EPICS control instructions for He3 target

NOTE: Things are still changing, so if something isn't exactly as described,
use your best judgement.

0.1 How to Start the GUIs

At this time, the GUIs are only accessible from the hacsbc2 computer.
Under the "Hall A Main Menu" GUI, you'll find the choice
"Polarized He3 Target Controls". If you click on the button next to
that choice, the GUI "Polarized He3 Target Main Menu" will appear.
At this time there are six choices: RTD Readback, Ref. Cell RTD Readback,
Half-Wave Plate Motion, Vertical Target Lifting, Main Laser Control and
Oven Control. If you click on the buttons next to these choices, the
subscreens pop up.

0.2 RTD Readback

This GUI displays the temperature at various places along the target cell.
The bottom five monitors display the helium cell temperatures, while the
top two monitors display the RTDs on the pumping cell.

The alarm limits for these channels can be set by clicking on the
"Set Alarm Limits" Gui. Currently these alarms reset when the IOC is rebooted,
but they will be built-in someday.

0.3 Reference Cell RTD Readback

This GUI displays the three RTDs on the Reference Cell. At this
moment, they read bizarre values, but soon they will read the correct
reading, which is around 40 C. When the target is filled with gas
(nitrogen, He3 or He4) you'll find the pressure next to the variable
"Gas Pressure". The vacuum level is found by "System Vacuum". There
are helium jets to cool the ends of the target and reference cell. The
helium flow in liters/minute is found by the variable "Helium Flow".

0.4 How to Move the Half-Wave Plates

The target polarization can be reversed by insertion or removal of a set
of half-wave plates. The GUI for the half-wave plate control is invoked
with the "Half-Wave Plate Motion" button. The lenses only have two
positions, IN the beam path and OUT of the beam path.
The speed, acceleration, deceleration and number of steps can be defined
for the motor, but the defaults should be
fine. The distance between the IN and OUT position is 1,200,000 steps.
That number should be in the "Steps to move" box. It's the default.

The "motor position" box tells the current position of the half-wave
plates. Zero is the defined IN position and 1,200,000 is the defined
OUT position. If the half-wave plates are OUT and you want to move them
IN, click on the "GO" button
under "Move half-wave plates IN". Next to this button an "Active" sign
will appear, and the word "Moving" will appear next to the "Motor
Position" box. When the move is done, the words will disappear and the
"Motor Position" box will read "0". If the half-wave plates are IN and
you want to move them OUT, click on the "Go" button under "Move half-wave
plates OUT". The same words will pop up until the movement is finished,
then the position in the "Motor Position" box will read 1200000
(1,200,000, the out position). The is a camera set up look at the
half-wave plate motor base, and you should be able to see the carriage
over the words "IN" and "OUT" to visually verify the position.

The RS-232 communication for this device is sometimes flaky.
If the message "RS-232 failure - press the button ->" appears next
to the purple button in the middle right of the GUI, press this
button until the fault clears.

If you need to halt the motion, there's an "Emergency Stop" button located
in the upper right. Click on "HALT" and hopefully the motion will stop.
Do this if you see the motor about to drive off the motion plate
onto the floor. There are software limits set, so this shouldn't happen,
but just in case . . .

0.5 How to Move the Target

The target lifting GUI is invoked with the "Vertical Target Lifting"
button on the "Polarized He3 Target Main Menu" Gui.
There are five allowed target positions: Reference Cell, Empty Target,
BeO+12C foils, Polarized He Cell and Pick-Up Coils. These positions are
selected by clicking on the appropriate choice and then pressing the
"Start" button. The motion doesn't begin until the "Start Motor" button is
pressed. There is currently no way to cancel a motion one it has begun,
so make sure you've clicked on the correct target before you click start.
When you click on a target a number will appear in the "Dist. Abs."
readback. That number is the preset target position, in encoder
revolutions from a home switch. That number can be compared with allowed
positions by clicking on the "Display Allowed Positions" button. The
desired position, velocity, and acceleration can be set manually.
This GUI is invoked using by clicking on the "Manual Controls" button.