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Adaptive Optics Views of the Hubble Deep Fields Final report on LLNL LDRD Project 03-ERD-002

Description: We used laser guide star adaptive optics at the Lick and Keck Observatories to study active galactic nuclei and galaxies, with emphasis on those in the early Universe. The goals were to observe large galaxies like our own Milky Way in the process of their initial assembly from sub-components, to identify central active galactic nuclei due to accreting black holes in galaxy cores, and to measure rates of star formation and evolution in galaxies. In the distant universe our focus was on the GOODS and GEMS fields (regions in the Northern and Southern sky that include the Hubble Deep Fields) as well as the Extended Groth Strip and COSMOS fields. Each of these parts of the sky has been intensively studied at multiple wavelengths by the Hubble Space Telescope, the Chandra X-Ray Observatory, the XMM Space Telescope, the Spitzer Space Telescope, and several ground-based telescopes including the Very Large Array radio interferometer, in order to gain an unbiased view of a significant statistical sample of galaxies in the early universe.
Date: February 17, 2007
Creator: Max, C E; Gavel, D; Pennington, D; Gibbard, S; van Dam, M; Larkin, J et al.
Partner: UNT Libraries Government Documents Department

Sonoma Persistent Surveillance System

Description: Sonoma offers the first cost-effective, broad-area, high-resolution, real-time motion imagery system for surveillance applications. Sonoma is unique in its ability to provide continuous, real-time video imagery of an area the size of a small city with resolutions sufficient to track 8,000 moving objects in the field of view. At higher resolutions and over smaller areas, Sonoma can even track the movement of individual people. The visual impact of the data available from Sonoma is already causing a paradigm shift in the architecture and operation of other surveillance systems. Sonoma is expected to cost just one-tenth the price of comparably sized sensor systems. Cameras mounted on an airborne platform constantly monitor an area, feeding data to the ground for real-time analysis. Sonoma was designed to provide real-time data for actionable intelligence in situations such as monitoring traffic, special events, border security, and harbors. If a Sonoma system had been available in the aftermath of the Katrina and Rita hurricanes, emergency responders would have had real-time information on roads, water levels, and traffic conditions, perhaps saving many lives.
Date: March 24, 2006
Creator: Pennington, D M
Partner: UNT Libraries Government Documents Department

Multi-watt 589nm fiber laser source

Description: We have demonstrated 3.5W of 589nm light from a fiber laser using periodically poled stoichiometric Lithium Tantalate (PPSLT) as the frequency conversion crystal. The system employs 938nm and 1583nm fiber lasers, which were sum-frequency mixed in PPSLT to generate 589nm light. The 938nm fiber laser consists of a single frequency diode laser master oscillator (200mW), which was amplified in two stages to >15W using cladding pumped Nd{sup 3+} fiber amplifiers. The fiber amplifiers operate at 938nm and minimize amplified spontaneous emission at 1088nm by employing a specialty fiber design, which maximizes the core size relative to the cladding diameter. This design allows the 3-level laser system to operate at high inversion, thus making it competitive with the competing 1088nm 4-level laser transition. At 15W, the 938nm laser has an M{sup 2} of 1.1 and good polarization (correctable with a quarter and half wave plate to >15:1). The 1583nm fiber laser consists of a Koheras 1583nm fiber DFB laser that is pre-amplified to 100mW, phase modulated and then amplified to 14W in a commercial IPG fiber amplifier. As a part of our research efforts we are also investigating pulsed laser formats and power scaling of the 589nm system. We will discuss the fiber laser design and operation as well as our results in power scaling at 589nm.
Date: January 19, 2006
Creator: Dawson, J. W.; Drobshoff, A. D.; Beach, R. J.; Messerly, M. J.; Payne, S. A.; Brown A. et al.
Partner: UNT Libraries Government Documents Department

