Study of High Speed Photomultiplier Systems

Hyman, L.; Schwarcz, Robert; Schluter, R. A.

doi:10.1063/1.1718829

Cited by 96 publications

(22 citation statements)

References 8 publications

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“…Integrating Equation 2 over time from zero to infinity to get the total light output L, we see that

L = {normalI}_{0} τ or {normalI}_{0} = L / τ .

Finally, we note that when the initial intensity is relatively high, the theoretical timing resolution of a scintillator scales inversely with the square root of the initial photoelectron rate [27, 28], which is equal to the initial intensity I 0 multiplied by two constants (the photon collection efficiency and the PMT quantum efficiency), that is:

Timing Resolution \propto 1 / sqrt (ε \cdot QE \cdot {normalI}_{0}),

where ε is the collection efficiency and QE is the quantum efficiency.…”

Section: Optimizationmentioning

confidence: 99%

Optimization of a LSO-Based Detector Module for Time-of-Flight PET

Moses

Janecek

Spurrier

et al. 2010

IEEE Trans. Nucl. Sci.

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We have explored methods for optimizing the timing resolution of an LSO-based detector module for a single-ring, “demonstration” time-of-flight PET camera. By maximizing the area that couples the scintillator to the PMT and minimizing the average path length that the scintillation photons travel, a single detector timing resolution of 218 ps fwhm is measured, which is considerably better than the ~385 ps fwhm obtained by commercial LSO or LYSO TOF detector modules. We explored different surface treatments (saw-cut, mechanically polished, and chemically etched) and reflector materials (Teflon tape, ESR, Lumirror, Melinex, white epoxy, and white paint), and found that for our geometry, a chemically etched surface had 5% better timing resolution than the saw-cut or mechanically polished surfaces, and while there was little dependence on the timing resolution between the various reflectors, white paint and white epoxy were a few percent better. Adding co-dopants to LSO shortened the decay time from 40 ns to ~30 ns but maintained the same or higher total light output. This increased the initial photoelectron rate and so improved the timing resolution by 15%. Using photomultiplier tubes with higher quantum efficiency (blue sensitivity index of 13.5 rather than 12) improved the timing resolution by an additional 5%. By choosing the optimum surface treatment (chemically etched), reflector (white paint), LSO composition (co-doped), and PMT (13.5 blue sensitivity index), the coincidence timing resolution of our detector module was reduced from 309 ps to 220 ps fwhm.

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“…Integrating Equation 2 over time from zero to infinity to get the total light output L, we see that

L = {normalI}_{0} τ or {normalI}_{0} = L / τ .

Timing Resolution \propto 1 / sqrt (ε \cdot QE \cdot {normalI}_{0}),

where ε is the collection efficiency and QE is the quantum efficiency.…”

Section: Optimizationmentioning

confidence: 99%

Optimization of a LSO-Based Detector Module for Time-of-Flight PET

Moses

Janecek

Spurrier

et al. 2010

IEEE Trans. Nucl. Sci.

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“…We show that with a small array (∼ 54 kg) of such detectors it is possible to yield in only one year of measurement a competitive physics result in the search for the neutrinoless double beta decay of 100 Mo using natural CaMoO 4 scintillating crystals (i.e. without enriching in 100 Mo or depleting in 48 Ca isotopes). This result would pave the way to a new class of ton scale experiments to search not only for neutrinoless double beta decay with potentially zero background, but also for dark matter and neutrino charged current reactions.…”

Section: Introductionmentioning

confidence: 99%

A flexible scintillation light apparatus for rare event searches

et al. 2014

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Compelling experimental evidences of neutrino oscillations and their implication that neutrinos are massive particles have given neutrinoless double beta decay (ββ0ν) a central role in astroparticle physics. In fact, the discovery of this elusive decay would be a major breakthrough, unveiling that neutrino and antineutrino are the same particle and that the lepton number is not conserved. It would also impact our efforts to establish the absolute neutrino mass scale and, ultimately, understand elementary particle interaction unification. All current experimental programs to search for ββ0ν are facing with the technical and financial challenge of increasing the experimental mass while maintaining incredibly low levels of spurious background. The new concept described in this paper could be the answer which combines all the features of an ideal experiment: energy resolution, low cost mass scalability, isotope choice flexibility and many powerful handles to make the background negligible. The proposed technology is based on the use of arrays of silicon detectors cooled to 120 K to optimize the collection of the scintillation light emitted by ultra-pure crystals. It is shown that with a 54 kg array of natural CaMoO4 scintillation detectors of this type it is possible to yield a competitive sensitivity on the half-life of the ββ0ν of 100 Mo as high as ∼ 10 24 years in only one year of data taking. The same array made of 40 Ca nat MoO4 scintillation detectors (to get rid of the continuous background coming from the two neutrino double beta decay of 48 Ca) will instead be capable of achieving the remarkable sensitivity of ∼ 10 25 years on the half-life of 100 Mo ββ0ν in only one year of measurement.

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“…It can be demonstrated [28][29][30] that if the individual photoelectrons in the leading edge of the signal are resolved in time, the First Signal algorithm should have the best performance. However, the photoelectron rate from 511 keV interactions in LSO is high enough that individual photoelectrons are not resolved.…”

Section: Discussionmentioning

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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Study of High Speed Photomultiplier Systems

Cited by 96 publications

References 8 publications

Optimization of a LSO-Based Detector Module for Time-of-Flight PET

Optimization of a LSO-Based Detector Module for Time-of-Flight PET

A flexible scintillation light apparatus for rare event searches

Multi-CFD Timing Estimators for PET Block Detectors

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