei eXplorer (HNX) and an upgrade of the Super Trans-Iron Galactic Element Recorder (SuperTIGER) balloon experiment, was evaluated in a CERN test beam (H8A) during Nov - Dec 2018. The 500 μm thick, single-sided silicon detectors have 32 DC-coupled strips with 3 mm pitch on the junction side with 9.6×9.6 cm^2 active area. Discrete charge-preamplifiers and shaping amplifiers were used to read out the ohmic and junction side signals simultaneously using the SuperTIGER DAQ system. We report on the response in a configuration where all 32 strips were joined and read out together. The strip detector-under-test was situated 

between planar silicon detectors, which provided the charge selection as well as a comparison of the measured response of each detector. The combined data set shows excellent charge resolution and finely resolved elemental peaks from helium (Z=2) through lead (Z=82). In this paper, we provide a description of the test beam experiment and the results of the charge resolution analysis

Krizmanic, John F.

Labrador, Allan W.

Mewaldt, Richard A.

Caltech Authors - Main

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HNX/SuperTIGER Silicon Strip Detector Response to
Nuclei in Lead Primary and Fragmented Test Beams
John F. Krizmanic∗1,2,3†, Yosui Akaike1,2,3, Dana Braun4, Richard Bose4, James
Buckley4, Georgia De Nolfo2, Jeff Dumonthier2, Paul Dowkontt4, Zachary Hughes4,
Iker Liceaga Indart2,10, Jason Link1,2,3, John W. Mitchell2, J. Grant Mitchell2,11,
Martin A. Olevitch4, Scott Nutter5, Garry E. Simburger4, George Suarez2, Teresa
Tatoli1,2,3, Mark E. Wiedenbeck6, W. Robert Binns4, Theresa .J. Brandt2, Martin H.
Israel4, Allan W. Labrador7, Richard A. Mewaldt7, Brian F. Rauch4, Kenichi Sakai1,2,3,
Makoto Sasaki1,2,8, Edward C. Stone6, Nathan E. Walsh4, C. Jake Waddington9
1Center for Research and Exploration in Space Science & Technology
2NASA/Goddard Space Flight Center, Greenbelt, MD, USA
3University of Maryland, Baltimore County, Baltimore, MD, USA
4Dept. of Physics, Washington University in St. Louis, St. Louis, MO, USA
5Dept. of Physics, Northern Kentucky University, Highland Heights, KY, USA
6Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
7Space Radiation Lab, California Institute of Technology, Pasadena, CA, USA
8University of Maryland, College Park, College Park, MD USA
9School of Physics & Astronomy,University of Minnesota, Minneapolis, MN, USA
10Catholic University of America, Washington, DC, USA
11Dept. of Physics, George Washington University, Washington, DC, USA
The response to 150 GeV/nuc primary lead (208Pb) and fragmented (A/Z=2.4, 2.2, 2.0) beams
measured a silicon strip detector, designed for use in the Heavy Nuclei eXplorer (HNX) and an
upgrade of the Super Trans-Iron Galactic Element Recorder (SuperTIGER) balloon experiment,
was evaluated in a CERN test beam (H8A) during Nov - Dec 2018. The 500 µm thick, single-
sided silicon detectors have 32 DC-coupled strips with 3 mm pitch on the junction side with
9.6×9.6 cm2 active area. Discrete charge-preamplifiers and shaping amplifiers were used to read
out the ohmic and junction side signals simultaneously using the SuperTIGER DAQ system. We
report on the response in a configuration where all 32 strips were joined and read out together. The
strip detector-under-test was situated between planar silicon detectors, which provided the charge
selection as well as a comparison of the measured response of each detector. The combined data
set shows excellent charge resolution and finely resolved elemental peaks from helium (Z=2)
through lead (Z=82). In this paper, we provide a description of the test beam experiment and the
results of the charge resolution analysis.
36th International Cosmic Ray Conference -ICRC2019-
July 24th - August 1st, 2019
Madison, WI, U.S.A.
∗Speaker.
†Corresponding Author: E-mail: john.f.krizmanic@nasa.gov
c© Copyright owned by the author(s) under the terms of the Creative Commons
Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND 4.0). http://pos.sissa.it/
P
