Bug #1332

Incorrect transport of time-energy phase space in Optics

Added by Rogers, Chris almost 9 years ago. Updated almost 9 years ago.

Target version:
Start date:
16 August 2013
Due date:
% Done:


Estimated time:
New Issue


While working on #1293, I found that the time-energy transport in the optics routines is incorrect. The polynomial map seems to be expanded about 0 not about the reference particle trajectory.

Somewhere in the TransferMap bureaucracy, should do


to transform into coordinates relative to the reference trajectory (could be in the PolynomialMap or in the TransferMap, it used to be done in the TransferMap).


Updated by Rogers, Chris almost 9 years ago

  • Status changed from Open to Rejected

Ack, I made a maths error - my mistake... looks okay.


Updated by Lane, Peter almost 9 years ago

This is likely still a bug. The class that would do this is PolynomialTransferMap in it's Transport() function. I took out the V-V_{ref} because it didn't seem to be transporting V properly. The other relevant code is in PolynomialOpticsModel::CalculateTransferMap() where the maps are generated. The input and output vectors that are used to fit the polynomial are not relative to the reference trajectory. It sounds like I should have adjusted this code instead of removing the code in the Transport function.


Updated by Rogers, Chris almost 9 years ago

Well, think about it carefully. I have to confess, given you are having trouble with time recon I would at least look at this code carefully...


Updated by Lane, Peter almost 9 years ago

I recently finished a mapper that creates residuals between virtual detector hits (MC truth) and "hits" produced by transporting the primary to the virtual detector locations using the polynomial maps. I ran some tests on two geometries: 1) a 7.8 meter drift with virtual detectors instead of TOF detectors, and 2) the same as #1 except with three quads right before the TOF1 virtual detector (where the quads would be in step 4).

I first generated residuals using absolute phase space vectors. I then modified the code to calculate the polynomial maps using phase space vectors relative to the reference particle and transport the vectors again relative to the reference particle.

I observed no significant difference between the absolute and relative versions of the code for both geometries, with all but the transverse momenta residual RMS being identical. The transverse momenta experienced a 10% drop between absolute and relative at TOF0, but those residuals are on the order 1e-7 (i.e essentially zero).

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