469nm Fiber Laser Source

Description: We have demonstrated 466mW of 469nm light from a frequency doubled continuous wave fiber laser. The system consisted of a 938nm single frequency laser diode master oscillator, which was amplified in two stages to 5 Watts using cladding pumped Nd{sup 3+} fiber amplifiers and then frequency doubled in a single pass through periodically poled KTP. The 3cm long PPKTP crystal was made by Raicol Crystals Ltd. with a period of 5.9 {micro}m and had a phase match temperature of 47 degrees Centigrade. The beam was focused to a 1/e{sup 2} diameter in the crystal of 29 {micro}m. Overall conversion efficiency was 11% and the results agreed well with standard models. Our 938nm fiber amplifier design minimizes amplified spontaneous emission at 1088nm by employing an optimized core to cladding size ratio. This design allows the 3-level transition to operate at high inversion, thus making it competitive with the 1088nm 4-level transition. We have also carefully chosen the fiber coil diameter to help suppress propagation of wavelengths longer than 938 nm. At 2 Watts, the 938nm laser had an M{sup 2} of 1.1 and good polarization (correctable with a quarter and half wave plate to >10:1).
Date: January 20, 2005
Creator: Drobshoff, A; Dawson, J W; Pennington, D M; Payne, S A & Beach, R
Partner: UNT Libraries Government Documents Department

Precision damage tests of multilayer dielectric gratings for high-energy petawatt lasers

Description: The next generation of high-energy petawatt (HEPW)-class lasers will utilize multilayer dielectric diffraction gratings for pulse compression due to their high efficiency and high damage threshold for picosecond pulses. We have developed a short-pulse damage test station for accurate determination of the damage threshold of the optics used on future HEPW lasers. The design and performance of the damage test laser source, based on a highly stable, high-beam-quality optical parametric chirped-pulse amplifier, is presented. Our short-pulse damage measurement methodology and results are discussed. The damage initiation is attributed to multiphoton-induced avalanche ionization, strongly dependent on the electric field enhancement in the grating groove structure and surface defects. Measurement results of the dependence of damage threshold on the pulse width, angular dependence of damage threshold of diffraction gratings, and an investigation of short-pulse conditioning effects are presented. We report record >4 J/cm{sup 2} right section surface damage thresholds obtained on multilayer dielectric diffraction gratings at 76.5 incidence angles for 10-ps pulses.
Date: November 8, 2004
Creator: Jovanovic, I; Brown, C G; Stuart, B C; Molander, W; Nielsen, N; Wattellier, B et al.
Partner: UNT Libraries Government Documents Department

An Overview of High Energy Short Pulse Technology for Advanced Radiography of Laser Fusion Experiments

Description: The technical challenges and motivations for high-energy, short-pulse generation with NIF-class, Nd:glass laser systems are reviewed. High energy short pulse generation (multi-kilojoule, picosecond pulses) will be possible via the adaptation of chirped pulse amplification laser techniques on the NIF. Development of meter-scale, high efficiency, high-damage-threshold final optics is a key technical challenge. In addition, deployment of HEPW pulses on NIF is constrained by existing laser infrastructure and requires new, compact compressor designs and short-pulse, fiber-based, seed-laser systems. The key motivations for high energy petawatt pulses on NIF is briefly outlined and includes high-energy, x-ray radiography, proton beam radiography, proton isochoric heating and tests of the fast ignitor concept for inertial confinement fusion.
Date: June 18, 2004
Creator: Barty, C J; Key, M; Britten, J; Beach, R; Beer, G; Brown, C et al.
Partner: UNT Libraries Government Documents Department

Precision short-pulse damage test station utilizing optical parametric chirped-pulse amplification

Description: The next generation of high-energy petawatt (HEPW)-class lasers will utilize multilayer dielectric diffraction gratings for pulse compression, due to their high efficiency and high damage threshold for picosecond pulses. The peak power of HEPW lasers will be determined by the aperture and damage threshold of the final dielectric grating in the pulse compressor and final focusing optics. We have developed a short-pulse damage test station for accurate determination of the damage threshold of the optics used on future HEPW lasers. Our damage test station is based on a highly stable, high-beam-quality optical parametric chirped-pulse amplifier (OPCPA) operating at 1053 nm at a repetition rate of 10 Hz. We present the design of our OPCPA system pumped by a commercial Q-switched pump laser and the results of the full system characterization. Initial short-pulse damage experiments in the far field using our system have been performed.
Date: March 22, 2004
Creator: Jovanovic, I; Brown, C; Wattellier, B; Nielsen, N; Molander, W; Stuart, B et al.
Partner: UNT Libraries Government Documents Department

Thermally induced dephasing in periodically poled KTiOPO4 nonlinear crystals

Description: Experimental data that exhibits a continuous-wave, second-harmonic intensity threshold (15 kW/cm{sup 2}) that causes two-photon nonlinear absorption which leads to time-dependent photochromic damage in periodically poled KTiOPO{sub 4} is presented and verified through a thermal dephasing model.
Date: March 18, 2004
Creator: Dawson, J W; Pennington, D M; Jovanovic, I; Liao, Z M; Payne, S A; Drobshoff, A D et al.
Partner: UNT Libraries Government Documents Department

