[Clas12_rgb] [EXTERNAL] Re: RC meeting: today @ 2pm!
Daria Sokhan
daria at jlab.org
Tue Dec 10 13:51:26 EST 2019
Dear Stepan,
That's a good idea -- we can discuss this in the meeting today.
Thanks,
Daria
On Mon, 9 Dec 2019 at 18:39, Stepan Stepanyan <stepanya at jlab.org> wrote:
> Dear Daria,
>
> Thanks for a detail summary of the meeting.
>
> As we discussed, this Q2 cut proposed by Valery is good/reasonable for
> electron scattering experiments. We have another experiment in RG-B that
> requires electron detection, J/psi production. In the J/psi kinematics off
> the proton, electrons have >2.5 GeV/c momentum, production on deuterium
> will have electrons even lower momentum. So, for J/psi physics and in
> general for vector meson / time-like photon production, going below 2 GeV/c
> for electron momentum is unacceptable. We talked a bit with Valery about
> combined energy and Q2 cut trigger, e.g. have a trigger setup with
> E(PCAL_EC)>450 MeV OR Q2>0.4 GeV^2 (I think Q2>0.5 GeV^2 bit too much).
>
> Regards, Stepan
>
>
> On Dec 9, 2019, at 5:48 PM, Daria Sokhan <daria at jlab.org> wrote:
>
> Dear all,
>
> Apologies for losing the audio connection in the meeting today, it was
> quite heated and I didn't see that the phone switched off from speak-mode
> -- I will summarise the main points below.
>
> During controlled access today, while the accelerator vacuum leak was
> being repaired:
>
> * Krister worked on the over-heating connector lead on the power supply
> for the Moller magnet. He has disconnected it, cleaned it, applied a
> special sort of lubricant (details in his logbook entry, will appear
> tomorrow morning) and tested it by switching the magnet on for a few hours.
> The temperature crept up slightly, but both leads seemed to be behaving
> equally, which is a good sign. Krister will test it more extensively
> tomorrow morning.
> * Rafo adjusted FC offset (from ~40 to 250 Hz).
> * Florian tried to debug discriminator channel in slot 20 channel 2 of
> BAND, which was giving a slightly lower rate: unplugging and replugging
> didn't change that, so it'll be kept as it is.
> * Raffaella replaced a broken cable on the missing FT Hodoscope channel
> and saw a signal on fADC -- issue appears fixed:
> https://logbooks.jlab.org/entry/3750244
> * Yuri is looking into possible relation between radiation levels and the
> leakage current on SVT. For the moment inconclusive, but he would like to
> install an extra gamma monitor between SVT and the solenoid.
> * Raffaella and I unplugged and replugged HV cable and fADC connector for
> the CND channel S14L1R, which has been occasionally tripping off. It seems
> responsive, but needs to be watched.
>
> Raffaella has checked the RF offset for the recent runs and it looks
> stable: https://logbooks.jlab.org/entry/3750178
>
> Nick Z has completed gain-matching of the FT Hodoscope and uploaded the
> new constants, which will be implemented from the next run:
> https://logbooks.jlab.org/entry/3750212
>
> Yordanka is producing monitoring histograms for the runs as they get
> cooked, they are now saved here:
> https://clasweb.jlab.org/clas12mon/rg-b/pass0/v17_fall2019/offline/
>
> Nick M. presented a study of HTCC response (please find his slides
> attached), where he compared the distributions between a spring run and one
> from now. There is a spike at low values in the Sping data, no spike in the
> current runs -- it was suggested that the difference is due to the new
> trigger parameters (addition of DC roads). He also pointed out that the
> distribution for S2 HS2 R1 is skewed to lower values and suggested that
> this can be corrected by calibrating to the peak position, rather than the
> mean of the distribution. Accuracy of the the gain matching for the HTCC
> channels is on the order of 5-10%, so the slights skew in that one channel
> was not considered to be a big issue.
>
> Yuri S. gave a verbal update on the status of HTCC. The mirror
> manufacturers are still not providing info on the exact composition of the
> mirror coating (it's therefore hard to evaluate their aging). Near-future
> plans include replacement of quartz-window PMTs and of active dividers with
> passive dividers. New power supplies have also been ordered but not yet
> received.
