Extending the range of the Time Projection Compton Spectrometer to lower energy

The Time Projection Compton Spectrometer (TPCS) has previously been used with a 12.7-μm-thick polypropylene target to measure the time-integrated energy spectrum of intense flash X-ray sources. In the present work, the authors investigated the application of the TPCS to photoelectron spectrometry, substituting a 2-μm thick gold target to improve device sensitivity to low-energy photons. Experiments with a gold target, a polypropylene target, and no target (background) were done at the Saturn pulsed X-ray source for various endpoint bremsstrahlung up to about 2 MV. Response functions were calculated using the TIGERP electron/photon Monte Carlo code. The signal from gold is larger and persists longer, as expected. The spectrum unfolded from the gold signals has problems, however. Alternative approaches to the unfold problem that combine data from both targets may prove more successful. If so, a future spectrometer could be designed to incorporate both low-Z and high-Z targets in a single instrument