Readout Pitch Research Articles

Position reconstruction for segmented detectors

The topic of the paper is the position reconstruction from signals of segmented detectors. With the help of a simple simulation, it is shown that the position reconstruction using the centre-of-gravity method is strongly biased, if the width of the charge (or e.g. light) distribution at the electrodes (or photo detectors) is less than the read-out pitch. A method is proposed which removes this bias for events with signals in two or more read-out channels and thereby improves the position resolution. The method also provides an estimate of the position–response function for every event. Examples are given for which its width as a function of the reconstructed position varies by as much as an order of magnitude.A fast Monte Carlo program is described which simulates the signals from a silicon pixel detector traversed by charged particles under different angles, and the results obtained with the proposed reconstruction method and with the centre-of-gravity method are compared. The simulation includes the local energy-loss fluctuations, the position-dependent electric field, the diffusion of the charge carriers, the electronics noise and charge thresholds for clustering, A comparison to test-beam-data is used to validate the simulation.

Direct Annihilation Position Classification Based on Deep Learning Using Paired Cherenkov Detectors: A Monte Carlo Study

To apply deep learning to estimate the three-dimensional interaction position of a Cherenkov detector, an experimental measurement of the true depth of interaction is needed. This requires significant time and effort. Therefore, in this study, we propose a direct annihilation position classification method based on deep learning using paired Cherenkov detectors. The proposed method does not explicitly estimate the interaction position or time-of-flight information and instead directly estimates the annihilation position from the raw data of photon information measured by paired Cherenkov detectors. We validated the feasibility of the proposed method using Monte Carlo simulation data of point sources. A total of 125 point sources were arranged three-dimensionally with 5 mm intervals, and two Cherenkov detectors were placed face-to-face, 50 mm apart. The Cherenkov detector consisted of a monolithic PbF2 crystal with a size of 40 × 40 × 10 mm3 and a photodetector with a single photon time resolution (SPTR) of 0 to 100 picosecond (ps) and readout pitch of 0 to 10 mm. The proposed method obtained a classification accuracy of 80% and spatial resolution with a root mean square error of less than 1.5 mm when the SPTR was 10 ps and the readout pitch was 3 mm.

The CLAS12 Silicon Vertex Tracker

For the 12 GeV upgrade of Jefferson Laboratory, a Silicon Vertex Tracker (SVT) has been designed for the CLAS12 spectrometer using single-sided microstrip sensors fabricated by Hamamatsu Photonics. The sensors have a graded angle design to minimize dead areas and a readout pitch of 156μm, with intermediate strips. Each double-sided SVT module hosts three daisy-chained sensors on each side with a full strip length of 33 cm. There are 512 channels per module, read out by four Fermilab Silicon Strip Readout (FSSR2) chips, featuring data-driven architecture, mounted on a rigid–flex hybrid board. The modules are assembled in a barrel configuration using a unique cantilevered geometry to minimize the amount of material in the tracking volume. This paper is focused on the design, qualification of the performance, and experience in operating and commissioning the tracker during the first year of the data taking.

Measurement of the energy spectra and of the angular distribution of the Transition Radiation with a silicon strip detector

We plan to develop an advanced Transition Radiation Detector (TRD) for hadron identification in the TeV momentum range, based on the simultaneous measurement of the energies and of the emission angles of the Transition Radiation (TR) X-rays with respect to the radiating particles. To study the feasibility of this project, we have carried out a beam test campaign at the CERN SPS facility with 20 GeV/c electrons and muons up to 300 GeV/c. To detect the TR X-rays and the radiating particles, we used a 300 μm thick double-sided silicon strip detector, with a strip readout pitch of 50 μm. A 2 m long helium pipe was placed between the radiators and the detector, in order to ensure adequate separation between the TR X-rays and the radiating particle on the detector plane and to limit the X-ray absorption before the detector. We measured the double-differential (in energy and angle) spectra of the TR emitted by several radiators. The results are in good agreement with the predictions obtained from the TR theory.

A feasibility test run for the MUonE project

The 3.4 σ discrepancy between the experimental value of the muon anomalous magnetic moment g-2 and the Standard Model prediction is one of the most intriguing indications of physics beyond the Standard Model. The MUonE project plans to measure the leading hadronic corrections to the muon g-2 by scattering high energy ( ∼ 150 GeV) muons off the atomic electrons of a low-Z target through the elastic process μ +e → μ +e. The angles of the incoming muons and the outcoming muons and electrons have to be measured precisely, to exploit the kinematical correlation of the μ -e collision. To reach this goal a modular target is foreseen, consisting of 60 low-Z (Be or C) elements, 1 cm thick, each sandwiched in layers of Si-microstrip detectors, organized in XY, XU and VY planes ( ± 45 °, to disentangle double tracks). In 2018, a feasibility test at the CERN North Area is foreseen, running parasitically on the beamline behind COMPASS. The setup consist of 16 layers with an area of 9.5 × 9.5 cm 2 , 410 μ m thick, single side AGILE silicon detectors, which have a readout pitch of 242 μ m and a floating strip scheme, resulting in a position resolution of the order of 40 μ m . The DAQ rate is of the order of a few kHz. The contribution will describe the setup, the DAQ system and the first data collected during the commissioning phase in April/May.