Sodium Laser Guide Star Adaptive Optics Imaging Polarimetry of Herbig Ae/Be Stars

Description: The future of high-resolution ground-based optical and infrared astronomy requires the successful implementation of laser guide star adaptive optics systems. We present the first science results from the Lick Observatory sodium beacon laser guide star system. By coupling this system to a near-infrared (J;H;Ks bands) dual-channel imaging polarimeter, we achieve very high sensitivity to light scattered in the circumstellar enviroment of Herbig Ae/Be stars on scales of 100-300 AU. Observations of LkH{alpha} 198 reveal a highly polarized, biconical nebula 10 arcseconds in diameter (6000 AU) . We also observe a polarized jet-like feature associated with the deeply embedded source LkH{alpha} 198-IR. The star LkH{alpha} 233 presents a narrow, unpolarized dark lane dividing its characteristic butterfly-shaped polarized reflection nebulosity. This linear structure is oriented perpendicular to an optical jet and bipolar cavity and is consistent with the presence of an optically thick circumstellar disk blocking our direct view of the star. These data suggest that the evolutionary picture developed for the lower-mass T Tauri stars is also relevant to the Herbig Ae/Be stars and demonstrate the ability of laser guide star adaptive optics systems to obtain scientific results competitive with natural guide star adaptive optics or space-based telescopes.
Date: January 8, 2004
Creator: Perrin, M D; Graham, J R; Lloyd, J P; Kalas, P; Gates, E L; Gavel, D T et al.
Partner: UNT Libraries Government Documents Department

Design and Test of Advanced Multi-Layer Dielectric Gratings for High Energy Petawatt

Description: In this paper we discuss recent work on the development of high damage threshold, high efficiency MLD (multilayer dielectric) diffraction gratings for use in high energy, petawatt laser systems. This effort involves a close integration between modeling, fabrication, and testing. The modeling work is used to identify grating designs that satisfy the constraints of high efficiency (>94%) and low field enhancement which is a necessary condition for high damage threshold. Subscale MLD gratings for test are being fabricated in an advanced ion-etch machine we have recently built. The testing effort is being conducted in a dedicated laboratory. The laser beam used to test the samples is based on an OPCPA (optical parametric chirped-pulse amplifier) and a compressor that can provide pulse energies up to 50mJ with pulse lengths variable from 0.3-20 ps. This test station is equipped with diagnostics to fully characterize both the spatial and temporal characteristics of the test beam at the plane of the sample. Initial results have demonstrated a dependence of damage threshold on incident angle that is in good agreement with the field enhancement calculations. We have demonstrated a grating design with a damage threshold of 3J/cm{sup 2} and are investigating manufacturability and reproducibility issues as well.
Date: September 5, 2003
Creator: Molander, W; Komashko, A; Britten, J; Jones, L; Brown, C; Caird, J et al.
Partner: UNT Libraries Government Documents Department

High Power 938nm Cladding Pumped Fiber Laser

Description: We have developed a Nd:doped cladding pumped fiber amplifier, which operates at 938nm with greater than 2W of output power. The core co-dopants were specifically chosen to enhance emission at 938nm. The fiber was liquid nitrogen cooled in order to achieve four-level laser operation on a laser transition that is normally three level at room temperature, thus permitting efficient cladding pumping of the amplifier. Wavelength selective attenuation was induced by bending the fiber around a mandrel, which permitted near complete suppression of amplified spontaneous emission at 1088nm. We are presently seeking to scale the output of this laser to 10W. We will discuss the fiber and laser design issues involved in scaling the laser to the 10W power level and present our most recent results.
Date: December 26, 2002
Creator: Dawson, J; Beach, R; Brobshoff, A; Liao, Z; Payne, S; Pennington, D et al.
Partner: UNT Libraries Government Documents Department

Recent Science and Engineering Results with the Laser Guidestar Adaptive Optics System at Lick Observatory

