Problem 1530

Summary:	error in the magnetic field for Bx to control the track along y
Product:	Geant4	Reporter:	Fada Guan <guanfada>
Component:	geometry/magneticfield	Assignee:	John Apostolakis <John.Apostolakis>
Status:	RESOLVED WORKSFORME
Severity:	critical
Priority:	P5
Version:	9.6
Hardware:	All
OS:	All
Attachments:	spot

Description Fada Guan 2013-10-25 21:41:21 CEST

I used two uniform magnetic fields to bend proton beam in x and y directions for proton spot scanning.

For example, I want to deliver a spot on (-10 cm, -10 cm) on one plane.

In Geant4.9.5.p01, the proton spot position is correct as specified.
However, in Geant4.9.6.p02, for the same problem with the same source code, the spot position is away from the specified position in y direction. It was delivered to (-10 cm, -14 cm).

Please see the attached two pictures.

Who can help check the source code of G4UniformMagField.

Thanks a lot!

Fada Guan

Comment 1 Fada Guan 2013-10-25 21:49:14 CEST

Created attachment 241 [details]
spot

      http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2013/10/25/12.47-7864-_guanfada_Desktop_9.5.png
      http://hypernews.slac.stanford.edu/HyperNews/geant4/get/AUX/2013/10/25/12.47-80530-_guanfada_Desktop_9.6.png

Comment 2 Fada Guan 2013-12-25 00:36:42 CET

I tested the same problem using Geant4.10.0, and the result was correct.
Hence, I believe it is only the Geant4.9.6 specific problem.

Comment 3 Fada Guan 2014-01-24 18:02:05 CET

I guess it is due to the MSC algorithm in magnetic field.