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[Opal] Electrostatic Quadrupole

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  • From: Andreas Adelmann <andreas.adelmann AT>
  • To: opal AT
  • Cc: Norman Huang <norman-huang AT>
  • Subject: [Opal] Electrostatic Quadrupole
  • Date: Wed, 12 Oct 2011 09:54:47 +0200
  • List-archive: <>
  • List-id: The OPAL Discussion Forum <>

Hi Andreas,

We are trying to implement the analytic model of an electrostatic quadrupole by attaching an additional attribute 'EK' to OpalQuadrupole. This is the quadrupole coefficient, calculated from the electrode voltage and the aperture radius. 

Then we calculate the electric field vector:

Multipole::apply(const int &i, const double &t, Vector_T &E, Vector_t &B)
E(0) -= ENormalComponents[0] * R(0);
E(1) += ENormalComponents[0] * R(1);

Where ENormalComponents[0] equals to the value of the 'EK' attribute. 

The computed E vectors in the above code are getting passed correctly to BorisPusher::kick. But the actual algorithm for the momentum is too complicated to figure out by looking at the code. The problem for us now is that we don't know what unit or scaling factor is expected of E in the equation of motion; and a simple FODO test comes up with crazy results, so I think there's something wrong here...

It'd be great if you could share some insight!


(this is a repost on an email to me)

Dr. sc. math. Andreas (Andy) Adelmann
Staff Scientist
Paul Scherrer Institut WLGB/132 CH-5232 Villigen PSI
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