The DMAPS upgrade of the Belle II vertex detector Babeluk, M.; Barbero, M.; Baudot, J. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
07/2024, Letnik:
1064
Journal Article
Recenzirano
The Belle II experiment at KEK in Japan considers an upgrade for the vertex detector system in line with the accelerator upgrade for higher luminosity at long shutdown 2 planned for 2028.
One ...proposal for the upgrade of the vertex detector called VTX aims to improve background robustness and reduce occupancy using small and fast pixels. VTX accommodates the OBELIX depleted monolithic active CMOS pixel sensor (DMAPS) on all five proposed layers. OBELIX is specifically developed for the VTX application and based on the TJ-Monopix2 chip initially developed to meet the requirements of the outer layers of the ATLAS inner tracker (ITk).
This paper will review recent tests of the TJ-Monopix2 chip as well as various design aspects of the OBELIX-1 chip currently under development.
The ultra-thin and highly granular CMOS Monolithic Active Pixel Sensors (MAPS) are typically optimized for high rate high precision tracking, which implies the use of a very thin active medium and ...digital readout. Both features hamper using the devices for identifying low momentum particles by means of dE/dx. Still, MAPS feature charge sharing and typically clusters of more than one fired pixel per impinging particles are formed. It was previously shown that the number of fired pixels per cluster scales with the dE/dx, which allowed identifying highly ionizing nuclear fragments 1. Assuming a sufficiently strong response to different dE/dx, this approach could also be considered for distinguishing minimum ionizing particles (MIP) from light fragments like alpha particles in tracking detectors. In this work, we study this response with particle beams with a dE/dx of up to four times the ones of MIPs, for non-irradiated and irradiated chips, with different sensing nodes as implemented in the MIMOSIS-1 prototype used for the vertex detector of the CBM experiment.
CMOS pixel sensors are foreseen to equip the vertex detector (called PXL) of the upgraded inner tracking system of the STAR experiment at RHIC. The sensors (called ULTIMATE) are being designed and ...their architecture is being optimized for the PXL specifications, extrapolating from the MIMOSA-26 sensor realized for the EUDET beam telescope.
The paper gives an overview of the ULTIMATE sensor specifications and of the adaptation of its forerunner, MIMOSA-26, to the PXL specifications.
One of the main changes between MIMOSA-26 and ULTIMATE is the use of a high resistivity epitaxial layer. Recent performance assessments obtained with MIMOSA-26 sensors manufactured on such an epitaxial layer are presented, as well as results of beam tests obtained with a prototype probing improved versions of the MIMOSA-26 pixel design. They show drastic improvements of the pixel signal-to-noise ratio and of the sensor radiation tolerance with respect to the performances achieved with a standard, i.e. low resistivity, layer.
In order to develop precision vertex detectors for the future linear collider, fast monolithic active pixel sensors are studied. A standard CMOS 0.25 mum digital process is used to design a test chip ...which includes different pixel types, column-level discriminators, and a fully programmable digital sequencer. In-pixel amplification is implemented together with double sampling. Different charge-to-voltage conversion factors were obtained using amplifiers with different gains or diode sizes. Pixel architectures with dc and ac coupling to charge sensing element were proposed. Hits from conversion of 55 Fe photons were recorded for the dc-coupled and ac-coupled pixel versions. Double sampling is functional and allows almost a complete cancellation of fixed pattern noise
Improved radiation tolerance of MAPS using a depleted epitaxial layer Dorokhov, A.; Bertolone, G.; Baudot, J. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2010, Letnik:
624, Številka:
2
Journal Article
Recenzirano
Tracking performance of Monolithic Active Pixel Sensors (MAPS) developed at IPHC (Turchetta, et al., 2001)
1 have been extensively studied (Winter, et al., 2001; Gornushkin, et al., 2002)
2,3. ...Numerous sensor prototypes, called MIMOSA,
1
1
Standing for Minimum Ionising particle MOS Active pixel sensors.
were fabricated and tested since 1999 in order to optimise the charge collection efficiency and power dissipation, to minimise the noise and to increase the readout speed.
The radiation tolerance was also investigated. The highest fluence tolerable for a
10
μ
m
pitch device was found to be
∼
10
13
n
eq
/
cm
2
, while it was only
2
×
10
12
n
eq
/
cm
2
for a
20
μ
m
pitch device. The purpose of this paper is to show that the tolerance to non-ionising radiation may be extended up to
O(10
14) n
eq/cm
2. This goal relies on a fabrication process featuring a
15
μ
m
thin, high resistivity (
∼
1
k
Ω
cm
) epitaxial layer. A sensor prototype (MIMOSA-25) was fabricated in this process to explore its detection performance. The depletion depth of the epitaxial layer at standard CMOS voltages (
<
5
V
) is similar to the layer thickness. Measurements with m.i.p.s
2
2
Standing for minimum ionising particle.
show that the charge collected in the seed pixel is at least twice larger for the depleted epitaxial layer than for the undepleted one, translating into a signal-to-noise ratio (SNR) of
∼
50
. Tests after irradiation have shown that this excellent performance is maintained up to the highest fluence considered (
3
×
10
13
n
eq
/
cm
2
)
, making evidence of a significant extension of the radiation tolerance limits of MAPS.
We report on the performance of the MIMOSA8 (HiMAPS1) chip. The chip is a 128times32 pixels array where 24 columns have discriminated binary outputs and eight columns analog test outputs. Offset ...correction techniques are used extensively in this chip to overcome process related mismatches. The array is divided in four blocks of pixels with different conversion factors and is controlled by a serially programmable sequencer. MIMOSA8 is a representative of the CMOS sensors development option considered as a promising candidate for the Vertex Detector of the future International Linear Collider (ILC). The readout technique, implemented on the chip, combines high spatial resolution capabilities with high processing readout speed. Data acquisition, providing control of the chip and signal buffering and linked to a VME system, was made on the eight analog outputs. Analog data, without and with a 55 Fe X-ray source, were acquired and processed using off-line analysis software. From the reconstruction of pixel clusters, built around a central pixel, we deduce that the charge spread is limited to the closest 25 pixels and almost all the available charge is collected. The position of the total charge collection peak (and subsequently the charge-to-voltage conversion factor) stays unaffected when the clock frequency is increased even up to 150 MHz (13.6 mus readout time per frame). The discriminators, placed in the readout chain, have proved to be fully functional. Beam tests have been made with high energy electrons at DESY (Germany) to study detection efficiency. The results prove that MIMOSA8 is the first and fastest successful monolithic active pixel sensor with on-chip signal discrimination for detection of MIPs
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