[Halld-cpp] CPP Meeting minutes 2/28/2018

David Lawrence davidl at jlab.org
Wed Feb 28 10:50:43 EST 2018


Hi All,

  Today turned out to not be a great day for most people to meet. It ended up being
just Ilya and I. We did have a discussion on what we would like to do with the chamber
and any remaining beam opportunity. Here are the ideas we came up with so others
may comment:

1. Change the gas mixture to 90/10. We have not yet spoken with Tom/Scot on how
difficult this is. We will do that this week.

2. Change the scintillator paddle position to be closer to the beam line.

3. Machine a hole in the 10.75” steel plate and center it on the beam line. This will
give a much closer approximation of beam conditions. The hole should be round with
a diameter between 6.6cm and 8cm. According to my notes, the dead region in this
chamber is 3.4” in diameter (=8.64 cm). Studies from last year set the beam hole
size to 2cm smaller in diameter compared to the dead region so if we follow that,
the hole size should be ~6.6 cm. The final design parameter for the dead region from
those same studies was 10 cm with a beam hole of 8cm diameter. 

One option is to try and do both by cutting the smaller hole, taking data, and then cutting
the larger hole. Alternatively, we could cut the larger hole and then make a plug or mask
to get data with the smaller hole size.
 
The chamber is currently out of the beam. There may be opportunity on Monday to 
reinstall it along with any of these modifications. There is also a possibility they will
extend the run for one more week.

Rory and Elton: please think about this and let us know what you think and if there are
any other things you would like to do during the remainder of this run period.

Regards,
-David

-------------------------------------------------------------
David Lawrence Ph.D.
Staff Scientist, Thomas Jefferson National Accelerator Facility
Newport News, VA
davidl at jlab.org
(757) 269-5567 W
(757) 746-6697 C


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