High Level Physics Applications XAL – An Accelerator Hierarchy by rpv32164


									               High Level Physics Applications
               XAL – An Accelerator Hierarchy

            Day 1: Accelerator View from the Physicist

8/30/2010                    J-PARC                      1
         Tree Structure Data Representation

   Commonly used structure in computer science

June 16-27, 2008                       USPAS     2
Accelerator Hierarchy



                 BPM           RF Cavity              Magnet            BCM          WireScanner

                        EM Magnet                                             Perm Magnet

               Dipole        Quadrupole

                                                                              Hor.         Ver.

       Hor.        Ver.         Hor.       Ver.
       Corr.       Corr.

   Accelerator hierarchy from the accelerator physicist point-of-view
Advantages to using Accelerator

   Straightforward to create general purpose applications
    that can applied to multiple parts of the accelerator
       Getting ready for commissioning new parts of the accelerator
        just requires creating the definition of the new sequences
   Allows writing applications from the “physicist or
    commissioner’s point of view
       As opposed to creating many specific applications, each
        pertinent to only one special part of the accelerator
   Easily adaptable
       Can add new sequences, nodes, etc.
Accelerator Hierarchies
   The concept of using an Accelerator hierarchy is not unique:
        UAL (Java - http://www.ual.bnl.gov)
             Online and offline accelerator modeling
             Used at BNL
        CDeV (http://www.jlab.org/cdev/)
             Developed at JLab
             Interface to control system
        MAD 8 (http://hansg.home.cern.ch/hansg/mad/mad8/mad8.html )
             MAD with C++ Class structure
             Used for optics modeling
        LEGO
           SLAC (beamline modeling, C++)
        Many others

     We will use XAL as the vehicle for exploring accelerator class
       structures – see JavaDoc
Accelerator Tree

   The accelerator can be a big mess – a collection of
    many different linear accelerators, transport lines,
    rings, etc.
        The Accelerator

   The accelerator is the highest level interface to
    information you need
        This object contains everything you want to know, but were afraid
         to ask, about the accelerator
   Typically all this information is stored in a permanent,
    semi-static data source (e.g. a database).
        At SNS the database schema does not directly reflect the XAL
         class structure – it must meet the needs of many other groups
   In XAL, we use an XML representation of the accelerator
    as the immediate data source for applications
        The XML can be automatically generated from a database –
        This file reflects the class structure used in XAL
   Details on the XML file specifics will be covered later
         XML Accelerator Representation
         (To be covered in more detail later)
<sequence id="MEBT" len="3.633"> form to represent structured data
       XML is a convenient text
       Fast enough to parse an entire accelerator (35 k lines) ~ 1 second
   <sequence predecessors="RFQ"/>
       XML
 </attributes> file is generated from a database representation for SNS
  <node type="marker" id="Begin_Of_MEBT" pos="0" len="0"/>
       Can easily add temporary “bad status” flags for broken equipment
  <node type="QH" id="MEBT_Mag:QH01" pos=".128" len=".061" status="true">
           that may be quickly repaired.
             len=".061" polarity="-1" tightly configuration controlled
      <magnetDatabases tend to be moredfltMagFld="-34.636"/>
      <align x="0.0" y="0.0" z="0.0" pitch="0" yaw="0" roll="0"/>
      <aperture shape="0" x=".016"/>
    <ps main="MEBT_Mag:PS_QH01"/>
    <channelsuite name="magnetsuite">
      <channel handle="fieldRB" signal="MEBT_Mag:QH01:B" settable="false"/>
    Getting the Accelerator in XAL

•From an XML file, use methods in the class

•If you have set a default accelerator using the optics switcher
     •Accelerator accelerator =

•Or manually read an accelerator from a file:
    •Accelerator accel =
    XMLDataManager.acceleratorWithPath(java.lang.String filePath)

•+ many other options
Accelerator Sequence
(gov.sns.xal.smf.AcceleratorSeq )

                                              Each colored section can be a
                                              different sequence

