Page History

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1. Java Channel Access (JCA). JCA is the EPICS Channel Access client used by XAL. JCA can also be used directly from any Java application or from Matlab.
2. Channel Access in Java (CAJ). CAJ is a Java native EPICS channel access client, which should be easier to use and higher performance, for applications that are not using XAL.
3. XAL package gov.sns.xal.smf is a javabean oriented package which offers object oriented device control to devices accessible through EPICS channel access.
4. Accelerator Independent Data Access (AIDA) gives access to SLC db, model (Twiss and R-mats), and History and EPICS archiver data, plus will soon give access to collectively controlled SLC devices (BPMs and magnets - so can acquire whole beamline at a time etc).

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1. the existing SCP + plus minor additons additions for LCLS
2. existing XAL applications
3. new applications - most of which are likely to be based on XAL, but may use data APIs like JCA or AIDA if XAL is not indicated
4. Matlab Applications, and matlab used on an add-hoc basis.

Each of these 4 classes of applications will use each of the 3 major data sources/APIs: control data, model data and history data. The following data flow diagrams show data sources, and the status of APIs (black shows a existing data source, blue shows where work is needed to get the required data to the required application class ).

Control Data

SCP applications will control EPICS devices through the "SLC-aware-IOC". The SLC Channel Access Server gives read-only data access to SLC application data (Magnets in particular, plus SLC bpm data but without meas-def packaged acquisitions). XAL applications (both existing, and new those new applications which will use the XAL framework for control), obviously will use the XAL smf package, which is an Object Oriented device control layer on top of JCA. New applications may use XAL's smf, or may choose to use JCA directly, or AIDA. Matlab applications can also use any of XAL smf, or JCA or AIDA employing Matlab's ability to script java directly.

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The existing SLC model system is shown at right. A user initiates the Kmod-to-bdes operation from a SCP. Dimad gets the kmods, plus the model skeleton deck and initial conditions from the database. It "runs" the model, and resulting Twiss parameters and R-matrices for most devices are put in the SLC db (basically those used for 1st order optics diagnostics). The .TWSS output file contains all twiss, rmatsR-mats, plus other per-unit parameters (kmods, effective lengths).

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At the time of writing it has not been decided which new history data system to use LCLS. The nominal EPICS archive protocol stack is given at left. Paul Chu reports that SNS used PVlogger rather than EPICS archiver. The existing SLC history system is show at right; SLC history data can now be acquired by new applications or by matlab through Aida.

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