Showing papers on "Photomultiplier published in 2009"

Advances in solid state photon detectors

Abstract: Semiconductor photodiodes were developed in the early `Forties approximately at the time when the photomultiplier tube became a commercial product (RCA 1939) Only in recent years, with the invention of the Geiger-mode avalanche photodiodes, have the semiconductor photo detectors reached sensitivity comparable to that of photomultiplier tubes The evolution started in the `Sixties with the p-i-n (PIN) photodiode, a very successful device, which is still used in many detectors for high energy physics and a large number of other applications like radiation detection and medical imaging The next step was the development of the avalanche photodiode (APD) leading to a substantial reduction of noise but not yet achieving single photon response The weakest light flashes that can be detected by the PIN diode need to contain several hundreds of photons An improvement of the sensitivity by 2 orders of magnitude was achieved by the development of the avalanche photodiode, a device with internal gain At the end of the millennium, the semiconductor detectors evolved with the Geiger-mode avalanche photodiode into highly sensitive devices, which have an internal gain comparable to the gain of photomultiplier tubes and a response to single photons A review of the semiconductor photo detector design and development, the properties and problems, some applications and a speculative outlook on the future evolution will be presented

The digital silicon photomultiplier — Principle of operation and intrinsic detector performance

Abstract: We developed a fully digital implementation of the Silicon Photomultiplier. The sensor is based on a single photon avalanche photodiode (SPAD) integrated in a standard CMOS process. Photons are detected directly by sensing the voltage at the SPAD anode using a dedicated cell electronics block next to each diode. This block also contains active quenching and recharge circuits as well as a one bit memory for the selective inhibit of detector cells. A balanced trigger network is used to propagate the trigger signal from all cells to the integrated time-to-digital converter (TDC). Photons are detected and counted as digital signals, thus making the sensor less susceptible to temperature variations and electronic noise. The integration with CMOS logic has the added benefit of low power consumption and possible integration of data post-processing. In this paper, we discuss the sensor architecture and present first measurements of the technology demonstrator test chip.

The digital Silicon Photomultiplier — A novel sensor for the detection of scintillation light

Abstract: We developed a fully digital Silicon Photomultiplier (dSiPM) of 3.8 mm × 3.3 mm in size containing 8188 individual Geiger-mode cells. Each detected photon is directly converted into a digital signal in each of the Geiger-mode cells of the sensor. In addition, the complete trigger logic and a time-to-digital converter are integrated into the sensor. To show the performance of the sensor, LYSO crystals of different sizes were coupled to the sensor. The coincidence timing resolution for 3 mm × 3 mm × 5 mm LYSO crystals using a 22Na source amounts to 153 ps FWHM. The energy resolution at 511 keV was determined to be 10.7 % for 4 mm × 4 mm × 22 mm crystals. It is shown that saturation correction can be done without prior need for sensor calibration. The temperature dependence of the photon detection efficiency was found to be -0.6 %/°C including the temperature variation of the light output of LYSO.

Simulation of Silicon Photomultiplier Signals

Abstract: In a silicon photomultiplier (SiPM), also referred to as multi-pixel photon counter (MPPC), many Geiger-mode avalanche photodiodes (GM-APDs) are connected in parallel so as to combine the photon counting capabilities of each of these so-called microcells into a proportional light sensor. The discharge of a single microcell is relatively well understood and electronic models exist to simulate this process. In this paper we introduce an extended model that is able to simulate the simultaneous discharge of multiple cells. This model is used to predict the SiPM signal in response to fast light pulses as a function of the number of fired cells, taking into account the influence of the input impedance of the SiPM preamplifier. The model predicts that the electronic signal is not proportional to the number of fired cells if the preamplifier input impedance is not zero. This effect becomes more important for SiPMs with lower parasitic capacitance (which otherwise is a favorable property). The model is validated by comparing its predictions to experimental data obtained with two different SiPMs (Hamamatsu S10362-11-25u and Hamamatsu S10362-33-25c) illuminated with ps laser pulses. The experimental results are in good agreement with the model predictions.

