Angularly resolved spectral reconstruction of x rays via filter pack attenuation.

Area of Science:

• Plasma Physics
• Accelerator Physics
• X-ray Optics

Background:

• Laser wakefield accelerators (LWFAs) produce high-energy electrons and betatron X-rays.
• Measuring the spectral evolution of these X-rays is crucial for understanding electron dynamics.
• Existing methods often struggle with shot-to-shot variations and angular resolution.

Purpose of the Study:

• To develop and validate a new filter pack array for single-shot measurement of angular X-ray spectral variations.
• To investigate the energy evolution of betatron X-rays in an LWFA by correlating spectral changes with emission angles.
• To provide insights into the dynamics of electrons within the accelerator.

Main Methods:

• Designed a filter pack array with repeating columns of varying thickness aluminum and copper filters.
• Utilized the array with an X-ray charge-coupled device (CCD) camera in an LWFA experiment.
• Employed image processing techniques including background subtraction and flattening.
• Calculated critical energy at each position for optimal agreement with measured signals.

Main Results:

• Demonstrated clear changes in critical energy with angle, indicating distinct emission times.
• Successfully measured angular X-ray spectral variations within a single shot.
• The filter pack array effectively recovered angular details without shot-to-shot errors.
• Provided insights into electron dynamics by analyzing spectral evolution across different angles.

Conclusions:

• The designed filter pack array is a robust tool for characterizing angular X-ray spectra in LWFAs.
• This method enables the study of electron dynamics and energy evolution on picosecond timescales.
• The technique minimizes errors associated with shot-to-shot variability, enhancing measurement reliability.