Fast Silicon Detectors Research Articles

Burst laser ablation in distilled and heavy water

The laser water ablation initiates several physical effects: ionization of atoms and optical breakdown of the liquid, phase explosion and cavitation, shockwave propagation, and even the potential to yield neutrons. The goal of this paper is to compare ablation plasma glow and thermal changes in distilled and heavy water under single pulses and bursts of ultrashort laser pulses. The laser ablation was performed beneath the water surface in a circular laser scanned trajectory. There were two regimes of water ablation: burst regime and single pulses ablation. The absorption processes and ablation plasma glow were evaluated with visible and infrared cameras, fast silicon detector and thermocouple. The study revealed that the heavy water ablation process is 3.5 times more intense in the burst regime with the same laser power. Unexpectedly, the plasma glow with a lower power density of laser 2.6·1013 W/cm2 was four times higher than with higher power density of 8·1013 W/cm2. In burst mode and at a higher power density, heavy water produced nearly two times higher plasma glow.

STOPGAP—A time-of-flight extension for the Belle II TOP barrel PID system

The BelleII barrel region is instrumented with the Time of Propagation (TOP) particle identification system. Due to its mechanical design, the individual TOP modules do not overlap, leaving a gap of around 2 cm between them in the azimuthal direction. This leads to a 6%–9% drop in acceptance, depending on the track’s momentum. We propose a solution to remedy these gaps by instrumenting them with fast silicon detectors to directly measure the time-of-flight of traversing particles. We present here a simulation study discussing the performance requirements and the possible sensor technologies, and we demonstrate that such a project could be realized with novel, fast monolithic CMOS sensors, or alternatively AC-LGAD sensors, both of which are expected to reach MIP timing resolutions of down to 50 ps or better.

Calibration method and performance of a time-of-flight detector to measure absolute beam energy in proton therapy.

The beam energy is one of the most significant parameters in particle therapy since it is directly correlated to the particles' penetration depth inside the patient. Nowadays, the range accuracy is guaranteed by offline routine quality control checks mainly performed with water phantoms, 2D detectors with PMMA wedges, or multi-layer ionization chambers. The latter feature low sensitivity, slow collection time, and response dependent on external parameters, which represent limiting factors for the quality controls of beams delivered with fast energy switching modalities, as foreseen in future treatments. In this context, a device based on solid-state detectors technology, able to perform a direct and absolute beam energy measurement, is proposed as a viable alternative for quality assurance measurements and beam commissioning, paving the way for online range monitoring and treatment verification. This work follows the proof of concept of an energy monitoring system for clinical proton beams, based on Ultra Fast Silicon Detectors (featuring tenths of ps time resolution in 50μm active thickness, and single particle detection capability) and time-of-flight techniques. An upgrade of such a system is presented here, together with the description of a dedicated self-calibration method, proving that this second prototype is able to assess the mean particles energy of a monoenergetic beam without any constraint on the beam temporal structure, neither any a priori knowledge of the beam energy for the calibration of the system. A new detector geometry, consisting of sensors segmented in strips, has been designed and implemented in order to enhance the statistics of coincident protons, thus improving the accuracy of the measured time differences. The prototype was tested on the cyclotron proton beam of the Trento Protontherapy Center (TPC). In addition, a dedicated self-calibration method, exploiting the measurement of monoenergetic beams crossing the two telescope sensors for different flight distances, was introduced to remove the systematic uncertainties independently from any external reference. The novel calibration strategy was applied to the experimental data collected at TPC (Trento) and CNAO (Pavia). Deviations between measured and reference beam energies in the order of a few hundreds of keV with a maximum uncertainty of 0.5 MeV were found, in compliance with the clinically required water range accuracy of 1mm. The presented version of the telescope system, minimally perturbative of the beam, relies on a few seconds of acquisition time to achieve the required clinical accuracy and therefore represents a feasible solution for beam commission, quality assurance checks, and online beam energy monitoring.

Fast Timing Detectors and Applications in Cosmic Ray Physics and Medical Science

We use fast silicon detectors and the fast sampling method originally developed for high energy physics for two applications: cosmic ray measurements in collaboration with NASA and dose measurements during flash beam cancer treatment. The cosmic ray measurement will benefit from the fast sampling method to measure the Bragg peak where the particle stops in the silicon detector and the dose measurement is performed by counting the number of particles that enter the detector.