Time based readout of a silicon photomultiplier (SiPM) for time of flight positron emission tomography (TOF-PET)

Abstract: Time of flight (TOF) measurements in positron emission tomography (PET) are very challenging in terms of timing performance, and should ideally achieve less than 100 ps FWHM precision. We present a time-based differential technique to read out silicon photomultipliers (SiPMs) which has less than 20 ps FWHM electronic jitter. The novel readout is a fast front end circuit (NINO) based on a first stage differential current mode amplifier with 20 Ω input resistance. Therefore the amplifier inputs are connected differentially to the SiPM's anode and cathode ports. The leading edge of the output signal provides the time information, while the trailing edge provides the energy information. Based on a Monte Carlo photon-generation model, HSPICE simulations were run with a 3 × 3 mm2 SiPM-model, read out with a differential current amplifier. The results of these simulations are presented here and compared with experimental data obtained with a 3 × 3 × 15 mm3 LSO crystal coupled to a SiPM. The measured time coincidence precision and the limitations in the overall timing accuracy are interpreted using Monte Carlo/SPICE simulation, Poisson statistics, and geometric effects of the crystal.

Optical readout tracking detector concept using secondary scintillation from liquid argon generated by a thick gas electron multiplier

Abstract: For the first time secondary scintillation, generated within the holes of a thick gas electron multiplier (THGEM) immersed in liquid argon, has been observed and measured using a silicon photomultiplier device (SiPM). 250 electron-ion pairs, generated in liquid argon via the interaction of a 5.9 keV Fe-55 gamma source, were drifted under the influence of a 2.5 kV/cm field towards a 1.5 mm thickness THGEM, the local field sufficiently high to generate secondary scintillation light within the liquid as the charge traversed the central region of the THGEM hole. The resulting VUV light was incident on an immersed SiPM device coated in the waveshifter tetraphenyl butadiene (TPB), the emission spectrum peaked at 460 nm in the high quantum efficiency region of the device. For a SiPM over-voltage of 1 V, a THGEM voltage of 9.91 kV, and a drift field of 2.5 kV/cm, a total of 62±20 photoelectrons were produced at the SiPM device per Fe-55 event, corresponding to an estimated gain of 150±66 photoelectrons per drifted electron.

Silicon Photomultiplier Technology at STMicroelectronics

Abstract: In this paper we present the results of the first electrical and optical characterization performed on 1 mm2 total area Silicon Photomultipliers (SiPM) fabricated in standard silicon planar technology at the STMicroelectronics Catania R&D clean room facility. The device consists of 289 microcells and has a geometrical fill factor of 48%. Breakdown voltage, gain, dark noise rate, crosstalk, photon detection efficiency and linearity have been measured in our laboratories. The optical characterization has been performed by varying the temperature applied to the device. The results shown in the manuscript demonstrate that the device already exhibits relevant features in terms of low dark noise rate and inter-pixel crosstalk probability, high photon detection efficiency, good linearity and single photoelectron resolution. These characteristics can be considered really promising in view of the final application of the photodetector in the Positron Emission Tomography (PET).

An ion cooler-buncher for high-sensitivity collinear laser spectroscopy at ISOLDE

Abstract: A gas-filled segmented linear Paul trap has been installed at the focal plane of the high-resolution separator (HRS) at CERN-ISOLDE. As well as providing beams with a reduced transverse emittance, this device is also able to accumulate the ions and release the sample in bunches with a well-defined time structure. This has recently permitted collinear laser spectroscopy with stable and radioactive bunched beams to be demonstrated at ISOLDE. Surface-ionized 39, 44, 46K and 85Rb beams were accelerated to 30keV, mass separated and injected into the trap for subsequent extraction and delivery to the laser setup. The ions were neutralized in a charge exchange cell and excited with a co-propagating laser. The small ion beam emittance allowed focussing in the ion-laser overlap region, which is essential to achieve the best experimental sensitivity. Fluorescent photons were detected by a photomultiplier tube as a frequency scan was taken. A gate (typically 7-12μs wide) was set on the photomultiplier signal to accept the fluorescent photons within the time window defined by the bunch. Thus, using accumulation times of 100ms, the dominant contribution to background due to continuous laser scattering could be reduced by a factor of up to 4×104 .

Fast Photomultipliers for TOF PET

Abstract: Presently, a majority of detectors for PET systems is based on scintillator crystals read by photomultipliers. In our previous work, very good time resolution recorded with a 10times10times5 mm3 LSO crystal coupled to Photonis XP20D0 and Hamamatsu R5320 photomultipliers was shown. Results were almost identical for both detectors and close to 170 ps but the properties such us quantum efficiency of the photocathode and transit time jitter were significantly different. The XP20D0 possessed high QE and the measured photoelectron number was 40% higher than that of the R5320. The R5320 had the time jitter of 140plusmn7 ps at FWHM, three times better than that of the XP20D0. The fact, that despite of the large differences in the parameters of the used PMTs comparable time resolution was achieved, triggered our further study of the most important properties of the photomultipliers and their influence on timing and energy resolution, with a goal of optimizing time-of-flight (TOF) PET systems. Thanks to a close cooperation with Photonis, during last few years we gathered large amount of information and experimental data of various types of PMTs. The aim of this paper is to present general conclusions and dependencies that were derived from these multiple experiments. This should help to develop an ultimate, PMT based detector, for TOF PET systems.

