During the previous three years, a Compton spectrometer has successfully measured the x-ray spectra of both continuous
and flash radiographic sources. In this method, a collimated beam of x-rays incident on a convertor foil ejects Compton
electrons. A collimator in the entrance to the spectrometer selects the forward-scattered electrons, which enter the
magnetic field region of the spectrometer. The position of the electrons at the magnet’s focal plane is proportional to the
square root of their momentum, allowing the x-ray spectrum to be reconstructed. The spectrometer is a neodymium-iron
magnet which measures spectra in the <1 MeV to 20 MeV energy range. The energy resolution of the spectrometer was
experimentally tested with the 44 MeV Short-Pulse Electron LINAC at the Idaho Accelerator Center. The measured
values are mostly consistent with the design specification and historical values of the greater of 1% or 0.1 MeV.
Experimental results from this study are presented in these proceedings.
A Compton spectrometer has been re-commissioned for measurements of flash radiographic sources. The determination of the energy spectrum of these sources is difficult due to the high count rates and short nature of the pulses (~50 ns). The spectrometer is a 300 kg neodymium-iron magnet which measures spectra in the <1 MeV to 20 MeV energy range. Incoming x-rays are collimated into a narrow beam incident on a converter foil. The ejected Compton electrons are collimated so that the forward-directed electrons enter the magnetic field region of the spectrometer. The position of the electrons at the magnet’s focal plane is a function of their momentum, allowing the x-ray spectrum to be reconstructed. Recent measurements of flash sources are presented.
The self-magnetic pinch (SMP) diode is an intense radiographic source fielded on the Radiographic Integrated Test Stand (RITS-6) accelerator at Sandia National Laboratories in Albuquerque, NM. The accelerator is an inductive voltage adder (IVA) that can operate from 2-10 MV with currents up to 160 kA (at 7 MV). The SMP diode consists of an annular cathode separated from a flat anode, holding the bremsstrahlung conversion target, by a vacuum gap. Until recently the primary imaging diagnostic utilized image plates (storage phosphors) which has generally low DQE at these photon energies along with other problems. The benefits of using image plates include a high-dynamic range, good spatial resolution, and ease of use. A scintillator-based X-ray imaging system or “gamma camera” has been fielded in front of RITS and the SMP diode which has been able to provide vastly superior images in terms of signal-to-noise with similar resolution and acceptable dynamic range.