5 kV floating Picoammeter Video

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This post has been updated to include a video that shows how the High Voltage 9103  (PN 91035K) picoammeter can float up to +/- 5 kV.

RBD Instruments has released a new version of its 9103 USB Picoammeter which incorporates faster reads per second as well as 5000 DC volts of isolation to chassis ground.

9103 HV

9103 HV

Increasing the DC voltage isolation from chassis ground to 5000 volts (5kV) opens up new possibilities for researchers such as direct DC current measurement of very small electron and photo multiplier signals. Electron and ion beam measurements can be biased to reduce secondary electrons or to retard the beam as needed for experiments.

Designed to provide accurate bipolar DC current measurements in noisy environments such as synchrotron beam lines, the 9103 can measure bi-polar DC currents from low picoamps to milliamps.

The drawing below shows how the 9103 is floated on your HV power supply. The high voltage is referenced to chassis ground, and the signal ground is referenced to the high voltage. To help keep the supply and signal connections clear, the HV connection is a MHV connector and the signal input is a SHV connector.

Floating picoammeter

Floating picoammeter

There are a number of manufacturers of programmable DC power supplies that can be used to float the 9103 up to whatever voltage is needed (as long as you do not exceed +/- 5 kV).

For example, TDK-Lambda provides a programmable 0 to 6.5kV supply that can be voltage limited to 5 kV and can drive up to 2 mA of current.

The model number for a 120 VAC line input is PHV6.5P2-USB-1P115.  The base model has a ripple of 700mV which is somewhat high, but TDK-Lambda does offer a low ripple option that gets the ripple down to 75mV.  You can also easily make a simple RC filter to do the same thing. A number of interface options are available including USB, Ethernet, Serial and analog.

TDK Lambda supply

TDK Lambda supply

PHV series

PHV series

The new high speed option for the 9103 increases the reads per second from 40 to over 500, which is fast enough to perform optical chopper experiments. And, by taking more reads in the same amount of time as the first generation 9103 could, the accuracy is improved.

The Actuel software included with the 9103 provides new features for high speed acquisitions and display, but you can also write your own software to control the 9103 using the simple ASCII commands or in LabVIEW.

Since 9103s can be synced, it is now possible to configure a multichannel DC Picoammeter with up to 256 channels that has high speed, high voltage, or both options.

And if you do not need the high speed or high voltage options, the standard 9103 USB Picoammeter is still available as well.

For more information visit the RBD Instruments website at http://www.rbdinstruments.com

CMapp New Features

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We have added a few new features to CMapp, our microCMA acquisition and data massage software.

For example, when you first open the electron gun dialog box, a filament warm-up reminder pops up:

It is recommended that you warm up the filament at the beginning of each session so that the microCMA can thermally stabilize. The filament warm-up routine brings the filament current up over a 5-minute period and then keeps the filament on.  What is nice about this feature is that you can just click “Yes” and then walk away and come back later when you want to use the microCMA.

Another new feature is the “Auto Set the Beam Voltage to 2 kV ” for alignments:

The alignment acquisition is typically used to acquire a 2 kV elastic peak that sets the analyzer to the sample distance. Surveys and multiplexes are typically acquired with the beam voltage set to 3 kV.  Then, if you move to a new sample, or if you move the same sample to a new location, you would need to re-acquire a 2 kV elastic peak. With the “Auto Set beam to 2 kV” feature, you can just acquire the elastic peak alignment and the beam voltage will automatically change from 3 kV to 2 kV.

The new Diff/Smooth feature combines the differentiate and smooth commands into one click:

Related to the Diff/Smooth command is the ability to automatically Diff/Smooth at the end of an acquisition:

By checking the “Auto Diff/Smooth After Acquisition” box, the data will automatically differentiate and then smooth when the acquisition is complete. The “Auto Diff/Smooth” feature works for surveys, multiplexes, and alignments. Since you need to differentiate the data for quantification anyway, you might as well have it happen automatically.

Finally, we have added a feature that provides estimated target current. This is helpful if your target is grounded internally on your sample manipulator and you have no way to measure the actual electron beam current. Rather than using the emission current to set the relative target current, you can use the estimated target current to set the electron beam current to the recommend 300 nA.

First, select Estimate Target (Beam) Current in the Hardware Properties dialog box:

The estimated target current will be displayed in the Electron Gun dialog box as shown below:

Each electron gun filament behaves a little bit differently so the user-settable Emission Current-to-Target Current ratio can be adjusted in the Hardware Properties dialog box. We will have a video soon that will show you how to set this ratio.

If you have our 9103 USB picoammeter or some other picoammeter, you can measure the target current and enter the value into an acquisition manually (or, in the case of the 9103, automatically). You define this setting in the Hardware Properties dialog box.

If Estimate Target Current is selected, then the estimated target current will be entered into the acquisition before the acquisition starts. Whether entered manually, automatically, or estimated, the target current is displayed on the left-hand side of the alignment, survey, or multiplex acquisition.

For more information on our microCMA compact Auger Electron Spectrometer visit our website:

RBD Instruments microCMA



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