SOP: Changing the RuH3R/Ru200 X-ray Filament

Symptoms

Red FC warning light (ALARM section of X-RAY controller) with buzzer.
No Filament Current in ammeter
Cannot generate X-rays

Preparations

You will need:

Phillips head screwdriver
Anode bleed screw tool or large flat head screwdriver
Hex wrench to remove anode lead screws/cathode assembly
Ethanol and kimwipes, perhaps a mild abrasive

Timeframe

Less than one hour to clean and replace filament
Intermittent attention over next several hours during burn-in
Leave running overnight
One to two hours to align optics and phi axis

Removal

WARNING: if the filament has just blown, the cathode will be extremely hot. Wait until it cools down before working on it. But you can get as far as bleeding the vacuum system up to air pressure while you are waiting.

On the VACUUM section of the front panel, press the red STOP button. (This works if the vacuum system is in AUTO - if in manual, use the back panel to flip IG off, then TMP off, wait 15 mins, then RP off).
WAIT at least 15 minutes to allow the Turbo Molecular Pump (TMP) to spin down
VERIFY that TMP Accel light is not flashing on rear panel of generator (TMP DRIVE UNIT panel).
Open the bleed screw on the anode tower just enough to that air is let SLOWLY into the system (do it too quickly and you'll damage the TMP).
Once the vacuum system has been bled up to air, undo the four screws that hold the cathode cover in place (large fat plate on the front face of the anode tower).
Remove cathode cover, taking care not to damage the O-ring
Take one kimwipe, stuff it down the front of the tube tower in front of the cathode (acts as a screw catcher)
Back off the phillips head screws that secure the cathode lead cover plate (lower front of cathode) just far enough so that the lead cover slides down.

DO NOT DROP THE SCREWS DOWN THE TUBE TOWER.

Loosen and remove the cathode power lead bolts - the bolts are captive in the leads but you can remove them accidentally if you are not careful. It's a major disaster if you drop these down the tube tower, too. The power leads are fragile, so be careful with them.
Loosen the two allen bolts that attach the cathode to the tube tower and remove the cathode.
There are two phillips head screws on the back of the cathode - remove these and the back plate of the cathode.
Note the location of the filament within the cathode - usually it's dead center in the cathode slot.
Remove the two allen bolts that hold the filament into the cathode. Discard the old filament (but keep the bolts).
Thoroughly clean the cathode with kimwipes and ethanol. Some gentle abrasion will remove some of the deposits - I use mild emory cloth.
Allow cathode to dry (air gun will help get all the ethanol out).

Assembly

Make sure you keep your fingerprints off all of the cathode surfaces on reassembly - either was with ethanol or use gloves.

Put in a new filament (part # CN4892V2) - make sure the filament sits in the middle of the cathode slot, and that the filament support posts aren't touching any of the screws inside the cathode - this causes a short in the bias voltage and reduces beam intensity.
Tighten down the filament bolts, checking again the filament position.
Replace the back of the cathode and the two screws that hold it in place. Align the back carefully with the rest of the cathode.
Clean the inner surface of the tube tower with an ethanol-soaked kimwipe - but DO NOT TOUCH THE BERYLLIUM WINDOWS - Beryllium is fragile and toxic.

Do not use abrasion

Replace the cathode - making sure that you leave it clean (use gloves or a kimwipe) without grease from your fingers on it. If you do get grease on it, clean it off with ethanol. There is a pin on the anode tower that mates with a slot in the cathode and helps locate it in the correct position.
Reattach the cathode leads - make sure that the leads are vertical and that they do not touch any other part of the system - I use tweezers to hold them in place while they are being tightened.
Slide the cathode lead cover plate back up and tighten down the screws to secure it.
Take out the O-ring from the cathode cover plate and clean it with a dry kimwipe.
Clean the cathode cover plate with ethanol and let it dry.
Replace the cover plate O-ring with a fresh thin coating of vacuum grease (it's not normally necessary to replace the O-ring).
Put the cover plate back onto the tube tower, install the screws only finger tight.
Screw down the air bleed screw until it is fully closed.
Start the vacuum with the START button on the vacuum panel.
The Roughing Pump (RP) kicks in first and will pull the cathode cover plate down and seat it.
After a few seconds the RP will pull good vacuum - tighten down the cathode cover plate screws in an X pattern - do this before the TMP starts.
Within one minute the TMP should start. The ACCEL light will be lit on the rear panel of the generator. It takes the TMP a few minutes to reach full speed (RUN light on the rear panel) and you should hear the TMP whine in an increasing pitch. If there is an air leak or other TMP-related problem the TMP will not reach full speed and usually throw an overload light (OLL on the read TMP Drive Unit panel; ALARM on the front Vacuum panel). Check all seals if this happens more than once. The IV++ is relatively cranky and often requires overnight pumping with the RP and personal attention to the TMP to get it up and running.

