HacDC is in the process of refurbishing a scanning electron microscope: a Cambridge Stereoscan 200.

Current Status

Roughing pump works, turbo spins up to full speed for a while but then slows down. The vacuum controls operate but don't light up as expected, and the pressure readout is not showing a reading. The console turns on and produces video output with the correct data overlay. The filament control reads "bad filament," despite the filament continuity being OK. There is an interlock between the pressure gauge and console that may be keeping the filament off. We'll need to verify the pressure gauge output and see how to trigger that interlock.

We received and installed an MKS Micropiriani 925 vacuum gauge that measures vacuum up to atmosphere. After pumping down, we bottom out at .34 torr. There is a gross leak in the tube on the side of the machine. we are now reverse engineering the electronics. we have replaced the seals on the up-tube, and are working on controlling the column with a microcontroller, rather than the giant desk-sized console.

See Stereoscan_Operators_Log for details.

Documentation

• A suspected leak between the main imaging chamber and the top of the electron gun cylinder is preventing the chamber from reaching pressures low enough to sustain a proper beam. The plumbing connecting the two consists of two elbow brackets. The top and bottom of the long elbow bracket use 2-1/4" diameter black rubber (Viton?) gaskets/O-rings. The bottom elbow bracket uses a 2-3/4" gasket to couple to the chamber proper, and has an adapter between 2-3/8" and the 2-1/4" at the bottom of the long elbow bracket. These are compression-style fittings; the rubber is compressed between two metal pieces and completes the seal.

[Image of Vacuum Bracket](https://i.imgur.com/3k8zrL5.png)

Manuals and Images

• the web archive's copy of RIT's [200 Operating Instructions]
• Stereoscan 200 Operating Instructions
• Stereoscan Student Guide
• Vacuum gauge: Edwards Penning CP25-k: http://www.idealvac.com/files/manuals/Edwards_CP25K_Cold_Cathode_Gauge_Sensor_Manual.pdf
• 925 MicroPirani (TM) Vacuum Pressure Transducer RS232 / 485 / Display Operation and Installation Manual
• Roughing Pump: Edwards E2M-12 255 LPM two stage oil filled rotating vane pump File:Edwards E2M2 to E2M12 Users Instruction Manual.pdf
• Turbo Pump: Pfeiffer Balzers TPH 190

Pfeiffer Balzers TPU TPH 170 manual

Similar but smaller unit manual File:Pfeiffer Balzers TPH TPU 110 .pdf

Table of pumps to compatible controllers File:Pfeiffer table.pdf

View of pump 1 Media:PfeifferTHP190_1.gif

View of pump 2 (connector side) Media:PfeifferTHP190_2.gif

View of pump 3 (other side) Media:PfeifferTHP190_3.gif

• Turbo Pump Controller: Pfeiffer Balzers TCP 300 Controller

Original

• Stereoscan 200 dimensions

• S200 operating instructions (2 MB zip)

• Edwards E2M-12 roughing pump user instruction manual

757 Labs

Previous owners (757 Labs, another hackerspace) attempting repairs compiled some information at:

• http://757labs.org/2012/09/scanning-electron-microscope-update/ (archival link -- text only) (Internet Archive)

• http://757labs.org/wiki/Projects/SEM (archival link -- text only)

Additional Resources

• The original S200 operating instructions are available at the space in a three-ring binder near the machine.

• If possible, members will also have access to a PDF copy of Scanning Electron Microscopy - A Student's Handbook, 1980, self-published by Michael Postek, et al. This book was widely used by microscopists and is still regarded as a good learning reference, but the original binding is rare and prone to falling apart. It might be possible to use the PDF copy for private, educational use.

More Photos

• SEM install and overview

• Close-ups of assembly and components

• Cleaning and vacuum components

Contacts

We have a list here of HacDC members who are responsible for the SEM, including people that should be notified about problems.

Mirage335 (talk) Custom electronic control replacement circuitry.

Juri_ Julia Longtin, Juri_ on IRC. SEM repair project.