Multifunctional optical correlator for picosecond ultraviolet laser pulse measurement.

A compact multifunctional optical correlator system for pulse width measurement of ultrashort ultraviolet (UV) pulses has been designed and experimentally demonstrated. Both autocorrelation and cross-correlation functions are measured using a single nonlinear crystal, and the switching between two measurements requires no adjustment of phase matching and detector. The system can measure UV pulse widths from sub-picoseconds to 100 ps, and it involves no auxiliary pulse in the measurement. The measurement results on a burst-mode picosecond UV laser show a high-quality performance on speed, accuracy, resolution, and dynamic range. The proposed correlator can be applied to measure any ultrashort UV pulses produced through sum-frequency generation or second-harmonic generation.

Active beam position stabilization of pulsed lasers for long-distance ion profile diagnostics at the Spallation Neutron Source (SNS).

A high peak-power Q-switched laser has been used to monitor the ion beam profiles in the superconducting linac at the Spallation Neutron Source (SNS). The laser beam suffers from position drift due to movement, vibration, or thermal effects on the optical components in the 250-meter long laser beam transport line. We have designed, bench-tested, and implemented a beam position stabilization system by using an Ethernet CMOS camera, computer image processing and analysis, and a piezo-driven mirror platform. The system can respond at frequencies up to 30 Hz with a high position detection accuracy. With the beam stabilization system, we have achieved a laser beam pointing stability within a range of 2 µrad (horizontal) to 4 µrad (vertical), corresponding to beam drifts of only 0.5 mm × 1 mm at the furthest measurement station located 250 meters away from the light source.

Measurement of ion beam profiles in a superconducting linac with a laser wire.

A laser wire ion beam profile monitor system has been developed at the Spallation Neutron Source accelerator complex. The laser wire system uses a single laser source to measure the horizontal and vertical profiles of a pulsed hydrogen ion (H(-)) beam along a 230 m long superconducting linac, which accelerates H(-) from 200 MeV to 1 GeV. In this paper, we describe the laser optics requirement for the system, the performance of the profile measurement, and the effects of laser parameters on the measurement reliability. The result provides a practical guideline for the development of a large-scale, operational, laser-based diagnostics in accelerator facilities.