[Halld-tagger] specs for microscope readout power supplies
Fernando J Barbosa
barbosa at jlab.org
Mon Dec 9 10:37:23 EST 2013
Hi Richard,
OK, looks good. I will look at options for the supplies.
Thanks and best regards,
Fernando
On 12/9/2013 10:28 AM, Richard Jones wrote:
> Fernando,
>
> Our background study showed that we could continue to function for 10
> years of high-rate running without annealing, just allowing the dark
> rate to increase at the rate that was measured in Hall B and allowing
> the supply current to increase. Under the zero-shielding scenario,
> just leaving the electronics unshielded in the tagger hall, we
> estimated that we would reach the point where we would need to do
> something (eg. anneal or replace the SiPM's) after 10 years of
> high-rate running. The usual assumptions were applied (100 days of
> running per year, standard 20 micron diamond, 12 GeV electrons at 2.2
> microAmps). With shielding, we expect to reduce this figure by a
> factor of 5-10 (the simulation gave a factor around 8), so we should
> be able to run for the duration of GlueX without annealing.
>
> I agree with you that we can segment the supplies. Each of them can
> be split up to 6 ways, because there are 6 identical backplanes in the
> system. The specs we posted were for the total sum of all 6 backplanes.
>
> -Richard J.
>
>
> On Mon, Dec 9, 2013 at 9:52 AM, Fernando J Barbosa <barbosa at jlab.org
> <mailto:barbosa at jlab.org>> wrote:
>
> Hi Richard,
>
> Certainly the rates in the tagger are higher but what is your
> planning for annealing the SiPMs? I am just curious given the
> higher rates.
>
> Regarding the power supplies, you mentioned the possibility of
> having three supplies instead of one for the whole system. Is it
> possible to consider further segmentation? One channel per
> backplane? Do you have a document that shows the whole system as
> installed? The issue is also related to the space available under
> the magnet.
>
> Best regards,
> Fernando
>
>
>
> On 12/6/2013 10:09 AM, Richard Jones wrote:
>> Fernando,
>>
>> These estimates for the BCal do not apply to the TAGM, where the
>> rates are much higher. We can set up a meeting to discuss this
>> further if you feel we need it. We worked out these rates back
>> during the design phase for the readout electronics, and had them
>> reviewed within the photon beam working group. Also keep in mind
>> that the neutron flux is much higher in the tagger hall than in
>> the experimental hall. On the other hand, the TAGM can operate
>> efficiently at much higher single-pixel rates than can a
>> calorimeter because it is not producing an energy measurement,
>> but only time, and the photon statistics are high, <n> = 350-400
>> within a 15ns window. We are shielding these electronics, but we
>> only expect to cut down the neutron flux by about a factor 10-20
>> in this way. Alex Somov did the neutron rates and shielding
>> studies for us, and can provide more details in this regard.
>>
>> -Richard J.
>>
>>
>> On Fri, Dec 6, 2013 at 9:04 AM, Fernando J Barbosa
>> <barbosa at jlab.org <mailto:barbosa at jlab.org>> wrote:
>>
>> 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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