Download or read book Using X Rays to Test CVD Diamond Detectors for Areal Density Measurement at the National Ignition Facility written by and published by . This book was released on 2008 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: At the National Ignition Facility (NIF), 192 laser beams will compress a target containing a mixture of deuterium and tritium (DT) that will release fusion neutrons, photons, and other radiation. Diagnostics are being designed to measure this emitted radiation to infer crucial parameters of an ignition shot. Chemical Vapor Deposited (CVD) diamond is one of the ignition diagnostics that will be used as a neutron time-of-flight detector for measuring primary (14.1 MeV) neutron yield, ion temperature, and plasma areal density. This last quantity is the subject of this study and is inferred from the number of downscattered neutrons arriving late in time, divided by the number of primary neutrons. We determine in this study the accuracy with which this detector can measure areal density, when the limiting factor is detector and electronics saturation. We used laser-produced x-rays to reproduce NIF signals in terms of charge carriers density, time between pulses, and amplitude contrast and found that the effect of the large pulse on the small pulse is at most 8.4%, which is less than the NIF accuracy requirement of ± 10%.
Download or read book Recovery of a CVD Diamond Detection System from Strong Pulses of Laser Produced X rays written by J. A. Koch and published by . This book was released on 2006 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: We are studying the response of a CVD diamond detector to a strong x-ray pulse followed by a second weaker pulse arriving 50 to 300 ns later, with a contrast in amplitude of about 1000. These tests, performed at the LLNL Jupiter laser facility, are intended to produce charge carrier densities similar to those expected during a DT implosion at NIF, where a large 14.1 MeV neutron pulse is followed by a weak downscattered neutron signal produced by slower 6-10 MeV neutrons. The number of downscattered neutrons must be carefully measured in order to obtain an accurate value for the areal density, which is proportional to the ratio of downscattered to primary neutrons. The effects of the first strong pulse may include saturation of the diamond wafer, saturation of the oscilloscope, or saturation of the associated power and data acquisition electronics. We are presenting a double pulse experiment that will use a system of several polycrystalline CVD diamond detectors irradiated by 8.6 keV x-rays emitted from a zinc target. We will discuss implication for a NIF areal density measurement.
Download or read book Response Of A CVD Diamond Detector To Typical Deuterium Tritium NIF Implosions For Areal Density Measurement written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: CVD diamond detector signals from Deuterium-Tritium implosions have been simulated in order to study the feasibility of measuring areal density using the ratio of downscattered to primary neutrons during the ignition campaign at the NIF. Simulated neutron spectra for three ''typical'' DT implosions were weighted with the CVD diamond sensitivity to obtain an estimated signal at several distances from the target chamber center. The 14 MeV peak was found to have an amplitude about three orders of magnitude larger than the down-scattered signal for the three spectra. At a target to detector distance of 17 m (just outside the target bay wall) and for a 1 cm2 wafer, signals are large enough to be recorded, well above any background and electronic noise. The uncertainty in the areal density measurement comes mainly from the uncertainty in the CVD diamond energy dependent sensitivity, the accuracy of the background simulation, and the effect of the saturation of both detector and electronics after the large 14 MeV peak. Nevertheless, the results found in this study are encouraging, and the remaining sources of uncertainty should now be addressed.
Download or read book A Diamond Detector for Inertial Confinement Fusion X ray Bang time Measurements at the National Ignition Facility written by and published by . This book was released on 2010 with total page 18 pages. Available in PDF, EPUB and Kindle. Book excerpt: An instrument has been developed to measure X-ray bang-time for inertial confinement fusion capsules; the time interval between the start of the laser pulse and peak X-ray emission from the fuel core. The instrument comprises chemical vapor deposited polycrystalline diamond photoconductive X-ray detectors with highly ordered pyrolytic graphite X-ray monochromator crystals at the input. Capsule bang-time can be measured in the presence of relatively high thermal and hard X-ray background components due to the selective band pass of the crystals combined with direct and indirect X-ray shielding of the detector elements. A five channel system is being commissioned at the National Ignition Facility at Lawrence Livermore National Laboratory for implosion optimization measurements as part of the National Ignition Campaign. Characteristics of the instrument have been measured demonstrating that X-ray bang-time can be measured with ± 30ps precision, characterizing the soft X-ray drive to +/- 1eV or 1.5%.
