Disclaimer...

Dear Friend,
    You are reading this because you are looking for information on the GMX Detector Annealing System.  I regret that I'm not there to answer your question directly.  I have thrown this information together rather quickly, so it may be less than desirable.  However, I hope that it can at least point you in the right direction.  I will provide contact information as soon as I have it.

System Components

• Plenum - The plenum is the long pipe that extends from the pump area to the far end of the room.  It consists of a 304SS pipe about 4" in diameter.  There are four NW16 ISO vacuum fittings welded to smaller pipes along its length.  I will refer to these as "ports" and number them 1 through 4, starting from the pump end.  All of my log entries have been done this way.   At the far end of the plenum (farthest from the pumps) is a 1" compression fitting that is used for the cold cathode ionization gauge head.
• Valves - There are four valves that open to/from the plenum.
• Gate Valve - this is a 4.5in, pneumatically operated gate valve with conflat flanges.  It provides a low impedance pumping path to the turbo, interlock protection valving on alarm, and is the only device that requires compressed air.  The source of compressed air is through the wall, into the pipe chase (1/4 polyflo tubing), over the ceiling and into room 123 to a manifold on the old Alton Source.  The source of air for the manifold is via a larger diameter polyflo tube that goes through the floor and into the student machine shop behind the glass bead blaster.  There is a small, black handled valve which can be used to isolate the air.  The line should be tagged.
• Large 90 degree valve - provides pumping path to the sorption pump.  It a hand operated, right angle, stainless-steel bellows valve with 2.75in conflat flanges.  This valve also provides structural support for the sorption pump.
• Small 90 degree valve - provides pumping path to the carbon-vane roughing pump.  Same construction as the large valve, but smaller flanges.  It is located to the right of the sorption pump near the bourdon-tube vacuum gauge ( 30in Hg - 30psi )
• 1psi pressure releif valve - This valve is a spring-loaded, elastomer-sealed valve located near the plenum and to the left of the sorption pump.  Should the plenum pressure exceed 1psi on venting or due to detector gasload, it will open to relieve the pressure.  *It can be a source of leaks if it has been opened.  The valve body is SS and has a 1.33 conflat flange.
• Pumps - There are four pumps used on the system
• Carbon Vane - The carbon vane pump is a rotary vane pump that uses carbon vanes and no oil for lubrication or seal formation.  It is the first pump used for roughing out the system.  This pump is capable of producing rough vacuum only.  Consequelty, the bourdon-tube pressure gauge was installed to ensure that its effectiveness could be monitored.  The pump is not rated for continuous duty, and should be operated for only a few minutes at a time - which is all that is necessary in this application.  The pump is started by plugging in the power cord.
• Sorption - The sorption pump is a liquid-nitrogen-cooled, molecular-seive-filled capture pump.  It is used to provide an oil-free intermediate vacuum stage on roughing.  The MKS thermocouple gauge should be monitored when in use.  The pump should be regenerated occasionally by heating, using the installed clamp heater.  Typically, this pump can produce a reading of 10 - 30 mTorr on the MKS thermocouple gauge - a sufficient transition pressure for switching to the turbopump.
• Rotary Vane - The rotary vane pump is a Welch, model 1402, oil-sealed rotary-vane pump that is used only for providing a suitable backing pressure for the turbo pump.  A molecular seive trap is used to assist in preventing oil backstreaming.  This, in conjunction with the turbo pump, provide the oil-free high-vacuum pumping that the system uses on a long term basis.  Note that this system is only "oil-free" to some finite degree.  What we really mean is that we are willing to tolerate the extremely low level of oil backstreaming produced by this type of system.  On redesign, a wide-range or high-compression turbo should be considered along with a diaphragm backing pump.
• Turbomolecular - The turbo is a small Alcatel 50L/s (nitrogen) pump.  The inlet is an ISO 63 flange, which requires a centering ring, o-ring, and 4 clamps.  This flange is sexless, and rotatable.  It is also unique in that the pump inlet screen is incorporated into the o-ring's centering ring.  The discharge port is an NW 25 ISO vacuum flange.  The controller is mounted and tightly integrated into the interlock logic system.  Phil Allen had to alter the controller electronics to obtain a "normal operation" logic signal from the controller.  Most turbo controllers have a relay that provides this function.  There is some question as to whether this works or not, but I can't really recall now.  It is difficult to generate a true turbo failure without damaging anything.  It is not terribly important however, because on loss of the turbo, the plenum pressure will fairlyl quickly rise high enough to set off the alarm system on a penning gauge fault.
• Gauges and Instrumentation - There are three vacuum gauges used by this system.
• Bourdon Tube - The bourdon tube gauge is a compound gauge that meaures vacuum to 30 in Hg and pressure to about 30 psi.  A reading of 0 on this gauge indicates atmospheric pressure.  The gauge is physically located imediately next to the small 90 degree bellows valve and has about a 2 in dial.  One must either lean down or squat down to read this gauge as it is buried up under the table top.  This gauge is used for three basic purposes, namely, roughing out the system, conducting a rate-of-rise test to check for gross leaks, and to monitor pressure when venting the system to dry nitrogen.
• MKS Thermocouple - I have stressed the brand name of this thermocouple gauge throughout this document because Phil regrettably used it to refer to the alarm indicator on the interlock logic panel.  There are two thermocouple gauge heads installed on the system.  One measures the pressure in the plenum (channel 1) and the other measures the pressure in the foreline of the turbo (channel 2).  Only channel 1 is monitored by the interlock system.  The gauge controller for has two, red, led bar graphs to indicate the pressure.  There are two trip points per channel, and two green leds to indicate when the trip points have been reached.  When the green led is lit, the pressure is less than its trip point set pressure.  Refer to the manual (See Greg Brown) for further information on this unit.
• Cold Cathode Ionization or Penning - The penning gauge is used to monitor the high vacuum in the plenum.  It should not be turned on until the plenum has been open to the turbo for a few minutes.  There is a single trip point integrated into the gauge.  The current setting for this trip point is about 7 x 10e-5 Torr.  The setting can be adjusted by using a resistor box (see electronics shop) and the adjusting screw.  Occasional calibration is also required.