A feasibility study on 3D interaction position estimation using deep neural network in Cherenkov-based detector: a Monte Carlo simulation study

Cherenkov-based radiation detectors have been developed for time-of-flight positron emission tomography. As Cherenkov photons are emitted in an extremely short time, their use can improve time resolution. However, only up to 10 Cherenkov photons are yielded when a 511 keV gamma ray interacts with Cherenkov radiators, such as lead tungstate and lead fluoride (PbF2). Therefore, accurate estimation of the interaction position was difficult, and intense effort has been devoted to its improvement. We propose an estimation method for the 3D interaction position using a deep neural network. The network was evaluated by Monte Carlo simulations. For the simulations, a Cherenkov-based detector with a monolithic PbF2 radiator of 40 × 40 × 10 mm3 and a photodetector array were used. The gamma-ray interaction position in the radiator was estimated in 3D space by the neural network, whose inputs were the detection positions on the photodetector plane (xy plane) and timestamps of each photon from the detector. Training and validation datasets were generated while varying the single photon time resolution (SPTR) and readout pitch of the photodetector. By comparing several neural network architectures, we determined the best configuration to be the multilayer perceptron with 3 layers and 256 units. The full widths at half maximum of the xy plane and z axis (i.e., depth of interaction) were 1.54 and 1.59 mm with SPTR σ = 10 ps, respectively, and their cumulative histograms at half maximum were 0.65 and 0.81 mm also with σ = 10 ps, respectively. The proposed method retrieved higher estimation accuracy of the interaction position than an existing method based on the center of gravity and principal component analysis. Therefore, it is feasible to estimate the 3D interaction position in the Cherenkov-based detectors using deep neural networks.

Cherenkov radiation-based three-dimensional position-sensitive PET detector: A Monte Carlo study.

Cherenkov radiation has recently received attention due to its prompt emission phenomenon, which has the potential to improve the timing performance of radiation detectors dedicated to positron emission tomography (PET). In this study, a Cherenkov-based three-dimensional (3D) position-sensitive radiation detector was proposed, which is composed of a monolithic lead fluoride (PbF2 ) crystal and a photodetector array of which the signals can be readout independently. Monte Carlo simulations were performed to estimate the performance of the proposed detector. The position- and time resolution were evaluated under various practical conditions. The radiator size and various properties of the photodetector, e.g., readout pitch and single photon timing resolution (SPTR), were parameterized. The single photon time response of the photodetector was assumed to be a single Gaussian for the simplification. The photo detection efficiency of the photodetector was ideally 100% for all wavelengths. Compton scattering was included in simulations, but partly analyzed. To estimate the position at which a γ-ray interacted in the Cherenkov radiator, the center-of-gravity (COG) method was employed. In addition, to estimate the depth-of-interaction (DOI) principal component analysis (PCA), which is a multivariate analysis method and has been used to identify the patterns in data, was employed. The time-space distribution of Cherenkov photons was quantified to perform PCA. To evaluate coincidence time resolution (CTR), the time difference of two independent γ-ray events was calculated. The detection time was defined as the first photon time after the SPTR of the photodetector was taken into account. The position resolution on the photodetector plane could be estimated with high accuracy, by using a small number of Cherenkov photons. Moreover, PCA showed an ability to estimate the DOI. The position resolution heavily depends on the pitch of the photodetector array and the radiator thickness. If the readout pitch were ideally 0 and practically 3 mm, a full-width at half-maximum (FWHM) of 0.348 and 1.92 mm was achievable with a 10-mm-thick PbF2 crystal, respectively. Furthermore, first-order correlation could be observed between the primary principal component and the true DOI. To obtain a coincidence timing resolution better than 100-ps FWHM with a 20-mm-thick PbF2 crystal, a photodetector with SPTR of better than σ = 30 ps was necessary. From these results, the improvement of SPTR allows us to achieve CTR better than 100-ps FWHM, even in the case where a 20-mm-thick radiator is used. Our proposed detector has the potential to estimate the 3D interaction position of γ-rays in the radiator, using only time and space information of Cherenkov photons.

