CERN, Geneva, Switzerland
CEA, LE BARP cedex, France
CEA/DAM/DIF, Arpajon, France
LULI, Palaiseaux, France
Cilex-Apollon is a high intensity laser facility delivering at least 5 PW pulses on targets at one shot per minute, to study physics such as laser plasma electron or ion accelerator and laser plasma X-Ray sources. Under construction, Apollon is a four beam laser installation with two target areas. To control the laser beam characteristics and alignment, more than 75 CCD cameras and 100 motors are dispatched in the facility and controlled through a Tango bus. The image acquisition and display are made at 10 Hz. Different operations are made on line, at the same rate on acquired images like binarisation, centroid calculation, size and energy of laser beam. Other operations are made off line, on stored images. The beam alignment can be operated manually or automatically. The automatic mode is based on a close loop using a transfer matrix and can correct the laser beam centering and pointing 5 times per second. The article presents the architecture, functionality, performances and feedback from a first deployment on a demonstrator.
ORNL RAD, Oak Ridge, Tennessee, USA
ORNL, Oak Ridge, Tennessee, USA
The Liquids Reflectometer instrument installed at the Spallation Neutron Source (SNS) enables observations of chemical kinetics, solid-state reactions and phase-transitions of thin film materials at both solid and liquid surfaces. Effective measurement of these behaviors requires each sample to be calibrated dynamically using the neutron beam and the data acquisition system in a feedback loop. Since the SNS is an intense neutron source, the time needed to perform the measurement can be the same as the alignment process, leading to a labor-intensive operation that is exhausting to users. An update to the instrument control system, completed in March 2013, implemented the key features of automated sample alignment and robot-driven sample management, allowing for unattended operation over extended periods, lasting as long as 20 hours. We present a case study of the effort, detailing the mechanical, electrical and software modifications that were made as well as the lessons learned during the integration, verification and testing process.
CERN, Geneva, Switzerland
University of Malta, Information and Communication Technology, Msida, Malta
LLNL, Livermore, California, USA
The Disposable Debris-Shield (DDS) Attenuation Tool is software that leverages Automatic Alignment image analysis results and takes advantage of the DDS motorized insertion and removal to compute the in-situ transmission of the 192 NIF DDS. The NIF employs glass DDS to protect the final optics from debris and shrapnel generated by the laser-target interaction. Each DDS transmission must be closely monitored and replaced when its physical characteristics impact laser performance. The tool was developed to calculate the transmission by obtaining the total pixel intensity of acquired images with the debris shield inserted and removed. These total intensities existed in the Automatic Alignment image processing algorithms. The tool uses this data, adding the capability to specify DDS to test, moves the DDS, performs calculations, and saves data to an output file. It operates on all 192 beams of the NIF in parallel, and has shown a discrepancy between laser predictive models and actual. As qualification the transmission of new DDS were tested, with known transmissions supplied by the vendor. This demonstrated the tool capable of measuring in-situ DDS transmission to better than 0.5% rms.
LLNL, Livermore, California, USA
The Advanced Radiographic Capability (ARC) at the National Ignition Facility was developed to produce a sequence of short laser pulses that are used to backlight an imploding fuel capsule. This backlighting capability will enable the creation of a sequence of radiographs during capsule implosion and provide an unprecedented view into the dynamics of the implosion. A critical element of the ARC is the diagnostic instrumentation used to assess the quality of the pulses. Pulses are steered to the diagnostic package through a complex optical path that requires precision alignment. A central component of the alignment system is the image analysis algorithms, which are used to extract information from alignment imagery and provide feedback for the optical alignment control loops. Alignment imagery consists of complex patterns of light resulting from the diffraction of pilot beams around cross-hairs and other fiducials placed in the optical path. This paper describes the alignment imagery, and the image analysis algorithms used to extract the information needed for proper operation of the ARC automated alignment loops.
LLNL, Livermore, California, USA
For many experiments planned on the National Ignition Facility (NIF), high-energy x-ray backlighters are an important diagnostic. NIF will be deploying this year a new Advanced Radiographic Capability (ARC) for generating these high-energy short-pulses. The precision of the Automatic Alignment (AA) for ARC is an important element in the success of the enhancement. A key aspect of the ARC AA is integration of the new alignment capabilities without disturbing the existing AA operations of NIF. Small pointing tolerances of 5 micron precision to a 10 micron target are required. After main amplification the beams are shortened by up to 1,000x in time in the ARC compressor vessel and aimed at backlighter targets in the NIF target chamber. Alignment Stability and Verification of the compressor gratings is critical to ensuring the ARC pulses meet their experimental specifications.
CERN, Geneva, Switzerland
University of Malta, Information and Communication Technology, Msida, Malta