Filament Burn-In

This method is simple - one must condition (recrystallize) the filament while slowly increasing power on the generator. If we increase the power too quickly we can get arcs between the anode and cathode, which makes the system unstable and locally melts the anode surface (not good). You can tell if this happens because the Ion Gauge voltage jumps and the large variacs often click as they try to restore stability to the power system. Once the filament is at full power, we must optimize the optics.

The Ion Gauge will come on automatically a little while after the TMP reaches RUN condition (in manual turn it on yourself). The voltage reading (red LED numeric display) on the far front right panel of the generator monitors the vacuum.
Turn on the power to the X-RAY system (left-hand buttons on front panel).
Once the mV drop below 250mV, the yellow "Operate" light on the Vacuum panel comes on - but we never operate the machine under such high vacuum readings.
When the Ion Gauge reads <200mV, start the rotating anode by pressing the TARGET ON button on the X-RAY panel. The vacuum will probably jump a little then start to come back down.
Let the Ion Gauge reading drop to < 160mV, and turn X-RAYS on via the front panel X-RAY ON switch. Power will come up to 20kV/10mA. The Ion Gauge (IG) reading will jump somewhat.
Each time the IG reading returns to < 160mV, you can turn up the power a little. Go to 20kV/20mA first then work up to 48kV/48mA and then onto 48kV/70mA. Make only a 2kV/2mA change each time, then wait and watch the IG reading.
At 48kV/70mA I usually leave it like that overnight and take it slowly up to full power the next morning. If you are in a rush you might be able to take it up to full power within 6 hours of changing the filament but the system is likely to be unstable at that point (OL and TC alarm/errors are common) and it's difficult to optimize the mirrors in that state. Running it at 50kV/90mA might be more practical if you are in a tearing rush.
Full power is 50kV/100mA. Take it slowly to full power and monitor the behavior of the IG reading to see if the machine appears stable. Reduce power if there is any sign of arcing.

Aligning the Mirrors

To a certain approximation, if you put the filament back in roughly the same place you removed the old one from, the mirrors won't be too far out of alignment but they will need to be optimized. The major optimizations are usually the mirror translations, followed by the mirror focus. The slit placement should be fairly reproducible so initially I don't back them off (as per the full installation protocol). However I'll typically re-verify the clipping point once I have optimized mirror translation/focus.

I do mirror optimization with the thinnest Nickel filter in place because to be this best represents the sort of performance one wants to optimize. Again the installation protocol indicates not using any filter at all, since the CuKα peak should be much brighter than the CuKβ shoulder.

As with any procedure with open X-ray beam, take great precautions to minimize potential X-ray exposure.

Procedure:

