/**
*
*
* <h2>Back-propagates the Defining State of the Probe Object</h2>
*
* <p>This method uses the same basic algorithm as in <code>EnvelopeTracker#advanceState()</code>,
* only the probe object is back-propagated. The method utilizes all the space charge mechanisms
* of the base class <code>EnvelopeTracker</code>.
*
* @param ifcElem interface to the beam element
* @param ifcProbe interface to the probe
* @param dblLen length of element subsection to retract
* @throws ModelException bad element transfer matrix/corrupt probe state
* @author Christopher K. Allen
* @since Feb 9, 2009
* @see xal.model.alg.EnvelopeTracker#advanceState(xal.model.IProbe, xal.model.IElement, double)
*/
protected void retractState(IProbe ifcProbe, IElement ifcElem, double dblLen)
throws ModelException {
// Identify probe
EnvelopeProbe probe = (EnvelopeProbe) ifcProbe;
// Get initial conditions of probe
// R3 vecPhs0 = probe.getBetatronPhase();
// Twiss[] twiss0 = probe.getCovariance().computeTwiss();
PhaseMatrix matResp0 = probe.getResponseMatrix();
PhaseMatrix matTau0 = probe.getCovariance();
// Remove the emittance growth
if (this.getEmittanceGrowth()) matTau0 = this.removeEmittanceGrowth(probe, ifcElem, matTau0);
// Compute the transfer matrix
// def PhaseMatrix matPhi = compTransferMatrix(dblLen, probe, ifcElem);
PhaseMatrix matPhi = compTransferMatrix(dblLen, probe, ifcElem);
// Advance the probe states
PhaseMatrix matResp1 = matPhi.times(matResp0);
PhaseMatrix matTau1 = matTau0.conjugateTrans(matPhi);
// Save the new state variables in the probe
probe.setResponseMatrix(matResp1);
probe.setCurrentResponseMatrix(matPhi);
probe.setCovariance(new CovarianceMatrix(matTau1));
// probe.advanceTwiss(matPhi, ifcElem.energyGain(probe, dblLen) );
// phase update:
// Twiss [] twiss1 = probe.getCovariance().computeTwiss();
// R3 vecPhs1 = vecPhs0.plus( matPhi.compPhaseAdvance(twiss0, twiss1) );
// probe.setBetatronPhase(vecPhs1);
/** sako treatment of ChargeExchangeFoil */
treatChargeExchange(probe, ifcElem);
}
