Difference between revisions of "BCM calibration E06007"

Latest revision as of 22:13, 12 February 2010

Wiki Entry

https://hallaweb.jlab.org/wiki/index.php/BCM_calibration_E04-018

PVDIS entry

http://hallaweb.jlab.org/experiment/E08-011/documents/bcm/AboutBCMcalibrations.html

BCM LOGS

http://hallaweb.jlab.org/experiment/E08-011/documents/bcm/bcmLogs

Previous SCALERS CALIBRATION used in end of run information

http://www.jlab.org/~adaq/halog/html/0705_archive/070530235058.html

I-scan runs in E06007 http://spreadsheets.google.com/ccc?key=0AomwfAy24yA3dEpFQ3k0QnhUQzJ2VEFKei0xaVdIY1E&hl=en

Steps for BCM calibration

The Run faraday cup vs I0L02 is in [BcmLog125]

Faraday vs Injector current - From BCMLOg-125 - 20Feb07

Faraday_Current = (0.28+-0.03) + (0.994+-0.001) * IBC0L02_Current

Faraday / Injector = 1.0027 +- 0.0006 , for Current >5uA

Ratio Faraday vs I0L02 (All range)	Ratio Faraday vs I0L02 (Current > 5uA)

Check of the Average Beam Current used in E06007 -- Only initial optics calibration runs used low currents -

A complete list of run information can be found in the link in the initial page: https://hallaweb.jlab.org/wiki/index.php/E06-007

EPICS calibration from bcmlog-127 (Offsets without current in Hall from bcmlog-125)

Note that the constants differ significantly from the ones used in the Start of Run info. The values obtained in CSR are: 43.399±0.558 and 42.913±0.358, which are similar (within error bars) to the ones obtained here.

Start of Run info: Upstream Cavity Coefficient : 45.218 Downstream Cavity Coefficient : 45.532

Production Runs without Current in Hall C --> Run 1326, 1327, 1328 (Bi,80uA)

Sample of Cosmics Runs for Scalers Offset along the experiment--> Run 1335, 1488, 1752, 2006

They can be used to check offset variations as showed in Vince's Tech note.

http://hallaweb.jlab.org/experiment/E97-110/tech/bcm_info.pdf

BCM Epics variables

--> "hac_bcm_average hac_bcm_dvm1_read hac_bcm_dvm2_read hac_bcm_dvm1_current hac_bcm_dvm2_current hac_unser_current IPM2C24A.IENG IBC0R07CRCUR1 IBC1H04CRCUR2 FCupsCORRECTED.VAL EHAR_LIXWidth EHAR_LIYWidth EHAR_ENABLE EHAR_IXPEAK EHAR_IYPEAK"

--> hac_bcm_average = 0.5*(hac_bcm_dvm1_current + hac_bcm_dvm2_current) [dvm1-->upstream, dvm2-->downstream]

--> hac_bcm_dvm1_current = (hac_bcm_dvm1_read - offset)*Calibration_constant

Instead of hac_bcm_average (that uses the uncalibrated end of run constant), using hac_bcm_dvm(1,2)_read and the calibrated constant from bcmlog_127 a value closer to the Injector Current IOLO2 is obtained:

The ratio can be also obtained for each BCM. It can be seen that the upstream seems to perform better. Nevertheless the range around 40uA (where most of the production data were acquired) is very close to 1.0.

BCM Scalers offset calibration from Run 1335 (Without Current).

METHOD 1: Linear fit from the plot of number of counts vs time: T->Draw("left_bcmd10cnt:left_clkcount/1024","abs(IBCxxxxCRCUR1)<1");

METHOD 2: Average of counts (Fit with zeroth order pol.) T->Draw("left_bcm_d10:left_clkcount/1024","abs(IBCxxxxCRCUR1)<1");

BCM Scalers Calibration from I-scan runs (1179-1188) I obtained it from a macro that I have created. It can be found at:

http://jlab.org/~juaky/scaler_calib.C

In the CSR, the constant obtained for U3 was: 7294 +- 7 , so compared to our 7281 +- 2 there is a good agreement. http://www.jlab.org/%7Exyan/CSR/Meeting/BcmCalib.pdf

In order to get the charge from a file:

Q = (scaler_bcm - offset(Hz) * time(s) ) / calib_constant

Q(C) = 1e-6 *( right_bcmu3cnt - 449.124 * (right_clkcount/1024) ) / 7281.35

Example of difference between End-Of-Run Charge measurement and the new calibrated values (From the formula above)

Differences are below 0.25% (So End-of-Run measurement can be used - That's good)

RUN 1518 - iQ_OLD= 0.06444 iQ_NEW= 0.0643114 RUN 1519 - iQ_OLD= 0.0404 iQ_NEW= 0.040319 RUN 1520 - iQ_OLD= 0.01537 iQ_NEW= 0.0153399