beamline

[Jim Stewart <jstewart@jlab.org>]

Dear Richard

Could you look this over? As I just started I suspect I have overlooked a
lot.

I wanted to start with something easy so I decided to look at the beamline
in the tagger hall. Just for the hell of it I decided to start at the 10"
pipe in the tagger hall.

This is a 10" schedule 40 stainless steel pipe terminated with a 13-1/4"
conflat flange. It sticks out from the wall 1' and when we receive the
hall it will be blanked off.

10" is really big so we should immediately reduce down. I propose we mount
a 1' long reducer from 13-1/4 to 4-5/8" cf made with 3"OD stn.stl. tube.
3" is a convenient size pipe as it is self supporting. This helps later.


This is followed by a 4-5/8" tee which we need to connect a pump.
On the side flange we can connect a zero length reducer to go to 2-3/4" cf
and then a hybrid adapter to go to an NW-40 ISO-K fitting. From ISO-K
everything is easy. We need 1 tee with a valve so we can connect a
portable JLAB roots pump when we want to pump down the system. Then
another tee for a convectron pressure gage ($360 good down to 10^-3
Torr) and a valve to a pump station. Tim recommends a pfeiffer turbo pump
station. The turbo pump stand costs $5.5K but is a self contained plug and
play unit with minimal maintenance. It is also clean so there are no
worries about getting oil where we don't want. The pfeiffer turbos with
a DIN40 flange have a pumping speed of 33l/s. If we go to a DIN63 it goes
up to 59 l/s.

Back to the beamline.

After the tee comes a short metal bellows. The MDC 4-5/8" bellows has a
free length of 7-1/4".

We are now 1'+1'+7-1/4+7-1/4 = 38.5 or 3' 2-1/2" from the wall. I hope
this is OK.

Then we can put a straight piece of 3"OD pipe up to the permanent magnet
dipole.

The upstream end of the permanent magnet is 42'-8 1/4" from the downstream
wall. I hope the means the start of the iron. The iron is 145" long and we
need about 3" to get to the vacuum flange. The pipe in the magnet is an
elliptical 3-1/2" by 1-1/2" pipe. 3 1/2" is too big for the 4-5/8" cf. As
we don't care about pumping speed we can make an adapter to go from the
elliptical to 4" OD pipe then adapt to 3inch OD pipe and put the 4-5/8" cf
on the end of the 3" pipe. 4" is comfortable for this. We anyway have to
cut and weld on the elliptical beam pipe so this is not too much work.

Assuming all the above then the downstream flange of the permanent
magnet is 42'-8 1/4" - 145" - 4" = 363.25 or 30'-3 1/4 inches from the
downstream hall wall. Just to be sure we can put another 4-5/8" bellows
here to make it easy to connect the flanges.
The beam pipe is then 363.25 - 38.5 -7-1/4" = 307.5" or
25'-7 1/2" long. I guess we need 3 supports going to the floor.

To keep things symmetric we should do the same on other side of the
dipole. Assume 4" to adapt to 4-5/8 cf. Then I would put a zero length
reducer on to go to 2-3/4". This changes diameter so you need to take up
the vacuum force. I guess we can add a bracket to the dipole iron and use
the dipole support to take up the force.

We can mount a 2-3/4" flexible coupling onto this which takes up 3-1/2".
Then I would put a gatevalve and what I am guessing is 7' of 1-1/2" pipe.
This should get us close to the tagger vacuum vessel. This is where I run
out of concrete number. The 1-1/2" pipe 7' long will have a conductance
for air at 20C of about 1.8 l/s so it will give us a bit of a differential
pumping system.

This has no windows up to the goniometer. Is this what we want?

I am using conflat because I like conflat. Once you leak chase the
connections you can forget about them forever.



Jim