High-performance phase camera as a frequency selective laser wavefront sensor for gravitational wave detectors.

We have designed, built and tested a high-performance phase camera, which can observe laser wavefronts in a large range of sideband frequencies. Our phase camera scans the laser beam over a pinhole diode and uses a heterodyne technique to independently assess the information in the upper and lower sidebands of up to five different modulation frequencies. Amplitude and phase images, consisting of 214 points each, are obtained every second for each of the 11 demodulated frequencies in parallel. The achieved sensitivity is about 4×10-3 rad (λ/1600 at λ = 1064 nm) at the center of the beam, corresponding to a wavefront deformation of 0.7 nm, and drops to about 3 nm over the beam size. This sensitivity is extremely useful for diagnostic purposes in gravitational wave detectors and fits the requirements for control loops in Advanced Virgo. We report on the design, realization and performance of our phase camera.

Coincidence velocity map imaging using Tpx3Cam, a time stamping optical camera with 1.5 ns timing resolution.

We demonstrate a coincidence velocity map imaging apparatus equipped with a novel time-stamping fast optical camera, Tpx3Cam, whose high sensitivity and nanosecond timing resolution allow for simultaneous position and time-of-flight detection. This single detector design is simple, flexible, and capable of highly differential measurements. We show detailed characterization of the camera and its application in strong field ionization experiments.

Proton Radiography With Timepix Based Time Projection Chambers.

The development of a proton radiography system to improve the imaging of patients in proton beam therapy is described. The system comprises gridpix based time projection chambers, which are based on the Timepix chip designed by the Medipix collaboration, for tracking the protons. This type of detector was chosen to have minimal impact on the actual determination of the proton tracks by the tracking detectors. To determine the residual energy of the protons, a BaF 2 crystal with a photomultiplier tube is used. We present data taken in a feasibility experiment with phantoms that represent tissue equivalent materials found in the human body. The obtained experimental results show a good agreement with the performed simulations.