   Sequences are contiguous sections of beamline that are logically related
   They are defined so that they may conveniently pasted together, e.g.
    whenever there is a “fork in the road”, create a new sequence
   Longer sequences can be composed as collections of connected
   Sequences have names, lengths and allowed predecessors
    Getting a Sequence from an
   Get a single specified sequence you are interested in:
        AcceleratorSeq sequence =
   Or you can paste together a collection of sequences
        # Make a list containing sequences we'd like to paste together

        list = ArrayList();

        # make the new "combo" sequence containing the stuff we want:
        newSeq = AcceleratorSeqCombo("testSeq", list);

   Sequences are the component that many applications
    work with
       Display a beam trajectory through a part of the machine
       Set the RF phase and amplitude for a Drift Tube Linac Tank
       Make a bump in the beam trajectory in a section
   General purpose application will first select a sequence
    and then perform its function on this piece of
   See gov.sns.xal.samples.xalSeqs.py for example usage
    Sequences contain Nodes

    A node is an abstract representation of a beamline element that you’d
     likely be interested in using when writing a high level application:
         Magnet, RF cavity, diagnostic device, …
    Nodes are real pieces of equipment, typically in or near a beamline
         No drift spaces are included – these are calculated later – stay tuned
    Drift spaces between pieces of equipment are NOT included (stay tuned
     for the lattice view)
    Nodes have properties including name, distance from start of the
     sequence, status, etc.
    Location refers to the longitudinal center of the device
    Nodes can be at the same location
         E.g. Quadrupole magnet with dipole corrector windings
    The same device can be in two sequences
    Nodes have methods that can be used to get/put information directly
     to/from the machine
Node types
(see interface gov.sns.xal.smf.AcceleratorSeq )

   Magnets – to affect the transverse dynamics of the
   RF cavities – to affect the longitudinal dynamics of the
   Beam Position Monitor (BPM) – to measure the
    transverse (and sometimes longitudinal) position of
    the beam
   Beam Current Monitor (BCM) – to measure the beam
   See gov.sns.xal.samples.xalNodes.py for example
XAL Node Types used at SNS
 Bend                PermanentMagnet
 BLM                 PermQuadrupole
 BPM                 ProfileFit
 CCL                 ProfileMonitor
 CurrentMonitor      Quadrupole
 CvgGauge            ReBuncher
 Dipole              RfCavity
 DTLTank             RfGap
 Electromagnet       RingBPM
 ExtractionKicker    SCLCavity
 GenericNode         Sextupole
 HDipoleCorr         Solenoid
 IonGauge            TrimmedQuadrupole
 Magnet              Vacuum
 MagnetMainSupply    VDipoleCorr
What should be an AcceleratorNode ?

   A single piece of hardware may contain several
    components that affect the beam in different ways
   At SNS we have a “quadrupole” with dipole windings
    and a BPM inside it
   Treat it as 3 separate items – all at the same location
       Quadrupole
       Dipole corrector
       BPM
   Nodes are “hardware” devices
       No drift spaces are included in the accelerator XML
        description – this comes later with the model view creation
Getting a Node

   Node types have identification strings (e.g. “Q” for quad)
   Nodes can be selected from a sequence by type
        quads = sequence.getNodesOfType("Q")
        Magnets = sequence.getNodesOfType(“magnet")
   You can use and create filters (and / or etc.)
        Package gov.sns.xal.smf.impl.qualify
        See gov.sns.xal.samples.Qualifier.py for usage examples
   Many nodes have convienience methods to directly perform
        BPM – get beam position
        Magnet – get magnetic field
        Typically blocking actions
Name Conventions

   Hardware devices in accelerators typically follow a
    naming convention
       This is a good thing
       Typical naming pattern = Sequence:device_type:instance
       Control system signals extend from this
   The class hierarchy (Accelerator / Sequence / Node)
    allows structuring with no name convention
   Relying on a name convention to specify a hierarchy is
    error prone
       You will likely end up with exceptions
       High maintenance
       How are Nodes Connected to Signals in
         A Node can have a “ChannelSuite” – a collection of
          control system channels associated with this node
             Each element of the suite is a handle-signal pair, where the
              handle is used in XAL, and the pair is created in the XML file
             Thus if a control system channel is changed, the XAL
              software does not have to change
             Example:
 <node type="DCH" id="DTL_Mag:DCH513" pos="3.345482" len=".0225"
     <ps main="DTL_Mag:PS_DCH513"/>
     <channelsuite name="magnetsuite">
       <channel handle="fieldRB" signal="DTL_Mag:DCH513:B" settable="false"/>
XAL Nodes Often have Transparent
Machine Interfaces

