Performance of HPGe detectors in high magnetic fields

A new generation of high-resolution hypernuclear gamma-spectroscopy experiments with high-purity germanium detectors (HPGe) are presently designed at the FINUDA spectrometer at DA Phi NE, the Frascati phi-factory, and at (P) over bar ANDA, the (p) over barp hadron spectrometer at the future FAIR facility. Both, the FINUDA and (P) over bar ANDA spectrometers are built around the target region covering a large solid angle. To maximise the detection efficiency the HPGe detectors have to be located near the target, and therefore they have to be operated in strong magnetic fields (B approximate to I T). The performance of HPGe detectors in such an environment has not been well investigated so far. In the present work VEGA and EUROBALL Cluster HPGe detectors were tested in the field provided by the ALADiN magnet at GSI. No significant degradation of the energy resolution was found, and a change in the rise time distribution of the pulses from preamplifiers was observed. A correlation between rise time and pulse height was observed and is used to correct the measured energy, recovering the energy resolution almost completely. Moreover, no problems in the electronics due to the magnetic field were observed.