Zero-field spin relaxation of the positive muon in copper

The spin relaxation of the μ+ in high purity single crystal and polycrystallilne copper has been measured at temperatures between 0.5K and 5.2K by the zero-field μ + SR technique. In both types of sample the experiments show a temperature independent dipolar width Δ/sub z/ = 0.389 +/- 0.003 μs-1 and a hopping rate decreasing from approx. =0.5 μs-1 at 0.5 K to approx. =0.05 μs-1 above 5K. This is the first direct proof of a dynamic effect in low temperature μ+ spin relaxation in copper. The relationship between the zero-field and transverse-field dipolar widths is discussed, and the measured zero-field width is found to be approx. =10% larger than expected based on the known transverse-field widths. A new μ +SR spectrometer has been constructed and used in this work. The spectrometer and the associated beam lines and data acquisition facilities are discussed