\documentclass{chowto}
\title{HALL C M\o ller Step-By-Step Guide - How to take a M\o ller Run}
\howtotype{user} % ``expert'', ``user'', ``reference''
\author{Howard Fenker}
\category{beamline}
\date{May 6, 2003}
\begin{document}

\begin{abstract}
A step-by-step guide for shift personnel to follow in order to take
a M\o ller run. It is assumed that the polarimeter has already been
set up and tuned for the present beam energy by an expert. 

Two modes of operation are addressed, depending on whether your experiment
normally takes data with the Moller beamline magnets ON or OFF. You should
skip to the section relevant to your experiment.
\end{abstract}

\section{GENERAL CONSIDERATIONS}

If the beam conditions, notably the current, during collection of 
physics data is significantly
different than the conditions required for M\o ller runs, there is
a significant probability that the polarization of the beam will
be different for the two cases. This contributes a systematic error
in the polarization measurement that each experiment must understand
and deal with. Clearly what you want is a measure of the polariztion
of the beam delivered during physics data taking.

It was found during e93038, for example, that the
polarization of the beam to Hall-C was noticably diluted by cross-talk
from Hall-A, and that this dilution was different when the beam
current was reduced from the nominal data condition ($50\mu$A) to the
M\o ller-run current ($1\mu$A). The best solution at that time was to
assure that beam current for M\o ller runs was reduced by using the
SLIT rather than the laser attenuator. In this way, electrons generated
by both the Hall-A laser and the Hall-C laser were attenuated by the
same amount. However, adjusting the slit also modifies the time
window during which source electrons can enter the accelerator. If there
is any time dependence of the beam polarization, slit adjustment will
affect the delivered polarization.  If, however,  one uses 
attenuation of the laser
beam to reduce the beam current to Hall-C, without making a similar
change in the Hall-A laser attenuation, one changes the fractional
amount of cross-talk, which, again, changes the delivered beam polarization.

The message here is that there is no trivial solution to this problem, and
that each experiment collaboration must perform studies and analyses
of the effective beam polarization which are appropriate for
its own particular running conditions.

\newpage


\section{HOW TO TAKE A M\o ller RUN WHEN MAGNETS ARE NORMALLY OFF}

This document describes the steps to be taken by a Hall-C experimenter
performing a M\o ller beam polarization measurement when the M\o ller magnetic elements
are normally OFF during data-taking. There is a complimentary
\htmladdnormallinkfoot{procedure}{http://opsntsrv.acc.jlab.org/ops\_docs/online\_document\_files/
MCC\_online\_files/HallC\_moller\_pol\_measurement\_proc.pdf}
which the MCC operators will follow.


\begin{enumerate}

\item {\bf M\o ller GUI}: if not displayed already, bring up the main M\o ller
	screen:
	\begin{enumerate}
	\item Login: ssh cvxwrks@cdaqh1. Standard {\bf cvxwrks} password.
	\item {\tt cd MEDM/moller}
	\item {\tt medme -x moller.adl}
	\item You should now see the main M\o ller control screen.
	\end{enumerate}

\item {\bf Verify the Cryo status}: If both the liquid nitrogen and liquid helium 
	levels in the M\o ller cryostat (shown on the above screen) are about 40\% 
	or higher, the solenoid
	is cold and ready to go. If not, fill them if your are qualified,
	or consult a M\o ller cryo
	expert to fill them for you. The M\o ller cryo screen is 
	available on the cdaqh1 left mouse button. The page is\\
	{\tt /cdaqh1/d1/cvxwrks/MEDM/moller/CRYO/hcmcryo.adl} ).

\item {\bf M\o ller BPMs}: if not displayed already, bring up the relevant BPM
	screen:
	\begin{enumerate}
	\item Log in and change directory (cd MEDM/moller) as above.
	\item {\tt medme -x BPMs\_for\_moller.adl}
	\item You should now see the M\o ller BPM screen.
	\end{enumerate}

\item {\bf Alert MCC}: Inform MCC that you are preparing for a M\o ller run.
	They will ask you what beam current you need. (Normally the lesser of
	your nominal data-run beam current or 1-2 $\mu$A, but
	see below for upper limits and when to use the moller raster.) 
	If they will be delivering less than your nominal beam current,
	ask them to reduce the current by using the SLITS. The
	laser attenuator should remain at the same setting as during
	physics data-taking (but see GENERAL CONSIDERATIONS, above).