Download or read book CVD Diamond Detectors for Current Mode Neutron Time of Flight Spectroscopy at OMEGA written by and published by . This book was released on 2001 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: We have performed pulsed neutron and pulsed laser tests of a CVD diamond detector manufactured from DIAFILM, a commercial grade of CVD diamond. The laser tests were performed at the short pulse UV laser at Bechtel Nevada in Livermore, CA. The pulsed neutrons were provided by DT capsule implosions at the OMEGA laser fusion facility in Rochester, NY. From these tests, we have determined the impulse response to be 250 ps fwhm for an applied E-field of 500 V/mm. Additionally, we have determined the sensitivity to be 2.4 mA/W at 500 V/mm and 4.0 mA/W at 1000 V/mm. These values are approximately 2 to 5x times higher than those reported for natural Type IIa diamond at similar E-field and thickness (1mm). These characteristics allow us to conceive of a neutron time-of-flight current mode spectrometer based on CVD diamond. Such an instrument would sit inside the laser fusion target chamber close to target chamber center (TCC), and would record neutron spectra fast enough such that backscattered neutrons and x-rays from the target chamber wall would not be a concern. The acquired neutron spectra could then be used to extract DD fuel areal density from the downscattered secondary to secondary ratio.
Download or read book Physics and Applications of CVD Diamond written by Satoshi Koizumi and published by John Wiley & Sons. This book was released on 2008-09-08 with total page 374 pages. Available in PDF, EPUB and Kindle. Book excerpt: Here, leading scientists report on why and how diamond can be optimized for applications in bioelectronic and electronics. They cover such topics as growth techniques, new and conventional doping mechanisms, superconductivity in diamond, and excitonic properties, while application aspects include quantum electronics at room temperature, biosensors as well as diamond nanocantilevers and SAWs. Written in a review style to make the topic accessible for a wider community of scientists working in interdisciplinary fields with backgrounds in physics, chemistry, biology and engineering, this is essential reading for everyone working in environments that involve conventional electronics, biotechnology, quantum computing, quantum cryptography, superconductivity and light emission from highly excited excitonic systems.
Download or read book Ion Beam Induced Surface Graphitization of CVD Diamond for X ray Beam Position Monitor Applications written by and published by . This book was released on 1996 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Advanced Photon Source at ANL is a third-generation synchrotron facility that generates powerful x-ray beams on its undulator beamlines. It is important to know the position and angle of the x- ray beam during experiments. Due to very high heat flux levels, several patented x-ray beam position monitors (XBPM) exploiting chemical vapor deposition (CVD) diamond have been developed. These XBPMs have a thin layer of low-atomic-mass metallic coating so that photoemission from the x rays generate a minute but measurable current for position determination. Graphitization of the CVD diamond surface creates a very thin, intrinsic and conducting layer that can stand much higher temperatures and minimal x-ray transmission losses compared to the coated metallic layers. In this paper, a laboratory sputter ion source was used to transform selected surfaces of a CVD diamond substrate into graphite. The effect of 1-5 keV argon ion bombardment on CVD diamond surfaces at various target temperatures from 200 to 500 C was studied using Auger electron spectroscopy and in-situ electrical resistivity measurements. Graphitization after the ion bombardment has been confirmed and optimum conditions for graphitization studied. Raman spectroscopy was used to identify the overall diamond structure in the bulk of CVD diamond substrate after the ion bombardments. It was found that target temperature plays an important role in stability and electrical conductivity of the irradiated CVD diamonds.
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1994 with total page 564 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book X ray Calibration of Radiation Survey Meters written by Frank H. Day and published by . This book was released on 1951 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Response of Diamond Photoconductors to Soft X ray in the Spectral Range 125 to 240 written by and published by . This book was released on 1995 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt: Due to the large bandgap of diamond, it is transparent to the visible spectrum, making it an attractive material for soft x-ray detection. Response of diamond photoconductors fabricated using Polycrystalline chemical-vapor-deposited (CVD) diamond to soft x-rays has been measured using x-rays emitted from a laser-produced plasma source in the spectral range 125 Å to 240 Å. These photoconductors have interdigitated electrode structure in order to increase the active area as well as detector sensitivity. Contributions to the detector sensitivity by the photoelectrons is discussed.