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HNX/SuperTIGER SSD Lead Test Beam Response John F. Krizmanic
1. Introduction
Figure 1: A schematic of the Cos-
micTIGER instrument illustrating the SSD
and Cherenkov detector subsystems.
The Heavy Nuclei eXplorer (HNX) mission [1,
2, 3] is comprised of two instruments to measure
the individual cosmic ray elemental abundances from
carbon through curium in a two year mission. The
Extremely-heavy Cosmic-ray Composition Observer
(ECCO) employs∼ 21 m2 of barium phosphate (BP-1)
glass tiles to record individual CR nuclei with Z ≥ 70
with high sensitivity through the actinides. ECCO,
based on the Trek experiment [4], requires the BP-
1 tiles to be returned to the Earth for processing.
The Cosmic-ray Trans-Iron Galactic Element Recorder
(CosmicTIGER) is an electronic instrument with suffi-
cient dynamic range to measure cosmic-ray (CR) nuclei from carbon through curium, but with an
area of 2 m2. Thus CosmicTIGER has a large measurement overlap with ECCO, especially in the
70≤ Z ≤ 82 region where event statistics are sufficiently large. CosmicTIGER employs three de-
tector subsystems: silicon strip detector (SSD) arrays, an acrylic (n=1.5) Cherenkov detector, and
an aerogel (n=1.04) Cherenkov detector. The Cherenkov detectors provide measurement of cosmic
ray charge and velocity with two different energy thresholds. The SSD array provides the charge
measurements with excellent charge resolution while also providing measurement of individual
nuclei trajectories. These allow the identification of CR nuclei at the individual element level via
the use of the dE/dx versus Cherenkov and Cherenkov versus Cherenkov techniques.
Figure 2: The strip side of a corner of an SSD
mounted on its window-pane board (from Ref. [7]).
A schematic of CosmicTIGER is shown
in Figure 1, showing the four planes of SSDs
in a orthogonal x-y arrangement above and
below the Cherenkov detectors, Each SSD
plane is a mosaic of 10×20 SSDs each with
∼ 10× 10 cm2 active area. Each SSD is a
single-sided DC-coupled silicon strip detec-
tor with 32 channels with 3 mm pitch on the
junction side and are 500 µm thick, The cur-
rent design has ten SSDs daisy-chained to-
gether to form ladders, with each ladder be-
ing readout by a two PHASIC ASICs [5] pro-
viding both tracking and charge measurement of the traversing CR. The ohmic side of each SSD
will be read out by a discrete charge-preamplifier chain to provide precision charge measurement
and event triggering signals. Based on the performance of the SSD and electronics, the anticipated
charge resolution is σZ < 0.25 up to Z=96. The SDD detectors developed for HNX could be em-
ployed in an upgrade in the long duration balloon (LDB) SuperTIGER instrument [6] to provide
both the tracking an charge measurements.
Five prototype single-sided, DC-coupled HNX/SuperTIGER SSD detectors, each with active
area of 96×96 mm2, were fabricated by Micron Semiconductors, LTD. Each detector was mounted
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HNX/SuperTIGER SSD Lead Test Beam Response John F. Krizmanic
to a window pane circuit board, with the SSD strip, guard ring, field plate, and ohmic side channels
wire bonded to traces connected to a two row-pin connector on opposite ends of the board. Figure 2
shows the corner of a strip side of a mounted SSD. Each of the SSDs fully deplete ∼< 32 V with a
total leakage current (32 strips + guard ring) of ∼ 100 nA at 100 V and at room temperature. The
individual strip leakage currents for each SSD was determined to be ∼ 1 nA/strip for two SSDs
and ∼ 3 nA/strip for three SSDs. The two detectors with the lower leakage current were tested in
CERN lead primary and fragmented beam in 2016 and the results were reported in Ref. [7]. In the
2018 beam test, the performance of one of the SSDs with ∼ 3 nA/strip was characterized.
2. 2018 CERN Beam Test Configuration
Figure 3: A schematic of the CERN test beam experimental setup used to determine the silicon detector
charge resolution performance.
Figure 4: The mounting of two calibration
