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The feedback of positive ions in gas amplification detectors of a time projection chamber (TPC) causes adverse effects on the electric field in the drift region, thereby degrading the spatial resolution of the TPC. Instead of employing a conventional wire-grid as a gating device, as often done to alleviate this problem, there is a proposed solution to use a gas electron multiplier (GEM) operated in...
A combination of Monte Carlo (MC) and deterministic approaches was employed as a means of creating a simulation tool capable of providing energy resolved x-ray primary and scatter images within a reasonable time interval. Libraries of Sindbad, a previously developed x-ray simulation software, were used in the development. A cross-validation of the method against an analog MC (EGS4) simulation and...
One of the challenging applications of PET is implementing it for in-beam PET, which is an in situ monitoring method for charged particle therapy. For this purpose, we previously proposed the world's first open-type geometries which we named OpenPET. For in-beam PET, careful designing and testing of detectors are important because secondary particles generated in a target degrade detector performance...
The reduction of detectors in PET systems, without significantly compromising the PET utility, is an important cost consideration in a PET-system design. Recent advances in algorithm development can be used for enabling the design and assessment of innovative PET systems. In this work, we investigate PET configurations with reduced number of detectors by using the ASD-POCS algorithm that was developed...
A low-noise wide-bandwidth charge-sensitive micro-probe is being developed, able to capture the charge signals of semiconductor detectors. The micro-probe works on a single terminated coaxial cable of whatever length, whose quality is crucial to achieving a good dynamic performance. The cable carries both the power supply (DC signal component) and the event pulses (AC signal component). No power-supply...
Compton scattering of gamma photons can give rise to inter-crystal crosstalk in detector arrays for positron emission tomography (PET). PET systems made of pixelated detectors with individual readout can recover inter-crystal scatter (ICS) events in the list-mode data file, but these events are generally ignored since their inclusion in the image reconstruction process leads to undesirable image noise...
We propose a new method for modeling the detector module crystal positioning-blur and mis-positioning errors based on the detector modules' flood histograms (crystal position map) and crystal segmentation maps and use simulations for validation. First, a statistical simulation tool is used to simulate signal pathways from gamma photons in crystals to photo-multiplier tube pulses and then to digitized...
Positron annihilation non-collinearity is one physical factor that constraints the achievable spatial resolution in PET. The quadHIDAC is a high resolution small animal PET scanner with a unique detection principle, relying on multi-wire proportional chamber detectors. In a comparison of simulation and measurement of a 22Na point source, slight discrepancies are observed, which are addressed to an...
Digital Silicon Photomultipliers have several advantages over their analog counterpart, such us lower after-pulsing probability, intrinsic digital conversion, reduction of system complexity, etc. In addition, multichannel digital silicon photomultipliers (MD-SiPMs) can achieve better time resolution and dark count rate immunity because of multiple time-to-digital converters on chip. In this work,...
A Colpitts mm-wave VCO is used for modulating and de-modulating high data rates using two modes of operation, enabling multi-Gbps transceiver with small size and low power. As a VCO 4 GHz tuning range is achieved with a peak output power of +5 dBm at 87 GHz and a phase noise of −93 dBc/Hz at 1 MHz offset. Gate bias modulation achieves up to 6 Gbps ASK modulation with only 9 mW power consumption. In...
The integration of a variety of IP cores into a single chip to meet the high demand of new applications leads to many challenges in timing issues, especially the interface between different clock domains. Globally Asynchronous, Locally Synchronous (GALS) approach addresses these challenges by dividing a chip into several independent subsystems working with different clock signals. In multi-synchronous...
A terahertz detector using an InAlAs/InGaAs high-electron-mobility-transistor (HEMT) integrated with a bow-tie antenna was proposed and fabricated. By utilizing ballistic transport in the short-channel, a current sensitivity of 1.5 A/W at 280 GHz was achieved by the detector having 70-nm T-gate HEMT without applying drain bias. We also measured the drain bias dependence of current sensitivity on the...
We report on the development of a tunable antenna coupled intersubband terahertz (TACIT) detector based on GaAs/AlGaAs two dimensional electron gas. A successful device design and micro-fabrication process have been developed which maintain the high mobility (1.1×106 cm2/V-s at 10K) of a 2DEG channel in the presence of a highly conducting backgate. Gate voltage-controlled device resistance and direct...
We present a TCAD simulation study for Silicon MOSFET terahertz detectors. The impact of transistor doping profile optimization on detector performance is analyzed. Timedomain simulations are used to extract the DC response to THz excitations and to explore the impact of different device parasitics. It is shown that the DC response can be improved by (1) minimizing the source-side parasitic resistance...
We report on terahertz detection experiments at 240 GHz using carbon-nanotube field-effect transistors with a single semiconducting single-walled tube as the transistor's channel. From DC channel resistance measurements, the voltage response is predicted theoretically from the dc transconductance of the devices. Rectification is shown for an electronically applied 2-MHz signal and for free-space illumination...
We report on room-temperature plasmonic detection of the thermal emission from a black body in the terahertz and mid-infrared domains by dual-grating-gate InAlAs/InGaAs/InP high electron mobility transistors (HEMTs). In such detectors, the asymmetric grating gate of a large area acts as an effective antenna that improves the performance in the two spectral domains.
We have fabricated 20 μm gate width graphene field effect transistors (GFETs) based on graphene grown by chemical vapor deposition (CVD). These GFETs are integrated with split bow-tie antennae for room temperature, direct detection of a 0.6 THz signal. Our detectors reach a maximum optical responsivity of 3.0 V/W and a minimum noise-equivalent power (NEP) of 700 pW/Hz0.5. The successful demonstration...
In a very large vessel, maintain ultrahigh vacuum (UHV) is a challenge. The LIGO (Laser Interferometer Gravitational Wave Observatory vacuum envelope is one of the large vacuum chambers in the world. LIGO vacuum system consists of two arms of 4 km long beam tubes of 1.2 meter diameter. Ultrahigh Vacuum (UHV) environment is required to reduce residual gas phase noise to enhance accuracy of measurement...
In principle, the photoresponse can be enhanced by scaling down the gate oxide thickness (tox), which is a key structural parameter for the channel 2DEG density modulation. By using our TCAD simulation framework, we found that the enhanced photoresponse by reducing tox has been originated from the increase of 2DEG density modulation by the improved subthreshold swing (SSW) of FET and the decrease...
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