Download or read book Impact of X ray Dose on the Response of CR 39 Nuclear Track Detector to 1 5 5 MeV Alphas and 0 5 9 1 MeV Protons for Spectroscopy at the OMEGA Laser Facility and the National Ignition Facility written by Rojas Herrera Rojas and published by . This book was released on 2016 with total page 47 pages. Available in PDF, EPUB and Kindle. Book excerpt: The CR-39 nuclear track detector is used in many nuclear diagnostics fielded at inertial confinement fusion (ICF) facilities. Large x-ray fluences generated by ICF experiments may impact the CR-39 response to incident charged particles. To determine the impact of x-ray exposure on the CR-39 response to protons and alpha particles, a thick-target bremsstrahlung x-ray generator was used to expose CR-39 to various doses of 30 and 8keV Cu-K[alpha] and K[beta] x-rays. The CR-39 detectors were then exposed to 1-5.5 MeV alphas or 0.5- 9.1 MeV protons. The regions of the CR-39 exposed to x-rays showed a smaller track diameter than those not exposed to x-rays: for example, a dose of 3.0±0.1 Gy causes a decrease of (19±2)% in the track diameter of a 5.5 MeV alpha, while a dose of 6.0±0.1 Gy results in a decrease of (29±1)% in the track diameter of a 3.0 MeV proton. The reduced track diameters were found to be predominantly caused by a comparable reduction in the bulk etch rate of the CR-39 with x-ray dose. A residual effect, due to changes in track etch rate and dependent on incident particle energy, was characterized by an empirical formula.
Download or read book Course Manual for X ray Measurements written by Oregon State University. X-Ray Science and Engineering Laboratory and published by . This book was released on 1973 with total page 486 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Recovery of CVD Diamond Detectors Using Laser Double Pulses written by J. A. Koch and published by . This book was released on 2005 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: A 5 x 0.25 mm Chemical Vapor Deposited (CVD) diamond detector, with a voltage bias of + 250V, was excited by a 400 nm laser (3.1 eV photons) in order to study the saturation of the wafer and its associated electronics. In a first experiment, the laser beam energy was increased from a few tens of a pJ to about 100 {micro}J, and the signal from the diamond was recorded until full saturation of the detection system was achieved. Clear saturation of the detection system was observed at about 40 V, which corresponds with the expected saturation at 10% of the applied bias (250V). The results indicate that the interaction mechanism of the 3.1 eV photons in the diamond (E{sub bandgap} = 5.45 eV) is not a multi-photon process but is linked to the impurities and defects of the crystal. In a second experiment, the detector was irradiated by a saturating first laser pulse and then by a delayed laser pulse of equal or smaller amplitude with delays of 5, 10, and 20 ns. The results suggest that the diamond and associated electronics recover within 10 to 20 ns after a strong saturating pulse.
Download or read book X ray Spectral Measurements with Semiconductor Detectors written by Orlando Velazquez and published by . This book was released on 2004 with total page 128 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book X ray Detector Calibrations in the 280 eV to 100 keV Energy Range written by and published by . This book was released on 1976 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The absolute sensitivity for several different types of radiation detectors has been measured using x-rays in the energy range of 280 eV to 100 keV. The photons in this energy range are produced using three separate x-ray-generating facilities. The detectors include a silicon semiconductor, two photoelectric diode detectors employing aluminum and gold photocathodes, and three detectors incorporating plastic scintillators and photodiodes. The plastic scintillators were MEL-150C, Pilot B, and NE102.
Download or read book A First Study of the Use of CVD diamond Detectors for Radiotherapy Dosimetry written by Rüdiger Meyfarth and published by . This book was released on 1996 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Flat Field Anomalies in an X Ray CCD Camera Measured Using a Manson X Ray Source written by and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The Static X-ray Imager (SXI) is a diagnostic used at the National Ignition Facility (NIF) to measure the position of the X-rays produced by lasers hitting a gold foil target. It determines how accurately NIF can point the laser beams and is critical to proper NIF operation. Imagers are located at the top and the bottom of the NIF target chamber. The CCD chip is an X-ray sensitive silicon sensor, with a large format array (2k x 2k), 24 [mu]m square pixels, and 15 [mu]m thick. A multi-anode Manson X-ray source, operating up to 10kV and 2mA, was used to characterize and calibrate the imagers. The output beam is heavily filtered to narrow the spectral beam width, giving a typical resolution E/[Delta]EH"2. The X-ray beam intensity was measured using an absolute photodiode that has accuracy better than 1% up to the Si K edge and better than 5% at higher energies. The X-ray beam provides full CCD illumination and is flat, within ±1.5% maximum to minimum. The spectral efficiency was measured at 10 energy bands ranging from 930 eV to 8470 eV. The efficiency pattern follows the properties of Si. The maximum quantum efficiency is 0.71. We observed an energy dependent pixel sensitivity variation that showed continuous change over a large portion of the CCD. The maximum sensitivity variation was>8% at 8470 eV. The geometric pattern did not change at lower energies, but the maximum contrast decreased and was less than the measurement uncertainty below 4 keV. We were also able to observe debris on the CCD chip. The debris showed maximum contrast at the lowest energy used, 930 eV, and disappeared by 4 keV. The Manson source is a powerful tool for characterizing the imaging errors of an X-ray CCD imager. These errors are quite different from those found in a visible CCD imager.
