sPHENIX EMCal discussion

[Edouard Kistenev <kistenev AT bnl.gov>]

It’s a good idea to try and see if there are any special conditions limiting scintillator life. The acute vs chronic dose difference in scintillators (is it the same in human?) is probably the only observation helpful to us (less effect of beam losses) but it is anyway at the worst is x2. Nevertheless - the idea to test it ourselves is great, we have plenty of samples and it is very easy to deconvolute effects of SiPM damage from scintillator damage - use few tiles measured in the test stand, expose with SiPM on or off the tile etc. My extra 2 cents are about EMC. If lightguides are of PMMA - expect a lot of damage. But it may be of little relevance, the actual problem can be with epoxy outgassing due to radiation exposure and PMMA (cladding) chemistry (mechanically epoxies are extremely rad hard).  Even without radiation the effect of powder filled epoxy on fiber cladding (epoxy shrinks when cured pressing the W particles into fiber coating) is not really documented (not too difficult - just build a module of ~5x5 mm2 in crossection with a single fiber, do fiber transmission measurements before embedding and after, then irradiate it).

As for polystyrene based scintillator - I would not say that in 2016 500 CMS authors added very much to what was published in 1997 by three detector physicists  (at least one of the three is well known to most of us - Vitaliy Semenov) https://link.springer.com/content/pdf/10.1007/BF02758996.pdf  from Russia.

Edward

On Jul 20, 2017, at 8:08 AM, Craig Woody <woody AT bnl.gov> wrote:

Hi John,
  Interesting. I'm a bit surprised at the magnitude of the effects a rather low dose. If I'm interpreting their results correctly, they see a decrease of ~ 20% for their PS scintillator for a maximum dose of ~ 30 Krad (Layer 7 in Fig. 3). That's not a very high dose. I'm not sure about the position dependence of the integrated doses we reached in PHENIX, but I know they were ~ 10's of Krad near the beam pipe. It's probably worth have a closer look at those numbers and see what it would be in the vicinity of the the Inner and Outer HCAL tiles. Also, we're planning to do some radiation damage studies of the injection molded acrylic light guides that we plan to use for the EMCAL, so we could also test some of the HCAL tiles at this time as well.

Cheers,
Craig

On 7/19/2017 9:23 PM, John Haggerty wrote:

It's been asked by one of our reviewers, so I was looking at the literature on radiation damage in plastic scintillator.  This paper is interesting and close to our situation in the HCAL:

https://arxiv.org/abs/1608.07267

One of the authors of this paper is going to be here for the Sambamurti Lecture on Monday, August 7, we could pick his brain.

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