  We discuss the proposal of Bell and Leinaas (BL) to measure the circular
Unruh effect in storage rings. The ideal concept `circular Unruh effect' has a
more realistic correspondent such as `circular vacuum noise' used by Shin
Takagi [Prog. Theor. Phys. Suppl. 88, 1 (1986)] The BL resonance behavior does
not fit to the SPEAR first order betatron resonance at 3.605 GeV, but of
course, the real experimental situation is much more complicated,
corresponding, as a matter of fact, to an even more general term that one may
call `synchrotron noise'. In the final section we focus on radiometric aspects
of storage ring physics, such as the problem of establishing better quantum
field radiometric standards at high energies. The Unruh-like effect could be a
useful guide for that purpose