DAMPE silicon tracker on-board data compression algorithm**Supported by Strategic Priority Research Program on Space Science of Chinese Academy of Sciences (XDA040402) and National Natural Science Foundation of China (1111403027)

The Dark Matter Particle Explorer (DAMPE) is an upcoming scientific satellite mission for high energy gamma-ray, electron and cosmic ray detection. The silicon tracker (STK) is a subdetector of the DAMPE payload. It has excellent position resolution (readout pitch of 242 μm), and measures the incident direction of particles as well as charge. The STK consists of 12 layers of Silicon Micro-strip Detector (SMD), equivalent to a total silicon area of 6.5 m2. The total number of readout channels of the STK is 73728, which leads to a huge amount of raw data to be processed. In this paper, we focus on the on-board data compression algorithm and procedure in the STK, and show the results of initial verification by cosmic-ray measurements.

Study of the readout configuration of the GAMMA-400 silicon tracker sensors

The GAMMA-400 satellite is an upcoming international space mission designed to detect gamma and cosmic rays in a broad energy range up to 3TeV, with an excellent angular and energy resolution. The present design foresees a 10 layers Si–W tracker formed by single sided silicon sensors with 80μm strip pitch, with a readout pitch of 240μm; the sensors are arranged in four towers, each one with an area of 50×50cm2, for a total of more than 150k channels. This paper presents an analysis of the spatial resolution of the proposed readout configuration, compared with different readout approaches, both in terms of readout pitch and strip/implant widths. The study has been performed with two specially developed silicon modules, each one divided into zones with different characteristics. The tests have been performed on the CERN PS-T9 beamline using 10GeV negative particles.

Performance of the CLAS12 Silicon Vertex Tracker modules

For the 12GeV upgrade, the CLAS12 experiment has designed a Silicon Vertex Tracker (SVT) using single sided microstrip sensors fabricated by Hamamatsu. The sensors have graded angle design to minimize dead areas and a readout pitch of 156μm, with intermediate strip. Double sided SVT module hosts three daisy-chained sensors on each side with a full strip length of 33cm. There are 512 channels per module read out by four Fermilab Silicon Strip Readout (FSSR2) chips featuring data driven architecture, mounted on a rigid-flex hybrid. Modules are assembled on the barrel using unique cantilevered geometry to minimize the amount of material in the tracking volume. Design and performance of the SVT modules are presented, focusing on results of electrical measurements.

Optimising the strip geometry for very fine pitch silicon strip sensors

Future collider experiments will require tracking detectors with more precise silicon sensors for improved track reconstruction precision and possibly with the ability to provide input to the first level trigger. One way to enhance the tracking performance is the minimization of the readout pitch. We investigated the performance of such fine pitch strip sensors using multigeometry testsensors with a fixed readout pitch of 50 μ m and a varying number of intermediate strips and different strip widths. Results from a testbeam with 120 GeV / c pions are presented, suggesting the best geometry for optimal spatial resolution. Furthermore we studied the possibility to derive the incidence angle of a particle from the cluster width, which could be used as a tracking trigger on transverse momentum.

2-D imaging with cascaded GEM/MHSP multipliers

The imaging properties of cascaded-GEM (Gas Electron Multiplier) and cascaded-GEM/MHSP (Micro-Hole and Strip Plate) gaseous electron multipliers, equipped with 2-DWedge & Strip (W&S) readout electrodes, are presented. The W&S electrode was capacitivelycoupled to the electron multiplier through a resistive electrode, to adapt the charge-cloud size tothe 1.6 mm readout pitch. The studies were carried out with soft X-rays and single UV-photonsin Ar/5%CH4 gas mixture at atmospheric pressure. Spatial resolutions of ∼225μm and ∼250μm(FWHM) were reached, with 5.9 keV X-rays, in 3-GEM and 2-GEM/MHSP based detectors,respectively. Single photoelectrons, emitted from a CsI photocathode deposited on the topelectrode of the first GEM in the cascade, were localized with resolution of ∼ 170μm (FWHM)in a 4-GEM gaseous photomultiplier.

Optimization of Tracking Performance of CMOS Monolithic Active Pixel Sensors

CMOS Monolithic Active Pixel Sensors (MAPS) provide an attractive solution for high precision tracking of minimum ionizing particles. In these devices, a thin, moderately doped, undepleted silicon layer is used as the active detector volume with the readout electronics implemented on top of it. Recently, a new MAPS prototype was fabricated using the AMS 0.35 mum OPTO process, featuring a thick epitaxial layer. A systematic study of tracking performance of that prototype using high-energy particle beam is presented in this work. Noise performance, signal amplitude from minimum ionizing particles, detection efficiency, spurious hit suppression and spatial resolution are shown as a function of the readout pitch and the charge collecting diode size. A test array with a novel readout circuitry was also fabricated and tested. Each pixel circuit consists of a front-end voltage amplifier, capacitively coupled to the charge collecting diode, followed by two analog memory cells. This architecture implements an on-pixel correlated double sampling method, allowing for optimization of integration independently of full frame readout time and strongly reduces the pixel-to-pixel output signal dispersion. First measurements using this structure are also presented

