854 research outputs found
G Electronics and Data Acquisition (Forward-Angle Measurements)
The G parity-violation experiment at Jefferson Lab (Newport News, VA) is
designed to determine the contribution of strange/anti-strange quark pairs to
the intrinsic properties of the proton. In the forward-angle part of the
experiment, the asymmetry in the cross section was measured for
elastic scattering by counting the recoil protons corresponding to the two
beam-helicity states. Due to the high accuracy required on the asymmetry, the
G experiment was based on a custom experimental setup with its own
associated electronics and data acquisition (DAQ) system. Highly specialized
time-encoding electronics provided time-of-flight spectra for each detector for
each helicity state. More conventional electronics was used for monitoring
(mainly FastBus). The time-encoding electronics and the DAQ system have been
designed to handle events at a mean rate of 2 MHz per detector with low
deadtime and to minimize helicity-correlated systematic errors. In this paper,
we outline the general architecture and the main features of the electronics
and the DAQ system dedicated to G forward-angle measurements.Comment: 35 pages. 17 figures. This article is to be submitted to NIM section
A. It has been written with Latex using \documentclass{elsart}. Nuclear
Instruments and Methods in Physics Research Section A: Accelerators,
Spectrometers, Detectors and Associated Equipment In Press (2007
A 64-channel personal computer based image reconstruction system and applications in single echo acquisition magnetic resonance elastography and ultra-fast magnetic resonance imaging.
Emerging technologies in parallel magnetic resonance imaging (MRI) with massive
receiver arrays have paved the way for ultra-fast imaging at increasingly high frame rates.
With the increase in the number of receiver channels used to implement parallel imaging
techniques, there is a corresponding increase in the amount of data that needs to be
processed, slowing down the process of image reconstruction. To develop a complete
reconstruction system which is easy to assemble in a single computer for a real-time
rendition of images is a relevant challenge demanding dedicated resources for high speed
digital data transfer and computation. We have enhanced a 64 channel parallel receiver
system designed for single echo acquisition (SEA) MRI into a real-time imaging system
by interfacing it with two commercially available digital signal processor (DSP) boards
which are capable of transferring large amounts of digital data via a dedicated bus from
two high performance digitizer boards. The resulting system has been used to demodulate
raw image data in real-time data and store them at rates of 200 frames per second (fps)
and subsequently display the processed data at rates of 26 fps. A further interest in realtime
reconstruction techniques is to reduce the data handling issues. Novel ways to
minimize the digitized data are presented using reduced sampling rate techniques. The
proposed techniques reduce the amount of data generated by a factor of 5 without
compromising the SNR and with no additional hardware. Finally, the usability of this tool
is demonstrated by investigating fast imaging applications. Of particular interest among
them are MR elastography applications. An exploratory study of SEA MRE was done to study the temperature dependency of shear stiffness in an agarose gel and the results
correlate well with existing literature. With the ability to make MRE images in a single
echo, the SEA MRE technique has an advantage over the conventional MRE techniques
FireFly v2: Advancing Hardware Support for High-Performance Spiking Neural Network with a Spatiotemporal FPGA Accelerator
Spiking Neural Networks (SNNs) are expected to be a promising alternative to
Artificial Neural Networks (ANNs) due to their strong biological
interpretability and high energy efficiency. Specialized SNN hardware offers
clear advantages over general-purpose devices in terms of power and
performance. However, there's still room to advance hardware support for
state-of-the-art (SOTA) SNN algorithms and improve computation and memory
efficiency. As a further step in supporting high-performance SNNs on
specialized hardware, we introduce FireFly v2, an FPGA SNN accelerator that can
address the issue of non-spike operation in current SOTA SNN algorithms, which
presents an obstacle in the end-to-end deployment onto existing SNN hardware.
To more effectively align with the SNN characteristics, we design a
spatiotemporal dataflow that allows four dimensions of parallelism and
eliminates the need for membrane potential storage, enabling on-the-fly spike
processing and spike generation. To further improve hardware acceleration
performance, we develop a high-performance spike computing engine as a backend
based on a systolic array operating at 500-600MHz. To the best of our
knowledge, FireFly v2 achieves the highest clock frequency among all FPGA-based
implementations. Furthermore, it stands as the first SNN accelerator capable of
supporting non-spike operations, which are commonly used in advanced SNN
algorithms. FireFly v2 has doubled the throughput and DSP efficiency when
compared to our previous version of FireFly and it exhibits 1.33 times the DSP
efficiency and 1.42 times the power efficiency compared to the current most
advanced FPGA accelerators
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