The high luminosity upgrade of the Large Hadron Collider (HL-LHC) at CERN is expected to provide instantaneous luminosities of 5 × 10^(34) cm^(−2) s^(−1). The high luminosities expected at the HL-LHC will be accompanied by a factor of 5 to 10 more pileup compared with LHC conditions in 2015, causing general confusion for particle identification and event reconstruction. Precision timing allows to extend calorimetric measurements into such a high density environment by subtracting the energy deposits from pileup interactions. Calorimeters employing silicon as the active component have recently become a popular choice for the HL- LHC and future collider experiments which face very high radiation environments. We present studies of basic calorimetric and precision timing measurements using a prototype composed of tungsten absorber and silicon sensor as the active medium. We show that for the bulk of electromagnetic showers induced by electrons in the range of 20 GeV to 30 GeV, we can achieve time resolutions better than 25 ps per single pad sensor

Apresyan, A.

Bolla, G.

Bornheim, A.

Kim, H.

Los, S.

Pena, C.

Ramberg, E.

Ronzhin, A.

Spiropulu, M.

Xie, S.

Caltech Authors - Main

Journal of Physics: Conference Series
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Precision Timing with Silicon Sensors for Use in
Calorimetry
To cite this article: A Bornheim et al 2017 J. Phys.: Conf. Ser. 928 012020
 
