[Halld-tagger] specs for microscope readout power supplies

[Fernando J Barbosa]

Hi Richard,

In reference to the BCAL and taking Yi's measurements in Hall A 
regarding radiation damage, we settled on a maximum of 10mA for 10 
arrays or 160 cells (3mm x 3mm). This works out to 62.5uA per cell and 
your estimate is higher by a factor greater than 10. What is your plan 
for annealing the SiPMs? Frequency?

Did you look into any supplies that might fit your requirements? I 
recall that each backplane of the TAGM has a single bias supply input, 
correct? This would be important in considering a multi-channel supply 
system. Please send me your latest drawings on the TAGM system and its 
installation in the Tagger hall.

Best regards,
Fernando


On 12/5/2013 10:50 PM, Richard Jones wrote:
> Hello Fernando,
>
> I am spec'ing the Vbias supply capacity at 500mA to allow for the 
> maximum SiPM draw current that is permitted by the bias voltage supply 
> system.  Initially we expect the average current to be around 15 mA at 
> full intensity (2.2 uA electrons on 20 micron diamond) but that it 
> will increase gradually over time due to radiation damage.  To get the 
> maximum current spec, I imagine the worst possible circumstances under 
> which the radiation damage might accumulate faster than expected, and 
> ask how much current could we sustain across all channels before the 
> resolution and efficiency degrade significantly due to dark current. 
>  The answer to that is approximately 800uA per channel, which totals 
> about 400mA from the supply.  I rounded that up to 500mA.
>
> -Richard Jones
>
>
> On Thu, Dec 5, 2013 at 4:51 PM, Fernando J Barbosa <barbosa at jlab.org 
> <mailto:barbosa at jlab.org>> wrote:
>
>     Hi Richard,
>
>     I looked at the specs and the bias supply current seems to be
>     excessive at 500mA. What's the reason for this?
>
>     Best regards,
>     Fernando
>
>
>
>     On 12/5/2013 3:33 PM, Richard Jones wrote:
>
>         Hello Alex,
>
>         Here is a draft of the specs for the microscope readout dc
>         power supplies.  They can be a single unit for each of 3
>         levels, or a few lower-capacity supplies in tandem with the
>         same total output capacity.  Please request justification for
>         any of the specs.  One thing we do not spec here, but think
>         would be useful, is separate delivery and sense terminals for
>         each output.  We have separate pins on the backplane connector
>         for this purpose.
>
>         http://zeus.phys.uconn.edu/wiki/index.php/Microscope_Electronics#Power_Supply_Requirements
>
>         -Richard Jones
>
>
>

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