The OPAL Discussion Forum

[Andrii Rusanov <arusanov AT hadronmedical.com>]

Hello everyone.

I'm a fresh OPAL user, so If my question will look odd to the
experienced users, please excuse me. My task is to simulate
propagation of a 70 MeV CW proton beam along a beam line which
consists of drifts and quadrupoles.

I'm trying to define the beam line with LINE command, but not sure
whether this is correct or not.

Let's assume the beam line is DRIFT(1.0 m) + QUADRUPOLE(0.25 m) +
DRIFT(1.0 m). The drifts are  implicitly given in OPAL-T, so I have to
define the beam line this way:

Q1: Quadrupole, L=0.25, K1=, ELEMEDGE=1.0;
BL: Line=(Q1);

But in this case, the program will know nothing about the length of
second drift space...

Or should I do like this:

D1: Drift, L=1.0;
D2: Drift, L=1.0;
Q1: Quadrupole, L=0.25, K1=, ELEMEDGE=1.0;

BL: Line=(D1,Q1,D2);

Another question regarding K1 quadrupole component.

Quadrupole chapter of the manual says: K1 is the normal quadrupole
component K1 = ∂By/∂x.
Dipole chapter says: K1 defines the field gradient index of the magnet
K1 = (1/Bρ)∂By/∂x...

I suppose for the quadrupole, K1 should be also  (1/Bρ)∂By/∂x. And if
OPAL follows MAD9 conventions,a positive K1 implies horizontal
focusing of positively charged particles. Am I right?

Any your comments are very appreciated. Thank you!
Andy Rusanov