On the comparison of analog and digital SiPM readout in terms of expected timing performance

AbstractIn time of flight positron emission tomography (TOF-PET) and in particular for the EndoTOFPET-US Project (Frisch, 2013 [1]), and other applications for high energy physics, the multi-digital silicon photomultiplier (MD-SiPM) was recently proposed (Mandai and Charbon, 2012 [2]), in which the time of every single photoelectron is being recorded. If such a photodetector is coupled to a scintillator, the largest and most accurate timing information can be extracted from the cascade of the scintillation photons, and the most probable time of positron emission determined. The readout concept of the MD-SiPM is very different from that of the analog SiPM, where the individual photoelectrons are merely summed up and the output signal fed into the readout electronics. We have developed a comprehensive Monte Carlo (MC) simulation tool that describes the timing properties of the photodetector and electronics, the scintillation properties of the crystal and the light transfer within the crystal. In previous studies we have compared MC simulations with coincidence time resolution (CTR) measurements and found good agreement within less than 10% for crystals of different lengths (from 3mm to 20mm) coupled to SiPMs from Hamamatsu. In this work we will use the developed MC tool to directly compare the highest possible time resolution for both the analog and digital readout of SiPMs with different scintillator lengths. The presented studies reveal that the analog readout of SiPMs with microcell signal pile-up and leading edge discrimination can lead to nearly the same time resolution as compared to the maximum likelihood time estimation applied to MD-SiPMs. Consequently there is no real preference for either a digital or analog SiPM for the sake of achieving highest time resolution. However, the best CTR in the analog SiPM is observed for a rather small range of optimal threshold values, whereas the MD-SiPM provides stable CTR after roughly 20 registered photoelectron timestamps in the time estimator

CARIOCA: a fast binary front-end implemented in 0.25μ0.25\mu CMOS using a Novel current-mode technique for the LHCb muon detector

The CARIOCA front-end is an amplifier discriminator chip, using 0.25mm CMOS technology, developed with a very fast and low noise preamplifier. This prototype was designed to have input impedance below 10W. Measurements showed a peaking time of 14ns and noise of 450e- at zero input capacitance, with a noise slope of 37.4 e-/pF. The sensitivity of 8mV/fC remains almost unchanged up to a detector capacitance of 120pF

Quiescent H2 Emission From Pre-Main Sequence Stars in Chamaeleon I

We report the discovery of quiescent emission from molecular hydrogen gas located in the circumstellar disks of six pre-main sequence stars, including two weak-line T Tauri stars (TTS), and one Herbig AeBe star, in the Chamaeleon I star forming region. For two of these stars, we also place upper limits on the 2->1 S(1)/1->0 S(1) line ratios of 0.4 and 0.5. Of the 11 pre-main sequence sources now known to be sources of quiescent near-infrared hydrogen emission, four possess transitional disks, which suggests that detectable levels of H$_2$ emission and the presence of inner disk holes are correlated. These H$_2$ detections demonstrate that these inner holes are not completely devoid of gas, in agreement with the presence of observable accretion signatures for all four of these stars and the recent detections of [Ne II] emission from three of them. The overlap in [Ne II] and H$_2$ detections hints at a possible correlation between these two features and suggests a shared excitation mechanism of high energy photons. Our models, combined with the kinematic information from the H$_2$ lines, locate the bulk of the emitting gas at a few tens of AU from the stars. We also find a correlation between H$_2$ detections and those targets which possess the largest H$\alpha$ equivalent widths, suggesting a link between accretion activity and quiescent H$_2$ emission. We conclude that quiescent H$_2$ emission from relatively hot gas within the disks of TTS is most likely related to on-going accretion activity, the production of UV photons and/or X-rays, and the evolutionary status of the dust grain populations in the inner disks.Comment: 12 pages, emulateapj, Accepted by Ap

Mid-Infrared High-Contrast Imaging of HD 114174 B : An Apparent Age Discrepancy in a "Sirius-Like" Binary System

