Ultra-Compact X-ray Spectrometer (UCXS) for high repetition rate laser plasma experiments

X-ray spectrometers have always been considered as indispensable tools for understanding plasma physics [1]. Indeed, they permit both reliable (direct and indirect) quantification and characterization of important physical properties such as absorbed laser energy, plasma temperature, plasma density etc... Thus, accessing such key parameters allows for a better description of laser plasma processes at extreme conditions.  

We present in this work the development of an ultra-compact multi-channel x-ray spectrometer (UCXS). This diagnostic has been especially built and adapted to perform at high repetition rate (>1 Hz) for high-intensity, short-pulse laser plasma experiments. X-ray filters of varying materials and thicknesses are specifically chosen to provide high spectral resolution (up to ΔE≈1keV) over the x-ray range of 1 keV to 25 keV via k-edge matching. These filters are distributed over a total of 10 channels, where each x-ray filter is coupled to a single scintillator to avoid optical bleeding between channels.  These fast scintillators [2] (few ns decay), allow for both high efficiency fluorescence, and high throughput for high rep rate operations. The UCXS is designed to detect and resolve a large variety of laser driven x-ray sources such as low energy bremsstrahlung emission, fluorescence emission and betatron radiation (up to 25keV).

Another advantage of the UCXS is a structure of optical fibres which transport the converted light out of the vacuum target chamber to a remote imaging detection station. This, as well as supple shielding, make the spectrometer flexible in terms of experimental layouts while being both reliable and robust against strong electro magnetic pulses (EMP) issues generated in these harsh laser plasma environments.

Preliminary results from commissioning experiments at the ALEPH laser facility at Colorado State University will be shown.