[Halld-tagger] specs for microscope readout power supplies
Hovanes Egiyan
hovanes.egiyan at gmail.com
Mon Dec 9 10:51:18 EST 2013
Hi Richard,
what type of controls is needed for these? Do we need to be able to
remotely
control them, turn them on/off, power cycle them?
Hovanes.
On 12/09/2013 10:37 AM, Fernando J Barbosa wrote:
> 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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