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Thanks Nathan,
 Applying the equation from Stepan this corresponds to ~ -0.33T .
I will then use the field map values from the file

125acm2_3kg.table

with a scaling factor of ~1.1.
Norman
________________________________________
From: Nathan Baltzell <[log in to unmask]>
Sent: Sunday, February 8, 2015 11:56 AM
To: Graf, Norman A.
Cc: Stepan Stepanyan; hps-software
Subject: Re: Bfield conditions

Hi Norman,

Here it is from the database every 30 minutes:
https://userweb.jlab.org/~baltzell/HPS/engrun/hps_pspec_current.txt

There was also a scale factor in the run spreadsheet,
which was copied to the data catalog under nChicaneOffset.

-Nathan



On Feb 8, 2015, at 14:39, Graf, Norman A. <[log in to unmask]> wrote:

> Hello Stepan,
> Where can I find a record of the analyzing dipole current for the engineering run?
> Norman
> ________________________________________
> From: Stepan Stepanyan <[log in to unmask]>
> Sent: Tuesday, February 3, 2015 8:40 AM
> To: Graf, Norman A.; McCormick, Jeremy I.; Nathan Baltzell
> Cc: hps-software
> Subject: Re: Bfield conditions
>
> Hi Norman,
>
> OK, fine, so we do not need a scaling factor in conditions DB.
> What we will need in addition to my list is the parameters
> of functions B_field(G)=a+b*I(A), and I(A)=c+d*B_field(G),
> relation between current and central field. Here are parameters:
> a=-4.298
> b=-6.506
> c=-0.6657
> d=-0.1537
>
> Regards, Stepan
>
>
> On 2/3/15 10:02 AM, Graf, Norman A. wrote:
>> Hello Stepan,
>>  For any particular analyzing dipole magnet setting, we would either use the
>> calculated field map at the next highest calculated point and scale it down, or
>> the next lower calculated point and scale it up.
>>
>> "Any scaling factor will depend on values of central fields of closest simulated
>> field maps and the value of the central field we run with."
>> Exactly.
>>
>> "So, where this independent scaling factor comes into play?"
>> There is no independent scaling factor. It is derived as you mentioned above.
>>
>> Norman
>> ________________________________________
>> From: Stepan Stepanyan <[log in to unmask]>
>> Sent: Tuesday, February 3, 2015 3:42 AM
>> To: Graf, Norman A.; McCormick, Jeremy I.; Nathan Baltzell
>> Cc: hps-software
>> Subject: Re: Bfield conditions
>>
>> Hi Norman,
>>
>> Thanks for the explanations, but I m not sure I got it.
>> Yes, we have field maps at some discrete values of central
>> fields (or currents) and highly unlikely experiment will run
>> at any of the existing values. The experimental setting will
>> be in between some of two existing maps. Any scaling factor
>> will depend on values of central fields of closest simulated
>> field maps and the value of the central field we run with.
>>
>> So, where this independent scaling factor comes into play?
>>
>> Regards, Stepan
>>
>> On 2/2/15 11:22 PM, Graf, Norman A. wrote:
>>> Hello Stepan,
>>>   You provided field maps calculated at discrete values of the central field.
>>> For simulation and reconstruction we will be using the field maps
>>> calculated for the nominal running field and apply an overall scaling
>>> factor to account for deviations in the analyzing dipole magnet current.
>>> Norman
>>> ________________________________________
>>> From: Stepan Stepanyan <[log in to unmask]>
>>> Sent: Monday, February 2, 2015 7:15 PM
>>> To: McCormick, Jeremy I.; Graf, Norman A.; Nathan Baltzell
>>> Cc: hps-software
>>> Subject: Re: Bfield conditions
>>>
>>> Hello Jeremy,
>>>
>>> My list for magnet settings will be the following:
>>> - beam energy (since magnet setting depends on it)
>>> - analyzing magnet current as measure on power supply
>>> - analyzing field as measured in the homogenous region
>>> - frascati magnet current as measured on the power supply
>>> - frascati magnet field value as measured in the homogenous region
>>> Frascati setting is important since the beam direction on the target
>>> depends on it.
>>> All of these will be injected to data stream as part of EPICS as well as
>>> will be
>>> available through the slow control data base (MYA).
>>>
>>> Of course, in addition to the field values in homogenous region we
>>> should have the full field
>>> maps stored, available somewhere. We should define how we will scale
>>> field maps, e.g.
>>> take the closest available (in current or in central field value) and
>>> scale, or fit point by point.
>>>
>>> By the way, I am not sure what it means scaling factor, may be some one
>>> can explain me.
>>>
>>> Regards, Stepan
>>>
>>>
>>> On 2/2/15 8:55 PM, McCormick, Jeremy I. wrote:
>>>> Hi, Norman.
>>>>
>>>> Thanks for the information.
>>>>
>>>> I basically need to know what the database table(s) should look like....
>>>>
>>>> e.g.
>>>>
>>>> What columns should it have?  What are the units on those columns?
>>>>