Disconnect collimator helium hose.
Flush the mirror box with Helium on FLOOD as per normal procedure for 10 mins.
Switch the helium flow to PURGE.
Reconnect collimator helium hose.
Remove the beamstop and carefully set aside.
Place the pin diode counter about 1-2cm from the collimator - there is a plexiglass cover that you should place over the pin diode to reduce scatter for this procedure.
Turn on the power to the pin diode meter and zero it on sensitivity 4.
Open the shutter and note the reading - CAUTION: THERE ARE NOW X-RAYS IN THE ROOM - stay away from the pin diode area. Keep the shutter closed unless you are doing pin diode readings or changing mirror settings.
If the reading is very low on sensitivity 4, switch down to sensitivity 5
Turn on the mirror control box.
Check that the 0.00015 Nickel filter is in position, and if not turn the rotary switch to filter, the motor speed to 5, and adjust as necessary.
Turn the motor speed down to 2 and select the Mirror 1 translation using the rotary switch.
Tweak the first mirror translation using the up/down toggle switch, using the pin diode reading as a target. If you are unsure if the mirror is moving look inside the mirror box at the dial labeled "1".
Turn the rotary switch to select Mirror 2 translation. Optimize the pin diode reading again.
Turn back to Mirror 1 translation, optimize again. Then optimize for Mirror 2 translation.
Turn the rotary switch to Mirror 1 focus. Turn the motor speed up to 7. Optimize the pin diode reading for mirror 1. Turn the rotary switch to Mirror 2 focus, and optimize again.
At this point, you might as well repeat the translation (slow motor speed) and focus (fast motor speed) optimizations - if you see no improvement you are mostly with optimization.
Typical target pin diode readings are >4.0 at sensitivity 4. If you cannot reach that value you may have problems with filament position, or you've forgetten to turn the Helium on, or you need to try more extensive mirror optimization.
Once you have fully optimized the mirrors, close the shutter. Locate the two adjustment screws for the collimator position. Make sure you have the scatter shield on the pin diode. Wear protective clothing (i.e. a lab coat helps a little and potentially lead-impregnated gloves).
Open the shutter and adjust the vertical and horizontal translation screws for the collimator. Often relatively little adjustment is required. Close the shutter.
Now you've finished tweaking the optics. But you still have to find the beam center.
Check that the shutter is closed. Move the pin diode out of your way. Find the goniometer head with the pin on it and put that on the goniostat. Center the pin in the microscope and note it's position. Remove the goniometer head.
Replace it with the goniometer head with the brass pinhole attached. Center the pinhole at the location of the phi axis center (i.e. where the pin centered at) and at the vertical position of the previous direct beam.
Note that since you'll be translating the pin-hole vertically while the beam is on, please minimize your exposure by closing the shutter whenever the diode reading is not necessary. The pin diode scatter shield has a gap that accommodates the pin-hole, so make sure you use it during this procedure.
Turn the pin-hole to face the collimator. Reposition the pin diode, now about 3cm from the end of the collimator.
Open the shutter. If you don't get any pin diode reading the usual problem is the pin diode is out of place. Often you can just close the shutter, translate the pin-hole out of the way, set the pin diode position and move the pin diode back in.
Translate the pin-hole vertically until you maximize the pin diode count. Do this is a couple of times because there is considerable hysterisis in the phi translation mechanism and it's not always trivial to get the best position.
Spin the pin-hole 180 degrees in phi and note the maximum reading.
If the two readings are the same, the center of the phi axis already passes through the beam within the tolerances needed. If the two readings are different by more than 0.1, it means you have to translate the phi axis until it passes through the beam.
Close the shutter and locate the two large allen bolts underneath the phi axis at the table surface. These control the phi axis position. Loosen one bolt. Point the pin-hole at the collimator again, open the shutter and note the reading changes as you move the phi axis with the other bolt. Push the phi axis back and forward with these opposing bolts until the pin diode reading is maximized.
Usually the maximal pin diode reading with the pin-hole in place is a little less than that with the pin-hole absent since a small amount of the beam is clipped even though the pin-hole is pretty large, and the pin diode is also now further from the collimator.
Verify that you get approximately the same readings with the pin-hole rotated by 180 degrees. Once you do, the phi axis is aligned and you can carefully re-tighten those bolts. Close the shutter.
Turn the pin-hole to face the microscope and record the vertical translation for the center of the beam.
Optionally, re-center the microscope by loosening the large knurled screw slightly and the two allen bolts fully, realigning the microscope so that the center of the cross hairs is the center of the pin-hole, and slowly retighten everything. Some drift as the bolts are retightened is normal and requires readjustment of the microscope center. This can be tedious and if the center of the beam is close to the center of the cross hairs (3 small divisions or less) you might want to skip this step.
Now you've aligned the phi axis and determined the vertical position of the beam - you're finished with optical and phi axis alignment. At this stage I usually move the Ni filter in the mirror box to 0.006 and take a single 1 second exposure to establish the direct beam position. You should see a small CuKβ "shoulder" separated from the main peak whose max height is <1% of the main beam. In XDISP this peak is at the top left of the direct beam, and in CrystalClear it's to the top right. Do not expose the image plate with a thinner filter than 0.006, and not for more than 1 second to avoid burning it.
Verify that the beamstop is centered around the collimator (there's a specific tool for this) and replace it on the collimator. If you've moved the filter to 0.006, return it to 0.00015. Turn off the mirror control box. Turn off the pin diode and store in a safe place.
The machine is now ready for use. I make a note of the beam center in the microscope and tape it to the mirror box for reference (otherwise nobody knows where to center their crystal !!).