We present new observations of the faint "Sirius-like" companion discovered to orbit HD 114174. Previous attempts to image HD 114174 B at mid-infrared wavelengths using NIRC2 at Keck have resulted in a non-detection. Our new L'-band observations taken with the Large Binocular Telescope and LMIRCam recover the companion ($\Delta L$ = 10.15 $\pm$ 0.15 mag, $\rho$ = 0.675'' $\pm$ 0.016'') with a high signal-to-noise ratio (10 $\sigma$). This measurement represents the deepest L' high-contrast imaging detection at sub-arcsecond separations to date, including extrasolar planets. We confirm that HD 114174 B has near-infrared colors consistent with the interpretation of a cool white dwarf ($J-L'$ = 0.76 $\pm$ 0.19 mag, $K-L'$ = 0.64 $\pm$ 0.20). New model fits to the object's spectral energy distribution indicate a temperature $T_{\rm eff}$ = 4260 $\pm$ 360 K, surface gravity log g = 7.94 $\pm$ 0.03, a cooling age t$_{c} \approx$ 7.8 Gyr, and mass $M$ = 0.54 $\pm$ 0.01 $M_{\odot}$. We find that the cooling age given by theoretical atmospheric models do not agree with the age of HD 114174 A derived from both isochronological and gyrochronological analyses. We speculate on possible scenarios to explain the apparent age discrepancy between the primary and secondary. HD 114174 B is a nearby benchmark white dwarf that will ultimately enable a dynamical mass estimate through continued Doppler and astrometric monitoring. Efforts to characterize its physical properties in detail will test theoretical atmospheric models and improve our understanding of white dwarf evolution, cooling, and progenitor masses.Comment: 6 pages, 3 figures, to be published in the Astrophysical Journal Letter

A Compact Gas Cerenkov Detector with Novel Optics

We discuss the design and performance of a threshold Cerenkov counter for identification of charged hadrons. The radiator is pressurized gas, which is contained in thin-walled cylindrical modules. A mirror system of novel design transports Cerenkov photons to photomultiplier tubes. This system is compact, contains relatively little material, and has a large fraction of active volume. A prototype of a module designed for the proposed CLEO III detector has been studied using cosmic rays. Results from these studies show good agreement with a detailed Monte Carlo simulation of the module and indicate that it should achieve separation of pions and kaons at the 2.5-3.0sigma level in the momentum range 0.8-2.8 GeV/c. We predict performance for specific physics analyses using a GEANT-based simulation package.Comment: Submitted to NIM. 23 pages, 11 postscript figures. Postscript file is also available at http://w4.lns.cornell.edu/public/CLNS/199

A low power, large dynamic range, CMOS amplifier and analog memory for capacitive sensors

This paper has been written to announce the design of a CMOS charge to voltage amplifier and it¹s integration within an analog memory. Together they provide the necessary front end electronics for the CMS electromagnetic calorimeter (ECAL) preshower detector systeAspell,Pm in the LHC experiment foreseen at the CERN particle physics laboratory. The design and measurements of the amplifier realised in a 1.5mm bulk CMOS process as a 16 channel prototype chip are presented. Results show the mean gain and peaking time of = 1.74mV/mip, = 18ns with channel to channel variations; s(peak_voltage) = 8% and s(peak_time) = 6.5%. The dynamic range is shown to be linear over 400mips with an integral non linearity (INL)=0.05mV as expressed in terms of sigma from the mean gain over the 400mip range. The measured noise of the amplifier was ENC=1800+41e/pF with a power consumption of 2.4mW/channel. The amplifier can support extreme levels of leakage current. The gain remains constant for up to 200mA of leakage current. The integration of this amplifier within a 32 channel, 128 cell analog memory chip ³DYNLDR² is then demonstrated. The DYNLDR offers sampling at 40MHz with a storage time of up to 3.2ms. It provides continuous Write/Read access with no dead time. Triggered data is protected within the memory until requested for readout which is performed at 2.5MHz. The memory is designed to have a steerable dc level enabling maximum dynamic range performance. Measurements of the DYNLDR are presented confirming the original amplifier performance. The memory itself has a very low pedestal non uniformity (s(ped)) of 0.9mV and a gain of 10mV/mip