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We have developed a new time calibration method for the DRS4 waveform sampler that enables us to precisely measure the non-uniform sampling interval inherent in the switched-capacitor cells of the DRS4. The method uses the proportionality between the differential amplitude and sampling interval of adjacent switched-capacitor cells responding to a s...
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We propose a new method to probe the magnetic and electric dipole moments of the τ lepton using precise measurements of the differential rates of radiative leptonic τ decays at high-luminosity B factories. Possible deviations of these moments from the Standard Model values are analyzed in an effective Lagrangian approach, thus providing model-indep...
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... Signals from the detector readout were directly connected to sixteen channels of a CAEN V1742, DRS4 chip-based (Ritt 2008) digitizer, which digitized detector waveforms at 5 Giga-Samples-per-second (GSa/sec). A custom calibration of the digitizer was performed according to the methods outlined in (Kim et al 2014), to provide <10 ps FWHM intrinsic jitter (figure 2(d)). Digitized waveforms were processed with a simple high pass filter, followed by polezero compensation. ...
Standard signal processing approaches for scintillation detectors in positron emission tomography (PET) derive accurate estimates for 511 keV photon time of interaction and energy imparted to the detection media from aggregate characteristics of electronic pulse shapes. The ultimate realization of a scintillation detector for PET is one that provides a unique timestamp and position for each detected scintillation photon. Detectors with these capabilities enable advanced concepts for three-dimensional (3D) position and time of interaction estimation with methods that exploit the spatiotemporal arrival time kinetics of individual scintillation photons.
In this work, we show that taking into consideration the temporal photon emission density of a scintillator, the channel density of an analog silicon photomultiplier (SiPM) array, and employing fast electronic readout with digital signal processing, a detector that counts and timestamps scintillation photons can be realized. To demonstrate this approach, a prototype detector was constructed, comprising multichannel electronic readout for a bismuth germanate (BGO) scintillator coupled to an SiPM array.
In proof-of-concept measurements, we were able to count and provide unique timestamps for 66% of all optical photons, where the remaining 34% (two-or-more-photon pulses) are also independently counted, but each photon bunch shares a common timestamp. We show this detector concept can implement 3D positioning of 511 keV photon interactions and thereby enable corrections for time of interaction estimators. The detector achieved 17.6% energy resolution at 511 keV and 237±10 ps full-width-at-half-maximum (FWHM) coincidence time resolution (CTR) (fast spectral component) versus a reference detector. We outline the methodology, readout, and approach for achieving this detector capability in first-ever, proof-of-concept measurements for scintillation photon counting detector with analog silicon photomultipliers.
The presented detector concept is a promising design for large area, high sensitivity TOF-PET detector modules that can implement advanced event positioning and time of interaction estimators, which could push state-of-the-art performance.
... Detailed discussions about the typical calibration method are reported in Refs. [16] [18] [20]. The principle of this method is to sample a sine wave (or a sawtooth wave) and measure the amplitude difference between two adjacent samples surrounding a zero-crossing point of the digitized waveform, and we address this method as the zero-crossing method in the following discussion. ...
A novel time calibration method for waveform sampling application specific integrated circuits (ASICs) based on switched capacitor arrays (SCAs) is proposed in this paper. Precision timing extraction using SCA ASICs has been proved to be a promising technique in many high energy physics experiments. However, such ASICs suffer from irregular sampling intervals caused by process variations. Therefore, careful calibration is required to improve the time resolution of such systems. We evaluated the limitation of a popular method using the proportionality between voltage amplitude and sampling interval of adjacent switched-capacitor cells responding to either a sawtooth wave or a sine wave. The new time calibration method presented here utilizes the relationship between sampling intervals and the known input signal period to establish overdetermined linear equations, and the roots of these equations correspond to the actual sampling intervals. We applied this new method to a pulse timing test with an ASIC designed by our team, and the test results indicate that the new time calibration method is effective.
... Several time calibration methods proposed for SCA ASICs are reported in Refs. [13,[16][17][18][19][20]. The basic ideas in Refs. ...