\item {\bf Beam Tune}: The beam requires tuning into and after the polarimeter. You will
	need to energize the solenoid, have MCC turn on the quadrupoles, and have
	MCC retune the beamline. 

	To turn on the M\o ller magnets...
	\begin{enumerate}
	\item Call MCC and ask them to begin preparations for a Hall C Moller run.
	\item Have MCC turn off the slow raster if it is on, in order to avoid steering a 
		fat beam all around the beamline while the M\o ller magnets
		ramp up. 
	\item MCC will turn off the beam and inform you that it is OK to begin ramping
		up the M\o ller solenoid. Turn on the solenoid to the nominal 
		field (3T). It will take about 12 minutes to ramp up.
		
		Under {\tt Solenoid Control} on the M\o ller GUI screen:
		\begin{enumerate}
		\item Press {\tt SDBY} and wait until {\tt HEATER} is {\tt ON}.
		\item Set Field to 3.000 (Tesla) and Ramping Speed to 8.000 A/m.
		\item Press {\tt GO SET} and observe field ramping up.
		\item Later, to ramp field down, press {\tt GO ZERO}, and, 
			when field is down, press {\tt OFF} to turn off heater.
		\end{enumerate}
	\item The M\o ller expert should have made  a
		log entry with a screen snapshot of the tuned settings for
		the system. Locate that log entry for reference.
	\item MCC will save the current beam conditions and download a save file
		with the M\o ller tune, if one exists. When they energize the
		quadrupoles, you should verify that the quad currents agree with
		those from the reference log entry.
	\item Inform MCC when the solenoid field stabilizes. They will then continue
		with the M\o ller setup procedure.
	\item MCC will establish beam and center it to within 0.5~mm of zero at
		3C16 and 3C17, with the positions on these two BPMs within 0.5~mm
		of one-another. The beam at 3C18, 3C19, and 3H00 should be within
		4~mm of center (a very loose requirement).
	\item MCC will turn on M\o ller Q1 and retune the beam on 3C19 and 3H00 while keeping
		3C16 and 3C17 fixed.
	\item MCC will turn on M\o ller Q2 and retune the beam on 3C19 and 3H00, if needed,
		while keeping 3C16 and 3C17 fixed.
	\item MCC should contact you when this is completed.
	\item Verify the final BPM positions: 3C16 = (3C17 $\pm0.5$~mm); |3C16|~$\leq0.5$~mm;
		|3C17|~$\leq0.5$~mm; |3C18|, |3C19|, |3H00| all $\leq4.0$mm.
	\end{enumerate}

\item {\bf Turn Beam OFF}: request MCC to turn off beam to Hall-C so that you may
	insert the M\o ller target. (NB: this is NOT the same as moving the
	experiment target, and does NOT require masking any FSDs.)

\item {\bf Ready M\o ller Detector}: Referring to the tune snapshot, verify that
		the M\o ller collimators are within 0.05cm of their tune positions.

\item {\bf Insert M\o ller Target}: from the M\o ller GUI, select target 
	3 (4 $\mu$m thick).
	(You may also use target 2 (1 $\mu$m thick), but this is primarily intended
	for high current tests.  NEVER insert target 1 unless specifically intructed
	to by an expert - this is the ``iron wire'' target that requires careful beam position
	tuning before use.)

\item {\bf Raster}: NEVER take more than 2$\mu$A beam on a M\o ller target
	unless the M\o ller raster system is turned on-- and then only
	if you are doing it with clearance from the M\o ller expert. NEVER take
	more than 10$\mu$A on any M\o ller target EVER.

	If you need the raster, this is the time to turn it on. Flip
	the switch from OFF to ON on the M\o ller raster control NIM
	module in relay rack CH03B14 of the electronics room. You should
	be able to observe the raster pattern (an ellipse) in the
	monitor oscilloscope above the NIM crate.

\item {\bf Check BCM Range}:  If your experiment is normally running at
	currents higher than 25$\mu$A you will probably need to adjust
	the BCM gain. The selector switch is on the left-hand side of a chassis
	in rack CH03B11 in the electronics room. If you had to alter the BCM 
	gain you might inform MCC that the
	BCM readings from Hall-C will appear to be wrong during the
	M\o ller run.


