RADIATION SOURCES: OUTPUT POWER vs. FREQUENCY

GYROKLYSTRON The development of the millimeter-wave Ka-band (34-36 GHz) and W-band (93-95 GHz) gyroklystrons was primarily stimulated by radar applications within the ranges of the atmospheric RF windows. Later, high power pulse gyroklystrons attracted attention as sources of coherent radiation for compact, high gradient linear accelerators. Pulsed 35 GHz two-cavity gyroklystron developed in IAP(1993) pulse length 00 μsec max power 750 kW max efficiency 32% at P = 300 kW gain 22 dB at P = 600 kW instantaneous bandwidth at -3 dB 0.6 % The bandwidth is limited by the Q-factor of the output cavity, which is about 320.

High average power four-cavity W-band (94 GHz) gyroklystron developed jointly by NRL, the University of Maryland, and industrial companies Litton and CPI (1999) Over 10 kW average power with 11% duty cycle (100 μsec pulse, 1.1 kHz repetition rate) instantaneous bandwidth at – 3 dB 420 MHz (0.5%) Gain 35 dB Efficiency 33%

High Power 95 GHz Gyro-Devices with Permanent or Solenoid Magnets PROBLEM STATEMENT Non-lethal weapons provide a less-than-lethal option that give war fighters the time and distance to better determine someone’s intent or make individuals comply without having to resort to deadly force.

The Active Denial System (ADS) is a counter-personnel, non-lethal, directed-energy weapon that can help troops fill the gap between shouting and shooting. It provides numerous advantages over existing non-lethal weapons, such as extended range and extremely small risk of injury.

The ADS produces millimeter waves at a frequency of 95GHz and uses an antenna to direct a focused, invisible beam toward a designated subject. Traveling at the speed of light, the energy strikes the subject and reaches a skin depth of only about 1/64th of an inch, or the equivalent of three sheets of paper. It produces a heat sensation that within seconds becomes intolerable and forces the targeted individual to instinctively move. TECHNOLOGY FEATURES A compact high average power millimeter wave gyrotron at 94 or 95 GHz that uses a normal magnet of low operating power has important applications for Area Denial Technology and Systems (ADT, ADS), communications, radar, particle accelerators, materials heating and processing, and more, at lower cost.

Gyroklystron Design Summary 50 MW 30 GHz gyrklystron amplifier for testing of high gradient accelerator structures at K and Ka bands Gyroklystron Design Summary Estimate Development Cost and Schedule • $750,000 • Two years

Sources for radar and communications systems Recent advances in radars are based on the development of two classes of HPM sources: high-peak power, short-pulse (ns) sources longer pulse (s) millimeter-wave sources Nanosecond Gigawatt Radar 10 GHz, 0.5 GW, 5 ns, 150 Hz, 3° beam width Moving targets of ~1m2 radar cross section are reliably tracked at distances up to 100 km over the sea and wood-covered terrain Near 1-m range resolution provided identification of targets and measurement of target parameters (in particular, the rotation of a helicopter’s blades) Nanosecond radar system (United Kingdom Ministry of Defense)

Millimeter-wave radars The gain of an antenna: limited to G < ( D / )2 (D: the antenna diameter) Tradeoffs in choosing the optimum operating frequency of a radar system: directionality, resolution, Doppler sensitivity, atmospheric attenuation, and the effective cross section of the scattering objects The potential advantages of millimeter-wave radars over lower frequency systems: smaller antennas, narrower beam widths, greater Doppler sensitivity, lower vulnerability to jamming or intercept, reduced clutter and multipath effects, and higher precision target location

Areas in which high-power millimeter-wave radars are strongly advantageous active monitoring of the atmosphere and search for debris in space Monitoring of the atmosphere by millimeter- wave radars makes it possible to study the dynamics of clouds and to resolve multiple cloud layers Increasing the average transmitter power by three orders of magnitude, a 94-GHz radar system could overcome an additional 30 dB of atmospheric absorp- tion, which would increase the useful range by at least 15 km in the most humid conditions Advances in the millimeter-wave radars are related to advances in millimeter-wave amplifier tubes, and in particular to the development of gyroklystrons

35-GHz gyroklystron producing 750 kW in 100-ms pulses at 5 Hz repetition rate 94 GHz, GKL with 65 kW output power and 0.3% bandwidth The progress in the development of high-power GKLs has led to the suggestion to build a 35-GHz radar capable of detecting small-size orbital debris that is dangerous for spacecraft and space stations Approximately 20 MW of power is required to detect a 1-cm object at a range of 1000 km using a 20-m tracking antenna Four such stations, distributed along the Earth’s equator, would be enough to catalog orbital debris larger than 1 cm