J04:Joint NSS/MIC 4
Tuesday, Oct. 2716:00-18:00; in International Ballroom North
J04-1: (16:00) The Digital Silicon Photomultiplier - A Novel Sensor for the Detection of Scintillation Light
C.Degenhardt, G.Prescher, T.Frach, R.deGruyter, A.Schmitz, R.Ballizany
Philips Corporate Technologies, Aachen, Germany
Silicon Photomultipliers (SiPMs), arrays of avalanche photodiodes operated in Geiger-mode, are attractive alternatives to Photomultiplier Tubes for reasons of ruggedness, compactness or insensitivity to magnetic fields. Other advantages of solid state detectors are their low operating voltage, low power consumption and large scale fabrication possibilities. On the other hand, current solid state detectors are limited when it comes to the detection of very low light fluxes or precise timing measurements and their gain is very sensitive to temperature variations. The Digital Silicon Photomultiplier (dSiPM) presented here overcomes those problems by early digitization of the Geiger-cell output and integrated electronics on chip.
We developed a Digital SiPM of 3.8x3.3mm2 in size containing 8188 individual cells. Each detected photon is converted into a digital signal as early as possible in each of the Geiger-mode cells of the sensor. In addition, the complete trigger logic and the time-to-digital converter are integrated into the sensor.
To show the performance of the sensor, scintillation crystals of different sizes and materials using different reflector materials were coupled to the sensor and irradiated by gamma radiation of 662keV, 511keV and 49keV. The energy resolution at 511keV using LYSO scintillators was determined to be 10.8%, being comparable to results obtained with PMTs. The timing resolution of 190ps FWHM for 4x4x5 mm3 LYSO crystals constitute the best timing resolution ever obtained with this scintillator material.
In addition, the influence of temperature on photon detection efficiency and timing characteristics of the sensor will be presented.
The results show that the Digital Silicon Photomultiplier is a promising novel detector for the detection of low light fluxes as encountered in scintillation detector readout, especially in cases where a good timing resolution is mandatory.
N22:Semiconductor Detectors II: Silicon Devices
Wednesday, Oct. 2808:00-10:00; in Grand Ballroom 2
N22-1 (invited) : (08:10) The First Measurements on an Avalanche Diode Array with Bulk Integrated Quench Resistors for Single Photon Detection
J.Ninkovic1, L.Andricek1, G.Liemann1, G.Lutz2, H.G.Moser1, R.H.Richter1
1Semiconductor Laboratory, Max Plancl Institute for Physics, Munich, Germany 2PN Sensor GmbH, Munich, Germany
A Silicon Photomultiplier (SiPM) is an avalanche photodetector that is entering many application areas as a replacement of conventional photomultiplier tubes (PMTs). Its Geiger mode operation requires high ohmic polysilicon as quench resistor that becomes an obstacle for light and is one of the most cost and yield driving technological issues. We have proposed a new detector concept which has the quench resistor integrated into the silicon bulk avoiding polysilicon resistors. Extensive simulation results showed the feasibility of the concept. The quenching mechanism has been demonstrated in a proof of principle production performed in house. The first prototype fabrication (second production run) on silicon on isolator substrates has been done and allows testing of the device performance. The results from the first measurements will be evaluated in comparison with the simulations. Based on these results the inherent advantages and drawbacks compared to standard SiPMs will be discussed.
N24:New Detector Concepts and Instrumentation II
Wednesday, Oct. 2808:00-10:00; in Grand Ballroom 7
N24-7: (09:40) Time Based Readout of Silicon Photomultiplier (SiPM) for Time of Flight PET Tomography
P.P.Jarron1, E.E.Auffray1, S.S.Brunner1, H.H.Hillemanns1, A.A.Kluge1, P.P.Lecoq1, M.M.Morel1, T.T.Meyer1, F.F.Powolony1, M.C.S.C.Williams2, M.M.Despeisse3
1PH, CERN, Geneva, Switzerland 2University of Bologna, Bologna, Italy 3IMT, EPFL, Neuchatel, Switzerland
Time of flight (TOF) technique for PET is very demanding in timing performance, ideally less than 100ps FWHM precision. We present a time based differential technique to readout SiPM having less than 10ps rms electronic jitter. The novel readout is a fast front end circuit based on a first stage differential current mode amplifier with 20 ohm input resistance. The amplifier inputs are connected differentially to the SiPM anode and cathode ports. DC current of the amplifier input branches are offset to provide a discrimination threshold. The second stage of the current mode front end circuit is a fast differential amplifierdiscriminator circuit performing a time-over-threshold signal processing. The leading edge of the output signal provides the time information, the trailing edge the energy information. SPICE simulation results of the precise 3x3 mm SiPM model and the front end electronics design in 0.25um CMOS technology are presented and compared to experimental results obtained with a 3x3x20mm LSO scintillator Crystal readout with a SiPM. Time coincidence precision and energy spectra are also presented and interpreted with the SPICE simulation.
