Hi Martijn - many thanks.

It looks like the radial evolution is very similar at the + and - ends.
The + end has a slightly higher Bz field 0f 0.005T if I interpret
correctly. Is this due to the one less turn on the -ve end?

Thanks,

Dave.

________________________________

From: dr.ir.mulders@gmail.com [mailto:dr.ir.mulders@gmail.com] On Behalf
Of Martijn Mulders

Sent: 16 February 2009 10:40

To: Dave Cockerill
Subject: Re: VPT effects in CMS as a function of angle to field


Hi Dave,

I extracted the values from the default (3.8T) TOSCA field map.
The detailed numbers ( R[cm]   Br[T]   Bz[T] ) are in
 http://home.cern.ch/~mulders/minus.txt   (for z=-339 cm)
 http://home.cern.ch/~mulders/plus.txt      (for z=+339 cm)

Some simple plots are attached, and linked here:
 http://home.cern.ch/~mulders/Br.png
 http://home.cern.ch/~mulders/Bz.png
 http://home.cern.ch/~mulders/tanB.png

B is parallel to the z-axis for R=0, and the angle increases almost
linearly to about 2.2 degrees at R=171 cm) ... does that agree
with expectations?

Cheers,
  Martijn


On Fri, Feb 13, 2009 at 10:40 AM, Dave Cockerill
<Dave.Cockerill@cern.ch> wrote:


       Hi Martijn,

       thanks for coming around to discuss the VPTs.

       With FIELD ON, the z value is +-3390mm.
       Max VPT radius 1.71m

       Cheers,

       Dave.

       ________________________________

       From: dr.ir.mulders@gmail.com [mailto:dr.ir.mulders@gmail.com]
On Behalf
       Of Martijn Mulders

       Sent: 12 February 2009 21:26

       To: Dave Cockerill
       Subject: Re: VPT effects in CMS as a function of angle to field


       Sounds good. See you tomorrow,

       Martijn


       On Thu, Feb 12, 2009 at 6:52 PM, Dave Cockerill
<Dave.Cockerill@cern.ch>
       wrote:


              Thanks - how about 10.00 at my office - 40-1-b20?

              Dave.

              ________________________________

              From: dr.ir.mulders@gmail.com
[mailto:dr.ir.mulders@gmail.com]
       On Behalf
              Of Martijn Mulders
              Sent: 12 February 2009 18:27
              To: Dave Cockerill
              Subject: Re: VPT effects in CMS as a function of angle to
field



              Hello Dave,

              Sure; my agenda is fairly open tomorrow. We could meet
              for a coffee in building 40 any time during the morning
if
              that works for you (?)

              Martijn


              On Thu, Feb 12, 2009 at 5:59 PM, Dave Cockerill
       <Dave.Cockerill@cern.ch>
              wrote:



                     Dear Martijn,

                     Austin suggested I contact you concerning the
magnetic
       field map
              in CMS.

                     I am the ECAL Endcap Project Manager. We have 7324
VPTs
       at
              varying
                     angles at each end of CMS, at a |z| of ~3.3m.
                     We see a subtle differnece in response as a
function of
              (supposed) angle
                     to field, between the -ve and +ve ends.

                     Would it be possible to meet to discuss what field
       information
              you have?

                     Many thanks,
                     Dave Cockerill.