[Halld] Proposed intensity scan for Fall 2018

Mon Nov 19 13:56:37 EST 2018

Probably would be best to prescale the main trigger, at least, otherwise we
could waste time fiddling with the DAQ.
-Richard

On Mon, Nov 19, 2018 at 1:51 PM Eugene Chudakov <gen at jlab.org> wrote:

> Let me remind you that with the currently used DAQ software we would
> be limited to about 1GB/s, or about 400nA without prescaling (or somewhat
> lower for reliable operations).
>
> The front-end limit would be about 80kHz, or also 400nA.
>
> We may try to use a new DAQ software (the Sergey's version), which can go
> to >2GB/s. The front-end limits would still apply.
>
> Eugene
>
> On Mon, 19 Nov 2018, Sean Dobbs wrote:
>
> > Hi Justin,
> >
> > If the high intensity points are cheap, maybe it would be useful to have
> a finer grained scan, just in case we find something that we need to
> investigate in more detail?  Say, adding 400 and 600 nA points?
> >
> > Cheers,
> > Sean
> >
> > On Mon, Nov 19, 2018 at 11:56 AM Justin Stevens <jrsteven at jlab.org
> <mailto:jrsteven at jlab.org>> wrote:
> > Hi Richard,
> >
> > Thanks for your feedback.  See below ->
> >
> > On Nov 19, 2018, at 11:34 AM, Richard Jones <richard.t.jones at uconn.edu
> <mailto:richard.t.jones at uconn.edu>> wrote:
> >
> > Hello Justin,
> >
> > If we want to understand rate-related systematics, wouldn't it be better
> to push the upper limit of the scan higher? This way we learn something
> about what starts to go wrong at lower intensities, where we might want to
> run during the high-intensity period.
> >
> > If it doesn't break anything, we should take some data at higher
> intensities, even if we have to prescale the trigger. I propose running two
> or three more points up to 700 nA on this diamond. This 700uA comes from
> the original design intensity for GlueX which was 1e8 photons per second on
> the target in the range 8.4 - 9.0 GeV (or 8.2 - 8.8 GeV with the present
> endpoint).
> >
> > Sure, high intensity points are “cheap”, so this puts us at ~30 hours at
> 100% efficiency.  I added these points to the scan, if we’re comfortable
> going to this high an intensity (from a detector safety and trigger point
> of view).
> >
> > I realize that this 5e-4 radlen in the spreadsheet for this diamond is
> just a placeholder, but that value should be closer to 3e-4. Radiation
> length is not really a valid metric for a coherent bremsstrahlung spectrum,
> but in the low-energy tail it is valid, where the radiation length of
> diamond is close to 15um as long as you stay away from the channeling
> condition. To get this, you cannot just take amorphous carbon and rescale
> it by the density, of course, as the crystal structure modifies the
> radiation length at all orientations.
> >
> > I agree the diamond radiation length is a bit of a fudge, but it
> actually cancels in my calculation of the expected run time.  The only
> thing I use is the total trigger rate for the nominal intensity (~45 kHz
> for diamond) and scale by the current to get the time required.
> >
> > -Justin
> >
> >
> > -Richard
> >
> > On Mon, Nov 19, 2018 at 10:11 AM Justin Stevens <jrsteven at jlab.org
> <mailto:jrsteven at jlab.org>> wrote:
> > Dear Collaborators,
> >
> > Following the discussion at this morning’s RC meeting for an intensity
> scan this Fall, here is what I would propose:
> https://urldefense.proofpoint.com/v2/url?u=https-3A__na01.safelinks.protection.outlook.com_-3Furl-3Dhttps-253A-252F-252Furldefense.proofpoint.com-252Fv2-252Furl-253Fu-253Dhttps-2D3A-5F-5Fdocs.google.com-5Fspreadsheets-5Fd-5F1UT3o4yJ-2D2DavlIQzmZKJo2nRrgVPzYKJvGPJ0oqAn81Oo-5Fedit-2D3Fusp-2D3Dsharing-2526d-253DDwIGaQ-2526c-253Dlz9TcOasaINaaC3U7FbMev2lsutwpI4-2D-2D09aP8Lu18s-2526r-253DMwj7jqW-5FGg8VvugDHdwA5w-2526m-253D-5FX3Z46cZYdB3Mq0066MeIIqspYRtV5uWmIdE3DKDD9E-2526s-253D27qXEoJLy9v6wZ7LpbadD07mVXM1aWPiEZiTuLYtHlE-2526e-26amp-3Bdata-3D02-257C01-257Crichard.t.jones-2540uconn.edu-257Cfb0599295e7f467e6fbc08d64e4ffcef-257C17f1a87e2a254eaab9df9d439034b080-257C0-257C0-257C636782502793219428-26amp-3Bsdata-3DXAShNOwPv7CBj7HipP-252FBZ-252Fea9oXBpNLvKCXJvyz-252Be1Y-253D-26amp-3Breserved-3D0-3D&d=DwIFaQ&c=lz9TcOasaINaaC3U7FbMev2lsutwpI4--09aP8Lu18s&r=Mwj7jqW_Gg8VvugDHdwA5w&m=t-5ZT_xIIaNrEwBR-18xFlZW_SF2qpyb3knpfqYvS2o&s=SHkMbYb9fOplOtUvT3eimhHf6wxUo1vqZAkyaL-gTLY&e= 
> <
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> There are two sheets at this link: RunPeriod-2018-08 (the proposal for this
> week) and RunPeriod-2018-01 (the data we've collected previously).  As a
> reminder, in Spring 2018 we did not have any high-statistics intensity scan
> with the final Tungsten foil installed in the beamline.
> >
> > The proposal covers the same range of intensity (Beam current x RL) as
> we had in Spring 2018, with 100M events at each setting (aside from the
> very low intensity, where the rate is too low).  As Sergey requested, this
> also includes a raw mode run at each setting of 1M events, assumed to run
> at ~3 kHz.  The goal is to have a complete set of intensity scan data for
> efficiency studies with this Fall 2018 data.
> >
> > The estimated beam time required for this proposal is ~28 hours at 100%
> efficiency, so it would likely take at least 2 days of calendar time to
> complete.
> >
> > Comments/suggestions welcome,
> > Justin
> > _______________________________________________
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> >
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