Performance

Performance

Numerical simulation of the performance of the laser facility and automated control of the laser setup process are crucial to the project's success. The virtual model is considered as a set of services and tools that enable transparent execution of computational software for modelling beam dynamics in particle accelerators on distributed computing resources. For laser facilities, these functions can be performed by two closely coupled computer codes: the virtual beam line (VBL) and the laser operations performance model (LPOM).

A complete engineering model of the laser beam performance will be developed, taking into account the various parameters to be delivered at the target, such as energy, power, and spatial, temporal, and spectral shaping. These predictive models will enable the user's experimental requirements to be critically assessed ahead of time and will ultimately be used to determine key system settings and parameters. Of course, a lot of work must be undertaken to validate these simulations against real system data, with the aim of creating predictive models of beam line performance.

The performance of the facility must be assessed to provide users with both a facility operating point and a facility operating range. These assessments can be made four different ways:

  • Design calculations can give a rough order of magnitude. Typical sizing calculations can be made with a one-dimensional code for rate equations like the Frantz and Nodvik set of equations.
  • Complex calculations can use a beam propagation method (BPM) as a core software with connections to external databases or software that can provide thermal management and parameters for real components. The BPM is the most widely used type of code, but there are two other methods that are more or less under development: finite elements and Wigner functions.
  • The LPOM, an operating model that can take over the main control system to drive the facility on its own, will be one of the high-level software supervisors for the integrated computer control system (ICCS). The primary role of the LPOM is to automate the setup of the individual laser beams. The LPOM will maintain a current model that includes the optical paths, configurations, and compression stage characteristics for each beam, as well as a database of diagnostic measurements at various locations along the beam line.
  • All other software deals with laser interaction with the target (gas and solid) and creating plasmas for generating secondary sources (high harmonic generation, X-rays, and particles) or accelerating electrons, protons, and ions.

What is the BPM (beam propagation method)? This is a software system that simulates the propagation and amplification of a laser beam in complex optical chains. The BPM is used to investigate linear and nonlinear phenomena in light wave propagation. It starts with Helmholtz's equation and goes up to the nonlinear Schrödinger equation. This method is based on fast Fourier transform (FFT) to switch between the time-space domain and the frequency-spectrum domain because Fourier transform is an essential part of the diffraction theory.

All-in-one software does not exist, but a multiphysics approach can combine optical response with thermo-mechanical analysis in real components. Thermal management of the main laser amplifiers is included in the wavefront allocations because this is the classical way of introducing thermal distortions into optical components.

The virtual beamline (VBL) is intended to be a tool both for internal use by ELI-Beamlines personnel and external use by ELI-Beamlines users. This VBL is a demonstrator that would allow researchers to do the following:

  • see experiments from a location that is remote from the facility
  • view instruments and work areas associated with beam lines
  • collaborate using advanced high-quality video-conferencing systems and shared applications
  • manipulate samples using motor controls through a secure, remote desktop and an interface to the controls
  • acquire data from experiments that can be transferred quickly and securely to computer resources or storage at the researcher's home institution using a storage gateway that would offer a range of file-transfer protocols
  • view images captured by the detectors on large screens at high resolution.

The VBL can also be used for the following:

  • to allow visitors to the facility to undergo safety training before arriving on site, thus reducing delays in getting up and running
  • to train students and visitors to understand how the beams propagate from lasers to experiments.