The start of PETRA and its experimental programme

On July 15, 1978, the first stored beam was able to be observed in PETRA, DESY Laboratory, Hamburg, West Germany. The commissioning of PETRA has been making fast progress. Of course, a lot of work remains to be done before the experimental programme can be strated, which is scheduled at the beginning of October, 1978. Apart from the obvious improvements (increase of peak average luminosity due to higher current, shorter filling time and longer beam life time, etc. ), there are several additions under preparation or discussion. The most important are positron intensity accumulator, polarized beam, and increase of beam energy to 23 GeV. In the PETRA design, high flexibility for later extension has been provided. Increase of the beam/energy beyond 23 GeV may be achieved by superconducting cavities for a given rf power. Another possibility is the addition of a superconducting proton ring to PETRA to study e-p interaction. The PETRA Research Committee has recommended five experiments to be carried out by international collaborations, namely PLUTO 2, CELLO, JADE, MARK J and TASSO. Because of the recent breathtaking developments, the physical questions to be investigated are even richer and more exciting than those mentioned in the PETRA proposal. At the beginning, interest will be concentrated on new thresholds in hadron production cross section, new particles (where is the 6th quark, states of exotic quarks, leptons, monopoles, etc.) and muon asymmetry. (Wakatsuki, Y.)