-------- Original Message --------
Subject: Predicted forces on E614 coils
Date: Sat, 02 Jun 2001 16:55:25 -0700
From: Michael Barnes 
Organization: TRIUMF
To: John Macdonald 
CC: drgill@triumf.ca, Ewart Blackmore ,Nathan Rodning
,Gary Wait 

John,

The results of force calculations that both Dennis and I previously
carried out on the coils were incorrect -- the finite element mesh were
not fine enough to accurately determine these forces.
After talking to the authors of the code, Vector Fields, I have carried
out some further Post Processing of the simulation results. The Post
Processing takes a lot of CPU time, i.e. approximately 25 hours CPU per
simulation -- but the results should be considerably more accurate.

Here are the results of force calculations for the assembly of 12 coils,
carried out as a function of displacement (dZ) of the coils:
dZ         Force in Z direction
+0.0             0
+0.1cm        +943 N (96 kg) -> 960 kg/cm
+0.5cm        +4717 N (480 kg) -> 960 kg/cm
+3.0cm        +28278 N (2890 kg) ->960 kg/cm

The force calculation now gives a predicted force which is monotonic
(this was previously not the case), and is approximately 960 kg/cm
displacement in Z, at a current of 114 A.

The force is positive, for a positive displacement in Z. Hence, when the
coils are centered in the iron this point is an unstable equilibrium.

Please note that the above forces are for a current of just under 114A.
At a (full) current of 245A I would anticipate the force on the assembly
of 12 coils would be approximately 4.7 (i.e. [245/113.85]^2) times
higher than shown above, i.e. 4500 kg/cm displacement in Z.

Best regards,
Mike Barnes

Created for the The Center for Subatomic Research E614 Project Projects Page.

Created by The CoCoBoard.