Note about RSS beam position
1.  Surveys: For survey +X is beam left, +Y is up and +Z is downstream. Find that the Z position at the target was +1.97mm for perpendicular target running and at -2.05mm from parallel target running. The horizontal center of the SEM was at +0.55mm for the perpendicular target running and at -0.02mm for parallel target running. Have ignore this since the experiment is not sensitive to horizontal position at the 0.5mm level.

2.  Beam position coordinates (+Z is downstream) :

Horizontal Postion
 Vertical Position
Epics variables
 +BPMX is beam right
 +BPMY is up
SEM  (ntuple)
 +ntbpmx is beam right
 +ntbpmy is up
calibADC (ntuple)
 +calSRx is beam right
 +calSRy is up
Raw Slow raster ADC (ntuple)
 small gsry_adc is beam left
 small grsx_adc is up
Internal Engine beam position variable
 +x_coord is beam right
 +y_coord is up
Internal Engine beam position variable
 +gSR_beamy is beam left
 +gSR_beamx is down

3.  The variables ntbpmx(y) , calSRx(y) and gsrx(y)_adc are ntuple variable names. ntpbmx(y) is from the SEM and has units of mm. ntpbm is a measure of the absolute beam position. gsrx(y)_adc is a measure of the slow raster ADC. calSRx(y) is a calibrated value of the gsrx(y)_adc . In the code SRC_gen/g_calc_sr_beampos.f

        x_coord = n_sr_slopex*(gsry_adc-n_sr_adcx_zero) + n_sr_offsetx
        y_coord = n_sr_slopey*(gsrx_adc-n_sr_adcy_zero) + n_sr_offsety


Typical values of  gsrx(y)_adc are shown in this plot. In DBASE/rss.database set n_sr_adcy_zero =3700 and n_sr_adcx_zero =4100 for all runs.  n_sr_slopex(y) and n_sr_offsetx(y) can be determined for each run by calibrating the slow raster ADC to the SEM ntbpm . There is a paw kumac which does that calibration. The ratio ( n_sr_slope) between the raster adc and the actual beam position at the SEM is assumed not to change during the experiment. In DBASE/rss.database set n_sr_slopex = 0.00285 and n_sr_slopey = -0.00285 . The n_sr_offsetx(y) can change during the experiment and could be determined for each run.

4.  A plot of the EPICS bpm positions (in mm) shows that the horizontal beam position was fairly steady with 4 main regions. The vertical beam position was steady for the perpendicular target running (runs 43231-43611), but for the parallel running there are distinct periods where the beam was at -1mm, -0.5mm or 0mm.

Tables of the horizontal and vertical positions:

Run range
 EPICS X bpm (mm) SEM (ntbpmx) (mm)
43231-43340
 -1.5
 -2.3
43341-43611
 -1.2
 -1.9
43702-43805
 -2.2
 -3.3
43806-99999
 -1.9
 -2.7


run range
 EPICS Y bpm (mm)
 SEM (ntbpmy) (mm)
43231-43650
 0.0
 -1.25
43651-43701
 na
 0.0
43702-43704
 -1.0
 -3.4
43705-43709
 na
 -3.4
43710-43710
 -0.5
 -2.3
43711-43719
 0.0
 -1.1
43720-43728
 -0.5
 -2.3
43729-43738
 0.0
 -1.1
43739-43741
 -0.5
 -2.3
43742-43755
 0.0
 -1.1
43756-43805
 -1.0
 -3.4
43806-99999
 0.0
 -1.1