AGILE: Development of a Compact, Low-Power, Low-Cost, and On-Board Detector for Ion Identification and Energy Measurement

An AGILE (Advanced enerGetic Ion eLectron tElescope) instrument is being developed at the University of Kansas and NASA Goddard Space Flight Center to be launched on board a CubeSat in 2022. The AGILE instrument aims to identify a large variety of ions (H-Fe) in a wide energy range (1–100 MeV/nucl) in real-time using fast silicon detectors and fast read-out electronics. This can be achieved by the first use of real-time Pulse Shape Discrimination in space instrumentation. This method of discrimination relies on specific amplitude and time characteristics of the signals sampled every 100 ps and produced by ions that stop in the detector medium. AGILE will be able to observe, in situ, the fluxes of a large variety of particles in a wide energy range to advance our knowledge of the fundamental processes in the universe. This work presents the current stage of development of the instrument, the discrimination method used through the performed simulations, and the first results from lab tests using an Am-241 source.

A new detector for the beam energy measurement in proton therapy: a feasibility study

The proof of concept of a new device, capable of determining in a few seconds the energy of clinical proton beams by measuring the time of flight (ToF) of protons, is presented. The prototype consists of two thin ultra fast silicon detector (UFSD) pads, aligned along the beam direction in a telescope configuration and readout by a digitizer. The method developed for extracting the energy at the isocenter from the measured ToF, validated by Monte Carlo simulations, and the procedure used to calibrate the system are also presented and discussed in detail. The prototype was tested at the Centro Nazionale di Adroterapia Oncologica (CNAO, Pavia, Italy), at several beam energies, covering the entire clinical range, and using different distances between the sensors. The measured beam energies were benchmarked against the nominal CNAO energy values, obtained during the commissioning of the centre from the measured ranges in water. Deviations of few hundreds of keV have been achieved for all considered proton beam energies for distances between the two sensors larger than 60 cm, indicating a sensitivity to the corresponding beam range in water smaller than the clinical tolerance of 1 mm. Moreover, few seconds of irradiation were necessary to collect the required statistics. These preliminary results indicate that a telescope of UFSDs could achieve in a short time the accuracy required for the clinical application and therefore encourage further investigations towards the improvement and the optimization of the present prototype.

PO-1327: Performances of new beam monitors based on Ultra Fast Silicon Detectors for proton therapy

PO-1327: Performances of new beam monitors based on Ultra Fast Silicon Detectors for proton therapy

Test of innovative silicon detectors for the monitoring of a therapeutic proton beam

Beam monitoring in particle therapy is a critical task that, because of the high flux and the time structure of the beam, can be challenging for the instrumentation. Recent developments in thin silicon detectors with moderate internal gain, optimized for timing applications (Ultra Fast Silicon Detectors, UFSD), offer a favourable technological option to conventional ionization chambers. Thanks to their fast collection time and good signal-to-noise ratio, properly segmented sensors allow discriminating and counting single protons up to the high fluxes of a therapeutic beam, while the excellent time resolution can be exploited for measuring the proton beam energy using time-of-flight techniques. We report here the results of the first tests performed with UFSD detector pads on a therapeutic beam. It is found that the signal of protons can be easily discriminated from the noise, and that the very good time resolution is confirmed. However, a careful design is necessary to limit large pile-up inefficiencies and early performance degradation due to radiation damage.

Thin low-gain avalanche detectors for particle therapy applications

The University of Torino (UniTO) and the National Institute for Nuclear Physics (INFN-TO) are investigating the use of Ultra Fast Silicon Detectors (UFSD) for beam monitoring in radiobiological experiments with therapeutic proton beams. The single particle identification approach of solid state detectors aims at increasing the sensitivity and reducing the response time of the conventional monitoring devices, based on gas detectors. Two prototype systems are being developed to count the number of beam particles and to measure the beam energy with time-of-flight (ToF) techniques. The clinically driven precision (< 1%) in the number of particles delivered and the uncertainty < 1 mm in the depth of penetration (range) in radiobiological experiments (up to 108 protons/s fluxes) are the goals to be pursued. The future translation into clinics would allow the implementation of faster and more accurate treatment modalities, nowadays prevented by the limits of state-of-the-art beam monitors. The experimental results performed with clinical proton beams at CNAO (Centro Nazionale di Adroterapia Oncologica, Pavia) and CPT (Centro di Protonterapia, Trento) showed a counting inefficiency <2% up to 100 MHz/cm2, and a deviation of few hundreds of keV of measured beam energies with respect to nominal ones. The progresses of the project are reported.

