Putting Together a Compact UHV (Ultra-high Vacuum) Chamber for Spectroscopy

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Small, inexpensive UHV chambers have been the backbone of many commercial labs and universities for decades. The cost of larger, feature-rich systems has gone up dramatically in recent years, making compact, DIY chambers even more cost-effective for specialized applications and education.

RBD has a range of products available to add value to your compact chamber, and in fact built our own recently to develop and test our microCMA compact Auger analyzer.

RBD Kimball Chamber
Kimball Physics chamber with RBD miniZ, IG2, and microCMA compact Auger analyzer

The Chamber

We started with an 8 inch spherical octagon chamber from Kimball Physics. This chamber has two 8.00″ CF and eight 2.75″ CF mounts, with an internal volume of  106.6 cu. in. (1,747 cc):

Kimball Physics Chamber
Kimball Physics 8.0″ Spherical Octagon – Vacuum Chamber

The vacuum chamber was fitted with an ion pump from Gamma Vacuum, and valves and windows from MDC. Affordable turbo pumps can be sourced from Pfeiffer (HiCube 80 Eco) and Edwards (nEXT85).

Rough vacuum gauges are available from a number of companies including Digivac.

Rough Vacuum Gauge
Rough vacuum gauge

Ion gauges and ion gauge controllers are available from a number of companies including Stanford Research Systems

Ion Gauge Controller
Ion gauge controller


To assist with water vapor desorption, the chamber is fitted with RBD’s miniZ. The mini-Z uses UVC radiation to desorb water from the chamber walls, resulting in faster pump-down times and lower ultimate vacuum.

RBD miniZ
RBD miniZ water vapor desorption system

This chamber is also fitted with RBD’s IG2 2 kV low cost sputter ion gun for specimen cleaning:


The ultimate purpose of this system was to house RBD’s microCMA compact Auger analyzer (shown below with the Z translator attached):

RBD microCMA
RBD’s microCMA compact Auger Analyzer

For applications that require elemental analysis, this chamber, with the addition of a PC and CMapp AES acquisition and data massage software, is now a complete system providing quantitative, surface-sensitive Auger electron spectroscopy. At around $50,000 for all the components listed here, this is one example of a budget-sensitive spectroscopy system that can be assembled, repaired and upgraded without costly field service visits.

50-096 X-ray source control DLL using Windows 10

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50-096 X-ray source DLL installation and setup for Windows 10


The 50-096 X-ray source control uses a RS232 serial port to communicate with the PC.    AugerScan talks to a Phi 50-096 DLL that in turn communicates with the 50-096.    This DLL was originally written for old 32 bit XP PCs and there are some tricks involved with getting it to install and operate correctly on a Windows 10 machine.

Note that the RS232 cable needs to be a straight rough type. Most newer PCs do not have a RS232 port so you will need to get a USB to RS232 adaptor.

The steps involved are as follows:

  1. Copy the 50-096 DLL to the windows/SysWOW64 folder
  2. Register the 50-096 DLL
  3. Set up the Com port

Step 1.  Copy the 50-096 DLL to the PC.    You can copy it anywhere on the PC, but initially copy it to the AugerScan directory.

Step 2.  Register the 50-096 DLL.  

  1. Right click on the Start icon and select Command Prompt (Admin).   Or if that does not work, search for Command Prompt and Run as Admin
  2. Type cd\Windows\SysWOW64 then press enter
  3. Type regSvr32 Model_50_096.dll and press enter

You should get a message that indicates that the Model_50_096.dll was registered.  

Step 3.  Set up the com port.

  1. Type Registry Editor in the search box and then run the registry editor as Admin
  3. Add a new string (which will add a new key)
  4. Name the new key ComPort
  5. Verify the type of key is REG_SZ
  6. Put in the com port number that you are connecting to the 50-096.  It needs to be COM (all caps) plus the com port number.  So for example, COM3.
  7. The 50-096 operates at 9600 baud with no parity and 8 data bits.

The 50-096 in now ready to operate with AugerScan.

Note: When first turned on, the Model 50-096 X-ray source power supply needs to be programmed to operate at 15 keV. To do this, perform the following steps:

1. Press the Local button under Control Select.

2. Press the Start button for the Water Pump.

3. Press the High Voltage button above the keypad.

4. Press the Display/Enter Setpoints button above the keypad. (LED should light.)

5. Press 1 – 5 – 0 – # on the keypad.

6. Press the remote button under Control Select. The 50-096 will retain the 15 keV setting until it is manually turned off or there is a power interruption.

Once this is set up AugerScan will automatically turn the 50-096 source on and off during and after acquisitions.  

Tip:   If you program in 12 or 13kV then that is what will be used when the 50-096 is turned on.

Stability testing of surface analysis optics

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There are two easy ways to check the stability of the electron or photon source on an X-ray photoelectron spectrometer, Auger electron spectrometer or Scanning Electron microscope:

  1. Measure the target current and plot the results vs. time using a data logging picoammeter such as RBD’s 9103.
  2. Acquire a depth profile region over a wide energy range but do not turn on the sputter ion gun.

Method 1 – Plot the target current vs. time.

As shown in the pictures below, plotting the target current versus time shows the stability of the electron beam as well as trends in the current.  In this case the current being measured is an electron beam in the range of approximately 300nA.

Electron Current vs time
current measurement display

By changing the scale of the plot, you can see finer details of the current stability and any trend. In this measurement the current drifted up by about 30 nA over a 2 hour period and started to stabilize after the first hour. Room temperature changes can effect the stability of electron optics as can thermal mass of the electron source.

close up of current measurement

Measuring target current vs. time works well for electron beams on Auger spectrometers and SEMs, as well as secondary electrons generated by X-ray sources on XPS systems.  The secondary electron current generated by X-ray sources is directly proportional to the X-ray flux.

Method 2 – Wide energy range depth profile.

For this method you want to set up a region for a depth profile that is at least 1000 eV wide.  In the example below we acquired from 1000 to 0 eV on a silver sample, 2 sweeps per cycle. Normally the ion gun is turned on for a depth profile but for this test the ion gun is not turned on.

In the picture below you can see the Profile vs. time display where the highest count in each cycle is displayed.   

Depth profile vs time

This picture of all 95 Ag cycles super imposed shows that the stability is pretty good.   A depth profile test like this tests not only the X-ray source stability, but also the analyzer voltages, electron multiplier and detector electronics. You can do the same test with an AES system which would test the electron gun as well as the analyzer,electron multiplier and detector electronics.

This picture below shows the first cycle and the next picture shows the last cycle.  If you look very closely you will see a small increase in the carbon peak that coincides with the over all slight drop in the intensity of the Ag profile vs. time display.  Carbon will typically increase over time in UHV systems due to adsorption and desorption effects.

If you have some extra time you may want to run one of these test methods on your XPS, AES or SEM.   The results can be interesting and if nothing else will let you know that your system is stable.