Setup Procedure for LFC (Mark Metzger, Rob Simcoe)


I.   Pumping and cooling the dewar
II.  Prime focus installation and cabling procedure
III. Swapping filters in the filter wheel


I. Pumping on the dewar with the turbo pump

Instructions for pumping LFC before cool-down.  You should start pumping on
the day before you want to mount it on the telescope, so that you can fill
the dewar about 24 hours before it needs to be used.  The LFC takes about 24
hours to reach operating temperature.

The LFC should be pumped only with a dry turbomolecular pump system.  This
is a special pump that uses a turbine combined with an oil-free backing
pump.  It is used to make sure that no oil (which is present in the other
Palomar pumps) can get into the dewar and contaminate the CCDs.

These instructions assume that the LFC is in its normal state.  That is, it
has simply warmed up in between runs, but is still close to vacuum
pressure.  (NOTE:  the LFC should never be opened up to atmospheric pressure
without first consulting Mark Metzger).  Do not attempt to pump the LFC
before it has completely warmed up: this can lead to Very Bad Things.

0. Connect the convectron gauge (made by Granville-Phillips) to the
   convectron mounted on the LFC.  It is opposite the valve, and has a blue
   plastic connector.  Plug in the gauge.  You should see it reading some
   number of milliTorr, but it should not be above 2 Torr.  (mTorr readings
   are when the small LED in the corner is illuminated.)  Plug in the

1. Remove the "blank" (cover) from the valve opening on the LFC.  DO NOT
   OPEN THE VALVE YET!!!  There is a piece of tape on the quick release
   clamp, for now, that makes sure it does not pop open: save this or use a
   new piece when you replace it at the end.

2. Connect the hose to the LFC valve, using the centering ring (which has a
   Viton rubber gasket on the outside that makes the seal).  You will have to
   remove a blank and a centering ring from the end of the hose as well.  Do
   not touch with your fingers any part of the inside of the hose, the
   inside of the valve, or the metal part of the centering ring.  Handle the
   centering ring only by the edges of the Viton.  When properly connected,
   the quick clamp should close fairly easily, but with a small amount of
   force in the middle which eases at the end and clicks closed.  Note that
   you are connecting to the end of the hose that has a reducer; the end
   without the reducer should connect to the valve on the pump in the same
   manner.  In all cases, try to keep the blanks clean: don't touch the
   inner part of the inside.  Even natural grease from your fingers can
   contaminate vacuum parts, and they're difficult to clean.

3. Make sure the valve on the top of the turbo pump is open to the hose
   (several turns counter-clockwise, but be sure not to turn the valve hard
   after it reaches the counter-clockwise stop.

4. Turn on the turbopump by pressing the Start/Stop button under the LCD.
   You should hear the backing pump start (and notice the hose being evacuated,
   which is important), and hear the turbopump start to spin up.

5. Leave the pump run for about 5 minutes.  This will ensure that the turbo
   has had enough time to spin up.  When the turbo is fully spun up, you
   should see on the pump display something like "Normal Operation" or "75K

6. Once the pump is in normal operation and up to speed, open the valve
   on the LFC about 3 turns counterclockwise.  You should immediately see
   the pressure gauge start to drop.

7. Leave the pump run for about 3 hours.  You should see the pressure drop
   steadily, but slow down toward the end.  You want to achieve a pressure
   of 2 mTorr or less, sometimes it will reach "0 with a dot (LED)", which
   is about 0.5 mTorr--this is ideal.
	NOTE: You should check the pump periodically to make sure that the 
	    turbo is operating properly at 75 KRPM.  The turbo has been known
	    to crap out in the past, reducing it's speed to 45 KRPM and 
	    causing the pump to work less efficiently.  If this happens,
	    immediately close off the valve to the dewar, and follow the 
	    procedure for turning off the pump.  Then, power the pump back on
	    and try again.  This may seem a little silly, but it works.
8. Before cooling LFC, nitrogen must be flowing through the instrument to
     prevent the possibility of a "Frost Ring" on the window.

9. When the pressure is less than 2 mTorr or 3 hours has expired, whichever
   is later, you can start filling the dewar.  Start putting LN2 into the
   dewar, and once the flow is started and you see a lot of gas blowing out,
   close the vacuum valve on the LFC.  You may see the pressure rise briefly,
   but once the can starts to cool down a bit, the pressure should drop to 0
   mTorr, and the LED in the corner to turn out (0 without a dot).  Continue
   filling the dewar--it takes a lot of nitrogen!!!

