[Halld-cal] Rework Plan for Glued Light Guides

Tue May 14 00:27:12 EDT 2013

Hi Elton:

I guess we'll discuss this in detail tomorrow, so I'll give feedback then. It definitely makes sense to do "touch ups" for modules that have only a few of the outside light guides with issues, and maybe those with the very odd inner one, provided its neighbour to the outside edge is removed.  

However, those that have more than a few (say, 5 and up) might need to be done entirely from scratch with the new method.  I would have not guessed that we would have had such trouble with the UV curing method as this is usually straight-forward, although perhaps the 40 small light guide configuration may have contributed.  In retrospect, the KLOE method would have worked far better, but of course had the risk of suspending the modules vertically.  Anyhow, we have salvage the current situation as best we can.  

As Will indicated, it would not be trivial to do the MC on the full HDGEANT, in any time that would a) be helpful in making LG decisions and b) so as to not completely derail the overall reconstruction effort, which rests on three people doing the work.  However, let's discuss the feasibility tomorrow of doing a toy MC, if we think this is the way to go.  I wonder whether longer cosmic runs may not be the best way to do this evaluation.  Shaun will show some plots tomorrow, and within a week will have plots showing the means from the energy depositions in the summed cells.  This may offer a promise in comparing neighbouring cells on the same row (subject to different SiPMs of course), and the same cell from module to module (with the same SiPM viewing these).

Let's chat tomorrow, Zisis...

On 2013-05-10, at 3:21 PM, Elton Smith <elton at jlab.org> wrote:

> Dear collaborators,
> 
> At the last Cal Working group meeting we discussed ideas for deciding which light guides with partial detachment should be reglued. We also discussed the effort required to complete simulations, which could provide some guidance about how to make this decision. This question was further discussed at the Bcal reconstruction meeting (see https://halldweb1.jlab.org/wiki/index.php/BCAL_Reconstruction_Meeting_2013-05-23). It seems the simulations are not easily adapted to the question before us and the long term stability of partially detached light guides stability is uncertain in any case. Therefore, we have decided to simply replace all light guides with detached surfaces. This may be slightly more work, but clearly this is the time to do any repairs.
> 
> We have put together a draft plan for the rework on the wiki at https://halldweb1.jlab.org/wiki/index.php/Light_Guide_Rework_Plan, which we will refine and follow in the coming weeks. Feedback and comments are welcome.
> 
> Cheers, Elton.
> 
> 
> -------- Original Message --------
> Subject:	Re: [Halld-offline] BCAL software update
> Date:	Tue, 7 May 2013 10:47:36 -0600
> From:	Zisis Papandreou <Zisis at uregina.ca>
> To:	Will Levine <wlevine at gmail.com>
> CC:	Elton Smith <elton at jlab.org>, David Lawrence <davidl at jlab.org>, Andrei Semenov JLab <semenov at jlab.org>, Beni Zihlmann <zihlmann at jlab.org>
> 
> Hi Will:
> 
> I will pout this item on the top of our agenda this Thursday so we can discuss whether going with the full code is a good way or maybe using a toy Monte Carlo.  We have a few of those kicking around in Regina.
> 
> Cheers, Zisis...
> 
> On 2013-05-07, at 10:02 AM, Will Levine <wlevine at gmail.com> wrote:
> 
>> I think what you are asking is that we simulate a light loss in a
>> specific area within a specific waveguide (rather than a smaller light
>> loss over the whole area of the waveguide). Is this correct? This
>> sounds non-trivial, but I'm not sure exactly how hard this would be to
>> implement in hdgeant, hopefully David can comment on this.
>> 
>> As far as observing the effects on energy and position resolution: the
>> shower reconstruction code is not yet extensively tested or
>> bulletproofed, but the total energy and the transverse position are
>> the easy quantities to calculate, so I think this will be fine.
>> Anything involving the timing or z-position is more iffy, but it
>> doesn't sound like you are worried about that.
>> 
>> Will
>> 
>> On Tue, May 7, 2013 at 8:28 AM, Elton Smith <elton at jlab.org> wrote:
>>> Hi Will,
>>> 
>>> Glad to hear that the software environment is getting settled. I have a
>>> practical question that I hope you or someone can help out with. We have run
>>> into problems with light guides detaching after gluing and need to develop a
>>> plan for fixes. In particular we need to establish clear guidelines for the
>>> technical staff about which light guides to reglue. Some situations are
>>> clear such as complete or major detachments. In addition, guides on the
>>> periphery of the array will be replaced since there is clear access. A
>>> single light guide with partial detachment (say 10-20%) in the middle of the
>>> array creates a conundrum. This situation will lead to a light decrease in
>>> the affected area of about 10%. The guides are difficult to pull off to
>>> begin with and cleaning the area before regluing is not easy.
>>> 
>>> We need to develop criteria over the next couple of weeks for deciding on
>>> precisely which guides to replace. The small detachments can affect both
>>> energy and position resolution. I assume the effect on energy resolution
>>> will be small (10% loss of 20% area is a 2% effect), but should be
>>> confirmed. The effect on transverse position resolution might be more
>>> dramatic, since it will create asymmetries in the energy profile
>>> distribution.
>>> 
>>> My question is: can our present simulation study the effects of partial
>>> light loss from areas on the light guide on energy and position resolution?
>>> I assume this would be done with single photons and not be complicated
>>> initially by multiple showers. I assume one would have to modify hdgeant to
>>> implement the light loss because the information is lost when the energy is
>>> collected into output channels.
>>> 
>>> Thanks, Elton.
>>> 
>>> Elton Smith
>>> Jefferson Lab MS 12H5
>>> 12000 Jefferson Ave STE 16
>>> Newport News, VA 23606
>>> (757) 269-7625
>>> (757) 269-6331 fax
>>> 
>>> 
>>> On 5/6/13 8:16 PM, Will Levine wrote:
>>>> 
>>>> I recently checked in some changes that enable the new BCAL simulation
>>>> and reconstruction code by default. This new code treats ADC and TDC
>>>> hits separately and does timewalk corrections, among other things. In
>>>> addition, the default BCAL clustering algorithm has been switched from
>>>> the KLOE algorithm to the IU algorithm.
>>>> 
>>>> A few notes:
>>>> 
>>>> When updating to the latest code, you must rerun the simulation
>>>> (mcsmear in particular) before running the reconstruction. Old hddm
>>>> files will not work properly with the new code.
>>>> 
>>>> Analyzing REST files from the data challenge is still possible, but
>>>> you must use the -PDEFTAG:DBCALShower=KLOE option.
>>>> 
>>>> Will
>>>> _______________________________________________
>>>> Halld-offline mailing list
>>>> Halld-offline at jlab.org
>>>> https://mailman.jlab.org/mailman/listinfo/halld-offline
>>> 
>>> 
> 
> 
> Dr. Zisis Papandreou
> Professor of Physics, Ph.D, P.Phys.
> ---------------------------------------------------------
> Department of Physics   
> University of Regina     
> 3737 Wascana Parkway
> Regina, SK  S4S 0A2  CANADA
> 
> Phone: (306) 585-5379
> Fax: (306) 585-5659
> Email:  zisis at uregina.ca
> Website: http://kronos.phys.uregina.ca/~zisis/professional/
> 
> 
> 
> 
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Dr. Zisis Papandreou
Professor of Physics, Ph.D, P.Phys.
---------------------------------------------------------
Department of Physics   
University of Regina	    
3737 Wascana Parkway
Regina, SK  S4S 0A2	 CANADA

Phone: (306) 585-5379
Fax: (306) 585-5659
Email:  zisis at uregina.ca
Website: http://kronos.phys.uregina.ca/~zisis/professional/

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