Gas pixel detectors

With the Gas Pixel Detector (GPD), the class of micro-pattern gas detectors has reached a complete integration between the gas amplification structure and the read-out electronics. To obtain this goal, three generations of application-specific integrated circuit of increased complexity and improved functionality has been designed and fabricated in deep sub-micron CMOS technology. This implementation has allowed manufacturing a monolithic device, which realizes, at the same time, the pixelized charge-collecting electrode and the amplifying, shaping and charge measuring front-end electronics of a GPD. A big step forward in terms of size and performances has been obtained in the last version of the 0.18 μm CMOS analog chip, where over a large active area of 15×15 mm 2 a very high channel density (470 pixels/mm 2) has been reached. On the top metal layer of the chip, 105,600 hexagonal pixels at 50 μm pitch have been patterned. The chip has customable self-trigger capability and includes a signal pre-processing function for the automatic localization of the event coordinates. In this way, by limiting the output signal to only those pixels belonging to the region of interest, it is possible to reduce significantly the read-out time and data volume. In-depth tests performed on a GPD built up by coupling this device to a fine pitch (50 μm) gas electron multiplier are reported. Matching of the gas amplification and read-out pitch has let to obtain optimal results. A possible application of this detector for X-ray polarimetry of astronomical sources is discussed.

LHCb Silicon Tracker Performance Studies

LHCb is one of the experiments for the Large Hadron Collider at CERN and is dedicated to B-physics and CP-violation measurements. To exploit its physics potential good tracking performance with high efficiency in a high particle density environment close to the beam pipe is required. Silicon strip detectors with large read-out pitch and long strips will be used for the LHCb Inner Tracker behind the magnet and the Trigger Tracker station in front of the magnet. We report here about the design of the Silicon Tracker, test beam results and the electrical tests foreseen during production

The use of capacitive charge division in silicon microstrip detectors

The structure of silicon microstrip detectors with a great number of passive strips located between the readout (active) strips is described. Owing to the use of capacitive charge division among the passive and active strips, it is possible to essentially increase the readout pitch and to reduce the number of electronic readout channels by five to ten times. Since the cost of the front-end electronics exceeds significantly that of the detectors themselves, this method allows the cost of the entire detector-electronics system to be decreased severalfold without substantial deterioration of the position resolution.

Long term performance studies of the silicon strip detectors of the LHCb Silicon Tracker

LHCb is one of the experiments at the Large Hadron Collider at CERN. It is dedicated to B-physics and CP-violation measurements. To fully exploit its physics potential, a good tracking performance with high efficiency in the high particle density environment close to the beam pipe is required. For this purpose, the LHCb Silicon Tracker uses strip detectors with large read-out pitch and long strips. We give a summary of the R&D program of the Silicon Tracker and of performance studies for the long term operation in the LHC radiation environment.

The LHCb Silicon Tracker

LHCb is one of the experiments for the Large Hadron Collider at CERN, dedicated to B-physics and CP-violation measurements. To fully exploit the physics potential, a good tracking performance with high efficiency in a high particle density environment close to the beam pipe is required. Silicon strip detectors with large readout pitch and long strips will be used for the LHCb Inner Tracker after the magnet and the Trigger Tracker station in front of the magnet. The design of the Silicon Tracker in LHCb and corresponding test beam results are presented here.

CMOS monolithic active pixel sensors for minimum ionizing particle tracking using non-epitaxial silicon substrate

Nonepitaxial, high resistivity silicon has been used as a substrate for implementation of CMOS monolithic active pixel sensors (MAPS) designed for high precision minimum ionizing particle tracking. The readout electronics circuitry is integrated directly on top of such a substrate using a standard commercial CMOS process. In this paper, measurements of these devices using a high-energy particle beam are presented. Efficient and performing MIP tracking is demonstrated for both small (20 /spl mu/m) and large (40 /spl mu/m) pixel readout pitch. Radiation hardness that satisfies many future particle physics applications is also proven. These results show that the use of epitaxial substrate for MAPS fabrication is not mandatory, opening a much larger choice of possible CMOS processes in the future.

The LHCb Inner Tracker

The inner part of the LHCb main tracking system will be realized in a silicon microstrip technology. The experimental requirements suggest approximately 20 cm -long ladders and a readout pitch of around 200 μm . The LHCb Inner Tracker system will consist of three tracking stations having a total of 12 detection layers summing to an overall silicon surface area of approximately 4.2 m 2 . A report about the status of the current R&D of the silicon ladders and tracking stations of the LHCb Inner Tracker is given.