Interlock System Logic and Operation

1. Valve off the detectors from any pumps and leave them under static vacuum if possible
2. Disable any heating that is currently underway
3. Call some poor sap in to deal with the problem

• Penning Gauge - The penning gauge is monitored by the vacuum interlock protection system because high vacuum while heating is very important.  The CVC model gauge controller that we use has an internal relay and trip point adjust that allows for a logic output when a pre-determined pressure is passed.  We currently set this trip point at about 7x10e-5 Torr, which, while arbitrarilly chosen, seems to work well.  It is high enough so that transient changes either in pressure (eg due to outgassing) or electrical noise do not generate false alarms.  As I recall, to generate a fault, the internal relay must be energized passing a ground through to the interlock box.  This leads to a logic flaw that can be exploited when necessary.  Because the relay must be energized to produce the fault, a no fault condition exists when the controller is off.  That is, Power Off = No Fault.  This can be handy when the system is taking a long time to pump down and you want to go home, because the penning gauge can be turned off and the system alarmed on only the thermocouple gauge.  This is less desirable, but it is better than leaving the system un-alarmed.
• MKS Thermocouple Gauge - Again, this fault is listed as an "MKS" fault on the system interlock logic box.  This should provide a good source of confusion if the brand of the TC gauges is ever changed.  The MKS model 286 controller provides 2 trip points per channel.  Only channel one is currently monitored, but it would be trivial to add channel 2, which was originally intended.  As I recall, the MKS controller provides both NO and NC relays, so the logic is selectable.  I don't remember how we did it.  There are two green LEDs for each channel.  Each LED is associated with a trip point and a set of relays.  We used both relays for channel one, which means that both trip points must be passed before a no fault condition is met.  To be clear, when channel one's pressure is less then the setting of both trip points for channel one, then a no fault condition occurs.
• Turbomolecular Pump Normal Operation - The idea here is to monitor the turbo to ensure that it is functioning normally.  Most turbos have a relay that indicates "Normal Operation" which is usually taken to be within 10% of full rotational speed.  Our turbo did not have this option, so our electrical engineer at the time, Phil Allen, altered our controller to provide it.  As I said earlier, there is some question as to whether this works or not.  One thing that you will notice is the small piece of tape of the controller's fault indicator.  This is there, becuse the alteration that Phil made to the controller produces a small load on the fault indicator circuit and thus slightly biases the fault LED.  With experience, one can distinguish between "normal glow" and "fault glow" but it really is not necessary.  To be frank, the High Vacuum trip point is so sensitive, that failure of the turbo will result in poor vacuum so rapidly, that monitoring the turbo controller is a bit excessive.
• Input AC Power - Built in to the interlock logic control box is a 12V battery, battery charger, and a circuit to sense when AC power is available.  When AC power is available, the battery is put into charge mode.  When AC power is lost, the circuit switches to battery power and an alarm condition is generated internally.  Loss of AC power is the most common alarm mode generated by this system, without question.  Someday, the battery will have to be replaced.  But frankly, it doesn't have to last very long - just long enough to sound the alarm.

