Active Denial System now being tested by the US Military. it's designed to cause excruciating pain without injury by projecting a beam of energy about two meters across. Victims describe the sensation as like a giant hairdryer on maximum heat.
Informally know as the 'Pain Ray', producing a beam of short-wavelength microwaves that penetrate about 0.4mm into the skin, rapidly heating the epidermis. heating skin to 55C causes intolerable pain. Intensity of the beam varies with range.
Dr Juergen Altmann a physicist with the Bochum Verification project calculates there's a dangerous and narrow safety margin.
In April the system underwent field testing. A report on a testing accident was obtained recently by journalist Sharon Weinberger using the Freedom of Information Act. The maximum range is classified but thought to be 750 metres. According to the report ADS operator P4 set power to 100% for four-second duration, so as to be effective at long range. A problem prevented the test from taking place- the system's magnet requires supercooling and can be temperamental in hot weather. moving onto the next scenario the crew forgot to change the setting. When the system was fired the Role Player P3 immediately knew he had received a stronger than usual shot from the ADS. The description of the injuries had been censored from the report. Clearly the safeguards do not prevent operator error says Dr Altmann.
...from 'The Guardian newspaper' December 13th.