10. As you are filling, double-check that the LFC valve is CLOSED.  

11. Close the valve on the top of the turbopump.

12. Turn off the power to the pump by pressing the start/stop button again.
    You should hear the backing pump shut off and the turbo start to spin

13. Disconnect the hose from the LFC, and replace the blank to close off the
    valve and keep it clean.  It will be slightly difficult to break the
    first connection, as there will still be a vacuum in the hose.

14. Once the dewar is full, you're done!  The dewar hold time is >24 hours,
    so it should only need filling once a day, and in the morning is best.
    However, after the initial fill it may be prudent to top things off
    again on the afternoon of the first night, since more LN2 will be burned
    off while cooling down the focal plane.  When performing the top-off,
    first check the vacuum with the convectron to make sure everything is
    happy (i.e., reading zero, no LEDs)

*** WARNINGS ***

the pump for some reason while you are running, close both valves first.

B. Don't vent the turbopump to atmosphere while the turbo is spinning
rapidly.  This can damage the rotor.

C. Under rare circumstances, the backing pump has been seen to turn off due
to overheating.  When this happens, you will notice the pressure on the GP
pressure gauge rising, and will rise to over 400 mTorr.  This is not good:
gas from the turbopump is seeping back into the dewar.  If this does happen,
close both valves, and turn off the pump for 5 minutes.  Then start again at
step 3 above.

D. Don't pump the LFC when it is cold.  If you check the pressure with
the Granville-Phillips gauge and the pressure is above 1 mTorr when
the LFC is cold, it needs to be pumped again.  However, you need to let
the instrument warm up completely before pumping, and this takes more than
24 hours.  If the cold pressure ever gets above 1 mTorr, contact Mark Metzger

E. If for some reason the dewar does not pump to below 2 mTorr warm, even
after 3 hours, something is leaking.  Perhaps the hose is not properly
connected.  Before checking this, though, CLOSE BOTH VALVES!  You don't want
to let air into the dewar, the primary reason being that we don't want water
(even the vapor in the air) or any other suspended particles/oils/colognes
getting inside.


II. Installing LFC in Prime Focus

1) Consider installing filters before the lift - it's easier on the ground.

2) Bring the following items up into the cage:

	- The temperature controller, mounted on a small V-plate
	- Fiber modem and associated power supply
	- 2 sets of fiber pairs
	- 1 small screwdriver
	- 1 AC power cable for temp controller
	- 1 temp controller cable

3) Set the counter on the photometric pedestal to 7500.

4) Install LFC mechanically.  The silver box strapped to the dewar should be 
	facing the North side.

5) Install the V-plate with the temperature controller.

NOTE: There are 2 power strips mounted on LFC.  One is along the south side,
	paralell to the edge.  The other is mounted diagonally.  NEVER
	change the power scheme on the diagonally mounted strip.  These feed
	the CCD power supplies, and changing these or adding other loads
	could add noise. 

6) Run the AC power cable from the temperature controller to the power strip
	parallel to the south edge of LFC.

7) The dry nitrogen hose is clear, and should be rolled up and stuffed
	behind the fiber patch panel in the PF cage.  Unroll it and attach
	it to the spigot located on the side on the structure containing the
	shutter and filter wheel.  the spigot is near the set of connectors
	for the cables running into the box.

8) Attach the fiber modem to the 25 pin D-connector located on the motor
	controller box.  This connector should be labeled "RS-232".  Plug
	the power for the fiber modem into the non-diagonal (non-CCD) power

9) Run fibers from the patch panel to LFC.  Fibers 1 & 2 from the panel
	should run to the CCD electronics box, and fibers 3 & 4 should run
	to the fiber modem.

10) Verify that both power strips are switched OFF.

11)                        *** IMPORTANT *** 

	Verify that the high-voltage power (located on the CCD electronics 
	box, labeled "HV") is turned OFF.  AS OF 2000/09/22, this
        switch should ALWAYS remain off.  (In the next engineering
	cycle, this switch will be internally disabled, but for now it
        should not be used.)

12) Plug the CCD power strip into the isobar outlet on the wall of the PF
	cage.  It should be on one of the outlets labeled "Filter Bank 3".

13) Plug the other power strip into the isobar, filter bank 1.