• Penning Gauge is turned on  - AND - Pressure exceeds 7 x 10E-5 Torr
• MKS Thermocouple Pressure exceeds either trip point setting for channel one
• Turbo controller indicates a fault (questionble)
• Loss of AC power

Recall that we stated earlier that we wanted to isolate the detectors from any pumping systems and disable the heaters.  Also, we wanted to call someone to deal with the problem.  Frankly, the first item is trivial.  In order to isolate the detectors, we need only shut the gate valve - the only vacuum valve that should be open when the system is alarmed.  Thus, the interlock protection system will de-energize the solenoid valve that controlls compressed air flow to the gate valve, effectively causing the compressed air to shut the valve.  That's it.  Alarm condition = no power to gate valve = gate valve closure.

The second action, disabling the heaters, is only slightly more complicated.  When I spec'ed the system for Phil, we had a mis-communication somewhere, that resulted in the logic box's internal heater relay not be rated for sufficient current to drive all of the heaters at once.  For this reason, a second, external heater power relay box was built that could accomodate all of the heaters at once.  Ok, stay with me now.  Power for the heaters comes from a wall outlet, though the external heater enable relay, to a power strip, and then to the heater controllers.  The power for the external heater enable relay comes from the logic box, through the internal heater enable relay and then to the control side of the external heater enable relay box.  The power controlling the internal heater enable relay comes from the logic box, of course.  Got it?  We're just using a relay, to control power to a relay, to control power to the outlet strip that distributes power to the heater controllers.  I'll try to draw a picture.  When a fault is detected, the logic box goes into alarm mode and the power to the internal heater relay is disabled.  This, in turn, disables power to the external heater power relay, which in turn, disables power to the heater controllers.  Alarm condition = no ac power to heaters.

All right.  So far, so good.  We've got the detectors in a tolerable condition at least.  But what we'd really like is to get the problem solved and the anneal back underway.  To do that, we will have to call someone in.  This is necessary, because there is no automated way to exit the alarm condition.  Once a fault is detected and the logic box goes into an alarm condition, someone must be physically present to reset the logic.  This was done, because automatic recovery was simply not possible and really wasn't necessary.

There are two methods used to call someone in.  First, the simple method.  The logic box contains a piezo-electric tranducer that screams its bloody little head off when the box goes into alarm mode.  Even with two doors shut, the alarm can be heard in the hallway.  The second, more complex method involves a radio shack phone dialer which has been integrated into the system.  The dialer will call 3 phone numbers and deliver a pre-recorded message.  The manual explains its operation.  The dialer can be configured to call someone's office, home, or the telecomunications device of your choice.  We have a pager for this purpose.  I used to use my cell phone.  It was particularly nice, because it had caller ID, so I didn't even have to answer the phone.