Features of Silicon Photo Multipliers: Precision Measurements of Noise, Cross-Talk, Afterpulsing, Detection Efficiency

Abstract: Solid state single photon detectors are an emerging issue, with applications in the wide field of sensors and transducers. A new kind of device named Silicon Photomultiplier (SiPM) shows timing and charge resolution features that in some respect could even replace traditional photomultiplier tubes. In this paper we illustrate a complete method for the evaluation of gain, dark noise, afterpulsing, cross-talk and detection efficiency of SiPM detectors. We show the application of the method by comparing the performance of our newly developed SiPM (produced by ST Microelectronics) with another sensor present on the market (produced by Hamamatsu), and proving that our device is indeed already outstanding.

Precision measurements of Photon Detection Efficiency for SiPM detectors

Abstract: We present the preliminary results of the characterization of silicon detectors in terms of Photon Detection Efficiency (PDE). The precision measurements are performed at controlled temperature, using a specially suited setup based on a monochromator, an integrating sphere to randomize the incident light and a calibrated reference photodiode. We exploit a measurement technique that we recently devised, based on single photon counting with subtraction of dark noise, and avoiding as much as possible cross-talk and afterpulses. We describe in detail the experimental setups and the techniques utilized to measure the PDE. The achieved results are here discussed in order to establish a methodology capable to give very precise PDE values for solid-state photomultiplier detectors.

New developments on photosensors for particle physics

Abstract: The needs of experiments in high-energy physics have been for many decades the stimulus for detector developments. For calorimetry, particle identification with ring image Cherenkov detectors, time-of-flight measurements, etc., sophisticated photosensors have been realized. Although photomultiplier tubes are a commercial product since 70 years, an impressive progress has been made recently. The bulky shape turned in a slim design and the quantum efficiency has been increased by almost a factor of 2. During the last 3 decades photodetectors made from semiconductor materials, photodiodes and avalanche photodiodes, have replaced in an increasing number the traditional photomultiplier tubes. The recently developed Geiger-mode avalanche photodiodes with high sensitivity to single photons will accelerate this trend.

Detection of reactor antineutrino coherent scattering off nuclei with a two-phase noble gas detector

Abstract: Estimation of the signal amplitudes and counting rates for coherent scattering of reactor antineutrino off atomic nuclei in two-phase xenon and argon detectors has been done. A conceptual design of detector based on the existing technologies and experience has been proposed. It is shown that a condensed xenon/argon two-phase detector possesses the necessary sensitivity for the use in experiment on detection of coherent scattering of the reactor antineutrino off nuclei. It is shown that a two-phase detector with both optical readout by PMTs and ionisation readout by GEM/THGEM possesses superior capability for identification of the events of coherent antineutrino scattering.

Deep UV photon-counting detectors and applications

Abstract: Photon counting detectors are used in many diverse applications and are well-suited to situations in which a weak signal is present in a relatively benign background. Examples of successful system applications of photon-counting detectors include ladar, bio-aerosol detection, communication, and low-light imaging. A variety of practical photon-counting detectors have been developed employing materials and technologies that cover the waveband from deep ultraviolet (UV) to the near-infrared. However, until recently, photoemissive detectors (photomultiplier tubes (PMTs) and their variants) were the only viable technology for photon-counting in the deep UV region of the spectrum. While PMTs exhibit extremely low dark count rates and large active area, they have other characteristics which make them unsuitable for certain applications. The characteristics and performance limitations of PMTs that prevent their use in some applications include bandwidth limitations, high bias voltages, sensitivity to magnetic fields, low quantum efficiency, large volume and high cost. Recently, DARPA has initiated a program called Deep UV Avalanche Photodiode (DUVAP) to develop semiconductor alternatives to PMTs for use in the deep UV. The higher quantum efficiency of Geiger-mode avalanche photodiode (GM-APD) detectors and the ability to fabricate arrays of individually-addressable detectors will open up new applications in the deep UV. In this paper, we discuss the system design trades that must be considered in order to successfully replace low-dark count, large-area PMTs with high-dark count, small-area GM-APD detectors. We also discuss applications that will be enabled by the successful development of deep UV GM-APD arrays, and we present preliminary performance data for recently fabricated silicon carbide GM-APD arrays.