... The basic ideas in Refs. [13,16,19,20] are similar; they all use the proportionality between voltage amplitude and sampling interval of adjacent switched-capacitor cells responding to sine waves or sawtooth waves. Furthermore, Ref. [18] is also based on this idea, and further improves the time resolution by applying a global time calibration. ...
... Detailed discussions about the typical calibration method are reported in Refs. [16,18,20]. The principle of this method is to sample a sine wave (or a sawtooth wave) and measure the amplitude difference between two adjacent samples surrounding a zero-crossing point of the digitized waveform, and we address this method as the zero-crossing method in the following discussion. ...
A novel time calibration method for waveform sampling application specific integrated circuits (ASICs) based on switched capacitor arrays (SCAs) is proposed in this paper. Precision timing extraction using SCA ASICs has been proved to be a promising technique in many high energy physics experiments. However, such ASICs suffer from irregular sampling intervals caused by process variations. Therefore, careful calibration is required to improve the time resolution of such systems. We evaluated the limitation of a popular method using the proportionality between voltage amplitude and sampling interval of adjacent switched-capacitor cells responding to either a sawtooth wave or a sine wave. The new time calibration method presented here utilizes the relationship between sampling intervals and the known input signal period to establish overdetermined linear equations, and the roots of these equations correspond to the actual sampling intervals. We applied this new method to a pulse timing test with an ASIC designed by our team, and the test results indicate that the new time calibration method is effective.
... Rocca et al. 3 subsequently used this unique platform to achieve In the present work, we demonstrate, for the first time, the feasibility of making fluorescence lifetime measurements using off-the-shelf analog silicon photomultipliers (SiPMs) 4 and switched-capacitor array based waveform sampling techniques. 5,6 Comparison of the fluorescence lifetimes derived from this simple cost-effective system to those made on a much larger and more elaborate commercial instrument revealed a surprisingly high degree of correlation and reproducibility. ...
... 4, Paul Scherrer Institute-PSI) evaluation board using a method previously reported by us for precise timing correction, with up to 30 ps timing resolution. 5,6 The DRS4 chip has 8 sampling channels, each 1024 cells deep, that can be daisy-chained to attain virtually unlimited sampling depth at frequencies ranging from 0.7 GS/s (giga-samples per second) to 5 GS/s. On-chip phase locked loop (PLL) is used to stabilize the sampling frequency with a jitter of less than 30 ps. ...
In fluorescence spectroscopy and imaging, fluorescence lifetime measurement—assessing the average time fluorophores spend in their excited state before returning to their ground state—offers a number of advantages over quantifying fluorescence intensities that include resistance to photo-bleaching and independence from fluorophore concentration, excitation intensity, and measurement methodology. Despite growing interest, fluorescence lifetime techniques frequently mandate relatively complex instrumentation, slow data acquisition rates, and significant data analyses. In this work, we demonstrate the feasibility of measuring fluorescence lifetimes using off-the-shelf analog silicon photomultipliers and switched-capacitor array waveform sampling techniques, with precision matching that of much larger and more elaborate commercial instruments.
p>Standard signal processing approaches for scintillation detectors in positron emission tomography (PET) derive accurate estimates for 511 keV photon time of interaction and energy imparted to the detection media from aggregate characteristics of electronic pulse shapes. The ultimate realization of a scintillation detector for PET is one that provides a unique timestamp and position for each detected scintillation photon. Detectors with these capabilities enable advanced concepts for three-dimensional (3D) position and time of interaction estimation with methods that exploit the spatiotemporal arrival time kinetics of individual scintillation photons. In this work, we show that taking into consideration the temporal photon emission density of a scintillator, the channel density of an analog silicon photomultiplier (SiPM) array, and employing fast electronic readout with digital signal processing, a detector that counts and timestamps scintillation photons can be realized. To demonstrate this approach, a prototype detector was constructed, comprising multichannel electronic readout for a bismuth germanate (BGO) scintillator coupled to a 4x4 SiPM array. In proof-of-concept measurements with this detector configuration, we are able to count and provide a timestamp for all optical photons produced by 511 keV photoelectric interactions. We show that this photon counting detector concept can implement 3D positioning of 511 keV photon interactions and thereby enable advanced corrections for time of interaction estimators. We outline the methodology, readout, and approach for achieving this detector capability in first-ever, proof-of-concept measurements for scintillation photon counting detector with analog silicon photomultipliers.</p
This paper presents the design and test results of a waveform sampling application-specific integrated circuit (ASIC) based on the switched capacitor array. It integrates 8 differential-input channels and each channel consists of a 256-cell capacitor array, 256 12-bit Wilkinson ADCs, and a serial data readout. A sampling rate of up to 5 Gsps is achieved with a low-jitter delay-locked loop (DLL). Two shared coarse counters running at the rising and falling edges of the reference clock are used to extend the time measurement range. Several crosstalk reduction strategies were adopted in the circuit design, especially in the clock generation circuit and the digitization circuit. The ASIC has been fabricated in 180 nm CMOS process. The test results show that the random noise is approximately 0.7 mV RMS after fixed-pattern noise correction and that the precision of waveform timing is better than 7 ps RMS with sampling interval correction.
