Minutes of the CPT Meeting, May 8 2014, 11:00 am PST

IEEE abstract (Cristian) :
Discussed first version of the summary. Main comments were to reduce the level of detail and the number of subsections
in the summary text. Meanwhile, second version has been circulated.
Please check and comment TODAY - to be submitted tomorrow at the latest.
Open questions : Is the titel too pretentious. Need to add qualifyer (R&D for ..).
Cristian mentioned that there is a dedicated LHC session.
Do we submit there ?

Hardware delivery and LYSO stack construction :
- Laser still with customs, we hope for the best.
-> Laser saftey training for those who do not have it.
-> Can we prepare the room already to be compliant with CIT saftey rules. The laser is classified class 3.

- Tungsten plates received (28, for one Shashlik cell). Matching TYVEK sheets to be recovered from the package.
  Paul Debbins will send TYVEK side covers and aluminum cell wrapping for one cell.

- Need to get four WLS fibers from Renyuan. Also check with him any relevant practicalities of reading LYSO
  tiles with a WLS fiber (eg. coupling to plates, coupling to photo sensor).

- Discussed machining parts for the LYSO stack holder. Dustin and Cristian will give it a try the day after the meeting.
  Workshop people suggested aluminum.
  Discussed how to test if the two plates can reliably hold the stack of 28 W and 29 LYSO plates without breaking
  any LYSO plates. May use thin layer of cushining material (eg. protective foam material) inside the pocket.
  Pocket size such that it can hold the full 100 plates of LYSO (15 cm + ~1cm extra space as margin eg. to hold
  a fixture at the end of the stack).
  General idea :
  The full stack of LYSO read by fibers will allow to measure the effect of the optical path through the plates and fibers
  on the optical transit time and the optical transit time jitter.
  The LYSO/W stack will in addition allow to meaure the impact of the reduced number of photos on the sensor and
  the effect of the sampling on the time measurement.

  The full LYSO stack will neither have the optimal depth nor transverse size to contain EM showers well, in particualr since
  the transverse size matches the Molier radius of the LYSO/W mix.
-> Need to do standalone simulation to explore how much this affects the fluctuations on the mean time.

  We want to give priority to the LYSO/W stack for now since it relates more closely to the Shashlik effort and time
  is short for this.
  The impact of the photo statistics (and ultimately measuring the sqrt(E) dependence of the resolution) can be studied  
  later (in particulae once we have actually produced a measurement from scintillation light).

  Additional items to machine : Shielding (see slides from last week) to reduce possible secondary hit contamination
  in the TB. Goal is to explore if signals (in particular in the transverse setup and on the far side MCP) are
  created by direct hits of secondaries.
 

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TB Program :

- Need to work out detailed plan for the next TB.
  See : https://docs.google.com/document/d/1OpyVtEf_bgWAt9kx1UeN8VGISV7mvAIOLpXeJdjgiLc/edit
  Basic idea :
  Repeat longitudinal and transverse measurements without pin hole with the 20 cm LYSO xtal.
  Need to digest outcome of SiDet results (Meeting on Friday).
  Need to check at the TB if MCPs saturate as well without pin hole. 
  If yes, need to optimize pin hole size.
  Consider other attenuation options ?
  Checks to be sure that we see scintillation light :
  * Signal correlation back and front xtal readout
  * Peak in the pulse hight spectrum

  If we achieve the above and if we understand the data, repeat the same with LYSO stack (if ready by then).

  To be further investigated : If we have a mix of direct hits and scintillation light, does out time and amplitude extraction
  pick up a possible early, short direct hit peak and ignores the longer scintiallation light tail ?
  -> To be checked already with current data (Adi).
  -> Standalone simulation : How many direct hits do we expect in the MCP on the front of the sensor ?
      Backscatter from the xtal ? Can we explain the pulse height spectrum we meaure ?

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SiDet results on laser with and without pin hole.
 
 To be reported Friday, May 9, 12:30 PST.


Adi