A CMOS time-resolved fluorescence lifetime analysis micro-system

Abstract: We describe a CMOS-based micro-system for time-resolved fluorescence lifetime analysis. It comprises a 16 × 4 array of single-photon avalanche diodes (SPADs) fabricated in 0.35 μm high-voltage CMOS technology with in-pixel time-gated photon counting circuitry and a second device incorporating an 8 × 8 AlInGaN blue micro-pixellated light-emitting diode (micro-LED) array bump-bonded to an equivalent array of LED drivers realized in a standard low-voltage 0.35 μm CMOS technology, capable of producing excitation pulses with a width of 777 ps (FWHM). This system replaces instrumentation based on lasers, photomultiplier tubes, bulk optics and discrete electronics with a PC-based micro-system. Demonstrator lifetime measurements of colloidal quantum dot and Rhodamine samples are presented.

Efficient ion blocking in gaseous detectors and its application to gas-avalanche photomultipliers sensitive in the visible-light range

Abstract: A novel concept for ion blocking in gas-avalanche detectors was developed, comprising cascaded micro-hole electron multipliers with patterned electrodes for ion defocusing. This leads to ion blocking at the 10 - 4 level, in DC mode, in operation conditions adequate for TPCs and for gaseous photomultipliers. The concept was validated in a cascaded visible-sensitive gas-avalanche photomultiplier operating at atmospheric pressure of Ar / CH 4 (95/5) with a bi-alkali photocathode. While in previous works high gain, in excess of 10 5 , was reached only in a pulse-gated cascaded-GEM gaseous photomultiplier, the present device yielded, for the first time, similar gain in DC mode. We describe shortly the physical processes involved in the charge transport within gaseous photomultipliers and the ion blocking method. We present results of ion back-flow fraction and of electron multiplication in cascaded patterned-electrode gaseous photomultiplier with K–Cs–Sb, Na–K–Sb and Cs–Sb visible-sensitive photocathodes, operated in DC mode.

Multipixel single-photon avalanche diode array for parallel photon counting applications

Abstract: In life science, optical techniques for the characterization of biological processes are well established and widely used. In most of them, to obtain the best performances, detectors with single-photon detection capability are required. Moreover, the growing demand for this type of information is pushing the technology towards a parallelization of the analysis. These requirements make it very challenging to develop new detection heads, because state-of-the-art detectors, such as photomultiplier tubes (PMTs) and charged coupled devices (CCDs), have some drawbacks. For example, in fluorescence correlation spectroscopy (FCS) fluorescence fluctuations must be monitored on a short time scale because typical time constants range from hundreds of nanoseconds to milliseconds. In this case, developing parallel modules for this application is very challenging. In fact, PMTs are bulky and they cannot be integrated, while the use of imaging detectors, such as CCDs and electron multiplying CCDs, is strongly limited by...

Novel electro-optical coupling technique for magnetic resonance-compatible positron emission tomography detectors.

Abstract: A new magnetic resonance imaging (MRI)-compatible positron emission tomography (PET) detector design is being developed that uses electro-optical coupling to bring the amplitude and arrival time information of high-speed PET detector scintillation pulses out of an MRI system. The electro-optical coupling technology consists of a magnetically insensitive photodetector output signal connected to a nonmagnetic vertical cavity surface emitting laser (VCSEL) diode that is coupled to a multimode optical fiber. This scheme essentially acts as an optical wire with no influence on the MRI system. To test the feasibility of this approach, a lutetium-yttrium oxyorthosilicate crystal coupled to a single pixel of a solid-state photomultiplier array was placed in coincidence with a lutetium oxyorthosilicate crystal coupled to a fast photomultiplier tube with both the new nonmagnetic VCSEL coupling and the standard coaxial cable signal transmission scheme. No significant change was observed in 511 keV photopeak energy resolution and coincidence time resolution. This electro-optical coupling technology enables an MRI-compatible PET block detector to have a reduced electromagnetic footprint compared with the signal transmission schemes deployed in the current MRI/PET designs.