\item {\bf Turn Beam ON}: request MCC to turn beam ON to the M\o ller run current.
	

\item {\bf Check M\o ller Scalers}: observe the rates by running {\tt realmoller}
	on cdaqs1 from the moller analysis directory ({\tt /home/cdaq/moller/anal/eXXXXX}) 
	where XXXXX is your experiment number. The left and right singles rates should
	be in the 100-1000 kHz range. The coincidence rate should be
	roughly 10\% of the singles rate (at LEAST 5\%), and the accidental
	rate should be no more than 5\% of the coincidence rate.
	
\item {\bf Take Data}: on the DAQ screen, which is presently waiting for you
	to begin a new run, click {\tt ABORT} then {\tt CONFIGURE}.
	Select run type {\tt MOLLER}. Then {\tt DOWNLOAD}, {\tt PRESTART}
	and {\tt GO}.  100,000 events is a typical M\o ller run size
	which should yield about 1\% statistical error.

\item {\bf Record Injector Parameters}: while taking data, record the conditions
	of the polarized source and the state of the beam to the other
	halls. (Run the script \newline
	{\tt cdaqs1>  /home/cdaq/moller/anal/eXXXXX/GetEpics.pl} \newline
	to get
	a snapshot of the polarized source settings. Capture this screen
	or transcribe its contents to the hclog.)

\item {\bf Take More Data}: while you have the system running, you may wish
	to take at least two or three runs to verify that beam conditions are
	stable. You may also wish to request a change of state for the
	half-wave plate (speak to MCC) for yet another run in order to
	verify your systematics. (The half-wave plate change requires
	agreement from any other halls taking polarized beam.)

\item {\bf Analyze Data}: 
	\begin{enumerate}
	\item ssh cdaq@cdaqs2. Standard {\bf cdaq} password.
	\item {\bf cd moller}
	\item {\bf cd anal}
	\item {\bf cd eXXXXX}, where XXXXX is your experiment number.
	\item {\bf replaynt RRRRR}, where RRRRR is the run number for M\o ller data.
	\item Answer any questions asked. Non-experts shoule answer {\tt ``n''} 
		for ntuples. The software will display
		the measured polarization and a number of other results.
		It also generates a .hbook file which may be of interest
		if something seems wrong with the result. 
	\item Use {\tt paw} or {\tt paw++} to view the histograms. Running the
		macro {\tt mscan RRRRR} (where {\tt RRRRR} is the run number)
		will present a slide show of the more interesting histograms.
		The critical one for non-experts is the color surface plot
		showing left/right hodoscope correlation. It
		should show a ridge along the x=y diagonal.
		If this ridge is not present or
		is significantly off center, the polarimeter is not properly
		tuned. You should consult a M\o ller expert in this case.
	\item Make a log entry summarizing all of your M\o ller runs and the results.
		The value to record is the beam polarization with accidentals removed.
		If the polarized source setup was changed between runs be sure to
		make a clear note of the conditions in the hclog.
	\end{enumerate}

\item {\bf Restore Conditions}: Undo whatever you did and go back to production running:
	\begin{enumerate}
	\item Request beam off.
	\item Retract M\o ller target.
	\item Restore BCM gain setting if necessary.
	\item Restore DAQ to production mode.
	\item Disable M\o ller Raster.
	\item Have MCC turn on the slow and/or fast raster if needed.
	\item Turn off the M\o ller magnets (MCC controls the two quadrupoles, you control
		the superconducting solenoid).
	\item  Have MCC re-tune the beamline to data-taking condtions.
	\end{enumerate}
\end{enumerate}
\newpage
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\section{HOW TO TAKE A M\o ller RUN WHEN MAGNETS ARE ALREADY ON}

This document describes the steps to be taken by a Hall-C experimenter
performing a M\o ller beam polarization measurement when the M\o ller magnetic elements
are normally ON during data-taking. There is a complimentary
\htmladdnormallinkfoot{procedure}{http://opsntsrv.acc.jlab.org/ops\_docs/online\_document\_files/
MCC\_online\_files/HallC\_moller\_pol\_measurement\_proc.pdf}
which the MCC operators will follow.


\begin{enumerate}

\item {\bf M\o ller GUI}: if not displayed already, bring up the main M\o ller
	screen:
	\begin{enumerate}
	\item Login: ssh cvxwrks@cdaqh1. Standard {\bf cvxwrks} password.
	\item {\tt cd MEDM/moller}
	\item {\tt medme -x moller.adl}
	\item You should now see the main M\o ller control screen.
	\end{enumerate}

\item {\bf Verify the Cryo status}: Verify that the liquid helium and
	liquid nitrogen levels in the M\o ller solenoid cryostat are
	reasonably stable and near full. The M\o ller cryo screen is 
	available on the cdaqh1 left mouse button. The page is\\
	{\tt /cdaqh1/d1/cvxwrks/MEDM/moller/CRYO/hcmcryo.adl} ).

\item {\bf M\o ller BPMs}: if not displayed already, bring up the relevant BPM
	screen:
	\begin{enumerate}
	\item Log in and change directory (cd MEDM/moller) as above.
	\item {\tt medme -x BPMs\_for\_moller.adl}
	\item You should now see the M\o ller BPM screen.
	\end{enumerate}

\item {\bf Alert MCC}: Inform MCC that you are preparing for a M\o ller run.
	They will ask you what beam current you need. (Normally the lesser of
	your nominal data-run beam current or 1-2 $\mu$A, but
	see below for upper limits and when to use the moller raster.) 
	If they will be delivering less than your nominal beam current,
	ask them to reduce the current by using the SLITS. The
	laser attenuator should remain at the same setting as during
	physics data-taking (but see GENERAL CONSIDERATIONS, above). 

\item {\bf Beam Tune}: The beam might require tuning into and after the polarimeter,
	since the tune at the polarimeter is not of particular concern during 
	data-taking for the experiment.

	To check/achieve beam tune for the M\o ller Polarimeter...
	\begin{enumerate}
	\item The M\o ller expert should have made  a
		log entry with a screen snapshot of the tuned settings for
		the system. Locate that log entry for reference.
	\item Verify that the M\o ller solenoid is on at 3~Tesla and that the two
		M\o ller quadrupoles are on at the established tune currents.
		(MCC controls the quads, you control the solenoid). 
	\item If they are not already doing it, request MCC to check and/or
		tune the beam for a Hall C Moller run.
	\item MCC will center the beam to within 0.5~mm of zero at
		3C16 and 3C17, with the positions on these two BPMs within 0.5~mm
		of one-another. The beam at 3C19, and 3H00 will be tuned
		to within 4~mm of center (a very loose requirement). You should
		expect 3C18 to be within 4~mm of zero, as well, just to assure
		that the beam is inside the pipe.
	\item MCC should contact you when this is completed.
	\item Verify the final BPM positions: 3C16 = (3C17 $\pm0.5$~mm); |3C16|~$\leq0.5$~mm;
		|3C17|~$\leq0.5$~mm; |3C18|, |3C19|, |3H00| all $\leq4.0$mm.
	\end{enumerate}

\item {\bf Turn Beam OFF}: request MCC to turn off beam to Hall-C so that you may
	insert the M\o ller target. (NB: this is NOT the same as moving the
	experiment target, and does NOT require masking any FSDs.)

\item {\bf Ready M\o ller Detector}: Referring to the tune snapshot, verify that
		the M\o ller collimators are within 0.05cm of their tune positions.

\item {\bf Insert M\o ller Target}: from the M\o ller GUI, select target 
	3 (4 $\mu$m thick).
	(You may also use target 2 (1 $\mu$m thick), but this is primarily intended
	for high current tests.  NEVER insert target 1 unless specifically intructed
	to by an expert - this is the ``iron wire'' target that requires careful beam position
	tuning before use.)

\item {\bf Raster}: NEVER take more than 2$\mu$A beam on a M\o ller target
	unless the M\o ller raster system is turned on-- and then only
	if you are doing it with clearance from the M\o ller expert. NEVER take
	more than 10$\mu$A on any M\o ller target EVER.

	If you need the raster, this is the time to turn it on. Flip
	the switch from OFF to ON on the M\o ller raster control NIM
	module in relay rack CH03B14 of the electronics room. You should
	be able to observe the raster pattern (an ellipse) in the
	monitor oscilloscope above the NIM crate.