Note that it is possible to disable the audio alarm and the phone dialer independantly.  Whenever the system is not in use, it is in the alarm condition because the plenum is at atmospheric pressure, filled with dry nitrogen.  Thus we will have an MKS TC gauge fault at all times.  Prior to removing detectors from the system, the operator simply disables both the audio transducer and the dialer and allows the system to go into alarm mode when the plenum is vented.

It is also possible to disable the gate valve interlock protection thus allowing the gate valve to remain open even when the logic box is in the alarm condition.  This is necessary on pumpdown, when the plenum pressure is not yet < 7 x 10e-5 but the turbo must pump on the plenum.

Because of these bypass options, it is imperitive that the operator ensure proper switch configuration before considering the system "safe" to leave.  Leaving the gate valve interlock switch in the bypass position effectively defeats the entire protection scheme and could cause failure of the turbo pump should a catastrophic vacuum failure occur.  Note that on loss of AC power the valve will still shut, leading one to think that this might not be as bad a thing to do as I've led you to believe.  However, the problem comes when power is restored and the valve automatically opens again, irrespective of any other conditions!

Operation of the interlock system is relatively straightforward.  One simply connects the detectors to the plenum ports, roughs out the plenum, opens the valves to the detectors, and then pumps until all fault indicators are out.  At that point, the interlock system may be enabled (ensure that the heaters are off until needed) and the dialer programmed.

Stick Heaters

The stick heaters are used in conjunction with the heater controllers.  Ortec took an Omega, Type K thermocouple-based temperature controller, added a switch and a lamp, and doubled the price.  The controllers have an AC power cord that is plugged into the relay protected power outlet strip.  The AC power cord of the stick heater is then plugged into the outlet on the back of the controller.  The thermocouple is also plugged into the back of the controller.  I like to plug the thermocouple cable in first, so that there is never any chance of having the heater going full blast withouth the thermocouple monitoring the temperature.  The controllers have an analog temperature dial on their front panel that may be locked at any setting with a small allen screw.   They also have an on/off switch and a power indicator lamp.  The lamp above the switch indicates that power is available to the controller.  The red LED on the Omega controller indiates that power is applied to the stick heater.  This LED indicates the heater's duty cycle.  On should verify that the controllers cycle when starting an anneal.

As of this my writing this (see date at bottom of page) the controllers are in desperate need of calibration.  Errors as much as 20-25 degrees C have been observed.  For this reason, it is imperative that the crystal temperature be monitored via the RTD and heat applied slowly until the calibration is determined.  Alternatively, one can use the seperate type K thermocouple system we have to measure the cal error of each of the sticks and adjust based on that.  I _strongly_  recommend monitoring the xtal temp on every detector on every anneal.

Measuring Crystal Temperature

1. Remove the 2-4 screws that hold the aluminum housing surrounding the electronics packages in place.  This usually has the tag indicating the model and serial number on it.  The screws are usually flat-head, phillips screws - probably #4-40 thread.
2. Slide the aluminum housing away from the dewar until the entire electronics section is exposed.
3. Carefully remove the plastic film used to insulate the electronics packages from the aluminum housing.
4. Locate the green and black wires that connect the pre-amp assy to the RTD pins.  Carefully remove them, noting their orientation.
5. Attach a digital ohm meter to these two pins.  Set the meter to measure resistance in the 0-1000 ohm range if the meter does not autorange.
6. Verify that the indication is reasonable for room temperature when starting!  Problems with bad connections can give false (elevated) readings.

The resistance that is measured can be correlated to a temperature using a chart located in the annealing lab.  It is in a protective plastic cover.  The resister's resistance increases with temperature.  At 0 degrees Celcius, the resistance is about 500 ohms, and the change is about 2 ohm/degree if you can't find the chart.