[Sbs_gems] [EXTERNAL] Chance for GEM study at 20 uA?

[Ezekiel Wertz]

Maybe that's more of a question for Evaristo. I do not know. I just want to
remind everyone that at 4100V (nominal setting for INFN GEM production) we
see about base current with no electron beam of 104 uAmp

Zeke

On Mon, Nov 15, 2021 at 11:26 AM Ezekiel Wertz <ewertz at email.wm.edu> wrote:

> Hi Nilanga,
>
> The INFN GEMs will see probably about a 20-30 uAmp increase in HV at at 20
> uAmp of beam current. Is that safe for the divider since excess current
> would then be like 20% of the overall current load of the divider?
>
> Zeke
>
> On Mon, Nov 15, 2021 at 11:17 AM Liyanage, Nilanga K (nl8n) <
> nl8n at virginia.edu> wrote:
>
>> Hi Sean
>>
>> Thanks for letting us know.
>>
>> Yes, it would be OK to get 20 uA on LH2. Please make sure to set the
>> current limits accordingly.
>>
>> Later, for GEP-5 we will have to go to much higher currents, of the order
>> of 70 uA; so going to 20 uA now would be a good data point for us.
>>
>> As Kondo has suggested before, while you are getting this current, please
>> monitor the GEM current, if it is not stable and keep going up (after the
>> initial increase following the beam current change), you my want to turn
>> the chambers off
>>
>> Best
>>
>> Nilanga
>> ------------------------------
>> *From:* Sbs_gems <sbs_gems-bounces at jlab.org> on behalf of Sean Jeffas <
>> sj9ry at virginia.edu>
>> *Sent:* Monday, November 15, 2021 11:01 AM
>> *To:* sbs_gems at jlab.org <sbs_gems at jlab.org>
>> *Subject:* [Sbs_gems] [EXTERNAL] Chance for GEM study at 20 uA?
>>
>> Hi Kondo, Nilanga, and Evaristo,
>>
>> The MCC is investigating some RF beam issues today, and they said that
>> they will send 20 uA of beam to hall A while doing their study. The
>> question is, can we keep the GEMs on to see the current draws at 20 uA? We
>> would try it on LH2, which has already been tested up to 10 uA. Here are
>> the numbers for currents at LH2 that we have taken so far:
>>
>> No beam: https://logbooks.jlab.org/entry/3943588
>> 8 uA on LH2: https://logbooks.jlab.org/entry/3943079
>> 10 uA on LD2: Sadly no screenshots were taken, so I will quote the EPICS
>> values
>> UV Layer 0: 812 uA        INFN J0 bot: 116
>> UV Layer 2: 804 uA        INFN J0 mid: 118
>> UVa XY 0: 743 uA           INFN J0 top: 112
>> UVa XY 1: 768 uA           INFN J2 bot: 113
>> UVa XY 2: 769                INFN J2 mid: 113
>> UVa XY 3: 771                INFN J2 top: 0 (off)
>>
>>
>> So if we go up to 20 uA on LH2 I assume we double the excess currents
>> found here we would certainly pass the trip limits on all modules on the
>> front tracker. This For example UV layer 0 will go up to probably 870 uA.
>> Would this be safe? Are you guys ok with this test?
>>
>> Best,
>> Sean
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>
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