Laser pulse detection method and apparatus

A sensor is described for detecting the difference in phase of a pair of returned light pulse components, such as two components of a light pulse of an optical gyro. In an optic gyro, the two light components have passed in opposite directions through a coil of optical fiber, with the difference in phase of the returned light components determining the intensity of light shining on the sensor. The sensor includes a CCD (charge coupled device) that receives the pair of returned light components to generate a charge proportional to the number of photons in the received light. The amount of the charge represents the phase difference between the two light components. At a time after the transmission of the light pulse and before the expected time of arrival of the interfering light components, charge accumulating in the CCD as a result of reflections from components in the system, are repeatedly removed from the CCD, by transferring out charges in the CCD and dumping these charges

Scientific CCD technology at JPL

Charge-coupled devices (CCD's) were recognized for their potential as an imaging technology almost immediately following their conception in 1970. Twenty years later, they are firmly established as the technology of choice for visible imaging. While consumer applications of CCD's, especially the emerging home video camera market, dominated manufacturing activity, the scientific market for CCD imagers has become significant. Activity of the Jet Propulsion Laboratory and its industrial partners in the area of CCD imagers for space scientific instruments is described. Requirements for scientific imagers are significantly different from those needed for home video cameras, and are described. An imager for an instrument on the CRAF/Cassini mission is described in detail to highlight achieved levels of performance

Fringe Science: Defringing CCD Images with Neon Lamp Flat Fields

Fringing in CCD images is troublesome from the aspect of photometric quality and image flatness in the final reduced product. Additionally, defringing during calibration requires the inefficient use of time during the night to collect and produce a "supersky" fringe frame. The fringe pattern observed in a CCD image for a given near-IR filter is dominated by small thickness variations across the detector with a second order effect caused by the wavelength extent of the emission lines within the bandpass which produce the interference pattern. We show that essentially any set of emission lines which generally match the wavelength coverage of the night sky emission lines within a bandpass will produce an identical fringe pattern. We present an easy, inexpensive, and efficient method which uses a neon lamp as a flat field source and produces high S/N fringe frames to use for defringing an image during the calibration process.Comment: accepted to PAS

Detection of sub-shot-noise spatial correlation in high-gain parametric down-conversion

Using a 1GW-1ps pump laser pulse in high gain parametric down-conversion allows us to detect sub-shot-noise spatial quantum correlation with up to one hundred photoelectrons per mode, by means of a high efficiency CCD. The statistics is performed in single-shot over independent spatial replica of the system. The paper highlights the evidence of quantum correlation between symmetrical signal and idler spatial areas in the far field, in the high gain regime. In accordance with the predictions of numerical calculations the observed transition from the quantum to the classical regime is interpreted as a consequence of the narrowing of the down-converted beams in the very high gain regime.Comment: 4,2 pages, 4 figure

Quadrant-CCD star tracker

We discuss the characteristics of a Quadrant-CCD developed by Tektronix for pointing and tracking applications. The device is discussed in the context of its application to the Johns Hopkins University adaptive optics program, where it is being used for the correction of stellar image motion resulting from atmospheric turbulence. The transfer function of the device is discussed and results are presented which demonstrate the Quadrant-CCDs capability to provide offset signals to control a rapid guiding mirror in the Johns Hopkins instrument

Background Rejection in the DMTPC Dark Matter Search Using Charge Signals

The Dark Matter Time Projection Chamber (DMTPC) collaboration is developing low-pressure gas TPC detectors for measuring WIMP-nucleon interactions. Optical readout with CCD cameras allows for the detection for the daily modulation in the direction of the dark matter wind, while several charge readout channels allow for the measurement of additional recoil properties. In this article, we show that the addition of the charge readout analysis to the CCD allows us too obtain a statistics-limited 90% C.L. upper limit on the $e^-$ rejection factor of $5.6\times10^{-6}$ for recoils with energies between 40 and 200 keV$_{\mathrm{ee}}$. In addition, requiring coincidence between charge signals and light in the CCD reduces CCD-specific backgrounds by more than two orders of magnitude.Comment: 8 pages, 6 figures. For proceedings of DPF 2011 conferenc

Radiation Hardness Studies in a CCD with High-Speed Column Parallel Readout

Charge Coupled Devices (CCDs) have been successfully used in several high energy physics experiments over the past two decades. Their high spatial resolution and thin sensitive layers make them an excellent tool for studying short-lived particles. The Linear Collider Flavour Identification (LCFI) collaboration is developing Column-Parallel CCDs (CPCCDs) for the vertex detector of the International Linear Collider (ILC). The CPCCDs can be read out many times faster than standard CCDs, significantly increasing their operating speed. The results of detailed simulations of the charge transfer inefficiency (CTI) of a prototype CPCCD are reported and studies of the influence of gate voltage on the CTI described. The effects of bulk radiation damage on the CTI of a CPCCD are studied by simulating the effects of two electron trap levels, 0.17 and 0.44 eV, at different concentrations and operating temperatures. The dependence of the CTI on different occupancy levels (percentage of hit pixels) and readout frequencies is also studied. The optimal operating temperature for the CPCCD, where the effects of the charge trapping are at a minimum, is found to be about 230 K for the range of readout speeds proposed for the ILC. The results of the full simulation have been compared with a simple analytic model.Comment: 3 pages, 6 figures; presented at IEEE'07, ALCPG'07, ICATPP'0

Electron-multiplying CCDs for future soft X-ray spectrometers

CCDs have been used in several high resolution soft X-ray spectrometers for both space and terrestrial applications such as the Reflection Grating Spectrometer on XMM-Newton and the Super Advanced X-ray Emission Spectrometer at the Paul Scherrer Institut in Switzerland. However, with their ability to use multiplication gain to amplify signal and suppress readout noise, EM-CCDs are being considered instead of CCDs for future soft X-ray spectrometers. When detecting low energy X-rays, EM-CCDs are able to increase the Signal-to-Noise ratio of the device, making the X-rays much easier to detect. If the signal is also significantly split between neighbouring pixels, the increase in the size of the signal will make complete charge collection and techniques such as centroiding easier to accomplish. However, multiplication gain from an EM-CCD does cause a degradation of the energy resolution of the device and there are questions about how the high field region in an EM-CCD will behave over time in high radiation environments. This paper analyses the possible advantages and disadvantages of using EM-CCDs for high resolution soft X-ray spectroscopy and suggests in which situations using them would not only be possible, but also beneficial to the instrument

First Dark Matter Search Results from a Surface Run of the 10-L DMTPC Directional Dark Matter Detector

The Dark Matter Time Projection Chamber (DMTPC) is a low pressure (75 Torr CF4) 10 liter detector capable of measuring the vector direction of nuclear recoils with the goal of directional dark matter detection. In this paper we present the first dark matter limit from DMTPC. In an analysis window of 80-200 keV recoil energy, based on a 35.7 g-day exposure, we set a 90% C.L. upper limit on the spin-dependent WIMP-proton cross section of 2.0 x 10^{-33} cm^{2} for 115 GeV/c^2 dark matter particle mass.Comment: accepted for publication in Physics Letters