N25:Posters II
Wednesday, Oct. 2810:30-12:00; in Palm 3, 4 & 5
N25-86: (10:30) Characterization of CMOS Position Sensitive Solid-State Photomultipliers
M.McClish, P.Dokhale, J.Christian, C.Stapels, E.Johnson, R.Robertson, K.S.Shah
Radiation Monitoring Devices, Inc., Watertown, MA, USA
We have designed position sensitive solid-state photomultipliers (PS-SSPM) using a complementary metal-oxide-semiconductor (CMOS) process. While only needing four signal output channels to readout, the device provides spatial information on the micro-pixel level. Three variations of the PS-SSPM design were characterized for their energy and coincidence timing resolution, spatial resolution, and scintillator array imaging. Each PS-SSPM is 1.5 x 1.5 mm2, however, each device has different micro-pixel geometries and different micro-pixel electrical readout for event position sensing. The FWHM energy resolution at 511 keV was measured using a 1 x 1 x 20 mm3 LYSO crystal. The resolution varied, however, one PS-SSPM design achieved 11.6%. The LYSO scintillator coincidence timing resolution also varied between designs with results ranging from 2.1 to 1.0 nsec. Spatial resolution studies were conducted using a focused (~ 15 μm beam spot diameter) pulsed 635 nm diode laser. For each PS-SSPM, its X and Y FWHM spatial resolution was measured. Lastly, we demonstrate the PS-SSPM imaging capabilities using a LYSO scintillator array with 500 x 500 μm2 pixels uniformly irradiated by 22Na.
N25-118: (10:30) Tests of Silicon Photomultiplier PET Modules
H.Chagani1, R.Dolenec1, S.Korpar1,2, P.Krizan1,3, R.Pestotnik1, A.Stanovnik1,4, R.Verheyden1
1Experimental Particle Physics Department, Jozef Stefan Institute, Ljubljana, Slovenia 2Department of Chemistry and Chemical Engineering, University of Maribor, Maribor, Slovenia 3Department of Mathematics and Physics, University of Ljubljana, Ljubljana, Slovenia 4Department of Electrical Engineering, University of Ljubljana, Ljubljana, Slovenia
The use of Silicon Photomultipliers (SiPMs) as photon detectors in Positron Emission Tomography (PET) modules offers significant advantages over conventional light sensors, including application in a magnetic field, better resolution and easier operation. Two PET modules have been constructed by coupling 4 x 4 arrays of LYSO scintillation crystals of area 4 x 4 mm2 and length 20 mm to SiPMs. Two types of SiPM have been tested: the Hamamatsu S10931-100P and Photonique PCB-PET07 of active surface areas 3 x 3 mm2 and 2.1 x 2.1 mm2 respectively. The energy, time and spatial resolutions of the arrays are presented in view of arrangement into a larger module. Results from both modules are also compared with light collection simulations performed in GEANT4.
N25-131: (10:30) Recent Developments for CMOS Solid-State Photomultipliers with Integrated Signal Processing
E.B.Johnson1, C.J.Stapels1, M.McClish1, P.Dokhale1, S.Mukhopadhyay1, E.C.Chapman1, F.L.Augustine2, J.F.Christian1
1Radiation Monitoring Devices, Inc., Watertown, MA, USA 2Augustine Engineering, Encinitas, CA, USA
Solid-state photomultipliers (SSPMs) are a compact, lightweight, potentially low-cost alternative to a photomultiplier tube for a variety of scintillation detector applications, including nuclear and medical-imaging applications. Manufacturing SSPMs with a commercial CMOS process provides the ability for rapid prototyping, and facilitates production to reduce the cost. On-chip integration of signal processing circuits is a distinct advantage of CMOS photodetectors beyond traditional phototubes. We will discuss the advances of the CMOS SSPM with integrated signal processing, which includes fabrication of large area (1 x 1 cm^2) devices and back illumination of thinned die.