Design and characterization of the FAST chip: a front-end for 4D tracking systems based on Ultra-Fast Silicon Detectors aiming at 30 ps time resolution

Detectors able to measure the time of flight with very high accuracy (∼10 ps RMS) are becoming fundamental in the design of new High Energy Physics experiments, where accurate time measurements will be used to mitigate pileup effects. The development of such detectors has spurred intense R&D in both silicon sensors and the associated readout electronics, aiming at obtaining silicon-based detectors with a time resolution in the few tens-of-picosecond range. This work presents FAST, a family of three different 20 channel amplifier-comparator chips, tailored to the readout of Ultra Fast Silicon Detectors. These ASICs have been designed optimizing the sensor-readout interplay with the aim of reaching the smallest possible jitter term. The three chips of the FAST family differ in the architecture of the front-end while sharing the channel back-end, consisting of a leading-edge discriminator and a LVDS driver. The goal of these front-ends is to achieve a time resolution of about 30 ps RMS while coupled to a sensor with a few pico-Farad capacitance, keeping the power budget of the single channel below 1.3 mW. This paper reports the description of the FAST design architecture and summarizes the results on the initial characterization of one chip of the FAST family, in a stand-alone test structure and when coupled to a UFSD.

Evolution of the design of ultra fast silicon detector to cope with high irradiation fluences and fine segmentation

The recent development in the design of Ultra Fast Silicon Detector (UFSD), aimed at combining radiation resistance up to fluences of 1015 neq/cm2 and fine read-out segmentation, makes these sensors suitable for high energy physics applications. UFSD is an evolution of standard silicon sensor, optimized to achieve excellent timing resolution (∼30 ps), thanks to an internal low gain (∼20). UFSD sensors are n in p Low Gain Avalanche Diode (LGAD) with an active thickness of ∼5 μm. The internal gain in LGAD is obtained by implanting an appropriate density of acceptors (of the order of ∼ 1016/cm3) close to the p-n junction, that, when depleted, locally generates an electric field high enough to activate the avalanche multiplication; this layer of acceptors is called gain layer. The two challenges in the development of UFSD for high energy physics detectors are the radiation hardness and the fine segmentation of large area sensors. Irradiation fluences of the order of 1015 neq/cm2 have a dramatic effect on the UFSD: neutrons and charged hadrons reduce the active acceptor density forming the gain layer; this mechanism, called initial acceptor removal, causes the complete disappearance of the internal gain above fluence of 1015 neq/ cm2. For the segmentation of UFSDs, the crucial point is the electrical insulation of pads and the extension of the inactive area between pads. In this paper we present the latest results on radiation resistance of LGADs with different gain layer designs, irradiated up to 3⋅1015 neq/ cm2. Three different segmentation technologies, developed by Fondazione Bruno Kessler in Trento, will also be discussed in detail in the second part of the paper.

Development of analysis methodology using Proton Induced X-ray Emission (PIXE) as a complementary technique to determine trace elements in environmental matrices

This article presents the methodology of analysis of industrial and environmental materials using Particle Induced X-ray Emission (PIXE) technique. The application of thick target PIXE technique using a 3 MeV proton beam at 3 MV Tandetron at Horia Hulubei National Institute for R&D in Physics and Nuclear Engineering (IFIN-HH), Romania, in industrial and environmental complex studies proved to be very useful for the identification of a large series of trace elements, some of them being toxic for living organisms and humans and others contributing to the elemental cycling in natural environments. The main elements determined by PIXE are K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, As, Br, Rb, Sr and Pb, using High Purity Germanium (HPGe) GDP-05145 (BSI) type detector of 20 mm2 surface, 8 mm thickness. In addition, Na, Mg, Al, Si, P, S, and Cl could be determined using external beam PIXE with X-123 SDD Fast Amptek silicon detector of 25 mm2 surface, 500 µm thickness. PIXE technique successfully complements other atomic and nuclear techniques, such as: energy dispersive X-ray fluorescence (ED-XRF), instrumental neutron activation analysis (INAA), inductively-coupled plasma mass spectrometry (ICP-MS), atomic absorption spectrometry (AAS) and ion beam technique particle-induced gamma-ray emission (PIGE). A discussion is made regarding the suitability of PIXE technique to be further used in studies related to soil-crop toxic metal transfer in an agroecosystem, as well as heavy metals biosorbtion from industrial wastewater, for the investigation of level of contamination with metals and toxicants occurrence in environmental factors and human health risk assessment. The paper was presented at the Scientific Conference of the Doctoral School of Dunarea de Jos University of Galati (SCDS-UDJG), 7th edition, Galati, Romania, 13-14 June, 2019.

