High Speed, Enhanced Resolution, Soft X-ray Detector

Energy-dispersive x-ray detectors (EDDs) are heavily used in biological research at synchrotronradiation facilities, particularly for absorption spectroscopy in fluorescence mode on dilute samples.Current research relies on semiconductor EDD spectrometers, which typically become pileup limited atfairly low count rates for the biologically important elements P, S and CI, due to the long electronicprocessing times required to obtain acceptable energy resolution for these soft x-rays. The presentresearch proposes to develop an alternative detector based on electron multiplication technology.Although electron multipliers are very low noise amplifiers and are capable of very high counting rates,presently available scintillator-photomultiplier (PMT) detectors are not competitive with semiconductorEDDs due to their extremely poor energy resolution, which arises from statistical fluctuations in theinefficient conversion between x-rays and electrons for amplification by the PMT. We are thereforegoing to investigate a novel technology for increasing the efficiency of the conversion process. Initialcalculations suggest that if this conversion process can be made to work close to its theoreticalefficiency, it would be possible to construct detectors having energy resolution superior to semiconduc-tor EDDs for energies below 4 keV and capable of throughputs in excess of 106 counts/sec. Becauseno complex electronics would be required to process these detectors' output pulses, they would alsobe relatively inexpensive to array for even higher count rate capability.