N25-133: (10:30) Advanced Study of Novel Radiation Detector Based on Silicon Photomultiplier
A.Osovizky1, D.Ginzburg1, M.Ghelman2, I.Cohen-Zada1, V.Pushkarsky1, E.Marcus2, A.Manor1, Y.Kadmon2, Y.Cohen2
1Health Physics Instrumentation Department, Rotem Industries Ltd, Beer-Sheva, Israel 2Electronics & Control Laboratories, Nuclear Research Center - Negev, Beer-Sheva, Israel
The Silicon Photomultiplier is a novel and rapidly developing solid state optical sensor. In contradiction to its use for photon counting the operating conditions of the SiPM are of main concern when used as a light sensor in portable radiation detection device due to the gain dependence in temperature and operating voltage. The detection of low energy at high temperature requires an improvement of the Photon Detection Efficiency (PDE). An optimization of the PDE can be achieved by increasing the pixel size which improves the detector sensitive area fill factor. However, an increase in the pixel size reduces the dynamic range. This work describes the measurements and the results obtained for different photo-coupling configurations of a CsI(Tl) scintillation crystal with SiPM and the effect of various operating conditions on the instability of the gain. An optimization of the dominant parameters, such as noise level, resolution and dynamic range, is discussed and concluded. The dependence of these parameters in crystal dimension was examined in series of measurements using about 10 different crystal sizes and 3x3mm active area SiPM device. The energy equivalent noise level was measured over a wide temperature range and optimal operating voltage was determined. An investigation of the pixel size had been performed testing pixels from 35μm to 50μm to determine the most suitable to achieve the required dynamic range for energies up to 3 MeV. Reduction of sensor noise was approached with the coincidence detection method using two SiPM devices and a coincidence circuit. The improvement in noise level was tested in two configurations of the photo-sensors. The described comprehensive evaluation of the SiPM device showed the sensor performances in variety of configurations. The results emphasize the potential of the technology in radiation detection applications and the issues yet to be solved before it can present a viable alternative to the currently used technology.
N25-137: (10:30) Fast, Large Area CMOS Solid-State Photomultiplier for Radiation Detection
P.Dokhale, J.Christian, C.Stapels, E.Johnson, K.Shah
Radiation Monitoring Devices Inc., Watertown, MA, USA
Current and next generation experiments in nuclear and particle physics require sensors with fast response and high signal-to-noise ratio for detection of low intensity optical signals. Photomultiplier tubes (PMT) have been widely used for sensing light in most nuclear physics and imaging research experiments. PMTs, however, have several drawbacks that limit their use in several applications and technologies. Solid-state photomultipliers (SSPM) are compact, have high gain at low bias, fast response time and they are insensitive to magnetic fields gives a potential alternative to photomultiplier tubes for a variety of scintillation detector applications. A novel solid-state photomultiplier (SSPM) has been designed and developed by Radiation Monitoring Devices Inc., using standard CMOS technology. In this paper, we report performance of large area SSPM detector for spectroscopy and imaging applications. A detector was built by directly coupling a 6x6x5 mm3 LYSO scintillator to the large area (36 mm2) SSPM. Energy, co-incidence timing, linearity and imaging performance of the detector was evaluated. Energy resolution measured for 661.7 keV gamma rays was 9.6% (FWHM). The timing resolution measured against LYSO-PMT detector with 511 keV gamma rays (22Na) source was 700 ps. The position sensitive SSPM (PS-SSPM) was also designed, built and evaluated. A flood image was recorded with a 4x4 LYSO array (each LYSO element measuring 1.5mm x 1.5mm x 20mm) coupled to a PS-SSPM with 36 mm2 active area. All 16 LYSO elements were clearly visible and well separated from each other in the flood image. We have also studied the performance of the 36 mm2 SSPM when coupled to 5x5x3 mm3 CsI(Tl) scintillator. The energy resolution measured with CsI(Tl) scintillator for 661.7 keV gamma rays was 7.2% (FWHM).
N25-141: (10:30) Time Resolving Characterization of HPK and FBK Silicon Photomultipliers for TOF and PET Applications
G.U.Pignatel1,2, G.Ambrosi1, P.Azzarello1, R.Battiston1, G.DiLorenzo2, M.Ionica1
1Physics Department, National Institute of Nuclear Physics, Perugia, Italy 2Electronic and Information Eng., University of Perugia, Perugia, Italy
In Time-of-Flight measurements, or Positron Emission Tomography experiments where two gamma rays are emitted in coincidence, the time resolution of the photon detector is of primary importance. SIPMs are very promising devices for these applications, since their intrinsic response time is very short, typically less than 1 ns. However the actual timing resolution of SIPMs is affected by the area (capacitance) of the device, by the type of electronics used to pre-amplify the signal, by the dark count rate which is detected as pure noise, and other second order effects like cross-talk and after dark pulsing. In this work we report the characteristics of different samples of HPK (Hamamatsu Photonics) and FBK (Fondazione-Bruno-Kessler) SIPMs, with pixel size ranging from 40 to 100 micron. In particular, we have investigated their time response when stimulated with O(100) ps pulsed laser with wavelength in the range 400 - 800 nm. SIPM performances are also compared with that of fast PIN diodes characterized with the same set-up.
