Re: info for tomorrow

["Guangliang Yang" <y.guangliang@physics.gla.ac.uk>]

Dear colleagues,



     Please find attached a document for the Gluex tagger magnet 
specification.



     About the tagger magnet drawings provided by the IHEP group, I have the 
following questions.



    1). what kind of steels are proposed to be used for the magnet yoke and 
magnet pole.  The quality of the steel will affect the magnet performance 
very much. If we use low quality steel to build the magnet, it will not be 
easy to meet the field uniformity requirement of the tagger (see attached 
document).



    2) Since the IHEP group decide to split each yoke into two layers, and 
also from their presentation, we find that the gap between these layers has 
significant effect on the magnetic field uniformity, so I want to know the 
precision of the machining they proposed, and also want to know if it is 
adequate to guarantee the field uniformity.



    3). I'd like to see a detailed finite element analysis for the vacuum 
chamber.  The drawing provided by IHEP reduced the number of the brackets 
used for compressing the O-ring and also counteract the vacuum forces, and 
they also move the external support for the vacuum chamber from the centre 
of the vacuum chamber to positions near the thin window, these will increase 
the forces applied to each rod used for compressing the O-ring and 
supporting the vacuum chamber.  The vacuum forces applied to the magnet are 
on the level of tens of tonnes, and also the forces needed to compress 
O-ring are very huge. So great cares should be paid to the O-ring 
compressing and vacuum chamber supporting brackets. A finite element 
analysis on this part is definitely needed.



   4). On the other hand, the forces applied to the brackets used to support 
the coils are relatively small. So possibly we don't need so many brackets 
for supporting coils. The weight of the each coil is around half tonne.



   5). The O-ring should be designed carefully, because the total length of 
the O-ring will be around 7 meters and once the magnet has bee assembled 
there is no access to the O-ring. So the O-ring should be defined very well. 
We don't want to have vacuum problem every year.



   6). Because the magnetic forces applied to a pair of the pole shoes is 
around 200 tonnes when the magnet is operating at 1.5 T, the pole gap 
reduction caused by these forces will be on the level of 100 to 300 microns, 
this will cause problem for the magnetic field distribution. Is there any 
calculation or finite element analysis for this gap reduction for the 
layered magnet design?



  7).  for the strong back support, in my original design, I just showed an 
idea about how it should look like. I didn't do any stress analysis for it. 
My question for this strongback support is, is it strong enough to support 
the whole tagger system? Again we need a stress analysis for that.



  8). For the power supply, bearing mind we have two identical magnets, so 
we need two power supply for each dipole magnet, or we need one big power 
supply for the two magnets and an additional balancing power supply to 
balance the filed. We also need an individual power supply for the 
quadrople.



 9). The most important thing is the field uniformity. We need a 
specification about how to get required field uniformity.



10). we need the materials specification for the vacuum camber and all the 
brackets. If stainless steel type 304 will be used to build the vacuum 
chamber, how to ensure that the machining will not alter the propertied of 
the steel too much. More clearly, machining and welding will affect the type 
304 stainless steel magnetic properties. (type 304 stainless steel is the 
cheapest one.  )



 If you have any comments on my questions, please send me a email.



Regards





Yang







----- Original Message ----- 
From: "Elke-Caroline Aschenauer" <elke@jlab.org>
To: <halld-tagger@jlab.org>
Sent: Sunday, April 29, 2007 4:07 PM
Subject: info for tomorrow


>
> Dear all,
>
> I booked a meeting room on evo called Gluex-Tagger password excited
> We will provide also the standard phone bridge for audio.
>
> To connect by telephone:
> 1.) dial:
> 800-377-8846 : US
> 888-276-7715 : Canada
> 302-709-8424 : International
>
> 2.) enter participant code: 39527048#  (remember the "#")
>
> We will start the meeting as already send around at 9.00 tomorrow morning.
> For the people being or comming to jlab we meet in room F324-325.
> This is the meeting room next to our offices.
>
> See you all tomorrow.
> bye elke
>
> p.s. Sergey please put your talk on the portal, so richard and Guangliang
>     can get it as well
>
>
>
>
> ( `,_' )+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=-+=
>  )    `\                                                  -
> /    '. |                                                  +
> |       `,              Elke-Caroline Aschenauer            =
>  \,_  `-/                                                    -
>  ,&&&&&V         Jefferson Lab                                +
> ,&&&&&&&&:       HALL-D 12C / F381       121-A Atlantic Avenue =
> ,&&&&&&&&&&;      Mailstop: 12H5          Hampton, VA 23664      -
> |  |&&&&&&&;\     12000 Jefferson Ave                             +
> |  |       :_) _  Newport News, VA 23606  Tel.:  001-757-224-1216  =
> |  |       ;--' | Mail:  elke@jlab.org    Mobil: 001-757-256-5224   -
> '--'   `-.--.   |                                                    +
>   _    |  |---' Tel.:  001-757-269-5352                             =
>     `-.___/     Fax.:  001-757-269-6248                              -
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>

Hall_D_Tagger_Spec.doc