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17th International Conference on Calorimetry in Particle Physics (CALOR2016) IOP Publishing
IOP Conf. Series: Journal of Physics: Conf. Series 9 8 (2017) 012020  doi :10.1088/1742-6596/928/1/012020
Precision Timing with Silicon Sensors for Use in
Calorimetry
A Bornheim1, A Ronzhin2, H Kim3, G Bolla2, C Pena1, S Xie1, A
Apresyan1, S Los2, M Spiropulu1, E Ramberg2
1Caltech, 1200 E. California Blvd., 91125 Pasadena, USA
2FNAL, Batavia, IL, USA
3University of Chicago, Chicago, IL, USA
E-mail: bornheim@hep.caltech.edu
Abstract. The high luminosity upgrade of the Large Hadron Collider (HL-LHC) at CERN
is expected to provide instantaneous luminosities of 5 × 1034cm−2s−1. The high luminosities
expected at the HL-LHC will be accompanied by a factor of 5 to 10 more pileup compared
with LHC conditions in 2015, causing general confusion for particle identification and event
reconstruction. Precision timing allows to extend calorimetric measurements into such a high
density environment by subtracting the energy deposits from pileup interactions. Calorimeters
employing silicon as the active component have recently become a popular choice for the HL-
LHC and future collider experiments which face very high radiation environments. We present
studies of basic calorimetric and precision timing measurements using a prototype composed
of tungsten absorber and silicon sensor as the active medium. We show that for the bulk of
electromagnetic showers induced by electrons in the range of 20 GeV to 30 GeV, we can achieve
time resolutions better than 25 ps per single pad sensor.
1. Introduction
To meet the challenges posed by current and future high energy colliders, particle physics
detectors have to operate in ever increasing particle fluxes and at higher interaction rates. Aside
from finer segmentation both for tracking devices as well as for calorimeters, precision timing
capabilities are being viewed as a very powerful additional functionality to enhance the physics
performance of the detectors. Timing resolutions of order few 10 ps allow to cleanly associate
signals to primary interactions. A 10 ps resolution is also equivalent to a spatial resolution of
a few mm. This allows tracking of photons with such a precision which is hugely important in
hadron collisions which have a significant fraction of the total energy carried by neutral mesons
decaying into photons. Precision timing calorimetry with scintillating crystals [1] and multi-
channel plates [2] is well established. In this paper we present our measurements using silicon
sensors as sensitive element in a precision timing calorimeter. Large scale silicon sensors are
considered as an upgrade option for the HL-LHC [3].
2. Experimental Setup
For our measurements, we used a silicon sensor produced by Hamamatsu [4]. The thickness of
the silicon was measured to be 325 µm. The transverse size of the sensor is 6 × 6 mm2. The
negative bias voltage was applied to the p-side of the silicon. We observe that the silicon is
21234567890
17th International Conference on Calorimetry in Particle Physics (CALOR2016) IOP Publishing
IOP Conf. Series: Journal of Physics: Conf. Series 9 8 (2017) 012020  doi :10.1088/1742-6596/928/1/012020
fully depleted above about 120 V. Timing measurements are expected to improve with larger
bias voltage as the the carrier velocity increases. Attention was paid to provide good filtering
for bias voltage, to reduce ground loop effects, and to minimize inductive loop for the signal
readout. The timing characteristics of the signal pulses are dominated primarily by properties
of the silicon sensor rather than the details of the circuit. The silicon diode was placed inside
a light-tight box of thickness 1.5 cm, which also provides electromagnetic shielding. The box is
made of 0.2 mm steel. The bias voltage was supplied to the circuitry by a cable with a balun
filter, terminated with an high voltage connector. The silicon diode output signal is read out
through an SMA connector electrically grounded to the box. The dark current was measured at
several values of the bias voltage. The maximum value of the dark current was less than 1.0 nA
at -500 V, which is the largest bias voltage used in the measurements reported in this paper.
The signals from the silicon sensor were amplified by two fast, high-bandwidth pre-amplifiers
connected in series. The first amplifier is an ORTEC VT120C pre-amplifier, and the second
amplifier is a Hamamatsu C5594 amplifier. Using a pulse-generator, we measured the combined
gain of the two amplifiers in series as a function of the input signal amplitude and found some
degree of non-linearity for typical signals produced by the silicon sensor under study, and we
corrected for them. Further details of the experimental setup can be found in [6]. As a reference
timing sensor we use a Photek MCP-PMT 240. The data are recorded with a DRS [5] based ring
sampler digitizer at at rate of 5 GS/s. Data was recorded at the FNAL M-test facility. Further
details on the reference timing system and its performance can be found in [2]. The timing
Figure 1. Experimental setup for the
precision timing measurement of the Si pad
sensor. The Si pad sensor is encapsulated in
a metal box and placed as close as possible
to the absorber. The beam impact point is
defined with a size of (2mm)2. The beam is
aligned transversely such that the response
of the the Si pad sensor is maximized. The
Photek reference counter is placed behind the
Si pad sensor with absorber
information from the Si sensor is extracted from the sampled pulses by fitting a straight line
to the rising edge of the pulse and determining the time at half the maximum amplitude. The
timing information of the reference detector is extracted from a Gaussian fit to the peak of the
pulses. A non-linearity from the amplifiers used is corrected in the data analysis. The quoted
time resolutions are one sigma width of the differential timing between the reference sensor and
the silicon pad sensor.
3. Experimental Results
Data were recorded at beam energies of 4, 8, 16 and 32 GeV with an electron beam, as well
as with 120 GeV protons for calibration and alignment purposes. Showers are induced with a
tungsten absorber of varying thickness to study the impact on the timing measurement. We
have demonstrated in [2] that the temporal evolution of showers is very coherent. This is of
crucial importance to exploit calorimeters as precision timing detectors. In Fig.: 2 we show
the response of the Si pad sensor for the four beam energies we used. The measurement was
performed after 6 radiation lengths of tungsten, approximately at the shower max. The mean
value of the response is well correlated with the beam energy, demonstrating that even a single
