Coaxial Electron-laser Interaction Chamber

Located on beam line #1, the “Compton chamber” has 40 liters of usable volume. It is mounted on an adjustable rail system and laser optical table, and has close proximity to a quadrupole triplet upstream and 90-degree dipole spectrometer system downstream. The cell has optical windows for delivery and extraction of highpower laser beams, and focusing parabolic mirrors with in-vacuum manipulators for precise alignment of the laser focus on the electron beam. Synchronization and alignment targets, as well as BPMs, can be inserted with actuators to allow monitoring of electron and laser beams. Permanent mini-quadrupoles mounted at the entrance port of the cell allow tight electron focus down to 20 µm RMS, to match the laser focus. Laser mirrors are arranged to provide the most efficient counter propagation interaction with the electron beam. To allow the electron beam transmission through the interaction point and out the cell, the laser mirrors have axial drilled holes. The same holes are used to extract Compton X-rays produced in the interaction point.

The Compton chamber is positioned on an optical table with an optical setup for precise alignment and characterization of the laser beam before entering the chamber and for visualizing the laser focus with an IR camera mounted in the spent laser beam port. The standardized chamber and optical setup, which has been perfected over a series of experiments, allows fast and efficient transition to any new experiment that requires the interaction of tight focused laser and electron beams. Although traditionally called “Compton chamber”, the cell allows reversal of the laser direction for co-propagation with the e-beam to explore mechanisms of laser acceleration. Hosted experiments include: AE22 Inverse Compton Scattering, AE27 Vacuum Laser Acceleration (VLA), and AE31 Current Filamentation Instability (CFI).

Primary operational features include:

• Large central volume and top flange with multi-axis translation stage accommodate interaction targets and beam diagnostics, side ports for laser windows (accommodates up to 3” diameter CO₂ laser beam), top and side ports for 3-axis mirror mounts with translation actuators.
• Beam profile monitors at interaction region as well as chamber entrance and exit.
• Available port for 200 l/s turbo pump. Operates in the 10-8 Torr range.