Editing Radar (section)

===Coolant===
Coherent microwave amplifiers operating above 1,000 watts microwave output, like [[traveling wave tube|travelling wave tubes]] and [[klystron]]s, require [[Coolant#Liquids|liquid coolant]]. The electron beam must contain 5 to 10 times more power than the microwave output, which can produce enough heat to generate plasma. This plasma flows from the collector toward the cathode. The same magnetic focusing that guides the electron beam forces the plasma into the path of the electron beam but flowing in the opposite direction. This introduces FM modulation which degrades Doppler performance. To prevent this, liquid coolant with minimum pressure and flow rate is required, and deionized water is normally used in most high power surface radar systems that use Doppler processing.<ref>{{cite web | url = http://www.cientificosaficionados.com/libros/CERN/vacio9-CERN.pdf | author = J.L. de Segovia | title = Physics of Outgassing | publisher = Instituto de Física Aplicada, CETEF "L. Torres Quevedo", CSIC | location = Madrid, Spain | access-date = 12 August 2012 | archive-date = 5 January 2012 | archive-url = https://web.archive.org/web/20120105205714/http://cientificosaficionados.com/libros/CERN/vacio9-CERN.pdf | url-status = live }}</ref>

[[Coolanol]] ([[silicate]] [[ester]]) was used in several military radars in the 1970s. However, it is [[hygroscopic]], leading to [[hydrolysis]] and formation of highly flammable alcohol. The loss of a U.S. Navy aircraft in 1978 was attributed to a silicate ester fire.<ref>{{cite web | url = http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA250517&Location=U2&doc=GetTRDoc.pdf | author = Stropki, Michael A. | year = 1992 | title = Polyalphaolefins: A New Improved Cost Effective Aircraft Radar Coolant | publisher = Aeronautical Research Laboratory, Defense Science and Technology Organisation, Department of Defense | location = Melbourne, Australia | access-date = 18 March 2010 | archive-date = 5 June 2011 | archive-url = https://web.archive.org/web/20110605100528/http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA250517&Location=U2&doc=GetTRDoc.pdf | url-status = dead }}</ref> Coolanol is also expensive and toxic. The U.S. Navy has instituted a program named [[Pollution prevention in the US|Pollution Prevention]] (P2) to eliminate or reduce the volume and toxicity of waste, air emissions, and effluent discharges. Because of this, Coolanol is used less often today.