[Sane-analysis] Update to CVS for g_analyze_scaler_bank.f

[O. A. Rondon]

Hi Mark,

Good analysis. What we need to do is to confirm that the parallel runs
with unpolarized targets do have the false 0.002 asymmetry that I see
for seven runs. Since the clocks were OK during parallel this asymmetry
should not be there due to clock issues. If it is really there anyway,
then it could also be in the 80 deg data, perhaps adding to the clock
asymmetry.

One thing that is interesting is that .998 (or 1/.998) is also like the
.002 unpolarized target asymmetry I see.

I have posted an updated table for the unpolarized target parallel
asymmetries, including conventional livetime corrections, i.e. using
0.985*{gscaler(510)-gscaler(538)) to get the number of hel. plus
recorded (gscaler(538) is hel. minus); this probably should be OK for
parallel, given the >90% livetimes and clocks working.

The table is here
http://www.jlab.org/~rondon/sane/analysis/asym/a_para_unpol_beta4.pdf

The errors for the last two asymmetry numbers (Q normalized and LT
correction) are not quite exact, I will update them. But the ~ -0.002
false beam asymmetry seems to persist.

Cheers,

Oscar

Mark Jones wrote:
> Hello all,
>       The scalers measure the average beam current (cur) ,
> the current with helicity plus (pcur) and helicity minus (mcur).
> The beam current is monitored by a cavity which produces a voltage
> which is then converted to a frequency (V to F converter).
> An additional complication is that the there is always a positive offset 
> voltage to the signal going into V to F converter, so even at zero
> current the "charge" scalers are counting. This frequency is about
> 250kHz. When there is a 100nA beam the frequency rise only to
> 257kHz. The time is needed to convert the current to a charge.
> The scalers measure the total time (time), the time with
> helicity plus (ptime) and helicity minus (mtime) using a 1Mhz clock.
> The actual beam current is calculated as
> 
> beam current = ( cur/time - 250kHz)*(conversion const)
> charge = beam current * time
> 
> There is a 500usec blanking period when the beam helicity
> is flipped to let the polarization of the beam settle.
> The beam is flipped at 30Hz so one expects that the
> ratio of (ptime + htime)/time = 0.985 . Also
> same for the charge (pch + mch)/charge = 0.985 .
> 
> 
>       Hoyoung noticed that for run 72377 that the
> (pch + mch)/charge  was not 0.985. I actually found
> it to be larger than one. Because of
> problems with the 1Mhz signal down in the hall
> during runs 72476 to 72588 we had be using scaler
> 174 which was also a 1mHz clock. I looked closer at
> run 72377 and found that scaler 503 was actually getting
> 0.998 MHz so this signal was also going to the helicity
> plus and minus clocks. So the total charge was using
> the 1Mhz clock while the charge scalers were using a
> 0.998MHz under the assumption that it was 1.0MHz.
> This change in the clock from 1MHz to 0.998MHz for run
> 72377 must be do to missing some of the pulses. Eventually
> the signal failed downstairs for runs 72476 to 72588.
> After run 72588 the scaler 503 is 1mhz and agrees with
> scaler 174, so the problem doesn't exist.
> 
> 
> To fix the problem before run 72476 I scaled
> 
> delta_time_help =delta_time*gscaler_change(516)/gscaler_change(503)
> delta_time_helm =delta_time*gscaler_change(515)/gscaler_change(503)
> 
> where delta_time is the time using scaler 174.
> 
> 
> For runs 72476 to 72588, I use the fact that over
> a long time period the time for each helicity is 0.985/2.
> and
> 
> delta_time_help = 0.4925*delta_time
> delta_time_helm = 0.4925*delta_time
> 
> Of course for a 2 sec period this is wrong, since 1/30
> is a significant part of 2.  But over the period
> of a run then 1/30 sec is small.
> 
> 
> I did notice the
>   (ptime + htime)/time = 0.98527 which is
> close to the expected 0.985 .
> But for the charge
> (pch + mch)/charge = 0.9839 .
> 
> The ratio is 1.0014 which is close the
> false asymmetry that we are seeing. But
> I can't assign the missing part to the
> plus or minus helicity since the charge
> asymmetry is at this level.
> 
> So I have put a new version of g_analyze_scaler_bank.f
> in the CVS.
> 
> 
>                         Mark
> 
> 
>