>
> Valery showed a 2D plot of the number of photoelectrons in each sector of
> the HTCC, from the current production data. Many of the half-sectors,
> especially in the outer ring, showed a structure where there were many more
> nphe in one half of the sector than in another. The half-sectors have a
> single mirror, so the sharp separation of these high- and low-nphe regions
> was decidedly odd. There was much heated discussion and argument over what
> might be causing this and whether this has been observed before (we lost
> audio connection in the scuffle). Valery called for HTCC simulations.
>
> Valery then presented a plot of theta vs momentum for the electrons, which
> showed a large number of events at low theta. low momentum -- with a Q^2
> below 0.5. He suggested that since they don't pose physics interest we
> could significantly reduce our electron trigger rate by cutting them out at
> the level of triggering (applying a Q^2 cut on DC roads). We agreed that he
> would produce new trigger firmware to do this and we would take a short
> (~half hour) run to test this. In the meantime we would continue taking
> data with the current trigger and only implement this once it's validated
> and if RG-B agrees. Current data rate (700 MB/s) is only sustainable if
> we're not taking data for about half the time, to meet the limits set for
> us. Should we get good, steady beam, our data rate will become a problem.
>
> About that -- the vacuum loss in the accelerator this morning was traced
> to a flange which was not properly closed (unclear why that was so or why
> it's only become a problem now -- mice?), they have tightened it and are
> pumping the vacuum down. This will take all night and it's not known
> whether it will fix the problem. Earliest beam delivery is expected
> tomorrow at noon. Swing and owl shifts are cancelled.
>
> The hall remains in Controlled Access and we have ramped down the solenoid
> and torus to 100A. If anyone needs access to the hall tonight, please
> contact me first -- the counting room will be unmanned. Access tomorrow
> morning will be as normal.
>
> Planned work for the hall tomorrow: Krister will check Moller magnet
> again, Florian will get neutron counters for BAND removed, Yuri plans to
> install the extra gamma monitor he needs for SVT studies.
>
> A spin dance was planned for tomorrow (Halls A + C) -- when this
> eventually happens the consensus was that we do not participate but use the
> time to make a zero-field alignment measurement and take empty target or
> low luminosity data. If they change the Wien angle, we will then do a
> Moller measurement.
>
> Have a good evening!
> Daria
>
>
>
>
>
>
>
>
>
> On Mon, 9 Dec 2019 at 11:40, Daria Sokhan <daria at jlab.org> wrote:
>
>> Dear all,
>>
>> We'll have the usual RC meeting upstairs in the counting house at 2pm.
>>
>> Bluejeans: https://urldefense.proofpoint.com/v2/url?u=https-3A__bluejeans.com_230805731&d=DwIBaQ&c=CJqEzB1piLOyyvZjb8YUQw&r=p0fOsYOqPes7kSrF0-ldLy8UQdwZWwpYV125WHZsrFE&m=mlZbdC_wZO8TolRqYjU2wpQ7IYHAtJV0TMB65Isbbs8&s=HWXcZR4BdwVkLopbjS7djIGoIsinbvtW-S_HJJYFdpA&e=
>> <https://urldefense.proofpoint.com/v2/url?u=https-3A__bluejeans.com_230805731&d=DwMFaQ&c=CJqEzB1piLOyyvZjb8YUQw&r=p0fOsYOqPes7kSrF0-ldLy8UQdwZWwpYV125WHZsrFE&m=bxMdN_MgodYZhFpK2RiAA3YZjwbYDgwEepbV0N-VDY4&s=0BPGwMe_soWKRhzk2lK-crzoQtg7vmiNMUWPakyPG00&e=>
>>
>> There has been another day of quiet physics running until ~5am this
>> morning, when everyone returned to work and the accelerator threw a
>> tantrum. MCC are currently down over vacuum problems.
>>
>> Hall B is in controlled access at the moment -- anyone who needs to do
>> anything down there, this is your chance! Current best MCC estimate for
>> beam return is 1pm -- pre-scale by the usual factor.
>>
>> Speak to you soon!
>> Daria
>>
>>
>>
>>
>>
>>
>>
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