Description: The Lick Observatory laser guide star adaptive optics system has undergone continual improvement and testing as it is being integrated as a facility science instrument on the Shane 3 meter telescope. Both Natural Guide Star (NGS) and Laser Guide Star (LGS) modes are now used in science observing programs. We report on system performance results as derived from data taken on both science and engineering nights and also describe the newly developed on-line techniques for seeing and system performance characterization. We also describe the future enhancements to the Lick system that will enable additional science goals such as long-exposure spectroscopy.
Date: October 17, 2002
Creator: Gavel, D T; Gates, E; Max, C; Olivier, S; Bauman, B; Pennington, D et al.
Partner: UNT Libraries Government Documents Department

938 nm Nd-Doped High Power Cladding Pumped Fiber Amplifier

Description: 2.1W of 938nm light has been produced in an Nd{sup 3+} doped fiber amplifier. Wavelength dependent bend losses can be employed to minimize 1088nm amplified spontaneous emission giving the optical fiber a distinct advantage over bulk media.
Date: September 19, 2002
Creator: Dawson, J; Beach, R; Drobshoff, A; Liao, Z; Pennington, D; Payne, S et al.
Partner: UNT Libraries Government Documents Department

Update on Optical Design of Adaptive Optics System at Lick Observatory

Description: In 1999, we presented our plan to upgrade the adaptive optics (AO) system on the Lick Observatory Shane telescope (3m) from a prototype instrument pressed into field service to a facility instrument. This paper updates the progress of that plan and details several important improvements in the alignment and calibration of the AO bench. The paper also includes a discussion of the problems seen in the original design of the tip/tilt (t/t) sensor used in laser guide star mode, and how these problems were corrected with excellent results.
Date: July 31, 2001
Creator: Bauman, B J; Gavel, D T; Waltjen, K E; Freeze, G J; Hurd, R L; Gates, E I et al.
Partner: UNT Libraries Government Documents Department

Advanced Wavefront Control Techniques

Description: Programs at LLNL that involve large laser systems--ranging from the National Ignition Facility to new tactical laser weapons--depend on the maintenance of laser beam quality through precise control of the optical wavefront. This can be accomplished using adaptive optics, which compensate for time-varying aberrations that are often caused by heating in a high-power laser system. Over the past two decades, LLNL has developed a broad capability in adaptive optics technology for both laser beam control and high-resolution imaging. This adaptive optics capability has been based on thin deformable glass mirrors with individual ceramic actuators bonded to the back. In the case of high-power lasers, these adaptive optics systems have successfully improved beam quality. However, as we continue to extend our applications requirements, the existing technology base for wavefront control cannot satisfy them. To address this issue, this project studied improved modeling tools to increase our detailed understanding of the performance of these systems, and evaluated novel approaches to low-order wavefront control that offer the possibility of reduced cost and complexity. We also investigated improved beam control technology for high-resolution wavefront control. Many high-power laser systems suffer from high-spatial-frequency aberrations that require control of hundreds or thousands of phase points to provide adequate correction. However, the cost and size of current deformable mirrors can become prohibitive for applications requiring more than a few tens of phase control points. New phase control technologies are becoming available which offer control of many phase points with small low-cost devices. The goal of this project was to expand our wavefront control capabilities with improved modeling tools, new devices that reduce system cost and complexity, and extensions to high spatial and temporal frequencies using new adaptive optics technologies. In FY 99, the second year of this project, work was performed in four areas (1) advanced modeling ...
Date: February 21, 2001
Creator: Olivier, S S; Brase, J M; Avicola, K; Thompson, C A; Kartz, M W; Winters, S et al.
Partner: UNT Libraries Government Documents Department

New Front End Technology

Description: The next generation of Petawatt class lasers will require the development of new laser technology. Optical parametric chirped pulse amplification (OPCPA) holds a potential to increase the peak power level to >10 PW with existing grating technology through ultrashort pulses. Furthermore, by utilizing a new type of front-end system based on optical parametric amplification, pulses can be produced with substantially higher contrast than with Ti:sapphire regenerative amplifier technology. We performed extensive study of OPCPA using a single crystal-based OPA. We developed a replacement for Ti:sapphire regenerative amplifier for high peak power lasers based on OPCPA, with an output of 30 mJ, at 10 Hz repetition rate and 16.5 nm spectral bandwidth. We developed a 3D numerical model for OPCPA and we performed a theoretical study of influences of pump laser beam quality on optical parametric amplification. Our results indicate that OPCPA represents a valid replacement for Ti:sapphire in the front end of high energy short pulse lasers.
Date: February 1, 2001
Creator: Pennington, D; Jovanovic, I & Comaskey, B J
Partner: UNT Libraries Government Documents Department

