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Solenoid field effect on the particle track theta! [message #9205] Mon, 17 August 2009 14:09 Go to next message
Huagen Xu is currently offline  Huagen Xu
Messages: 9
Registered: May 2009
Location: Juelich
occasional visitor
From: *ikp.kfa-juelich.de
Dear solenoid field experts,

Here I'd like to escalate a problem which I came across during the simulation for luminosity monitor detector. The problem is the solenoid field would bend the particles emitting from IP toward beam axis, for the worst case, the particle track theta would be shifted about 0.5mrad@1.5GeV/c for antiproton. Attached is the MC points plot on the 4 luminosity sensors viewed on xy plane with field and with no field. This effect absolutely would impact the theta resolution which was determined by the luminosity monitor detector.
Is this effect is normal or abnormal for solenoid field?

Best Regards!
Huagen Xu
IKP, Juelich
Re: Solenoid field effect on the particle track theta! [message #9206 is a reply to message #9205] Mon, 17 August 2009 17:57 Go to previous messageGo to next message
Jost Lühning is currently offline  Jost Lühning
Messages: 4
Registered: March 2006
occasional visitor
From: *gsi.de
Dear Huagen Xu,

the distortion of the circle is due to the rectangular shape of the aperture which we need in the downstream door of the solenoid. In the aperture the field component in y-direction is much bigger than in x-direction (see attachment).

Best regards,
Jost Luehning
Re: Solenoid field effect on the particle track theta! [message #9217 is a reply to message #9206] Tue, 18 August 2009 15:59 Go to previous messageGo to next message
Inti Lehmann is currently offline  Inti Lehmann
Messages: 3
Registered: September 2005
Location: Glasgow, UK
occasional visitor
From: *physics.gla.ac.uk
Hi Huagen and Jost,

That effect seems a stronger effect to me that I would have naively expected from the slight asymmetry of the door iron. In particular as we are talking about the field only 1.5cm off the beam axis, right?

Another thing which strikes me odd is that the deviation in theta seems more (at least double) than the rotation in phi. It also seems to bend the tracks to lower theta only. (It is difficult to read from the plots, but I would take ~5.5 without field, and 0.5-1deg less with field, right?) I'm not sure, if I am just confused, but wouldn't that mean, we had to have a circular field component larger than the radial one? Maybe I'm just lost....

Could you check what happens to protons? Will this be opposite and equal?

As I understand you only switch the solenoid on and off. What happens if you add a dipole field? Ideally the whole thing should just be shifted, but...

Cheers,
Inti
Re: Solenoid field effect on the particle track theta! [message #9219 is a reply to message #9217] Thu, 20 August 2009 09:57 Go to previous message
Jost Lühning is currently offline  Jost Lühning
Messages: 4
Registered: March 2006
occasional visitor
From: *gsi.de
Hi,

there are 2 files attached showing tracks in the x-y-plane at z=900cm (there is the end of my FEM-model).
In the second file we can see a symmetry for protons and antiprotons (as expected, so the model should be okay in this regard).

Jost
  • Attachment: Tracks1.pdf
    (Size: 22.52KB, Downloaded 276 times)
  • Attachment: Tracks2.pdf
    (Size: 15.62KB, Downloaded 260 times)
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