14) Attach the temp controller cable to the rear of the temperature
	controller.  the smaller of the 2 round connectors should go to port
	A, and the bannana plug will only fit in two out of the three holes
	(the spacing of the three holes on the back is not the same).  Don't
	worry about the polarity of the bannana plug, it is connected to a
	resistor so it shouldn't matter.  Attach the cable to the side of
	the PF cage with one of the velcro ties for strain relief.

15) Ground your hand along portions of the PF cage with bare
	metal (no paint), the cases of power outlets, and the outside of the
	CCD electronics box.

16) Once you're sure you're well grounded, attach the round connector at the
	other end of the temperature cable to the dewar.  The mating
	connector for this is located on the dewar itself, underneath the
	electronics box.

17) Turn on the non-CCD power supply (along the south edge).

18) Turn on the temperature controller.  You will see 2 numbers displayed.
	One of these should be -85.00.  This is the "set point", or target
	temperature at which we run the CCDs.  The other number is the
	actual temperature.  Next to the numbers, there is a scale labeled
	"50%" and "100%".  This indicates if the focal plane heater is
	working, and if so, at what percent of capacity.  There is a button
	marked "heater" on the panel display which toggles the heater
	on/off.  Press this until you're convinced the heater is on.  This
	should be clear from looking at the scale.  If the set point is
	something other than -85.00, something may be amiss, and it is
	probably better to leave the heater off if in doubt.  Note
	that in normal operation, the temperature may read as warm as -70C.

19) At this point you're ready to start up LFC.  To execute the startup
	procedure, refer to the HTML documentation of the LFC
	and power-up procedures for performing a cold start.


III. Swapping filters

	The LFC filters are each mounted in a custom built cartridge
designed to slide into place and lock in the filter wheel.  The filters
should never be removed from their cartridges.  Because the filters have
varying thicknesses, some are considerably heavier than others.  One
therefore needs to take care when mounting filters in the wheel, so as not
to put the wheel grossly out of balance.  This can lead to slippage in the
mechanics at high airmass.  A brief summary of the filter weights (4/3/01):

Rs	2.58 lbs
Is	2.52 lbs
g'	2.50 lbs
u'	2.45 lbs
5085	2.09 lbs
5200	2.05 lbs
r'	1.84 lbs
z'	1.83 lbs
i'	1.75 lbs

We will be attempting to bring the lighter filters up to ~2.5 lbs to avoid
any filter wheel imbalance.


We try to mount heavy filters opposite one another.  Usually observers will
want Un g'r'i' or g'r'i'z'.  In these cases, we mount as below:

 0 1 	  u' r'       g' i'       u' Rs 
 3 2	  i' g'       z' r'       Is  g'

Where the 0123 corresponds to the positions in the filter wheel.  Just try
not to mount u' and g' in adjacent filter slots opposite i' and z'.  This is
asking for trouble.

To change a filter, 

1) Open the filter port on the side of the shutter/filter wheel box.  The port
	is located on the same side of the cage as the temperature controller, 
	and can be accessed by loosening its 4 captive screws and pulling off the
	front panel.

2) DO NOT PUSH THE FILTER WHEEL BY HAND to move it to the desired
        If the LFC is powered up, ask someone in the control room use
        the software to move it for you.  If you must move the wheel
        from the PF cage, power off the filter wheel motor. Then, turn
        the gray plastic knob on top of the filter wheel motor (in the
        indicated direction ONLY) to move the wheel into it's proper
	location.  You should be able to feel the mechanical detent
	close to the appropriate position of the wheel.

 *** After powering the filter wheel back on, you should initiate a warm      ***
 *** start-up sequence as documented in Mark Metzger's LFC HTML documentation ***
3) The filter slots are labeled 0-4 on the wheel, which you can see from the
	port.  once the correct slot is in view, remove the filter there.
	This is done by loosening the captive screw you see on the slot.
	Once the screw is loose, reach into the slot and slide the filter
	out.  It can be tricky to get the filter started on it's slide.
	Tricks I've found helpful are to pull gently on the captive screw to
	pull until you can grab onto the filter, or to reach your fingers
	around under the large thin ring and try to poke the filter out.  If
	you haven't done this before, it's probably best to find someone who
	is more experienced to teach you the ropes in person.  The "feel" is
	important here.

4) Once you get the filter started, it should slide out easily.  Then slide
	the new filter into the slot in reverse fashion, and attach the
	captive screw.

5)  After installing filters, you will want to issue a "filter home"
	command (in mcdcom) to properly re-align the wheel in the beam.  
	You will also want to modify the filter names by editing the file