The Potential of Fast Ignition and Related Experiments with A Petawatt Laser Facility

Description: A model of energy gain induced by fast ignition of thermonuclear burn in compressed deuterium-tritium fuel, is used to show the potential for 300x gain with a driver energy of 1 M J, if the National Ignition Facility (NIF) were to be adapted for fast ignition. The physics of fast ignition has been studied using a petawatt laser facility at the Lawrence Livermore National Laboratory. Laser plasma interaction in a preformed plasma on a solid target leads to relativistic self-focusing evidenced by x-ray images. Absorption of the laser radiation transfers energy to an intense source of relativistic electrons. Good conversion efficiency into a wide angular distribution is reported. Heating by the electrons in solid density CD{sub 2} produces 0.5 to 1/keV temperature, inferred from the D-D thermo-nuclear neutron yield.
Date: April 6, 2000
Creator: Key, M.H.; Campbell, E.M.; Cowan, T.E.; Hatchett, S.P.; Henry, E.A.; Koch, J.A. et al.
Partner: UNT Libraries Government Documents Department

Energetic Proton Generation in Ultra-Intense Laser-Solid Interactions

Description: An explanation for the energetic ions observed in the PetaWatt experiments is presented. In solid target experiments with focused intensities exceeding 10{sup 20} W/cm{sup 2}, high-energy electron generation, hard bremsstrahlung, and energetic protons have been observed on the backside of the target. In this report, we attempt to explain the physical process present that will explain the presence of these energetic protons, as well as explain the number, energy, and angular spread of the protons observed in experiment. In particular, we hypothesize that hot electrons produced on the front of the target are sent through to the back off the target, where they ionize the hydrogen layer there. These ions are then accelerated by the hot electron cloud, to tens of MeV energies in distances of order tens of microns, whereupon they end up being detected in the radiographic and spectrographic detectors.
Date: March 1, 2000
Creator: Wilks, S.C.; Langdon, A.B.; Cowan, T.E.; Roth, M.; Singh, M.; Hatchett, S. et al.
Partner: UNT Libraries Government Documents Department

Laser Research and Development Studies for Laser Guide Star Systems

Description: In this paper we consider two CW solid state laser approaches to a 589 nm LGS system. Both are based on the technique of sum-frequency generation, but differ in the cavity architecture. Both technologies are very promising and are worth of further consideration. This preliminary proposal is intended to encompass both designs. A down select shall be performed early in the project execution to focus on the most promising option. The two design options consist of: (1) A dual-frequency resonator with intra-cavity doubling in LB0 offers the promise of a simple architecture and may scale more easily to high power. This design has been shown to be highly reliable, efficient and high power when used in frequency-doubled Nd:YAG lasers for programs at LLNL and in commercial products. The challenge in this design is the demonstration of a high power13 18 nm oscillator with adequate suppression of the 1064 nm line. (2) A MOPA based design uses commercial low power oscillators to produce both wavelengths, then amplifies the wavelengths before doubling. This design requires the demonstration of a 1318 nm amplifier, though the design is scaled from a kW CW amplifier already delivered to a customer at a different wavelength. The design must also demonstrate high power scaling of sum-frequency generation in the relatively new nonlinear material, PPLN. The first step in the process would be to further evaluate the two conceptual options for technical feasibility, cost and constructability. Then a down selection to one design would be conducted. Finally, R&D on that design would then proceed. Minimal testing should be required for this selection. The majority of the funding received would be allocated to development of the design selected.
Date: February 23, 2000
Creator: Pennington, D.; Beach, R.; Ebbers, C.; Erbert, G.; Nguyen, H.; Page, R. et al.
Partner: UNT Libraries Government Documents Department

Electron, Photon, and Ion Beams from the Relativistic Interaction of Petawatt Laser Pulses with Solid Targets