silicon detectors in their lightbox.
The CERN beam test occurred November 21,
2018 to December 2, 2018 in the H8A beamline in
the North Area of CERN. The primary beam con-
sisted of 208Pb nuclei with 150 GeV/nucleon kinetic
energy. Fragmented beams with A/Z = 2.4,2.2,&2.0
were used to determine the SSD response from he-
lium (Z = 2) through lead (Z = 82). While several
experimental configurations were employed during the
CERN test beam run, we report on the results from the
final configuration that achieved the best charge reso-
lution performance of the silicon detectors, especially
at the lowest atomic numbers (Z ∼< 10). The schematic
of this experimental setup is shown in Figure 5. The
HNX prototype silicon strip detector (pSSD) under test
was mounted in a separate lightbox and placed behind four calibration silicon detectors (cSDs),
with two upstream and two far downstream of the pSSD. This was followed an experiment that
assessed the performance of silicon photomultiplier (SiPM) versus standard PMT readout of a
Cherenkov detector with aerogel radiators followed by a Cherenkov detector with acrylic radiators.
The Cherenkov lightboxes were followed by a lightbox with a plastic scintillators used in the beam
trigger. Next a prototype Advanced Particle-astrophysics Telescope (APT) detector’s response to
heavy nuclei was characterized by researchers from Washington University in St. Louis. Next, the
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HNX/SuperTIGER SSD Lead Test Beam Response John F. Krizmanic
lightbox with two downstream cSDs was located immediately behind the WUSTL APT prototype
detector in order to tag non-interacting nuclei in the beam for this experiment. Finally, a lightbox
used for a SiPM beam radiation exposure ended the stack of instruments. The results of the SiPM
Cherenkov and irradiation experiments are reported in a separate paper in this conference [8].
The cSDs were ∼ 10× 10 cm2, 500 µm thick pad detectors with the ohmic side of each
detector read out separately. The 32 strips on the HNX pSSD were electrically connected together
with the junction and ohmic sides read out individually. Figure 4 shows two cSDs mounted in
their lightbox before the cover was attached, and the HNX pSSD was similarly mounted in its own
lightbox. The cSDs and pSSDs were mounted at a 10◦ angle with respect to the beam direction
in order to minimize any crystal channeling effects. The cSDs and pSSD were AC-coupled to
RL-724 charge preamplifiers (manufactured by Rel-Labs) charge preamplifiers with each coupled
to Canberra 2022 shaping amplifiers (using 1 µs shaping times) whose signals were then supplied
to the inputs of a SuperTIGER FEE boards interfaced to the SuperTIGER data acquisition (DAC)
system [6]. The polarity of the the shaping amplifier signal was adjusted to provide positive polarity
signals, for both the ohmic and junction side readouts, into the SuperTIGER FEE input channels
since the FEE requires a positive unipolar signal. The cSDs and pSSDs were biased at positive 60
volt depletion voltage on the ohmic sides during all tests. The guard rings and field plates of the
pSSD were grounded for all tests.
Figure 5: A schematic of the beam trigger used in the CERN test beam experiments.
The data acquisition system required a beam trigger that was delayed by ∼ 3 µs after a beam
particle’s passage through the stack of detectors. The trigger needed to be moderately efficient for
charges 1 ≤ Z ≤ 82, corresponding to the range of fragments available in the beam. The beam
rate was adjusted to ∼ 1 kHz, in order that pileup was not an issue. In addition, fast timing was
not a critical design parameter. The trigger used a coincidence between the Hamamatsu R1924
PMTs on the two integrating Cherenkov boxes (acrylic and aerogel) after the PMT signals were
split between the acquisition system and the trigger. Inverting transformers converted the positive
polarity PMT signals on the trigger path to negative polarity. The signals were then discriminated