   Many node types have convenience methods to get
    information directly from the machine without using
    Channel Access
       Magnets: getField(), setField()
       BPMs: getXAvg(), getYAvg()
   All the connection details are hidden
   The connections are blocking however – so use with
      Getting a Channel from a Node

   Sometimes it is useful to work directly with channels rather
    than use the convienience methods
   Example
    accelerator= XMLDataManager.loadDefaultAccelerator()
    sequence = accelerator.getSequence(“DTL5”)
    node = sequence.getNode(“DTL_Mag:DCH513”)
    channel = node.getChannel(“fieldRB”)
    value = channel.getValueRecord().doubleValue()
Magnet Nodes

   Magnets are the primary means on beam manipulation
    in the transverse plane in accelerators
   Some issues concerning organization / class structure
       Permanent magnets, electro magnets
       Dipoles for bending, quadrupoles for focusing, sextupoles for
        chromaticity correction
       Main magnets, corrector or trim magnets
       Several magnets may be on a common power supply, magnets
        on a single power supply
Magnet Nodes

   Methods for getting and setting field levels
       Details of channel connection are taken care of
       getField() – returns the field (XAL uses MKS units , i.e. T/mn,
        where n = 0 for dipole, 1 for quad, etc.)
       setField(xxx)
       Also are methods for current etc.
Magnet Perspectives

   From the beam’s point of view:
       A magnet produces a field(s) of a certain multipole(s)
       May also include a trim power supply
       Usually field readback is the proper value to use (includes the
        effects of all power supplies connected to this magnet)

   From the machine/physicist or operator’s point of view
       You adjust a power supply to change magnetic fields
       Multiple magnets may be connected to a power supply
       Power Supplies have a setpoint that controls all magnets
        associated with them in both the real world and XAL
         Power Supplies and Magnets
                                Main PS

                                                       Trim PS

   The user interacts with power supplies to affect the beam – this may actually
    modify the field in multiple magnets though – be careful!!!
   More than one power supply may be connected to the same Magnet !
   Power supplies have limits (e.g. max. current, max. field)
        In XAL these limits are the most constraining of the power-supply itself, any magnet
         that may be connected to it, the cable/bus-bar , etc.
        The power supply contains limits that may be useful in model calculations
   Most of the power supply limit methods are aliased through the Magnet devices
Power Supplies
   Power Supplies have setpoints and readbacks (current
    + Field)
       A P.S. field value is an average of all magnets connected to it
   A trim power supply is usually attached to a single
       The field and surrent associated with the Trim methods are
        only the contributions of the Trim Power Supply
   See gov.sns.xal.smf.MagnetPowerSupply.java,
BPMs (diagnostic example)

   The most fundamental information a beam position monitor
    returns is the beam position
   getXAvg(), getYAvg() – returns the beam position as last
    measured by the BPM in meters
        All control system connection details are hidden.
        Note: Users usually deal with position in mm – so many applications
         convert to mm for input /output
   When collecting many BPM signals (e.g. to calculate the beam
    trajectory) you need to consider verifying that the results are
    correlated (i.e. all from the same beam pulse, or for the same
        Use low beam rep-rate
        Use the correlator tool to compare timestamps on the signals
Summary: Hierarchal View of an

   The organization follows the natural working view of
    the machine
   This structure facilitates the writing of general purpose
   Many applications can share the same accelerator
    browsing methods, look and feel.
   Provides a natural framework to build on
   Is configurable from a single data-source (e.g.
   This is a view of the hardware devices – not yet
    appropriate for a model
XAL Package Organization
(More than just Accelerator Hierarchy)

Item                    Package (Location)
Accelerator Hierarchy   gov.sns.xal.smf
Application Framework   gov.sns.application
Channel Access          gov.sns.ca
General Tools           gov.sns.tools
Scripts                 gov/sns/scripts
Applications            gov.sns.apps
Online Model            gov.sns.xal.model
Services                gov.sns.services

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