• Output power. Approximately 1 megawatt class at the aperture (also address the 100 kilowatt step);

  • Wavelength. Three atmospheric windows (reduced absorption) at 1.04, 1.62, and 2 micrometers (1-2 micrometers); and

  • Power to the free-electron laser. Approximately 20 megawatts.

It is important to realize that although it may be possible to design and build a free-electron laser with the desired high levels of output power, that does not necessarily mean that an effective weapon system that uses the free-electron laser as a component can be built and operated in a naval environment of interest. To properly understand and interpret the meaning and applicability of the results of this study, it is critical to identify the factors it does not address. It does not address whether a megawatt-class free-electron laser will be an effective weapon in a naval context nor does it address operational lethality factors, such as duration of the beam on target or repetition rate. More specifically, the study does not address:

  • The effectiveness of the device to perform Navy missions of interest or

  • The physics associated with atmospheric propagation of the laser beam (thermal blooming, aerosols, weather effects, etc.).

This study and report also do not address the realistic constraints of shipboard operation and installation such as those that follow. These constraints are not insignificant and should be addressed in a follow-on study:

  • Sizing the free-electron laser beam generation system and engineering it to operate in a shipboard environment, including the following associated factors:

    • Inherent ship vibration and motion;

    • Radiation safety and shielding;

    • Protection of the free-electron laser system from warfighting damage;

    • Power conditioning;

    • Support for cryosystem operation;

    • Provision of vacuum;

    • Transmission of the beam between the free-electron laser and the beam director;

    • Engineering of the beam director; and

    • Manpower, personnel, and knowledge-base issues related to the operability, maintainability, and repairability of the system by sailors.

This study identifies the highest-priority scientific and technical gaps that will need to be overcome along the development path to achieve a megawatt-class free-electron laser. The development of a 100 kilowatt device is considered an interim step to demonstrate the scalability of component technologies to the megawatt class. While a 100 kilowatt device may exhibit naval utility in its own right, component-level scalability to the megawatt class is considered essential to this study. The committee’s principal findings are provided in the following section.

The information that follows this chapter is organized into two chapters. Chapter 2 describes the state of the art with free-electron lasers. It provides a history of free-electron lasers for Navy applications, gives an overview description of free-electron lasers, discusses the trade-offs between free-electron lasers and other types of high-energy lasers, and describes the relationship of free-electron lasers to scientific applications.

Chapter 3 provides a detailed assessment of free-electron laser technologies and challenges. It begins with a general discussion of how we get from the current state-of-the-art free-electron lasers to free-electron lasers in the 100 kilowatt class and 1 megawatt class. The discussion that follows is organized around the components and major operational issues of a free-electron laser and addresses the technical operation, state of the art, and challenges to progress associated with each aspect of an overall free-electron laser system.

Following Chapter 3, the appendixes include the statement of task for the study and report, agendas for the committee meetings, biographies of the committee members and staff, and a combined glossary and acronyms list.

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