352. Innovative thin silicon detectors for beam monitoring in particle therapy

Purpose For beam monitoring in particle therapy, silicon detectors could overcome the limitations of ionization chambers. In particular, silicon sensors with internal gain (Ultra Fast Silicon Detectors, UFSDs) provide high signal-to-noise ratio and fast collection times ( ∼1 ns in 50 μm thickness). A segmented sensor could allow discriminating and counting single protons up to high fluxes of therapeutic beams. Moreover, the excellent time resolution suggests using time-of-flight techniques for measuring the proton beam energy. Materials and Methods Several 50 μm thick UFSD prototypes, both single pads or segmented in strips, doped with Boron or Gallium, and with different doping concentrations were fully characterized at the Turin university laboratory and tested on the clinical proton beam of the CNAO particle therapy facility, up to fluxes of 109 p/s. Signal-to-noise ratio, pileup probability, internal gain and gain degradation with beam fluence were determined from the offline analysis of the collected waveforms and compared, whenever possible, to the laboratory measurements. Conclusions UFSDs are found to be a viable option for improving the qualification and the monitoring of a therapeutic proton beams. However, a careful design is necessary to avoid large pileup inefficiencies and early performance degradation.

Development of ultra fast silicon detector for 4D tracking

Abstract The Ultra Fast Silicon Detectors (UFSDs) are a new kind of silicon detectors based on Low Gain Avalanche Diodes technology. The UFSDs are optimised for time measurements with the goal of both excellent space and time resolution, which makes them a very good candidate for 4D tracking. In this paper, we will briefly explain their innovative design and show the status of the latest development. Recent measurements at the H8 beam line (CERN) will be reported, based on the UFSDs from two manufacturers: FBK and HPK. In particular, UFSDs of different thicknesses, with different doping concentrations and with different dopants of the gain layer have been studied. A time resolution of 35 ps has been achieved for a 50 μ m thick design and the results have been found to be in very good agreement with the expectations.

Characterization of a novel pixelated Silicon Drift Detector (PixDD) for high-throughput X-ray astrophysics

Multi-pixel fast silicon detectors represent the enabling technology for the next generation of space-borne experiments devoted to high-resolution spectral-timing studies of low-flux compact cosmic sources. Several imaging detectors based on frame-integration have been developed as focal plane devices for X-ray space-borne missions but, when coupled to large-area concentrator X-ray optics, these detectors are affected by strong pile-up and dead-time effects, thus limiting the time and energy resolution as well as the overall system sensitivity. The current technological gap in the capability to realize pixelated silicon detectors for soft X-rays with fast, photon-by-photon response and nearly Fano-limited energy resolution therefore translates into the unavailability of sparse read-out sensors suitable for high throughput X-ray astronomy applications. In the framework of the ReDSoX Italian collaboration, we developed a new, sparse read-out, pixelated silicon drift detector which operates in the energy range 0.5–15 keV with nearly Fano-limited energy resolution (⩽150 eV FWHM @ 6 keV) at room temperature or with moderate cooling (∼0°C to +20°C). In this paper, we present the design and the laboratory characterization of the first 16-pixel (4 × 4) drift detector prototype (PixDD), read-out by individual ultra low-noise charge sensitive preamplifiers (SIRIO) and we discuss the future PixDD prototype developments.

