R. Lerche

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Andrej Dujella

University of Zagreb

Hemin Koyi

Uppsala University

Jana Javornik

University of East London

Armando Marques-Guedes

UNL - New University of Lisbon

Graham Martin

University of Leicester

Gwen Robbins Schug

University of North Carolina at Greensboro

Gabriel Gutierrez-Alonso

University of Salamanca

John Sutton

Macquarie University

Eros Carvalho

Universidade Federal do Rio Grande do Sul

Kevin Arbuckle

Swansea University

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Papers by R. Lerche

3(omega) Power Balance Procedure on the NIF

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Comparison of Streak Tube Performance

The performance of four streak tubes in six streak camera configurations is reported. Evaluations... more The performance of four streak tubes in six streak camera configurations is reported. Evaluations were made as part of a search for a streak tube to replace the obsolete RCA C73435 used in the ICF Program's optical streak cameras. Characteristics measured include linearity, spatial and temporal resolution, line-spread function, contrast transfer ratio (CTR), and dynamic range. Tubes evaluated are the RCA C73435, Photonis P510, Photek ST-Y, and Hamamatsu N8059. The RCA C73435 was evaluated in three camera configurations: large format CCD coupled directly to the streak tube, CCD directly coupled to an image intensifier tube (IIT), and the original configuration with a smaller CCD lens coupled to the IIT output. The Photonis and Photek tubes were characterized in configurations where they were directly coupled to large format CCDs. Optimum spatial resolution is achieved when the IIT is removed. Maximum dynamic range requires a configuration where a single photoelectron from the photocathode produces a signal that is ~5 times the CCD read noise. The Photonis P510 tube with the E2V CCD forms a well-optimized streak camera system.

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LIDAR Thomson scattering for advanced tokamaks. Final report

This is an informal report intended primarily for internal or limited external distribution. The ... more

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Compact optical technique for streak camera calibration

Review of Scientific Instruments, 2004

To produce accurate data from optical streak cameras requires accurate temporal calibration sourc... more To produce accurate data from optical streak cameras requires accurate temporal calibration sources. We have reproduced an older technology for generating optical timing marks that had been lost due to component availability. Many improvements have been made which allow the modern units to service a much larger need. Optical calibrators are now available that produce optical pulse trains of 780 nm wavelength light at frequencies ranging from 0.1 to 10 GHz, with individual pulse widths of approximately 25 ps full width half maximum. Future plans include the development of single units that produce multiple frequencies to cover a wide temporal range, and that are fully controllable via an RS232 interface.

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Wide-dynamic-range “neutron bang time” detector on OMEGA

Review of Scientific Instruments, 2002

A simple, low-cost “neutron bang time” detector has been implemented on the OMEGA laser system to... more A simple, low-cost “neutron bang time” detector has been implemented on the OMEGA laser system to measure the average time of neutron emission from inertial confinement fusion targets. This detector uses fast plastic scintillators coupled to photomultiplier tubes. A fast digital real-time oscilloscope records the signals. Absolute timing accuracies of better than 100 ps are achieved over a wide dynamic range (107<YN<1011) for both D2 (2.45 MeV) and DT (14 MeV) neutrons using a two-channel setup. Instrument characterization and comparison of the timing accuracy with a streak camera-based neutron burn history diagnostic are presented.

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Algorithm for precision subsample timing between Gaussian-like pulses

Review of Scientific Instruments, 2010

Moderately priced oscilloscopes available for the NIF power sensors and target diagnostics have 6... more Moderately priced oscilloscopes available for the NIF power sensors and target diagnostics have 6 GHz bandwidths at 20–25 Gsamples/s (40 ps sample spacing). Some NIF experiments require cross timing between instruments be determined with accuracy better than 30 ps. A simple analysis algorithm for Gaussian-like pulses such as the 100-ps-wide NIF timing fiducial can achieve single-event cross-timing precision of 1 ps (1/50 of the sample spacing). The midpoint-timing algorithm is presented along with simulations that show why the technique produces good timing results. Optimum pulse width is found to be ∼2.5 times the sample spacing. Experimental measurements demonstrate use of the technique and highlight the conditions needed to obtain optimum timing performance.

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25 ps neutron detector for measuring ICF-target burn history

Review of Scientific Instruments, 1995

We have developed a fast, sensitive neutron detector for recording the fusion reaction-rate histo... more We have developed a fast, sensitive neutron detector for recording the fusion reaction-rate history of inertial-confinement fusion (ICF) experiments. The detector is based on the fast rise time of a commercial plastic scintillator (BC-422) and has a response <25 ps FWHM. A thin piece of scintillator material acts as a neutron-to-light converter. A zoom lens images scintillator light to a high-speed (15 ps) optical streak camera for recording. A retractable nose cone positions the scintillator between 1 and 50 cm from a target. A simultaneously recorded optical fiducial pulse allows the streak camera time base to be calibrated relative to the incident laser power. Burn histories have been measured for deuterium-tritium filled targets with yields ranging between 108 and 2×1013 neutrons.

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Lawson Criterion for Ignition Exceeded in an Inertial Fusion Experiment

Physical Review Letters

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Neutron emission time measurements for ICF targets

by Greg T. and R. Lerche

Review of Scientific Instruments, 1988

The neutron emission time for laser-driven inertial confinement fusion targets is determined from... more The neutron emission time for laser-driven inertial confinement fusion targets is determined from data recorded with fast neutron and optical detector systems. Two types of neutron detectors are used. Radiation-induced conductivity devices have a 130-ps FWHM response and are sensitive to targets with yields greater than 5×1010 DT neutrons. They measure the average neutron emission time with a precision of ±50 ps and are fast enough to measure the neutron production rate within a target core as a function of time. Plastic scintillators coupled to microchannel-plate photomultiplier tubes have a 1.2-ns FWHM response and measure the average neutron emission time with a precision of ±75 ps for targets with yields greater than 106 neutrons. Streak cameras record the incident laser power. Optical fiducial signals that are injected into each detector are used to cross time between the detector systems. Measurements made on 1-mm-diam spherical targets irradiated with 23 kJ of 0.35-μm light d...

3(omega) Power Balance Procedure on the NIF

This report has been reproduced directly from the best available copy.

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Comparison of Streak Tube Performance

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LIDAR Thomson scattering for advanced tokamaks. Final report

This is an informal report intended primarily for internal or limited external distribution. The ... more

Download

Compact optical technique for streak camera calibration

Review of Scientific Instruments, 2004