Description: In our Petawatt laser experiments several hundred joules of 1 {micro}m laser light in 0.5-5.0 ps pulses with intensities up to 3 x 10{sup 20}Wcm{sup -2} were incident on solid targets producing a strongly relativistic interaction. The energy content, spectra, and angular patterns of the photon, electron, and ion radiations were diagnosed in a number of ways, including several novel (to laser physics) nuclear activation techniques. From the beamed bremsstrahlung we infer that about 40-50% of the laser energy is converted to broadly beamed hot electrons. Their direction centroid varies from shot to shot, but the beam has a consistent width. Extraordinarily luminous ion beams almost precisely normal to the rear of various targets are seen--up to 3 x 10{sup 13} protons with kT{sub ion} {approx} several MeV representing {approx}6% of the laser energy. We observe ion energies up to at least 55 MeV. The ions appear to originate from the rear target surfaces. The edge of the ion beam is very sharp, and collimation increases with ion energy. At the highest energies, a narrow feature appears in the ion spectra, and the apparent size of the emitting spot is smaller than the full back surface area. Any ion emission from the front of the targets is much less than from the rear and is not sharply beamed. The hot electrons generate a Debye sheath with electrostatic fields of order MV per micron which apparently accelerate the ions.
Date: November 12, 1999
Creator: Hatchett, S.P.; Brown, C.G.; Cowan, T.E.; Henry, E.A.; Johnson, J.; Key, M.H. et al.
Partner: UNT Libraries Government Documents Department

Studies of the relativistic electron source and related phenomena in Petawatt Laser matter interactions

Description: The interaction of laser radiation with solid targets at 1 petawatt power and intensity up to 3x10{sup 20} Wcm{sup -2} has been studied with emphasis on relativistic electrons and high energy ions. Secondary effects including Bremsstrahlung radiation, nuclear interactions and heating have been characterized. A collimated beam of protons with up to 55 MeV energy is emitted normal to the rear surface of thin targets and its characteristics and origin are discussed. The significance of the data for radiography, fast ignition and proton beam applications is summarized.
Date: September 27, 1999
Creator: Key, M H; Campbell, E M; Cowan, T E; Hatchett, S P; Henry, E A; Koch, J A et al.
Partner: UNT Libraries Government Documents Department

High-energy electron, positron, ion and nuclear spectroscopy in ultra-intense laser-solid experiments on the petawatt

Description: The LLNL Petawatt Laser has achieved focused intensities up to 6 x 20 W/cm{sup 2}, which has opened a new, higher energy regime of relativistic laser-plasma interactions in which the quiver energies of the target electrons exceed the energy thresholds for many nuclear phenomena. We will describe recent experiments in which we have observed electrons accelerated to 100 MeV, photo-nuclear fission, and positron-electron pair creation.
Date: September 16, 1999
Creator: Brown, C; Christl, M; Cowan, T E; Fakahashi, Y; Fountain, W; Hatchett, S et al.
Partner: UNT Libraries Government Documents Department

High energy electrons, positrons and photonuclear reactions in petawatt laser-solid experiments

Description: The Petawatt laser at LLNL has opened a new regime of high-energy laser-matter interactions in which the quiver motion of plasma electrons is fully relativistic with energies extending well above the threshold for nuclear processes. We have observed that, in addition to the large flux of several MeV electrons ponderomotively expelled from the ultra-intense laser focus, there is a high energy component of electrons extending to -100 MeV, apparently from relativistic self-focusing and plasma acceleration in the underdense pre-formed plasma. The generation of hard bremsstrahlung cascade as these electrons traverse the solid target material, and the resulting photo-nuclear reactions, nuclear fission, and positron-electron pair production are described.
Date: September 9, 1999
Creator: Cowan, T E; Hunt, A W; Johnson, J; Perry, M D; Fountain, W; Hatchett, S et al.
Partner: UNT Libraries Government Documents Department

X-ray imaging to characterize MeV electronics propagation through plastic targets

Description: A high intensity laser pulse incident on an overdense plasma generates high energy electrons at the critical surface which propagate into the plasma. The details of this propagation is critical to the Fast Ignition process. The energetic electrons emerge as a jet on the far side, but the spread and propagation direction of the jet within the plasma is not well known. By embedding several thin high Z layers in a CH film one can directly image the progress of the electron beam. It loses enough energy to heat the medium through which it travels to hundreds of eV. At that temperature a film, even buried under CH, emits sufficiently hard thermal x-rays to allow imaging the heated area with an x-ray pinhole camera. The film can be thin enough to also see the emissions from another layer near the front of the film. If these two images are visible simultaneously, one can measure the beam spread and propagation direction within the plastic.
Date: September 3, 1999
Creator: Key, M H; Stephens, R B; Koch, J & Pennington, D
Partner: UNT Libraries Government Documents Department