[Halld-pid-upgrade] DIRC meeting tomorrow at 11 am

[Michael Williams]

Going from the cylindrical mirror geometry of FDIRC
to the flat mirror (albeit segmented) geometry of GlueX
does remove the focussing of the FDIRC design
and re-introduces the pin-hole "focussing"
as it was present in the BaBar DIRC.
The mirror segmentation "only" helps to reduce the MaPMT area,
using the vertical shift as described in lines 79-81.

— this comment does not require my action, right?

Doesn't seem like it.

Figure 3: middle flat mirror (in yellow) - what is the purpose
of this mirror? Given that there is the fused silica to water
transition before, changing photon directions, which renders
the continuation of the 30 degrees top wedge slope pointless.


Does he mean that no photons should hit the mirror that continues the top of the old wedge?  You and/or John can check how often photons hit there (I think it's not very many).

Fig. 3: Though it is no doubt true that a water filled camera is less expensive than fused silica, the magnification at the interface is a mixed blessing.
Our experience with long term reflectivity of mirrors in water is less optimistic than the test you describe in ref 9. Have you done accelerated tests (at high temperature)?

Here I'd remind him that we will use ordinary distilled water.

2. In the following pic the referee asked to add labels for the DIRC boxes and camera.
<2016-12-21_12-20-01.png>

Are you asking then for whoever made this plot to add the labeling?


3. Referee suggested to add PID performance plots (currently I have the ones below) for the forward part - I’m not sure I know where to take them from.
<2016-12-21_12-20-46.png>

Presumably there are some official ones to use that have been previously shown in public.

4. Comment is “slide vertically - swap” for the sentence:


The support structure of the DIRC will allow the pairs of bar boxes to slide vertically out of the active area of the detector for experiments requiring minimal material budget in front of the forward calorimeter.


I think in this sentence "slide vertically" can not be substituted by “swap” here. But I’m not sure.

I think "swap" is OK.

Mike



Thank you and have a nice holidays!!
Best regards,
Maria



On Dec 15, 2016, at 12:44 PM, Justin Stevens <jrsteven at jlab.org<mailto:jrsteven at jlab.org>> wrote:

Hi All,

We'll have a DIRC meeting tomorrow at 11 am.  You can find the agenda at https://halldweb.jlab.org/wiki/index.php/December_16,_2016_PID_Upgrade.

-Justin
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