sPHENIX EMCal discussion

[eric thorsland <ericthorslandwork AT gmail.com>]

Hello Oleg,

    Thank you for the links and the concern for the fibers in the high alcohol content blocks.  

    We have done many tests on the fibers with ethanol and have previous experience with some large calos and PMMA clad fibers in years past as well here at NPL.  I have tested fibers physical properties in pure ethanol, soaking overnight both at RT and elevated temps up to 50 C. There was no physical change to the cladding or fibers.  We instrumented a block with thermocouples several months back when we saw a few blocks with poor areas of scintillation to measure temperature during curing. The high temperature was 39-40 C depending on location during the cure.  The block in its present size does not go near the threshold temperature  for fiber damage during curing.  We then cooked the block by intent and verified that damage can happen at elevated temps over ~60 C.  Long exposure to above 50 C is also not recommended.  

    We did discover that the blocks with sections of damaged fibers were blocks that were repaired due to poor potting, the blocks had been patched and to speed curing the blocks were then put in an air oven presumably set to 45 C. The program was altered unintentionally and ran to near 100 C. This was the cause of the damage in the patched locations but the already potted areas actually continued to scintillate in most cases. The W powder may have acted as a sink for the heat there. 

    The end test and the most important, is the blocks made with the 35 g of ethanol have been tested for scintillation an all do so and match the non ethanol blocks.  We will compile data and send this to the list soon. 

    We have cut open several 35 g ethanol blocks that have cured for several weeks. There is potentially a residual odor of ethanol but the saw also heats the fibers enough you can smell cut plastic.  There were no bubbles or soft areas in any blocks. 

     The only remaining question would be if they pass a similar destructive test as previous blocks and we are preparing samples to ship today for that test at BNL. 

      Because of the physical properties of the HC Starck powder, the tight packing, reliable potting was not achieved until the higher amounts of ethanol were added to the epoxy at the time of potting.  With a large sample already showing no effect on fiber function or block machining it would indicate we are below the threshold of any change in the blocks properties other than the ability to make many of them reliably. 

     Thank you for the help along the way and the early lessons in production from my visit to UCLA, then and now you are always helpful. 

        Best, Eric T.   

On Wed, Jun 26, 2019 at 11:52 AM Oleg Tsai <tsai AT physics.ucla.edu> wrote:

John,

   I did a quick search about compatibility of PMMA (cladding on fibers) with chemicals,
in general it is not recommended to use alcohol and looks like at elevated T (during epoxy cure) it may be quite damaging (not clear what type of damages),
https://urldefense.proofpoint.com/v2/url?u=https-3A__marketing.industrialspec.com_acton_attachment_30397_f-2D006b_1_-2D_-2D_-2D_-2D_acrylic-2Dpmma-2Dchemical-2Dcompatibility-2Dchart-2Dfrom-2Dism.pdf&d=DwICaQ&c=aTOVZmpUfPKZuaG9NO7J7Mh6imZbfhL47t9CpZ-pCOw&r=ori09ca_gL08OyTCxMe8TXbcXP_40hDLclg-iQYISug&m=fJ0pU0IND-sA9gam_NumoYzC8ySg5rXC6e4JNZOm59Q&s=f40pBjDTOBeJn48uPNvsEwbc7GhVjLs0TmauIca04lw&e=
it is concerning, may be we should look at information from some other sources
Oleg

----- Original Message -----
From: "John Haggerty" <haggerty AT bnl.gov>
To: sphenix-emcal-l AT lists.bnl.gov
Sent: Tuesday, June 25, 2019 4:34:39 PM
Subject: [Sphenix-emcal-l] Powder review

We will be reviewing the plan for UIUC procurement of tungsten powder
for the EMCAL tomorrow morning at 9am in 2-219 and on BlueJeans:

> https://indico.bnl.gov/event/6345/

--
John Haggerty
email: haggerty AT bnl.gov
cell: 631 741 3358
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