Re: colli cave question

[Jim Stewart <jstewart@jlab.org>]

Hello Richard

We need to check with the radiation protection people here but activation
is probably not an issue. The magnets came from Fermilab and were selected
for there radiation hardness. They irradiated one magnet using a co source
with several Gigarads.

The magnets are made using a lot of iron and we can pack the gaps with
stainless steel so maybe they are good enough for the muons. The magnet
blocks themselves are Type 8 strontium ferrite (mostly O and Fe).


   ---------------------------
   |                         |
   |        iron ?           |
   --------------------------
   |       | dipole |        |
   |       |   o    |        |
   |       |        |        |
   --------------------------
   |                         |
   |                         |
   ---------------------------


The biggest concern is the real estate. The magnets are 3.683m long. If
the magnet replaces the sweep magnet and the iron absorber then we still
loose 1.183 m. To gain this we would need to remove something. I guess it
requires a study.

Jim

On Thu, 22 May 2008, Richard Jones wrote:

> Jim,
>
> This is certainly worth considering.  The main concern that I see right
> away is the real estate.  Right now the sequence following the first
> collimator is 50cm (sweep) + 200cm (iron) + 100cm (concrete) + 50cm
> (gaps) = 400cm.  The iron is there to stop muons from muon pair
> production in the primary collimator and from pion decays.  I think you
> still need the concrete in the forward direction to attenuate the
> forward neutron flux.  All of this could be simulated.
>
> I suppose the permanent magnets are some ceramic material, right?  Any
> rare earths that might activate?
>
> Richard Jones
>
> Jim Stewart wrote:
> > Hello Richard
> >
> > I was wondering if it would be reasonable to take one of the permanent
> > magnet dipoles and use it as the first sweep magnet? The field is large
> > with 1.5TM and we can put spacers in the gap to reduce the aperture to a
> > 2cm hole. If you pack the whole thing in concrete then you still absorb
> > neutrons.
> >
> >   -------------------------------
> >   |                             |
> >   |         concrete            |
> >   |                             |
> >   ------------------------------
> >   |         | dipole |          |
> >   |         |   o    |          |
> >   |         |        |          |
> >   -------------------------------
> >   |                             |
> >   |                             |
> >   |                             |
> >   -------------------------------
> >
> > Maybe you need a concrete block at the back.
> >
> > This may even have enough field to not need a second magnet.
> >
> >
> > Advantages:
> >    We have the magnet.
> >    No active parts.
> >    Nothing to fail.
> >
> >
> > Dis-advantage
> > The magnet is 4m long.
> >
> > Is this worth considering?
> > Jim
> >
> >
>
>
>