(∼ 1 V threshold on a LeCroy 821, 100 ns widths) and a coincidence generated by a LeCroy 622
logic module. The NIM-level signal started a gate generator set to a 1 µs width that was converted
by a LeCroy 688AL level converter to TTL. The TTL gate went to a Stanford DG535 gate generator
set to generate the trigger TTL pulse after a 3 µs delay. Based on the complete range of charges
seen by the silicon strip detectors, the trigger met the charge detection efficiency design goal.
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HNX/SuperTIGER SSD Lead Test Beam Response John F. Krizmanic
Pure Pb A/Z=2.4 A/Z=2.2 A/Z=2.0
Total Beam Triggers 1.2×105 1.6×105 5.0×105 3.1×105
Analyzed Events 2.2×104 3.2×104 1.3×105 1.2×105
Fraction Analyzed 17% 20% 25% 39%
Table 1: Test beam event statistics for the runs taken on Sunday Dec. 2, 2018.
2.1 Beam Test Results: Charge Resolution Analysis
The set of primary and fragmented lead beam runs that were used in the analysis as well as the
run statistics are summarized in Table 1. Pedestal runs occurred before and during the runs between
beam spills and were subtracted to obtain the measurement of the ionization energy in each silicon
detector. For the test beam runs used in this analysis, the width of the pedestals were σ ≈ 0.13 MIP
units for the cSDs and σ ≈ 0.1 MIP units for both the ohmic and strip sides of the HNX pSSD.
Here we present the details of the silicon detector charge resolution analysis.
Charge identification using the Calibration Silicon Detectors (cSDs) Using the information
from the upstream and downstream cSDs, the particle charge is identified and non-interacting
events are selected. Figure 6 is the charge distribution of two upstream layers of cSDs. The charge
resolution of cSDs is determined to be 0.22 e with using the first two CSDs and 0.19 with all four
layers. The charge consistency of all layers within the |Zi−Z|< 1 (i= 1−4), where i is the ID of
cSDs, are required for the HNX pSSD analysis.
Charge
0 10 20 30 40 50 60 70 80
Co
un
ts
1
10
210
310
(a) Z = 2−82
Charge
0 2 4 6 8 10 12 14 16
Co
un
ts
10
210
310
(b) Z = 2−16
Charge
70 72 74 76 78 80 82 84
Co
un
ts
1
10
210
310
(c) Z = 70−82
Figure 6: Charge distributions of first two upstream layers of calibration silicon detectors using the charge
selection defined by the four cSDs. Each color histograms show the events identified by the 4 layers of cSDs.
4
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HNX/SuperTIGER SSD Lead Test Beam Response John F. Krizmanic
Calibration of the HNX prototype Silicon Strip Detector (pSSD) Using the events tagged the
charge by 4 layers of cSDs, the detector response is calibrated. At first, the raw ADC signal is
normalized at the gaussian peak of Pb. Then, the all gaussian peaks are obtained in MIP units
as shown in Fig. 7. As shown in Fig. 7, the linearity is remarkable throughout the range 2 ∼<
Z ≤ 82 within 0.4% for both ohmic-side and strip-side for Z ∼> 5. After the correction of the
linearity, the particle charge with HNX-Silicon detector is calculated as Z =
√
Q, where Q is the
MIP. Figure 8 and 9 show the charge distribution of HNX pSSD with ohmic side and strip side
analyzed separately. The charge resolution of HNX pSSD shows in Fig. 10. The resolution is
constant with 0.24 e in the range of Z ∼> 5 for both the ohmic and strip side results.
M
IP
0
1000
2000
3000
4000
5000
6000
7000
8000
Pb
A/Z = 2.4
A/Z = 2.2
A/Z = 2.0
2Z
0 1000 2000 3000 4000 5000 6000 7000
R
at
io
0.9
0.92
0.94
0.96
0.98
1
1.02
1.04
1.06
1.08
1.1
(a) Ohmic-side
M
IP
0
1000
2000
3000
4000
5000
6000
7000
8000
Pb
A/Z = 2.4
A/Z = 2.2
A/Z = 2.0
2Z
0 1000 2000 3000 4000 5000 6000 7000
R
at
io
0.9
0.92
0.94
0.96
0.98
1
1.02
1.04
1.06
1.08
1.1
(b) Strip-side
Figure 7: The linearity of the HNX prototype Silicon Strip Detector as a function of Z2 which is normalized
by using Pb peak.
3. Discussion
The beam test results demonstrate that the HNX prototype silicon strip detectors can achieve
0.25 charge units of resolution for 5∼> Z ≤ 82 based on the 2018 CERN test beam results, assuming
