ORNL, Oak Ridge, Tennessee, USA
ORNL RAD, Oak Ridge, Tennessee, USA
Recently, a high-efficiency laser assisted hydrogen ion (H−) beam stripping was successfully carried out in the Spallation Neutron Source (SNS) accelerator. The experiment was not only an important step toward foil-less H− stripping for charge exchange injection, it also served as a first example of using megawatt ultraviolet (UV) laser in an operational high power proton accelerator facility. This talk reports the design, implementation, and commissioning results of the macropulse laser system, laser transport line, and laser operation for the laser stripping experiment. The macropulse laser consists of a mode-locked picosecond pulsed seed laser and a burst-mode Nd:YAG laser amplifier. The general design concept can be adapted to any temporal beam structures in most accelerators. We have achieved UV pulses with the pulse widths varying between 34 to 54 ps and a maximum peak power over 3.5 MW. A laser transport line is installed to deliver the UV beam to the laser stripping chamber at a transmission efficiency of 70%. Laser operation including remote control and monitor of laser parameters will be described.
ORNL, Oak Ridge, Tennessee, USA
To better understand the mechanical impact of the proton beam on the lifetime on Spallation Neutron Source (SNS*) mercury-filled, stainless steel targets, these targets are now instrumented with optical and metal strain sensors, temperature sensors, and accelerometers. The strain and temperature sensors are placed inside the target vessel, between the water shroud and mercury vessel, while the accelerators are placed outside on the target mount and on the mercury return line. We now have data from four targets. The first instrumented target used regular multimode optical sensors, while later targets have used radhard multimode sensors. We are also developing super-radhard single-mode optical strain sensors to get data further into the production cycle. In this paper, we describe the data-acquisition system, compare the measured strain to the simulated strain for the different targets, estimate the survivable radiation level for each type of sensor, and discuss the implications of the results on the lifetime of the target.