A recent trend in PET instrumentation is the use of silicon photomultipliers (SiPMs) for high resolution and time-of-flight (TOF) detection. Due to its small size, a PET system can use a large number of SiPMs and hence effective and scalable multiplexing readout methods become important. Unfortunately, multiplexing readout generally degrades the fast timing properties necessary for TOF, especially at high channel reduction. Previously, we developed a stripline (SL)-based readout method for PET that uses a time-based multiplexing mechanism. This method maintains fast timing by design and has been successfully used for TOF PET detectors. In this article, we present a more systematic study in which we examine how two important design parameters of the readout-the number of inputs on an SL ( n
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) and the pathlength between adjacent input positions (Δ
l
)-affect its detection performance properties for PET. Our result shows that up to n
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=32 the readout can achieve accurate pixel discrimination and causes little degradation in the energy resolution. The TOF resolution is compromised mildly and a coincidence resolving time on the order of 300-ps FWHM can be achieved for lutetium-yttrium oxyorthosilicate- and SiPM-based detectors. We also discuss strategies in using the readout to further reduce the number of electronic channels that a PET system would otherwise need.
An adaptable and compact fast pulse sampling module was developed for the neutron–gamma discrimination. The developed module is well suited for low-cost and low-power consumption applications. It is based on the Domino Ring Sampler 4 (DRS4) chip, which offers fast sampling speeds up to 5.12 giga samples per second (GSPS) to digitize pulses from front-end detectors. The high-resolution GSPS data is useful for obtaining precise real-time neutron–gamma discrimination results directly in this module. In this study, we have implemented real-time data analysis in a field programmable gate array. Real-time data analysis involves two aspects: digital waveform integral and digital pulse shape discrimination (PSD). It can significantly reduce the system dead time and data rate processed offline. Plastic scintillators (EJ-299-33), which have proven capable of PSD, were adopted as neutron detectors in the experiments. A photomultiplier tube (PMT) (model #XP2020) was coupled to one end of a detector to collect the output light from it. The pulse output from the anode of the PMT was directly passed onto the fast sampling module. The fast pulse sampling module was operated at 1 GSPS and 2 GSPS in these experiments, and the AmBe-241 source was used to examine the neutron–gamma discrimination quality. The PSD results with different sampling rates and energy thresholds were evaluated. The figure of merit (FOM) was used to describe the neutron–gamma discrimination quality. The best FOM value of 0.91 was obtained at 2 GSPS and 1 GSPS sampling rates with an energy threshold of 1.5 MeVee (electron equivalent).
The development of fast, highly pixelated photodetectors with single-photon sensitivity has the potential to enable a variety of new radiation detection concepts. Systems that desire to employ these detectors without loss of information demand waveform digitization with high sampling rates. Switched capacitor arrays provide a low-cost, low-power, compact solution to fast readout with high channel density. The Sandia Laboratories Compact Electronics for Modular Acquisition (SCEMA) was developed to meet these demands. A single module employs two domino ring sampling switched capacitor arrays (DRS4) [1] to provide 16 channels of up to 5 GS/s waveform digitization. This paper presents an overview of the board design and function. Calibration procedures for the module are discussed. Finally, temporal resolution tests are presented demonstrating the module's viability as readout for high fidelity temporal measurements of single photons in suitable photodetectors.
