LCLS Online Physics Applications Outline
From 20000 ft.
This document describes a possible architecture for physics applications for the LCLS. It outlines the existing support for accelerator optics modeling in XAL and in the online SLC control system, and includes recommendations for a technology track, the process for XAL modeling, how SLC and XAL modeling can be brought together to meet the commissioning schedule, and highlights issues that will require attention. It is assumed that both the SLC modeling environment and SCP applications will be replaced by XAL based equivalents over some period.
Desktop Hardware and Filesystem
Our target desktop processors will be x86 CPUs running RedHat linux, with the GTK window system (see details). The executables may be housed on either AFS or NFS filesystems, little difference. Each user (including control room heads) additionally requires their own configuration file area - the precise configuration seen by each head may be unique therefore. This is a feature of XAL and the other desktop technologies we'll use. That configuration file area will be NFS because a long-lived executable (>25hrs - the AFS token lifetime) must be able to write to it at any time.
X11
XAL (that is JFC/Swing) and SWT/Jface applications may be used on any X11 equipped workstation (Windows PC, Solaris) with some performance degradation since JFC/Swing performs poorly over X11. These apps could be run "natively" on Windows (Swing is pure Java, which is platform independent, and any SWT components could be delivered for Windows too, but the added complexity of synchronizing filesystem resources between the Unix filesystem and the Windows filesystem probably makes this option undesirable - see questions) and redflags.
Overall User Interface
Use Case: A user (physicst or operator) types "lips" (or iscp or any other name we like) at a Linux console - a GUI based application launches. This application can launch any EPICS display (DM, dm2k etc), any XAL application, the SCP (on MCC), or any EPICS extension application like archive browser, alarm handler watchdog, stripchart, cmlog browser etc. These are launched on the correct host for that application or display. The "local" messages generated by each application appear in a console window dedicated to that application - "global" messages appear in the jcmlog browser window.
Starting Applications
See figure 1, a screenshot of representative user applications for LCLS. This shows a minimally modified Eclipse Rich Client (that is, basically Eclipse out of the box) in the Resource Perspective where the Eclipse Workspace has been configured to launch various kinds of program. A number of execution modes are represented (in-process, out-of-process, using Swing and SWT GUI frameworks, plus EPICS display technologies):
#Eclipse external launching (epics displays, archive viewer, scp etc).
#Eclipse launching external java SWT/Jface application (jcmlog)
#Eclipse launching internal java SWT/Jface (same VM) application (aida probe)
#Eclipse launching external java JFC/Swing (XAL) application (NOT SHOWN YET)