Wasa Report 1/91 the Celsius Ring the Wasa Experiments

A superconducting solenoid for WASA. General project description and status (February 91) Abstract A thin walled superconducting warm bore solenoid with a central magnetic eld of 1.5 Tesla is being designed for the WASA 4 detector for particle physics experiments at the CELSIUS ring. The overall length of the solenoid is 550 mm, its inner and outer diameter are 490 mm and 650 mm respectively. The wall thickness can be kept below 0:2 X 0 (radiation length). The CELSIUS ring at the The Svedberg Laboratory (TSL) can store and accelerate protons up to energies of 1.3 GeV and heavier ions to corresponding energies at beam currents of several milliamperes on diierent internal targets. With the existing gas jet target luminosities of up to 10 31 cm ?2 s ?1 can be reached in proton-proton and proton-deutron reactions. Since the number of stored particles is relatively low (about 10 10) the background conditions are generally much better than for a conventional extracted beam setup at the same luminosity. This situation will be further improved when using electron cooling. Then the proton beam will have a cross section of a few millimeters and a relative momentum spread of about 210 ?4. The good energy deenition and the low background allow high precision measurements e.g. of particle production at threshold and studies of some rare processes. In addition the use of thin targets minimize the risk for secondary interactions of the reaction products in the target material. The main item in the WASA physics programme is the measurement of rare decays of the neutral pseudoscalar mesons: 0 and which are possible to produce at CELSIUS. The most interesting decays occur typically with a rate smaller than 10 ?6 of that of the 1