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

[Ezekiel Wertz]

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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