[Halld-pid] ST First Tests

[Mark M. Ito]

We have all talked and agree that we should go back to the 50 micron, 
including Sascha. We too want to do this ASAP.

On 07/18/2012 07:57 AM, Elton Smith wrote:
> HI Fernando, Mark and Werner,
>
> The order for the SiPMs is out and if a change is going to be made, it 
> should be done before Hamamatsu gets started. From Fernando's tests, 
> it seems wise to revert to the well-tested 50 um sensors for all 
> applications, including the ST. Sasha is planning to contact the 
> Hamamatsu rep to find out if and when the switch can be made. The 
> decision should be made a soon as possible.
>
> Cheers, Elton.
> Elton Smith
> Jefferson Lab MS 12H5
> 12000 Jefferson Ave
> Suite #16
> Newport News, VA 23606
> (757) 269-7625
> (757) 269-6331 fax
> On 7/16/12 10:34 PM, Fernando J Barbosa wrote:
>> Hi Mark, Werner,
>>
>> I have been optimizing and testing the ST readout for the 50 um and 
>> 100 um SiPMs. There are 4 SiPMs connected together (current sum) to 
>> one readout channel on each of two SiPM PCBs (50 um and 100 um). The 
>> sensor capacitance is the same in both cases so one optimization is 
>> all that is required for fast risetimes for the group of 4 SiPMs.
>>
>> The prototype is fully functional but I determined that the 
>> micro-coax ribbon cable assembly (connects the readout to the 
>> breakout PCB) is not good enough due to cross-talk (primarily due to 
>> the connectors on these cable assemblies - a single micro-coax cable 
>> assembly provides the power to the electronics, 3 bias supplies, 6 
>> outputs [3 channels w/ 3 for ADCs and 3 for TDCs] and has a 
>> thermocouple two-wire output for readout). The readout is temperature 
>> compensated via thermistors. The workaround has two coax cables (ADC 
>> and TDC), in addition to the micro-coax, which bypass the micro-coax 
>> signal connections. So, the final design will change but the current 
>> prototype will be useful for tests with ST detector prototype.
>>
>> I have attached two pics: ST50 is for the 50 um and ST100 is for the 
>> 100 um. These were taken with a laser and a diffuser stimulating all 
>> 4 SiPMs in the group. Some comments:
>>
>> 1. 50 um - Fast pulses with width of 37 ns (~10%-10%)
>> 2. 100 um - Fast pulses with width of 125 ns (~10%-10%), step/kink ~ 
>> 5 ns after peak.
>>
>> The leading edge slew rate is about the same for both but the 100 um 
>> has a slower recovery w/a kink (the quench resistor on each pixel 
>> would need to be ~3x smaller for similar recovery but there are other 
>> factors at play, i.e. Geiger current) . I will investigate this a 
>> little further but these are definitely characteristics of these 
>> SiPMs and I will write a GlueX note soon.
>>
>> In the meantime, let me know if there is interest in pursuing the 100 
>> um further. Even though the rates are expected to be in the KHz 
>> range, the long recovery time will likely lead to pileup.
>>
>> Best regards,
>> Fernando
>>
>>
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>
>
>
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-- 
Mark M. Ito
Jefferson Lab (www.jlab.org)
(757)269-5295



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