G. L. Morgan

Practical Free-Space Quantum Key Distribution over 1 km

A working free-space quantum key distribution system has been developed and tested over an outdoor optical path of {approximately}1 km at Los Alamos National Laboratory under nighttime conditions. Results show that free-space quantum key distribution can provide secure real-time key distribution between parties who have a need to communicate secretly. Finally, we examine the feasibility of surface to satellite quantum key distribution. {copyright} {ital 1998} {ital The American Physical Society}

Daylight quantum key distribution over 1.6 km

Quantum key distribution (QKD) has been demonstrated over a point-to-point 1.6-km atmospheric optical path in full daylight. This record transmission distance brings QKD a step closer to surface-to-satellite and other long-distance applications.

Free-space quantum-key distribution

Nonproliferation and International Security,Los Alamos, NM 87545(February 1, 2008)A working free-space quantum key distribution (QKD)system has been developed and tested over a 205-m indooroptical path at Los Alamos National Laboratory under fluo-rescent lighting conditions. Resultsshow that free-space QKDcan provide secure real-time key distribution between partieswho have a need to communicate secretly.PACS Numbers: 42.79.Sz, 03.65-w

Quantum cryptography for secure satellite communications

Quantum cryptography is an emerging technology in which two parties may simultaneously generate shared, secret cryptographic key material using the transmission of quantum states of light. The security of these transmissions is based on the inviolability of the laws of quantum mechanics and information-theoretically secure post-processing methods. An adversary can neither successfully tap the quantum transmissions, nor evade detection, owing to Heisenbergs uncertainty principle. In this paper we describe the theory of quantum cryptography, and recent results from our experimental free-space system with which we have demonstrated the feasibility of quantum key generation over a point-to-point outdoor atmospheric path in daylight. We achieved a transmission distance of 0.5 km, which was limited only by the length of the test range. Our results provide strong evidence that cryptographic key material could be generated on demand between a ground station and a satellite (or between two satellites), allowing a satellite to be securely re-keyed on orbit for encrypting the uplinked command path and downlinked data path; or to distribute keys between widely-separated ground stations with a satellite relay, enabling encrypted communications over even inter-continental distances. We present a feasibility analysis of surface-to-satellite quantum key generation.

Measurement of the parity violating asymmetry Aγ in n→+p→d+γ

The weak pion-nucleon coupling constant H{sub {pi}}{sup 1} remains poorly determined, despite many years of effort. The recent measurement of the {sup 133}Cs anapole moment has been interpreted to give a value of H{sub {pi}}{sup 1} almost an order of magnitude larger than the limit established in the {sup 18}F parity doublet experiments. A measurement of the gamma ray directional asymmetry A{sub {gamma}} for the capture of polarized neutrons by hydrogen has been proposed at Los Alamos National Laboratory. This experiment will determine H{sub {pi}}{sup 1} independent of nuclear structure effects. However, since the predicted asymmetry is small, A{sub {gamma}} {approximately} 5 x 10{sup {minus}8}, systematic effects must be reduced to < 5 x 10{sup {minus}9}. The design of the experiment will is presented, with an emphasis on the techniques used for controlling systematic errors.

Progress toward the development and testing of source reconstruction methods for NIF neutron imaging.

Development of analysis techniques for neutron imaging at the National Ignition Facility is an important and difficult task for the detailed understanding of high-neutron yield inertial confinement fusion implosions. Once developed, these methods must provide accurate images of the hot and cold fuels so that information about the implosion, such as symmetry and areal density, can be extracted. One method under development involves the numerical inversion of the pinhole image using knowledge of neutron transport through the pinhole aperture from Monte Carlo simulations. In this article we present results of source reconstructions based on simulated images that test the methods effectiveness with regard to pinhole misalignment.

Neutron imaging development for megajoule scale inertial confinement fusion experiments

Neutron imaging of Inertial Confinement Fusion (ICF) targets is useful for understanding the implosion conditions of deuterium and tritium filled targets at Mega-Joule/Tera-Watt scale laser facilities. The primary task for imaging ICF targets at the National Ignition Facility, Lawrence Livermore National Laboratory, Livermore CA, is to determine the asymmetry of the imploded target. The image data, along with other nuclear information, are to be used to provide insight into target drive conditions. The diagnostic goal at the National Ignition Facility is to provide neutron images with 10 μm resolution and peak signal-to-background values greater than 20 for neutron yields of ~ 1015. To achieve this requires signal multiplexing apertures with good resolution. In this paper we present results from imaging system development efforts aimed at achieving these requirements using neutron pinholes. The data were collected using directly driven ICF targets at the Omega Laser, University of Rochester, Rochester, NY., and include images collected from a 3 × 3 array of 15.5 μm pinholes. Combined images have peak signal-to-background values greater than 30 at neutron yields of ~ 1013.

Neutron imaging for inertial confinement fusion experiments

Neutron imaging of Inertial Confinement Fusion (ICF) targets provides a powerful tool for understanding the implosion conditions of deuterium and tritium filled targets at Mega-Joule/Tera-Watt scale laser facilities. The primary purpose of imaging ICF targets at that National Ignition Facility (NIF), sited at Lawrence Livermore National Laboratory, Livermore, California, is to determine the asymmetry of the fuel in an imploded ICF target. The image data are then combined with other nuclear information to gain insight into the laser and radiation conditions used to drive the target. This information is requisite to understanding the physics of Inertial Confinement Fusion targets and provides a failure mode diagnostic used to optimize the conditions of experiments aimed at obtaining ignition. We present an overview of neutron aperture imaging including a discussion of image formation and reconstruction, requirements for the future (NIF) neutron imaging systems, a description of current imaging system capabilities, and ongoing work to affect imaging systems capable of meeting future system requirements.

Neutron Induced Charged Particle Reactions on 23Na

High resolution measurements of neutron induced charged particle reactions on 23Na have been performed. A NaI(T1) detector served as both target and detector, with pulse shape discrimination being applied for the separation of protons and alpha-particles from each other and from events involving gamma-ray detection. The neutron energy was measured by time-of-flight, using an 80 m flight path at the Los Alamos National Laboratory WNR facility.

Investigations into reconstruction techniques for the National Ignition Facility Neutron Imaging System

Neutron imaging is currently being developed as a primary diagnostic for inertial fusion studies at the National Ignition Facility (NIF). It is an attractive diagnostic for measuring asymmetries in the burn region and will be able to operate at neutron fluences found during ignition scale implosions. The most straightforward technique for imaging of the spatial distribution of deuterium-tritium (DT) fusion neutrons utilizes a simple pinhole aperture, which blocks all neutrons outside of the solid angle defined by the pinhole and results in a blurred image at the detector. We are currently investigating source image reconstruction techniques from detector images. Source reconstructions from Monte Carlo neutron transport (MCNP) calculations are shown to emulate hydrodynamic simulations with imposed Legendre asymmetries to high accuracy.