Design of the constant fraction of pulse height trigger for optimum time resolution

Gedcke, D. A.; McDonald, W. J.

doi:10.1016/0029-554x(68)90473-4

Cited by 121 publications

(13 citation statements)

References 11 publications

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“…Over-ranged pulses, with amplitudes >30 mV, will drive the 9327 amplifier into saturation. Obviously, the constant-fraction (zero-crossing) circuitry cannot reliably trigger timing pulses for over-ranged signals [14]. For mid-energy electrons, over-ranged pulses have a negligible effect since the fraction of over-ranged detection events is only a few per cent.…”

Section: Electronic Tagging Of Over-range Pulsesmentioning

confidence: 99%

Phase Transition of Lipid Multilamellar Aqueous Suspension under High Pressure V. Ultrasonic Measurements in Temperature Range from 4th Transition to Main One under High Pressure

Utoh¹,

Takemura

Oyama

1989

Jpn. J. Appl. Phys.

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The concept and subsequent experimental verification of the proportionality between pulse amplitude and detector transit time for microchannel-plate detectors is presented. This discovery has led to considerable improvement in the overall timing resolution for detection of high-energy γ -photons. Utilizing a 22 Na positron source, a full width half maximum (FWHM) timing resolution of 138 ps has been achieved. This FWHM includes detector transit-time spread for both chevron-stack-type detectors, timing spread due to uncertainties in annihilation location, all electronic uncertainty and any remaining quantum mechanical uncertainty. The first measurement of the minimum quantum uncertainty in the time interval between detection of the two annihilation photons is reported. The experimental results give strong evidence against instantaneous spatial localization of γ -photons due to measurement-induced nonlocal quantum wavefunction collapse. The experimental results are also the first that imply momentum is conserved only after the quantum uncertainty in time has elapsed (Yukawa H 1935 Proc. Phys. Math. Soc. Japan 17 48).

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Section: Electronic Tagging Of Over-range Pulsesmentioning

confidence: 99%

Phase Transition of Lipid Multilamellar Aqueous Suspension under High Pressure V. Ultrasonic Measurements in Temperature Range from 4th Transition to Main One under High Pressure

Utoh¹,

Takemura

Oyama

1989

Jpn. J. Appl. Phys.

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“…This property of CFDs is accomplished by triggering a timing signal at a specific fraction of the input signal, thus avoiding the threshold problem of leading-edge discriminators that leads to walk. The reported walk in most commercial NIM-module CFDs is on the order of 100 ps over an input-signal dynamic range of 100:1 [4,5]. Over a dynamic range of 1000:1, which most CFDs accept, the walk will be worse.…”

Section: Introductionmentioning

confidence: 99%

“…CFDs are designed to provide a reliable timing signal from analog pulses that have the same rise time, with little variation of the timing on the amplitude of the input signal [4][5][6]. This property of CFDs is accomplished by triggering a timing signal at a specific fraction of the input signal, thus avoiding the threshold problem of leading-edge discriminators that leads to walk.…”

Section: Introductionmentioning

confidence: 99%

Off-line correction for excessive constant-fraction-discriminator walk in neutron time-of-flight experiments

Heilbronn

Iwata²,

Iwase

2004

Nuclear Instruments and Methods in Physics Research Section A:

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A method for reducing excessive constant-fraction-discriminator walk that utilizes experimental data in the off-line analysis stage is introduced. Excessive walk is defined here as any walk that leads to an overall timing resolution that is much greater than the intrinsic timing resolution of the detection system. The method is able to reduce the contribution to the overall timing resolution from the walk that is equal to or less than the intrinsic timing resolution of the detectors. Although the method is explained in the context of a neutron time-of-flight experiment, it is applicable to any data set that satisfies two conditions. (1) A measure of the signal amplitude for each event must be recorded on an event-by-event basis; and (2) There must be a distinguishable class of events present where the timing information is known a priori.

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“…A timing estimator is generated via an analog sum of the four PMT signals, then converting this analog signal into a digital timing signal using a CFD [3][4][5][6][7][8]. Differences in the propagation times between the 4 PMTs affect the leading edge of the summed signal and thus affect the timing resolution.…”

Section: Introductionmentioning

confidence: 99%

Multi-CFD Timing Estimators for PET Block Detectors

Ullisch

Moses

2007

IEEE Trans. Nucl. Sci.

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Abstract-In a conventional PET system with block detectors, a timing estimator is created by generating the analog sum of the signals from the four photomultiplier tubes (PMT) in a module and discriminating the sum with a single constant fraction discriminator (CFD). The differences in the propagation time between the PMTs in the module can potentially degrade the timing resolution of the module. While this degradation is probably too small to affect performance in conventional PET imaging, it may impact the timing inaccuracy for time-of-flight PET systems (which have higher timing resolution requirements). Using a separate CFD for each PMT would allow for propagation time differences to be removed through calibration and correction in software.In this paper we investigate and quantify the timing resolution achievable when the signal from each of the 4 PMTs is digitized by a separate CFD. Several methods are explored for both obtaining values for the propagation time differences between the PMTs and combining the four arrival times to form a single timing estimator. We find that the propagation time correction factors are best derived through an exhaustive search, and that the "weighted average" method provides the best timing estimator. Using these methods, the timing resolution achieved with 4 CFDs (1052 ± 82 ps) is equivalent to the timing resolution with the conventional single CFD setup (1067 ± 158 ps).

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Design of the constant fraction of pulse height trigger for optimum time resolution

Cited by 121 publications

References 11 publications

Phase Transition of Lipid Multilamellar Aqueous Suspension under High Pressure V. Ultrasonic Measurements in Temperature Range from 4th Transition to Main One under High Pressure

Phase Transition of Lipid Multilamellar Aqueous Suspension under High Pressure V. Ultrasonic Measurements in Temperature Range from 4th Transition to Main One under High Pressure

Off-line correction for excessive constant-fraction-discriminator walk in neutron time-of-flight experiments

Multi-CFD Timing Estimators for PET Block Detectors

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