BASIC: An 8-channel front-end ASIC for Silicon Photomultiplier detectors

Abstract: Multi-channel, integrated front-end electronics suitable for Silicon Photomultiplier detectors and mainly intended for medical imaging applications has been developed in a CMOS standard technology, according to a current-mode approach. Full exploitation of the good performance of the detector in terms of fast response and gain has been made possible by this design approach. An 8-channel, self-triggered prototype with an on-chip ADC has been designed and realized, also featuring a good degree of programmability and sparse read-out capabilities. Characterization measurements, carried out by coupling the circuit to both an injection capacitance and a SiPM manufactured from FBK-irst, confirm the expected results in terms of overall charge to voltage gain, dynamic range (more than 70pC at 1% non-linearity error), equivalent input noise charge (about 50fC) and timing accuracy.

Photomultiplier and detection systems

Abstract: The invention provides a switchable photomultiplier switchable between a detecting state and a non-detecting state including a cathode upon which incident radiation is arranged to impinge. The photomultiplier also includes a series of dynodes arranged to amplify a current created at the cathode upon detection of photoradiation. The invention also provides a detection system arranged to detect radiation-emitting material in an object. The system includes a detector switchable between a detecting state in which the detector is arranged to detect radiation and a non-detecting state in which the detector is arranged to not detect radiation. The system further includes a controller arranged to control switching of the detector between the states such that the detector is switched to the non-detecting state while an external radiation source is irradiating the object.

Thermal emittance and response time measurements of a GaN photocathode

Abstract: We present the measurements of thermal emittance and response time for a GaN photocathode illuminated with 5 ps pulses at 260 nm wavelength. The thermal emittance was measured downstream of a 100 kV dc gun using a solenoid scan with a wire scanner and a beam viewscreen and was found to be 1.35±0.11 mm mrad normalized rms emittance per 1 mm rms of illuminated spot size. The response time of the photoemitted electrons was evaluated using a deflecting mode rf cavity synchronized to the laser pulses and was found to be prompt within the time resolution capability of our setup.

Infrared quantum counting by nondegenerate two photon conductivity in GaAs

Abstract: We report on infrared quantum counting of photons at optical communication wavelengths based on nondegenerate two-photon absorption in a GaAs photomultiplier tube. The detected photon energy is lower than the GaAs band gap and the energy difference is complemented by a high intensity pump field. This detection setup is simple, compact, has a broad spectral bandwidth, and benefits from the intrinsic low noise and dark counts of large band gap semiconductor junctions.

Development of high-gain gaseous photomultipliers for the visible spectral range

Abstract: We summarize the development of visible-sensitive gaseous photomultipliers, combining a semitransparent bi-alkali photocathode with a state-of-the-art cascaded electron multiplier. The latter has high photoelectron collection efficiency and a record ion blocking capability. We describe in details the system and methods of photocathode production and characterization, their coupling with the electron multiplier and the gaseous-photomultiplier operation and characterization in a continuous mode. We present results on the properties of laboratory-produced K2CsSb, Cs3Sb and Na2KSb photocathodes and report on their stability and QE in gas; K2CsSb photocathodes yielded QE values in Ar/CH4(95/5) above 30% at wavelengths of 360–400 nm. The novel gaseous photomultiplier yielded stable operation at gains of 105, in continuous operation mode, in 700 Torr of this gas; its sensitivity to single photons was demonstrated. Other properties are described. The successful detection of visible light with this gas-photomultiplier pave ways towards further development of large-area sealed imaging detectors, of flat geometry, insensitive to magnetic fields, which might have significant impact on light detection in numerous fields.

High Count Rate Neutron Spectrometry With Liquid Scintillation Detectors

Abstract: Liquid scintillation detectors are widely used in nuclear/high-energy physics and nuclear fusion for spectral measurements in mixed radiation fields due to their compactness, fast response and neutron/gamma discrimination capabilities. The use of response functions evaluated for the specific system and of appropriate methods of data analysis allows such systems to be used as broadband spectrometers for photons and neutrons. System stability and ability to reach high throughput count rates are key challenges for several applications (e.g., neutron spectrometry for nuclear fusion devices), but standard analog electronics limits the operation of liquid scintillation neutron spectrometers to low count rates ( ~ 3 ldr 104 s-1) . The count rate capabilities of a liquid scintillation neutron spectrometer (NE213 detector) from the Physikalisch-Technische Bundesanstalt (PTB) has been extended up to ~ 4.2 ldr 105 s-1, by coupling it to a digital acquisition system developed at ENEA-Frascati. Measurements have been carried out at PTB using gamma sources and accelerator-produced 2.5 MeV and 14 MeV neutrons. For 14 MeV neutron measurements, digital pulse height spectra (PHS) obtained at high count rates have been compared to PHS recorded with standard analog electronics. The results show that stable PHS (within 1%) can be obtained at high count rate despite the high sensitivity of the gain of photomultiplier tubes to count rate variations.