OA055] Preliminary test of innovative strip silicon detectors for therapeutic proton beam monitoring

Purpose Unlike currently used gas ionization chambers, solid state detectors offer large granularity and sensitivity to single incoming particles, therefore being ideally suited to improve the present technology for beam monitoring in particle therapy. However, several drawbacks, such as radiation damage, prevented their use so far on high flux therapeutic beams. Two prototype devices for monitoring particle beams are under development, based on innovative silicon low-gain avalanche detectors optimized for time resolution (Ultra Fast Silicon Detectors – UFSDs). Preliminary results with proton beams are presented. Methods UFSDs are low-gain avalanche detectors optimized for time resolution, where sensors as thin as 50 μ m provide signals of ∼ 1 ns time duration with time resolutions of tenths of ps, and large enough signal-to-noise ratio to efficiently discriminate proton signal. One prototype device is being developed to directly count individual protons at high rates, while a second one is under investigation to measure the beam energy with time-of-flight techniques. This requires the design of custom UFSD sensors as well VLSI readout electronics. From simulations’ results and first beam tests with UFSD pads, strip detectors were produced, with two geometries (30 mm and 15 mm length) and different doping modalities to improve radiation hardness. In parallel, prototypes of a new readout chip have been submitted to the foundry. Results Strips sensors were characterized in the laboratory through laser test and I(V) curve studies, and a test with a therapeutic proton beam, with energy ranging from 62 to 227 MeV, was done. Results were obtained via offline analysis of the collected waveforms for Boron and Gallium doped sensors. Time resolution of 35 ps, signal duration of ns, and good S/N separation were found. A gain degradation of 20% was founded in single pad sensors after 10 12 protons/cm2 irradiation. Pile-up effects are under investigation. Conclusions Based on the preliminary results, UFSDs are found to be a promising improvement of monitor chamber. The aim of this contribution is to review the advancement of the project and to report on the results of the test of UFSD strip sensors with a therapeutic proton beam.

Innovative thin silicon detectors for monitoring of therapeutic proton beams: preliminary beam tests

To fully exploit the physics potentials of particle therapy in delivering dose with high accuracy and selectivity, charged particle therapy needs further improvement. To this scope, a multidisciplinary project (MoVeIT) of the Italian National Institute for Nuclear Physics (INFN) aims at translating research in charged particle therapy into clinical outcome. New models in the treatment planning system are being developed and validated, using dedicated devices for beam characterization and monitoring in radiobiological and clinical irradiations. Innovative silicon detectors with internal gain layer (LGAD) represent a promising option, overcoming the limits of currently used ionization chambers. Two devices are being developed: one to directly count individual protons at high rates, exploiting the large signal-to-noise ratio and fast collection time in small thicknesses (1 ns in 50 μm) of LGADs, the second to measure the beam energy with time-of-flight techniques, using LGADs optimized for excellent time resolutions (Ultra Fast Silicon Detectors, UFSDs). The preliminary results of first beam tests with therapeutic beam will be presented and discussed.

Test of Ultra Fast Silicon Detectors for picosecond time measurements with a new multipurpose read-out board

Ultra Fast Silicon Detectors (UFSD) are sensors optimized for timing measurements employing a thin multiplication layer to increase the output signal. A multipurpose read-out board hosting a low-cost, low-power fast amplifier was designed at the University of Kansas and tested at the European Organization for Nuclear Research (CERN) using a 180 GeV pion beam. The amplifier has been designed to read out a wide range of detectors and it was optimized in this test for the UFSD output signal. In this paper we report the results of the experimental tests using 50 μm thick UFSD with a sensitive area of 1.4mm2. A timing precision below 30 ps wasachieved.

Test of Ultra Fast Silicon Detectors for the TOTEM upgrade project

This paper describes the performance of a prototype timing detector, based on 50 μm thick Ultra Fast Silicon Detector, as measured in a beam test using a 180 GeV/c momentum pion beam. The dependence of the time precision on the pixel capacitance and bias voltage is investigated in this paper. A timing precision from 30 ps to 100 ps (RMS), depending on the pixel capacitance, has been measured at a bias voltage of 180 V.

Temperature dependence of the response of ultra fast silicon detectors

The Ultra Fast Silicon Detectors (UFSD) are a novel concept of silicon detectors based on the Low Gain Avalanche Diode (LGAD) technology, which are able to obtain time resolution of the order of few tens of picoseconds. First prototypes with different geometries (pads/pixels/strips), thickness (300 and 50 μm) and gain (between 5 and 20) have been recently designed and manufactured by CNM (Centro Nacional de Microelectrónica, Barcelona) and FBK (Fondazione Bruno Kessler, Trento). Several measurements on these devices have been performed in laboratory and in beam test and a dependence of the gain on the temperature has been observed. Some of the first measurements will be shown (leakage current, breakdown voltage, gain and time resolution on the 300 μm from FBK and gain on the 50 μm-thick sensor from CNM) and a comparison with the theoretically predicted trend will be discussed.