Re: possible pair spectrometer magnets (fwd)

[Alexander Somov <somov@jlab.org>]

Hello Richard,

Thanks a lot for your prompt reply.

I found some specifications of a photon beamline
in Phys.Rev.D vol.11,3, 1975 (W.Kaune, et al.).
"Inclusive cross sections for pion production
by photons using collimated coherent bremsstrahlung"

I don't know, there might be other experiments at SLAC
with different beamline design.

They use stronger, 0.7 T-m, dipole sweeping magnet
Actually there is only one sweeping magnet (as far as
I've understood) before their spectrometer. Another
one is used after a target before a beam monitor
detector (secondary-emission quantameter, SEQ).

We can discuss details during the next meeting. I am
preparing some plots now.

Cheers,
       Sascha



On Wed, 4 Jun 2008, Richard Jones wrote:

> Alexander Somov wrote:
> > Hello Richard,
> >
> > Obviously I don't want to spend much time on optimizing
> > beam line components and leaving them out from the current
> > design.
> >
> > However, I get the feeling that the current design is not
> > optimized:
> >
> > where do you get 0.2 T, 0.5 m long magnets from (do we have them
> > in JLab) ? They seem to be rather weak...
> >
> > Just a simple example (based on p = 0.3 H R): 6 GeV electron
> > flying along the beam is deflected by ~0.13 cm after the magnet
> > and has a deflection angle sin_theta ~ 5e-3, i.e. it would go
> > directly to the target (p = 0.3 H R). Most of low energy electrons
> > will interact with a beam pipe after the collimator cave.
> > There are quite a few electromagnetic interactions as there
> > is no vacuum pipe before the second sweeping magnet (~3% rad.
> > length). Do we need this background at all?
> >
> >
> > Cheers,
> >        Sascha
> >
> >
> Sascha,
>
> The magnetic field integral of the sweep magnets has not been
> optimized.  I don't think that the SLAC publication stated what the
> sweep fields were.  At any rate, we postponed that optimization.  The
> number and order of the elements was taken from the SLAC beamline.  You
> are right, it is the field integral of those sweeps that needs to be
> optimized.  Once that is done, we can write a spec for the sweep magnets.
>
> Richard Jones
>