Michael Loope

Performance Study of the New Hamamatsu R9779 and Photonis XP20D0 Fast 2” Photomultipliers

The focus of this paper is the evaluation of the new fast 51 mm-diameter, 8-stage Hamamatsu R9779 photomultipliers (PMTs) with an acceleration-ring at the front-end and the Photonis XP20D0 PMTs with a screening grid in front of the anode. The following performance characteristics are presented: Timing resolution, anode-scan-uniformity and transit-time spread. The unfolded timing resolution for two R9779 was 192 ps and 210 ps using plastic scintillators. The individual timing resolutions for two XP20D0 using plastic scintillators are 181 ps and 154 ps, respectively. The variation in time resolution across the windows of the two R9779 ranged between 117 ps and 171 ps, and 79 ps and 73 ps for the two XP20D0 PMTs.

CURRENT AND FUTURE USE OF LSO: CE SCINTILLATORS IN PET

Single crystal scintillators of Lu2SiO5:Ce (LSO:Ce) were first developed about 15 years ago and have been in commercial use in positron emission tomography systems for more than five years. Annual ...

Comparison of typical scintillators for PET

There has been a plethora of literature describing the various properties of scintillators that are commonly used in PET detectors. In this literature there usually is a comparison made with respect to light output and energy resolution. Unfortunately, any of these comparisons are misleading because the treatment of the different scintillators is not optimized to produce the best results that may, be possible through proper surface treatment of the scintillator. In this research, there is a comparison made between the following scintillators: BGO, LSO, GSO, LYSO, and YSO. Again, the figures-of-merit for comparison were light output and energy resolution at 511 keV.

Dynode-timing method for PET block-detectors

The focus of this paper is the investigation of a new dynode-timing technique optimized for PET block detectors. This method allows utilization of dynode signals from single but especially multiple photo-multiplier tubes (PMTs), operated with negative high-voltage. The technique will provide an event-timing trigger without deteriorating the anode signal. A printed circuit board has been developed and built for this investigation. Benchmark measurements have been performed, comparing timing of the anode signal with timing of the inverted last-dynode signal and timing of the dynode signal extracted via a newly developed LVPECL-logic based board. Timing measurements were performed with plastic as well as LSO scintillators. From single PMT measurements we find a 30 ps improvement with the dynode-timing method compared to the standard anode timing with two Photonis XP2020Q PMTs with LSO (10 mmtimes10 mmtimes10 mm). For a quad-PMT block detector, assembled of four Hamamatsu R9800 with a Hi-Rez block, the timing-resolution improves ~10%, by 43 ps compared to the standard anode timing.

A pulse shape restore method for event localization in PET scintillation detection

Localizing gamma-ray events accurately and performing pileup rejection/correction functions are desirable in positron-emission-tomography (PET) front-end electronics development. Two techniques, the traditional analog integration with charge-sensitive amplifiers and the recent digital integration by using free-running analog-to-digital converters (ADCs), are the typical methods to obtain the event energy and position information. Pileup issues have been extensively investigated in both these techniques. In this new study, a pulse-shape-restore (PSR) method for event localization is presented. From each PET scintillation detector, a photo-sensor current output signal is amplified then conditioned by a filter. Subsequently the signal is digitized with a fast sampling free-running ADC. The digitized signal is finally processed in a Field Programmable Gate Array (FPGA) by using a numerical line fitting method to restore the signal to its theoretic shape. The event energy is directly obtained from the restored pulse shape rather than from the integration calculation. With the PSR method, we may enhance the event localization accuracy and improve the signal energy resolution. Moreover, the PSR method will be implemented as a pileup rejection /correction algorithm to improve the detector count-rate ability and reduce the gamma ray mispositioning in high count-rate conditions

Evaluation of a Micro-Channel Plate PMT in PET

The focus of this paper is the evaluation of micro-channel plate PMTs for PET detectors. Several properties of MCPs make them interesting for PET applications, such as fast time response, high spatial resolution, compact size, low susceptibility to magnetic fields, high gain and low power consumption. The preliminary tests in this paper are performed with the 51 mm times 51 mm square Burle 85011-501 assembly with 64 anodes (8 times 8). A new version of this MCP will be examined for the full paper. Initial measurements have been performed with a pulsed LASER (Hamamatsu Picosecond Light Pulser PLP-10 with M8903 Laser diode head). The engineering sample of the 85011 exhibited a time resolution of 26 ps. Further measurements will be performed, such as transit time measurements and timing measurements with scintillators. Single-photon timing measurements were presented earlier in [Ref. 1], from the old version as well as the suitability of the device in Cherenkov detectors in [Ref. 2]. For the full paper it is also planned to develop a circuit which allows lossless splitting of the anode signal.