sensor features a calorimeter like response despite sampling only a very small part of the shower.
31234567890
17th International Conference on Calorimetry in Particle Physics (CALOR2016) IOP Publishing
IOP Conf. Series: Journal of Physics: Conf. Series 9 8 (2017) 012020  doi :10.1088/1742-6596/928/1/012020
The spread of the distributions in Fig.: 2 illustrates the RMS spread of the response. Due to
Figure 2. Mean signal amplitude and spread of
the signal amplitude as measured with the Si pad
sensor. The measurement was done for electron
beams of 4, 8, 16 and 32 GeV. We find a good
correlation between the beam energy and the mean
signal amplitude. This demonstrates that despite
the very limited containment of the Si sensor we
have a clear pattern of a calorimetric measurement.
the limited containment of the single sensor the spread is considerable.
In Fig.: 3 we show the time resolution of the Si pad sensor measured beam energies of 4, 8, 16
and 32 GeV. The measurement was performed with an absorber thickness of 6 radiation lengths,
approximately at shower max. The timing resolution improves with increased signal amplitude
and reaches about 22 ps for beam energies of 32 GeV. The contribution of the reference timing
sensor is not unfolded from this. It was determined to be less than 10 ps for an equivalent setup
[2]. As we have shown in [2] one can improve the timing precision for electromagnetic showers
Figure 3. Time resolution of the Si pad sensor as
a function of the incident beam energy. As shown
in Fig.: 2 the signal amplitude measured in the Si
pad sensor correlates well with the beam energy.
We see an improved timing resolution as a function
of the signal amplitude, reaching about 22 ps for
an electron beam with an energy of 32 GeV
by performing multiple measurements on a single shower. Si pads such as the one we use can
easily be arranged dense enough to perform 10 or more such measurements on a single shower.
This is expected to further improve the performance. Such studies are being carried out and will
be reported in the future. In Fig.: 4 we show the same data as used in Fig.: 3. However here the
data is more finely binned in signal amplitude. The data from the four different beam energies
is shown in different colors. We find that events with the same signal amplitude but different
beam energy show the same time resolution. As we see from Fig.: 2 the signal amplitude in
the Si pad fluctuates widely. Due to the small size of the pad the local shower fluctuations are
substantial. This demonstrates that the time resolution is dominated by the signal amplitude
in the sensor. Local shower fluctuations do not impact the timing measurement. This is further
evidence to the very coherent temporal evolution of electromagnetic showers as we discussed in
[1, 2]
4. Summary
We have measured the timing precision of a single silicon pad sensor in an electromagnetic
shower. We find that the timing precision improves with the signal amplitude, reaching 22 ps
on average measured with 32 GeV electrons after 6 radiation lengths of tungsten absorber. For
events in the tail of the signal amplitude distribution we measure down to 16 ps. This suggests
41234567890
17th International Conference on Calorimetry in Particle Physics (CALOR2016) IOP Publishing
IOP Conf. Series: Journal of Physics: Conf. Series 9 8 (2017) 012020  doi :10.1088/1742-6596/928/1/012020
Figure 4. Time resolution as a function of the
amplitude in the Si pad sensor. The data from
the four different beam energies are separated
by different colors. Due to the large spread
of the signal amplitude the data from different
beam energies overlaps. We find that the timing
resolution scales only with the signal amplitude.
Local shower fluctuations do not affect the timing
measurements at the precision of our measurement.
that for higher energies the timing precision would improve further. We conclude that a silicon
sampling calorimeter would allow to provide very precise timing information for electromagnetic
showers.
4.1. Acknowledgments
Operated by Fermi Research Alliance, LLC under Contract no. DE-AC02-07CH11359 with
the United States Department of Energy. Supported by funding from California Institute
of Technology High Energy Physics under Contract DE-SC0011925 with the United States
Department of Energy. We thank the FTBF personnel for very good beam conditions during
our test beam time. We also appreciate the technical support of the Fermilab SiDet department
for the production of high quality silicon samples.
References
[1] LYSO based precision timing calorimeters, A. Bornheim, CALOR2016, these proceedings
[2] Precision Timing with shower maximum detectors based on pixelated micro-channel plates, A. Bornheim,
CALOR2016, these proceedings
[3] HGCAL: A High-Granularity Calorimeter for the Endcaps of CMS at HL-LHC, C. Ochando, CMS
Collaboration, CALOR 2016, these proceedings
[4] www.hamamatsu.com
[5] https://www.psi.ch/drs/
[6] Test Beam Studies Of Silicon Timing for Use in Calorimetry, A. Apresyan, G. Bolla, A. Bornheim, H. Kim,
S. Los, C. Pena, E. Ramberg, A. Ronzhin, M. Spiropulu, S. Xie,NIM-A, doi:10.1016/j.nima.2016.04.031
[7] A. A. Derevshchikov, V. Yu. Khodyrev, V.I. Kryshkin, V.E. Rakhmatov, A. I. Ronzhin, On possibility to
make a new type of calorimeter: radiation resistant and fast. Preprint IFVE 90-99, Protvino, Russia, 1990.
[8] A 5 ps TOF-counter with an MCPPMT, K. Inami, , N. Kishimoto, Y. Enari, M. Nagamine, T. Ohshima,
NIM-A, doi:10.1016/j.nima.2015.05.029
[9] Development of a new fast shower maximum detector based on microchannel plates photomultipliers (MCP-
PMT) as an active element, A. Ronzhin, S. Los, E. Ramberg, M. Spiropulu, A. Apresyan, S. Xie, H. Kim,
A. Zatserklyaniy, NIM-A, doi.org/10.1016/j.nima.2014.05.039
[10] Study of the timing performance of micro-channel plate photomultiplier for use as an active layer in a shower
maximum detector, A. Ronzhin, S. Los, E. Ramberg, A. Apresyan, S. Xie, M. Spiropulu, H. Kim, NIM-A,
dx.doi.org/10.1016/j.nima.2015.06.006
[11] Direct tests of micro channel plates as the active element of a new shower maximum detector,
A. Ronzhin , S. Los, E. Ramberg, A. Apresyan, S. Xie, M. Spiropulu, H. Kim, NIM-A,
dx.doi.org/10.1016/j.nima.2015.05.029
[12] Calorimeters for Precision Timing Measurements in High Energy Physics, A. Bornheim, CALOR2014,
doi:10.1088/1742-6596/587/1/012057
[13] On timing properties of LYSO-based calorimeters, D. Anderson, A. Apresyan, A. Bornheim, J. Duarte, C.
Pena, A. Ronzhin, M. Spiropulu, J. Trevor, S. Xie, NIM-A, doi:10.1016/j.nima.2015.04.013, 2015


Precision Timing with Silicon Sensors for Use in Calorimetry

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Precision Timing with Silicon Sensors for Use in Calorimetry

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