[Halld-cal] FCAL Monitoring

[Matthew Shepherd]

Dear Christine,

The structure will likely be sealed on the sides and top as it all must be encased in a dark room.  Drilling cable passages from front to back is not a problem.  We need to know where you plan to place control boards and what size they are.  Perhaps they should go in the dark room on the back side of the FCAL so they can be accessed for service.  If the cables exit the dark room to control boards outside, then the cable passages will need to be light tight.  None of these issues are difficult to solve, but just need a little planning.

If the preliminary design is agreeable, then the next major step would likely be to try to prototype one of the four acrylic panes.  This would let you understand uniformity and intensity of LED signal.

One feature we would be very interested in having is the ability to pulse with several different colors of LED.  The radiation damage that we expect in the detector kills the blue component first.  If we had the ability to monitor the system over time at several different wavelengths, then this might help to get a handle on the extent (if any) of radiation damage.  I imagine this is not too hard for you to accommodate in your design.

-Matt


On Feb 25, 2011, at 1:13 PM, Christina Kourkoumeli wrote:

> Thank you,Matt.Now it is all clear.The LED board thickness is less than the acrylic so it will be OK.
> Regarding the "floor" etc,will be there space from both sides of the acrylic as well as top and bottom to pull few cables going to the bigger Board control? Cheers,Christine
> On 25/2/2011 4:37 μμ, Matthew Shepherd wrote:
>> Hi Christine,
>> 
>> I believe you have a full module that we shipped to you.  When it is assembled, there is a 1/8" plate on the front.  It is square with a large cutout to allow light from the monitoring system to pass through.  By construction, this plate must sit between the front face of the glass and the acrylic.
>> 
>> Whatever you place in the "corners" of the octagon must be relatively flat (no more than the thickness of the acrylic).  The reason for this is the time of flight scintillators will cover this region.  They sit in the same plane as the acrylic and we would like to have them as close to the acrylic as possible.  This location is probably a good area to mount your LEDs; however any control electronics should probably be wired away and outside the unit.  We can drill holes for wire passage in the corners of the frame.
>> 
>> I'm not sure what "floor" you refer to.  The plan is that the lower end of the frame will attach to jack plates that are on the forward platform.  If the floor is the forward platform, then the bottom of the detector is almost sitting on the floor.
>> 
>> -Matt
>> 
>> On Feb 25, 2011, at 9:15 AM, Christina Kourkoumeli wrote:
>> 
>>> Dear Matt,
>>> thanks for the prompt answer.About the octagon,we were thinking of placing
>>> LED boards there as you mentioned as well and probably in the horizontal
>>> dimensions.How far from the floor is the lower end?
>>> Can you explain better what is the "bar 1/8" thick face plate on the front
>>> end" that is flashed with the Pb-glass?We are not sure we fully understand
>>> that.
>>>                                Cheers,
>>>                                 Christine
>>>> Hi George and Christine,
>>>> 
>>>> I'm cc'ing John on this, so he can respond if needed.  Octagonal sheet is
>>>> fine.  I think it would actually be better since you could use the cutout
>>>> corners to place monitoring electronics.
>>>> 
>>>> Regarding spacing from the front of the bars:
>>>> 
>>>> The bar itself as a 1/8" thick face plate on the front end.  This sets the
>>>> minimum distance the acrylic can be from the bar:  1/8" if the acrylic
>>>> touches this plate.  However, I don't think we want the two to touch since
>>>> any vibration could create scratches in the acrylic that develop over
>>>> time, thereby modifying the light output.  Probably a gap of 1/4" or so
>>>> would be best.  This means a total distance of 3/8" or about 10 mm.
>>>> 
>>>> -Matt
>>>> 
>>>> 
>>>> On Feb 25, 2011, at 7:46 AM, Georgios Voulgaris wrote:
>>>> 
>>>>> Hi Matt,
>>>>> 
>>>>>  We have couple of questions for John :
>>>>>     Is it mechanically possible  to  support an octagon sheet (in four
>>>>> quarters) ?
>>>>>     Can we place the L.glass bars closer to the sheet?
>>>>> 
>>>>> Plexiglas with a thickness from 10 mm to 15 mm is O.K.
>>>>> LED boards can be glued directly on the sides of the sheet.
>>>>> We have some .5'' sheet in stock, for a test set up.
>>>>> 
>>>>> By,
>>>>> George.
>>>>> 
>>>>> Matthew Shepherd wrote:
>>>>>> Hi George and Christine,
>>>>>> 
>>>>>> Attached to this message is a quick sketch that John Frye made that is
>>>>>> a rough conceptual design for how to mount the acrylic pane in front of
>>>>>> the FCAL.  I think this conveys the general idea.  What we don't know
>>>>>> is how you plan to integrate your LED pulsing system into this.  Where
>>>>>> should boards go?  Should we revise to the design slightly so it could
>>>>>> be detached as a single unit (for example, if we want to do UV curing
>>>>>> of the glass)?  At our last meeting there seemed to be some confusion
>>>>>> about the general concept and geometry, so this is maybe a good place
>>>>>> to start.
>>>>>> 
>>>>>> Matt
>>>>>> 
>>>> 
>>> 
>