We present the design for OpenPET, an electronics readout system designed for prototype radiotracer imaging instruments. The critical requirements are that it has sufficient performance, channel count, channel density, and power consumption to service a complete camera, and yet be simple, flexible, and customizable enough to be used with almost any detector or camera design. An important feature of this system is that each analog input is processed independently. Each input can be configured to accept signals of either polarity as well as either differential or ground referenced signals. Each signal is digitized by a continuously sampled ADC, which is processed by an FPGA to extract pulse height information. A leading edge discriminator creates a timing edge that is "time stamped" by a TDC implemented inside the FPGA. This digital information from each channel is sent to an FPGA that services 16 analog channels, and information from multiple channels is processed by this FPGA to perform logic for crystal lookup, DOI calculation, calibration, etc. As all of this processing is controlled by firmware and software, it can be modified / customized easily. The system is open source, meaning that all technical data (specifications, schematics and board layout files, source code, and instructions) will be publicly available.
A first optical manifestation of the Chen-Lee-Liu-type derivative nonlinear Schrödinger equation results in self-steepening of ultrashort pulses and shock formation without simultaneous self-phase modulation and spectral broadening. Experiments verify theory. OCIS codes: (320.7110) Ultrafast nonlinear optics; (190.5530) Pulse propagation and solitonsNumerous ultrashort pulse applications have employed the cascaded-quadratic (χ (2) : χ (2) ) nonlinearity to produce Kerr-like nonlinear phase shifts [1]. In each of these applications propagation in cubic media is mimicked: an effective nonlinear Schrödinger equation governs propagation, but with features inaccessible from χ (3) , such as a negative (self-defocusing) Kerr term and Raman-or self-steepening-like terms of controllable sign and magnitude.Here we present a use of χ (2) : χ (2) nonlinearities that has no analog in cubic media. By mixing quadratic and cubic nonlinearities we find an effective propagation equation in the form of the Chen-Lee-Liu-type derivative nonlinear Schrödinger equation (dNLSE), the so-called Chen-Lee-Liu (CLL) equation [2]. The CLL features combined group-velocity dispersion (GVD) and self-steepening (SS), but has no Kerr term, i.e., no self-phase modulation (SPM) term of iA|A| 2 form. SS without SPM results in tilting of the pulse temporal profile without change to the temporal phase, meaning there is no change to the power spectrum. In this paper we investigate several novel effects of such propagation.In a recent paper [3], we summarized the leading-order nonlinear terms present in a quadratic medium with contributions from both χ (2) and χ (3) . Using perturbation methods, the 1D effective propagation equation for the fundamental (FF) field in a second-harmonic generation process with large wavevector mismatch was found to be
We report on coherent synthesis of two ultra-broadband optical parametric amplifiers, each compressed by chirped mirror pairs, resulting in almost-octave-spanning (520-1000 nm) spectra supporting nearly single-cycle sub-4 fs pulse duration. Synthesized pulse timing is locked to less than 30 as by a balanced optical cross-correlator. The synthesized pulse is characterized by two-dimensional spectral interferometry and has a 3.8 fs duration.
Editorial Conference Comments by the EditorsT HE Symposium on Radiation Measurements and Applications (SORMA) met for the first time on the West Coast June 2-5, 2008, in Berkeley, CA. With radiation detectors increasing in number, variety, and societal importance, we plan to alternate between SORMA East (in Ann Arbor, MI) and SORMA West so that the forum will be available every two years. The topic areas for SORMA West 2008 were much the same as those of recent Ann Arbor programs, and were meant to encompass the full breadth of ionizing radiation measurement applications and technologies, with both oral and poster presentations.The technical program of SORMA 2008 included 342 scientific presentations, 116 oral presentations plus eight invited keynote lectures in plenary sessions, as well as 218 presentations in poster sessions. The SORMA 2008 meetings were attended by 439 registered participants from 25 different countries. Topics of interest at the meeting ranged from room temperature semiconductor detectors, cryogenic detectors, photodetectors, neutron detectors, novel scintillators, nonproportionality and characterization of scintillators, simulation and analysis of radiation interactions, novel radiation sources, imaging technologies and homeland security and medical applications.
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