sufficient performance of the read out electronics. This is consistent with the results we obtained
on different HNX pSSDs in the 2016 CERN test beam run [7], except we were able to reduce the
effects of electronic noise in the 2018 run while running with higher beam rates, which allowed
a better measurement of the charge resolution below Z ∼> 10. We note that individual elements
from helium through lead are clearly resolved, with the modest reduction in the charge resolution
for Z ∼< 5 shown in Figure 10. The resolution degradation is consistent being due to the inherent
noisy environment associated with being in an accelerator test beam in terms of the charge selection
requirements used in the analysis. As shown in Figure 7, the uncorrected linearity of the HNX is
remarkable for both the ohmic and strip side readout of the pSSD. Finally, we note that the ability
to use the SuperTIGER FEE boards and DAQ system with the input signals defined by the output
of shaping amplifiers aided in obtaining the superb charge resolution and is an innovative way to
use this system. The FEE input channels each use shaping amplifiers with 1 µs time-to-peak which
are then processed by peak-sensitive ADCs [6]. Normally, the output of a charge preamplier would
provide the input signals to the FEE boards.
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HNX/SuperTIGER SSD Lead Test Beam Response John F. Krizmanic
Charge
0 10 20 30 40 50 60 70 80
Co
un
ts
1
10
210
310
(a) Z = 2−82
Charge
0 2 4 6 8 10 12 14 16
Co
un
ts
1
10
210
310
(b) Z = 2−16
Charge
70 72 74 76 78 80 82 84
Co
un
ts
1
10
210
310
(c) Z = 70−82
Figure 8: Charge distributions of ohmic side of a single HNX pSSD using the charge selection defined by
the four cSDs. Each color histograms show the events identified by the 4 layers of cSDs.
4. Acknowledgements
We thank Mark Wiedenbeck (CalTech/SRL/JPL) for the use of the silicon calibration detec-
tors, the Rel-Labs preamplifier electronics, and the Canberra shaping amplifiers used in this beam
test. We also thank Marco Ricci (INFN/Frascati) for help in obtaining electronics and supplies from
the CERN electronics pool. Finally, we thank CERN for the opportunity to perform this beam test
and providing exceptional particle beams.
References
[1] J.W. Mitchell, The Heavy Nuclei eXplorer, Proc of the 36th ICRC (Madison) (2019)
[2] T. Hams, et al., Proc of the 34th ICRC (The Hague), PoS(ICRC2015)038 (2015)
[3] W.R. Binns et al., Proc of the 31st ICRC (Łódz´), Paper 0441 (2009)
[4] B.A. Weaver et al., NIMB, Vol 145, 3, p. 409-428 (1998)
[5] R.A. Mewaldt et al., Space Sci. Rev., Vol 136, 1-4, p. 285-362 (2008)
[6] W.R. Binns et al., ApJ, Vol. 788, id. 18 (2014)
[7] J.F. Krizmanic et al., Proc of the 35th ICRC (Buson), PoS(ICRC2017)242 (2017)
[8] J. Link et al., Silicon Photomultiplier Use in Particle Astrophysics and Heliophysics Missions, Proc of
the 36th ICRC (Madison) (2019)
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HNX/SuperTIGER SSD Lead Test Beam Response John F. Krizmanic
Charge
0 10 20 30 40 50 60 70 80
Co
un
ts
1
10
210
310
(a) Z = 2−82
Charge
0 2 4 6 8 10 12 14 16
Co
un
ts
10
210
310
(b) Z = 2−16
Charge
70 72 74 76 78 80 82 84
Co
un
ts
1
10
210
310
(c) Z = 70−82
Figure 9: Charge distributions of strip side of of a single HNX pSSD using the charge selection defined by
the four cSDs. Each color histograms show the events identified by the 4 layers of cSDs.
Atomic number
0 10 20 30 40 50 60 70 80
Ch
ar
ge
 re
so
lu
tio
n
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
(a) Ohmic-side
Atomic number
0 10 20 30 40 50 60 70 80
Ch
ar
ge
 re
so
lu
tio
n
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
(b) Strip-side
Figure 10: The charge resolution of a single HNX pSSD.
7


HNX/SuperTIGER Silicon Strip Detector Response to Nuclei in Lead Primary and Fragmented Test Beams

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HNX/SuperTIGER Silicon Strip Detector Response to Nuclei in Lead Primary and Fragmented Test Beams

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