From GlueXWiki
Jump to: navigation, search

February 23, 2012 FDC meeting


  1. Production Construction Tracking (Dave)
    • Production status
    • Testing at Blue Crab (Lubomir)
  2. First package tests FDC ELOG (Beni, Lubomir)
  3. Engineering update[1],cooling manifold (Bill)
  4. Electronics update (Nick)
  5. Other


Participants: Bill, Dave, Nick, Elton, Mark, Simon, Beni, and Lubomir.


- Dave: Deadened the first wire plane of package 3 with the larger diameter using the procedure with increased current and the same time as for the smaller diameter, but adding extra polishing cycle. Working on four cathodes now and on the last wire frame for the third package. One more cathode to finish the package. There's not much space to start the fourth package. Testing the chambers of the third package will be the bottleneck since it takes time to flush the chambers with gas. We will try to use weekends for that if possible. Third package was started partially end of November, so less than three months ago. Still we need to work on the subsystems for both package 2 and 3.

- First cell of the third package was assembled yesterday, flushed with gas over night and today we were able to apply HV which by now is already the nominal one. The dark currents are very low. If it holds over the night we will assume that the wire deadening procedure works and we will continue tomorrow with the deadening of the next wire plane. Tomorrow also we will test the first cell and if everything is OK will try to assemble the second cell so that we can use the weekend to flush it.

First package testing

- Beni showed results posted in the new FDC Elog linked above. After all the gas problems have been fixed/identified, now the main concern is the chamber efficiency. The only time we had full efficiency was in cell#3 when it was leaking through the hole in the exhaust tube and was taking most of the gas flaw, but not clear what fraction of the total 200ccpm at that time. There are also two groups of 4 channels not working, but the problem is not in the chamber; Beni will investigate it.

- Obviously this is a gas problem and we discussed different ways to approach it. Beni: wanted to install the two new mass flow controllers that allow to have 500ccpm each, but before that we will install the oxygen sensor. Lubomir: we have to make sure there are no air bubbles between the cathode and ground planes; for that we will incline the package so that the supply is at the lowest and the exhaust at the highest point. For the electrons to be attached to the oxygen a third molecule is needed, it could be CO2 but water is 10 times more efficient than CO2. Water may come inside from the kapton that may have 1-2% water due to to foil aligning procedure. The foils stay in direct contact with water for at least 16 hours. Depending on the results for the oxygen content we will decide if we need moisture measurements (to 0.1% precision).


- Bill showed models (attached above) of the cooling system manifolds and their attachment to the package; four manifolds per package. Discussed what is the best material for the holding brackets. Bill offered two options, aluminum or G10, but prefers aluminum. Elton after checking the radiation lengths (what matters for the photon conversion): G10 is factor of 2 better if sizes are the same. Bill will look for the best solution.

- There was a long discussion how to survey the FDC packages outside and inside the magnet. Bill explained his ideas about the fiducial points. It will be a ball attached to the gusset ring with a post, holder and carbon-fiber rod. It can be surveyed outside of the magnet. For the inside survey we need optical targets. Precision will be about 0.5mm. Beni proposed to use something more rigid than the carbon fiber rods. Elton: if we can't get precision similar to the chamber resolution of 0.2mm then the survey will not help. Bill: this is what we can get with such light frames; due to deformations the positions will be different when inserted in the magnet. Bill wants to design g10 cylinders and rods between the packages firmly attached to the gusset rings so that such deformations are minimal. Thus, even if we don't have very precise positions from the survey we will make sure that the positions of the packages are stable and one can do the alignment with the data.


- Nick: all the pre-amp cards are assembled and now with Cody.