SEM

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Contents

The Scanning Electron Microscope at Noisebridge.

  • "TV Mini-SEM (R)" by ISI (International Scientific Instruments)
  • lives in the room that used to house the laser cutter
  • is tended by Alan Rockefeller, Jeff Miller, Chris and Jim and the rest of the SEM mailing list

Warnings

  1. If you release the vacuum without venting the pump hose, pump oil will flood the chamber and contaminate the entire mechanism, requiring 10 hours of cleanup.
  2. If you vent air into the column without powering down the filament, you'll probably destroy the filament ($100). The filament has a design lifetime of about 25 hours, depending on the current put through it. Adjust the specimen stage and other controls at low current, reserve higher currents for final photos.
  3. Mike Khan has warned that if anyone asks him anything about the SEM, he's going to move it to another hackerspace.

Startup procedures

  1. If the power cord is not already present, ask around or post to the list a few days prior to using the 'scope.
  2. See PDFs on vacuum start up and operators manual linked below.

Todo list

Short Term:

  1. Determine if their is sufficient interest in the SEM and morale among the group to rationalize going forward. (2013-6-20)
  2. Isolate vibration from external sources; buses, people, etc. Mostly finished. (2013-6-20)
  3. Figure out what to do about the person(s) now "occupying" the clean room which houses the SEM. (2013-6-20)
  4. Design/build/find a sputter coater so the SEM can be used as a useful tool as well as a curiosity.
  5. Create/obtain specimen stage clamp or spring to prevent specimen vibration. (2010-12-12)
  6. Obtain some sputter coated specimens. (2010-12-12)

Medium Term:

  1. Build a forepump line vibration isolator. (2013-6-20)
  2. Relocate or otherwise isolate the forepump. (2013-6-20)
  3. Replace most of the rubber tubing with metal tubing to reduce outgassing and pump-down times. (2013-6-20)

Long Term:

  1. Column liner needs to be replaced. Larry may be able to provide a clean liner. (2010-06-15) (update: Larry has taken column liner to his lab for cleaning)(update: column liner is now clean) (2013-6-20)
  2. Integrate the digital capture and control unit Jeff built for his own Mini-SEM into the unit. (2013-6-20)
  3. Test repair of X Stigmator circuit. Replaced 741 op amp. (completed, work began 2010-11-20, tested 2010-12-10)
  4. Adjust vertical overscan of CRT (completed 2010-12-12, including hack sawing access port to overscan potentiometers in the CRT module)
  5. Fix 2x magnification toggle switch (2010-12-12)
  6. Diagnose and repair barrel distortion and occlusion at low magnification (2010-12-12)
  7. Sew dust cover (2010-12-12). