Low-Cost High-Potter

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Occasionally Ion Pumps can short out from the flakes that accumulate over the years because of using titanium sublimation pumps (TSP).   An old trick is to use a high potter (high voltage potential generator) to create an arc which can sometimes (if you are lucky) burn off the short.   High potting can work well for ion pumps, ion guns and practically any electrical feedthrough on a vacuum chamber where flakes or deposition build up is an issue.

High potting will only work on small flakes as the current generated is low (100uA max).  But the voltage generated is extremely high at 20,000 to 50,000 volts.  Think of this as a small Van der Graaf generator where you can direct the arc towards the electrical feedthrough on the vacuum chamber. The voltage from the arc is applied to the shorted electrical feed though and will work it’s way to the short inside the vacuum chamber and if you are lucky, will melt the short.

High potting does not always work but when it does it buys you some time before you need to vent the chamber and perform the necessary maintenance to fix the underlying shorting issue.

Back in the 80s it was common to see high potters in labs that had vacuum chambers for analytical instruments or deposition systems. These days you do not see high potters as often due to more stringent electrical safety standards.   Used properly a high potter is perfectly safe.  Although it is a little bit exhilarating to be pointing a device that has a 50,000-volt arc coming out of the end.  😊

Electro-Technic Products, Inc. provides an assortment of high frequency generator testers that work well as high-potters (high voltage potential) to melt away small particles and flakes that can cause shorts in high and ultrahigh vacuum applications.  In particular, these are useful for high-potting shorted ion pumps and ion guns.

We prefer the BD-10AS as it has an ON-OFF switch.  As with all high voltage, only qualified personnel should use this device.  Check with your organizations’ electrical safety officer to make sure that your organization allows high potter use before purchasing a high potter.

For more information or to place an order, contact Electro-Technic at http://www.electrotechnicproduct.com/pinhole.html

Or by phone at 773-561-2349

Surface Analysis Systems and Unstable Line Voltage

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We all tend to take the stability of our electric power for granted. Some parts of the US and the rest of the world can have very unstable power, and experience frequent power outages or brownouts that cause loss of productivity and sometimes damage to the system. This is especially true in warmer months, when there can be frequent and severe thunderstorms.

This blog post will explore some UPS (uninterruptible power supply) options that are suitable for surface analysis instruments as well as SEMs and other vacuum-related systems.

Uninterruptible power supplies are rated in kilovolt-amps (kVA) so the first thing you need to do is to calculate the kVA for your system. For example, let’s say that my system draws a maximum of 30 amps at 208 VAC. Using this kVA calculator, I come up with 6.24 kVA, which means I would need a UPS with a rating of at least 6.24 kVA. The higher the kVA rating, the higher the cost of the UPS.

There are three other things to consider for the kVA rating.

The first consideration: What is the main breaker on the system rated at? On older Physical Electronics XPS and AES systems, the main breaker ranges from 30 amps up to 60 amps depending on the type of system. A 60-amp 208V kVA calculation comes out to 12.48 kVA.

The second consideration: What is the actual current draw of the system? Usually, this is much lower than the main breaker current rating. For example, a PHI 5600 XPS system may have a 50-amp main breaker and a kVA of 10.4, but the actual maximum current draw might be only 20 amps (during a bake-out), which comes out to only 4.16 kVA. So, technically, a 4 kVA UPS would be adequate for a 5600 system, except that most electrical codes require that the power connection to the system is rated higher than the main breaker. This means that a 50-amp main breaker system would need a 60-amp 12.48 kVA connection to the system. 

Before installing a UPS, refer to your local electrical codes because you may need to get a permit or have the UPS installed by a licensed electrician.

The third consideration: Do you need a battery backup or just a line conditioner? A line conditioner costs much less than a UPS with batteries, and batteries also require maintenance and occasional replacement. Batteries in the UPS provide backup power to the system. Longer backup times require more batteries, which drives up the cost and the maintenance of the UPS.

If you have only brownouts rather than a complete loss of power, then a line conditioner may be all that you need.

https://www.powervar.com/products/power-conditioners

This paper has a lot of useful information about things to consider when researching a UPS: https://www.falconups.com/cleanpowerpaper.htm

The links below show UPS providers that are recommended by some of the surface analysis system manufacturers. The key things to look for in a UPS are its kVA rating and that the input voltage is single phase, 208-to-240 VAC (this depends on what system you have and what your local line voltage is).

https://www.powervar.com/products/single-phase-ups

Here is a link to APC Smart-UPS:

https://www.apc.com/shop/us/en/categories/power/uninterruptible-power-supply-ups-/network-and-server/symmetra/N-1o37elj

This website has an extensive list of UPS units and conditioners for a variety of systems:

https://www.backupbatterypower.com/collections/laboratory-scientific-uninterruptible-power-supply-ups-systems-and-power-conditioners

This model is a 6 kV UPS with a single 30 amp plug on the input:

And finally, here are two more UPS providers for comparison purposes:

http://powerquality.eaton.com/Products-services/Backup-Power-UPS/FERRUPS.aspx?cx=5&GUID=C22CDBD3-77BB-46E1-8FF8-AF88CB138286

https://www.tripplite.com/smartonline-208-240-230v-6kva-5.4kw-double-conversion-ups-4u-rack-tower-extended-run-snmpwebcard-option-usb-db9-serial-bypass-switch-hardwire~SU6000RT4UHVHW

Monochromator upgrade for PHI 5600 XPS system

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Installing a monochromator

This blog post shows the steps required to install a monochromator upgrade on a PHI 5600 XPS system.

The components of a monochromator upgrade include the monochromator housing, the crystal substrate and aligner, the mono X-ray source, and the X-ray source aligner.    If your X-ray source is a 32-095 then you will need to replace that with a 32-096 that can drive two x-ray sources (standard dual anode and mono source). An additional water line is included to complete the cooling circuit between the standard and mono X-ray sources.

monochromator schematic

Step by step procedure:

First, vent the vacuum chamber.

Use a new 4 5/8” copper gasket and install X-ray source X Y Z aligner to the monochromator housing.  It is much easier to install the X Y Z aligner onto the mono housing before the mono housing is mounted to the chamber.

X Y Z aligner

Use a new 6” copper gasket and Install the monochromator housing to the chamber on the flange that is opposite of the hemispherical analyzer.  It is heavy and so you will need at least two people to mount the monochromator housing to the flange on the chamber. 

Once mounted tighten the nuts on the flange.  In my experience, going in a circular pattern is the best way to tighten flanges on UHV chambers.   The trick is to not over-tighten the nuts or bolts as you go around.  Start out with just a little bit of torque and gradually increase it as you go around.   One or two of the nuts on the back of the monochromator housing are exceedingly difficult to get to.  A ½” U-shaped or half-moon wrench makes getting to those nuts easier. 

Or you can simply cut a standard ½” wrench in half. 

Once the nuts are tight and there is no gap between the flanges it is sealed.

Install the mono crystal substrate into the top mono flange assembly:  Use gloves and very carefully remove the crystal substrate from its box and unwrap it, being careful not to touch the crystals.  There are 3 recesses in the crystal block that line up with flat spaces on the mono flange assembly. 

The crystal substrate is held in place with 3 clamps.  The clamps mount on a guide screw and then there are two spring loaded set screws that provide tension to hold the crystal substrate in place.  

Tighten the set screws to where they just start to tighten up, and then about 1/16” more.   Do not over-tighten the set screws.  They should be tight enough to hold the crystal substrate in place firmly, but not so tight that the springs inside the set screws are fully compressed.

Next, install a new rectangular Helicoflex type monochromator gasket into the top of the monochromator housing. It will sit into a recess and should be centered in the recess.

Put the mono housing shutter in the bakeout position.  The chamber will be baked out and so the shutter will need to be set prior to the bake out.  Also, you can see how the shutter works before the top mono flange is installed.

Install the top mono flange assembly onto the top of the mono housing.  This can be done by one person.  Make sure that the crystal substrate does not touch the sides of the mono housing as you lower the mono flange assembly.   There are two guide pins to hold the mono flange assembly in place.   The serial number on the mono flange assembly should line up with the serial number on the mono housing.

Install the bolts into the holes in the mono flange assembly and tighten them.   For this flange, use little torque as you tighten the flange in a circular (rectangular) pattern.  The bolts are coarse threads and you want to tighten the flange evenly. 

Once the bolts are tight and there is no gap between the two flanges then it should be sealed.

Use a new 6” copper gasket and mount the 10-610 mono X-ray source to the 6” flange on the X Y Z aligner and tighten the nuts until there is no gap between the flanges or until the nuts are very tight, which ever comes first. 

At this point the chamber can be pumped down and baked out.   Make sure that all the housing parts and O-ring seals are removed from the 10-610 mono source prior to bake out.

The pictures below show the components of the 10-610 X-ray source as they are reassembled after the bake out.

After the chamber has been baked out, refer to the 10-610 mono X-ray source and 10-420 monochromator manuals for outgas, operation, and alignment information.