Unruh Radiation

Unruh radiation is the analogue of Hawking radiation from black holes when the gravitational field of the black hole is replaced by an accelerating frame of reference. An observer in the accelerating frame should observe a black body radiation field with temperature kTU = ha/2c. For an electron accelerating in a laser field the Unruh temperature becomes large (kTU ~ mc2) coincidentally when the electric field is of order the Schwinger field. Chen and Tajima have suggested that Unruh radiation is detectable at much lower irradiances, around 1024Wcm-2, since the Unruh radiation has a different polar pattern compared with the orbital (Larmor) radiation of the electrons. HiPER can move well in to the realms of intense Unruh radiation since a high energy electron interacting with the laser field 'sees' an intensity higher by a factor of . 1GeV electrons (from an associated accelerator) interacting with the HiPER beam at 10M25 Wcm-2 will see an intensity of 1031 Wcm-2, and will be very strongly scattered from the MeV radiation field associated with the Unruh temperature.