ON A POSSIBILITY OF CONSTRUCTING A HIGH-INTENSITY, MONOCHROMATIC, POLARIZED GAMMA-SOURCE AT PETRA

A possibility of constructing a high-intensity, tunable, monochromatic , polarized gamma-source at the PETRA storage ring is discussed. It is proposed to produce gamma-quanta by means of Compton backscattering o f laser photons on the electrons. The laser light wavelength is chosen in such a way that after the scattering the electron does not leave t he separatrix. Since the probability of the scattering is rather small , energy oscillations are damped prior to the next scattering. As a re sult, the proposed source can operate in a ''parasitic'' mode not inte rfering with the main mode of the accelerator operation. It is propose d to install at PETRA a tunable free-electron laser operating in the 2 0-50 mu m wavelength band with peak and average output power similar t o 10 MW and similar to 1 kW, respectively. This will result in the int ensity of the gamma-source similar to 3 X 10(12) s(-1) with tunable ga mma-quantum energy up to 60 MeV. Gamma sources with a similar principl e of operation could be constructed also at other storage rings such a s HERA, TRISTAN, LEP(LEP 2), ESRF, SPring-8. Such gamma-sources could reveal unique possibilities for precision investigations in nuclear ph ysics.