N25-151: (10:30) Investigation of Timing Resolution and Energy Resolution for SiPM/PET Detectors Using the Silicon Flexible Optical Material
J.Zhu1,2, Z.Zhang1, B.Zhang1,2, M.Niu1,2, T.Xu1, X.Zhang3, Q.Xie1,2
1Department of Biomedical Engineering, Huazhong University of Science and Technology, Wuhan,Hubei, China 2Wuhan National Laboratory for Optoelectronics, Wuhan,Hubei, China 3Institute for Pattern Recognition & Artificial Intelligence, Huazhong University of Science and Technology, Wuhan,Hubei, China
Silicon photomultipliers (SiPMs) attract extensive attention for detecting optical photons in high energy physics and medical imaging due to its high gain, high photon detection efficiency (PDE), low operation voltage and fast timing response. We use the silicon flexible optical material to transform the Gaussian distribution of incident light intensity into uniform in space, making the incident photons being detected by SiPM equally. In this way, we can make full use of all cells of SiPM, and more cells operating means more photons being detected for a certain pulse, which can increase the count rate of the incident photons, and improve the detection efficiency of SiPM. Furthermore, by comparing the output of SiPM in different light intensity input, we can find out the best light intensity fit for SiPM and the suitable crystal and surface treatment for positron emission tomography (PET) imaging based on SiPM. In primary experiment, we use the laser pulse as SiPM input since that its light intensity expressed as Gaussian distribution in space, and analyze the readout of SiPM using the silicon flexible optical material or not. The result is consistent with our expectation. By the use of the silicon flexible optical material, the timing resolution and energy resolution of SiPM become better than without it, when the light intensity of input is appropriated. Considering the difference between the laser output and scintillation pulse, we will apply the silicon flexible optical material to SiPM/PET detectors by coupling it to crystal directly, and evaluate its effect on the timing resolution and energy resolution in PET imaging.
N28:Photodetectors and Scintillation Detectors II
Wednesday, Oct. 2813:30-15:30; in Grand Ballroom 7
N28-1: (13:30) SiPM Performance in PET Applications: an Experimental and Theoretical Analysis
D.Henseler1, R.Grazioso2, N.Zhang2, M.Schmand2
1Healthcare, Siemens AG, Forchheim, Germany 2Healthcare, Siemens Medical Solutions, Rockford, TN, USA
Silicon photomultipliers are increasingly being studied for their use in clinical and pre-clinical PET applications, both by industry and academia. Many groups have evaluated the performance of Multi-Pixel Photon Counters (MPPCs) from Hamamatsu Photonics. When coupled to typical PET scintillator crystals, these devices have shown promising results in terms of energy and timing resolution. The purpose of this paper is to analyze the main factors that determine the spectroscopic performance of SiPM based PET detectors and to provide guidelines for further optimization towards the performance levels of state-of-the-art PMT detectors. We present experimental results for the energy and timing resolution for different microcell types of Hamamatsu MPPCs coupled to single LSO crystals. For the 50 m microcell type, we show results for LSO arrays coupled to MPPC arrays with different coupling geometries. To explore the potential and the limitations of SiPM based detectors, we present a statistical signal analysis that links the detector performance to fundamental device characteristics, such as photon detection efficiency, cell density, crosstalk and afterpulsing probability and dark rate. The relative influence of each device parameter on the overall spectroscopic performance is analyzed and discussed. This theoretical analysis is carried out for several optical coupling configurations. The light distribution is modeled with the ray-tracing program ZEMAX, before applying the statistical model to the remaining signal chain (see Figs 1 and 2). Theoretical estimates will be given for both energy and timing resolution Our analysis concludes with a discussion of the impact of each fundamental device parameter on the spectroscopic and spatial resolution of a simple PET block detector. This way the model helps to predict the benefits of future device optimization efforts and to assign priorities to competing optimization targets.
N28-4: (14:15) Production of Large Area Silicon Photomultipliers for a PET/MR Scanner
C.Piemonte1, M.Melchiorri1, A.Piazza1, A.Tarolli1, N.Zorzi1, V.Schulz2, T.Solf2, P.Fischer3
1FBK, Trento, Italy 2Philips Research, Aachen, Germany 3University of Heidelberg, Heidelberg, Germany
We report on the production experience and the characteristics of silicon photomultipliers (SiPMs) fabricated at FBK to be used to fully equip a preclinical positron emission tomography (PET) system. More than 700 fully working, 2x2 monolithic arrays of 4x4mm2 SiPMs have been produced. A test procedure, based on forward and reverse IV measurements, has been implemented to extract the basic properties and, finally, to select the devices at the wafer level. Methodology, results from the on-wafer tests and functional performance are shown. Besides this production, test SiPMs featuring microcells with different designs have been fabricated to find the configuration which optimizes the timing and energy resolution performance of the sensor coupled with the scintillator. Tests on these structures are ongoing and the results will be shown at the conference.