A Geant4 simulation code for simulating optical photons in SPECT scintillation detectors

Abstract: Geant4 is an object oriented toolkit created for the simulation of High-Energy Physics detectors. Geant4 allows an accurate modeling of radiation sources and detector devices, with easy configuration and friendly interface and at the same time with great accuracy in the simulation of physical processes. While most Monte Carlo codes do not allow the simulation of the transport and boundary characteristics for optical photons transport generated by scintillating crystal, Geant4 allows the simulation of the optical photons. In this paper we present an application of the Geant4 program for simulating optical photons in SPECT cameras. We aim to study the light transport within scintillators, photomultiplier tubes and coupling devices. To this end, we simulated a detector based on a scintillator, coupled to a photomultiplier tube through a glass window. We compared simulated results with experimental data and theoretical models, in order to verify the good matching with our simulations. We simulated a pencil beam of 140 keV photons impinging the crystal at different locations. For each condition, we calculated the value of the Pulse Height Centroid and the spread of the charge distribution, as read out by the anode array of the photomultiplier. Finally, the spatial and the energy resolutions of the camera have been estimated by simulated data. In all cases, we found that simulations agree very well with experimental data.

A Comparative Study of Silicon Drift Detectors With Photomultipliers, Avalanche Photodiodes and PIN Photodiodes in Gamma Spectrometry With LaBr $_{3}$ Crystals

Abstract: The performance of a silicon drift detector (SDD) with an integrated FET, delivered by the company PNSensor, Munich, Germany, was studied in gamma spectrometry at room temperature (23-25degC) with a LaBr3:Ce crystal of 6 mm diameter and 6 mm height. The SDD characteristics were compared with those measured with a Photonis XP5212 photomultiplier, a Large Area Avalanche Photodiode (LAAPD) of Advanced Photonix, Inc., and a Hamamatsu S3590-18 Photodiode (PD). Energy resolution versus gamma ray energies and its components related to the photoelectron/electron-hole pair statistics and dark noise were measured and compared. At low energies, below 100 keV, the light readout by the photomultiplier gives the best results, while for high energies, above 300 keV, the light readout by the SDD delivers superior energy resolution. In particular, the best energy resolution of 2.7% was determined for 662 keV gamma rays from a 137Cs source.

Investigation of the secondary emission characteristics of CVD diamond films for electron amplification

Abstract: Chemical vapour deposition (CVD) diamond offers great potential as a low-cost, high-yield, easily manufactured secondary electron emitter for electron multiplication in devices such as photomultiplier tubes. Its potential for high secondary electron yield offers several significant benefits for these devices including higher time resolution, faster signal rise time, reduced pulse height distribution, low noise, and chemical stability. We describe an experiment to characterize the secondary emission yield of CVD diamond manufactured using different processes and process parameters and discuss the degradation of secondary electron yield and experimental difficulties encountered due to unwanted electron beam-induced contamination. We describe techniques utilized to overcome these difficulties, and present measurements of secondary yield from CVD diamond dynodes in reflection mode. We discuss the application of CVD diamond dynode technology, both in reflection and transmission mode, to advanced high-speed imaging and photon-counting detectors and describe future plans in this area.

Monte Carlo Simulation Study on the Time Resolution of a PMT-Quadrant-Sharing LSO Detector Block for Time-of-Flight PET

Abstract: We developed a detailed Monte Carlo simulation method to study the time resolution of detectors for time-of-flight positron emission tomography (TOF PET). The process of gamma ray interaction in detectors, scintillation light emission and transport inside the detectors, the photoelectron generation and anode signal generation in the photomultiplier tube (PMT), and the electronics process of discriminator are simulated. We tested this simulation method using published experimental data, and found that it can generate reliable results. Using this method, we simulated the time resolution for a 13 times 13 detector block of 4 times 4 times 20 mm3 lutetium orthosilicate (LSO) crystals coupled to four 2-inch PMTs using PMT-quadrant-sharing (PQS) technology. We analyzed the effects of several factors, including the number of photoelectrons, light transport, transit time spread (TTS), and the depth of interaction (DOI). The simulation results indicated that system time resolution of 360 ps should be possible with currently available fast PMTs. This simulation method can also be used to simulate the time resolution of other detector design method.