\item {\bf Check BCM Range}:  If your experiment is normally running at
	currents higher than 25$\mu$A you will probably need to adjust
	the BCM gain. The selector switch is on the left-hand side of a chassis
	in rack CH03B11 in the electronics room. If you had to alter the BCM 
	gain you might inform MCC that the
	BCM readings from Hall-C will appear to be wrong during the
	M\o ller run.


\item {\bf Turn Beam ON}: request MCC to turn beam ON to the M\o ller run current.
	

\item {\bf Check M\o ller Scalers}: observe the rates by running {\tt realmoller}
	on cdaqs1 from the moller analysis directory ({\tt /home/cdaq/moller/anal/eXXXXX}) 
	where XXXXX is your experiment number. The left and right singles rates should
	be in the 100-1000 kHz range. The coincidence rate should be
	roughly 10\% of the singles rate (at LEAST 5\%), and the accidental
	rate should be no more than 5\% of the coincidence rate.
	
\item {\bf Take Data}: on the DAQ screen, which is presently waiting for you
	to begin a new run, click {\tt ABORT} then {\tt CONFIGURE}.
	Select run type {\tt MOLLER}. Then {\tt DOWNLOAD}, {\tt PRESTART}
	and {\tt GO}.  100,000 events is a typical M\o ller run size
	which should yield about 1\% statistical error.

\item {\bf Record Injector Parameters}: while taking data, record the conditions
	of the polarized source and the state of the beam to the other
	halls. (Run the script \newline
	{\tt cdaqs1>  /home/cdaq/moller/anal/eXXXXX/GetEpics.pl} \newline
	to get
	a snapshot of the polarized source settings. Capture this screen
	or transcribe its contents to the hclog.)

\item {\bf Take More Data}: while you have the system running, you may wish
	to take at least two or three runs to verify that beam conditions are
	stable. You may also wish to request a change of state for the
	half-wave plate (speak to MCC) for yet another run in order to
	verify your systematics. (The half-wave plate change requires
	agreement from any other halls taking polarized beam.)

\item {\bf Analyze Data}: 
	\begin{enumerate}
	\item ssh cdaq@cdaqs2. Standard {\bf cdaq} password.
	\item {\bf cd moller}
	\item {\bf cd anal}
	\item {\bf cd eXXXXX}, where XXXXX is your experiment number.
	\item {\bf replaynt RRRRR}, where RRRRR is the run number for M\o ller data.
	\item Answer any questions asked. Non-experts shoule answer {\tt ``n''} 
		for ntuples. The software will display
		the measured polarization and a number of other results.
		It also generates a .hbook file which may be of interest
		if something seems wrong with the result. 
	\item Use {\tt paw} or {\tt paw++} to view the histograms. Running the
		macro {\tt mscan RRRRR} (where {\tt RRRRR} is the run number)
		will present a slide show of the more interesting histograms.
		The critical one for non-experts is the color surface plot
		showing left/right hodoscope correlation. It
		should show a ridge along the x=y diagonal.
		If this ridge is not present or
		is significantly off center, the polarimeter is not properly
		tuned. You should consult a M\o ller expert in this case.
	\item Make a log entry summarizing all of your M\o ller runs and the results.
		The value to record is the beam polarization with accidentals removed.
	\end{enumerate}

\item {\bf Restore Conditions}: Undo whatever you did and go back to production running:
	\begin{enumerate}
	\item Request beam off.
	\item Retract M\o ller target.
	\item Restore BCM gain setting if necessary.
	\item Restore DAQ to production mode.
	\item Disable M\o ller Raster.
	\item Have MCC turn on the slow and/or fast raster if needed.
	\item Verify that the M\o ller magnets (solenoid and two quads)
		are STILL on at the tune settings.
	\item  Have MCC re-tune the beamline, if needed, to data condtions.
	\end{enumerate}
\end{enumerate}

\end{document}

% Revision history:
% $Log: moller_sbys.tex,v $
% Revision 1.2  2003/11/18 14:44:38  saw
% (djg) Changed description of target configuration to reflect hardware changes.
%
% Revision 1.1  2003/06/12 16:16:47  saw
% Copied from existing document by hcf 5/6/03
%