>>>> The proposal on the JIRA item currently is....
>>>>
>>>> field - the measured By (I think?) in Tesla, presumably of the analyzing dipole
>>>>
>>>> scale - scaling factor of the B-field for the run (all components)
>>>>
>>>> So is that enough for what we want to do with this information in recon/analysis?  Or do we need more columns with additional information?
>>>>
>>>> If we need more columns, please tell me what they should be.
>>>>
>>>> Also, if there are different conditions measured at different times (multiple magnets?), then we can model them with other classes.
>>>>
>>>> Right now, I'd propose a generic "BfieldConditions" object but we aren't limited to having one type if more classes/tables are needed for this.
>>>>
>>>> Thanks.
>>>>
>>>> --Jeremy
>>>>
>>>> -----Original Message-----
>>>> From: Graf, Norman A.
>>>> Sent: Monday, February 02, 2015 5:47 PM
>>>> To: Nathan Baltzell; McCormick, Jeremy I.
>>>> Cc: hps-software
>>>> Subject: Re: Bfield conditions
>>>>
>>>> Jeremy, et al.,
>>>>     We will need to monitor the analyzing dipole current. I assume this is an EPICS variable, or should be. We will also be mounting a Hall probe onto the SVT support plate. This will give us a direct measure of the magnetic field strength. Deviations from nominal settings will give us the scaling factor to use for the simulation/reconstruction. I would use the magnet current as the primary and the Hall probe as check, but we can monitor both during early commissioning.
>>>> Norman
>>>> ________________________________________
>>>> From: [log in to unmask] <[log in to unmask]> on behalf of Nathan Baltzell <[log in to unmask]>
>>>> Sent: Monday, February 2, 2015 5:24 PM
>>>> To: McCormick, Jeremy I.
>>>> Cc: hps-software
>>>> Subject: Re: Bfield conditions
>>>>
>>>> Hi Jeremy,
>>>>
>>>>> current - the beam current in amps
>>>> I think beam current is not related to chicane settings.
>>>>
>>>>> But I'm not sure where this information all comes from...
>>>> Empirical numbers are magnet currents, from which comes a scale factor relative to some defined nominal value.
>>>>
>>>>> current - Will this be in the data stream for the upcoming runs?  Or
>>>>> should we access it through the MYA command line tool?  (Obviously
>>>>> prefer into the data stream.)
>>>> We will be putting various EPICs variables, including chicane current readbacks, into EVIO every few seconds for the next run.  How we will parse it needs to be written and tested.
>>>>
>>>> -Nathan
>>>>
>>>>
>>>>
>>>> On Feb 2, 2015, at 7:44 PM, "McCormick, Jeremy I." <[log in to unmask]> wrote:
>>>>
>>>>> -----Original Message-----
>>>>> From: McCormick, Jeremy I.
>>>>> Sent: Monday, February 02, 2015 4:43 PM
>>>>> To: 'Nathan Baltzell'
>>>>> Cc: Graham, Mathew Thomas; Graf, Norman A.
>>>>> Subject: RE: Bfield conditions
>>>>>
>>>>> Hi, Nathan.
>>>>>
>>>>> I'll CC a couple people who might be interested in this...
>>>>>
>>>>> It was requested that I add B-field information to the conditions system.
>>>>>
>>>>> https://jira.slac.stanford.edu/browse/HPSJAVA-312
>>>>>
>>>>> So I was planning to just add a single table with...
>>>>>
>>>>> current - the beam current in amps
>>>>>
>>>>> field - measured field value in tesla or kG
>>>>>
>>>>> scale - scaling factor of field map for the run
>>>>>
>>>>> But I'm not sure where this information all comes from...
>>>>>
>>>>> current - Will this be in the data stream for the upcoming runs?  Or
>>>>> should we access it through the MYA command line tool?  (Obviously
>>>>> prefer into the data stream.)
>>>>>
>>>>> field - Field value at the IP or some other position?  When is this measured?  How do we get it automatically?  Or do we just input this manually?
>>>>>
>>>>> scale -  I don't know how we get this number.  Is it derived from the current?  If it is derived should we even store it separately or just compute on the fly?
>>>>>
>>>>> I can add the API regardless of whether we know how to get the information, but we should discuss how to access/load this information up front.
>>>>>
>>>>> Thanks.
>>>>>
>>>>> --Jeremy
>>>>>
>>>>> -----Original Message-----
>>>>> From: Nathan Baltzell [mailto:[log in to unmask]]
>>>>> Sent: Monday, February 02, 2015 4:33 PM
>>>>> To: McCormick, Jeremy I.
>>>>> Subject: Re: Bfield conditions
>>>>>
>>>>> Chicane setting relative to nominal is in data catalog, done manually from the spreadsheet this time.  We also have magnet currents in epics.
>>>>>
>>>>> This will be something that will be in the jlab mysql run db next time (in progress ...).
>>>>>
>>>>>
>>>>>
>>>>> On Feb 2, 2015, at 7:23 PM, "McCormick, Jeremy I." <[log in to unmask]> wrote:
>>>>>
>>>>>> I might have missed this someplace....
>>>>>>
>>>>>> Do we have any B-field conditions for the runs?
>>>>>>
>>>>>> Like current, scaling, etc.
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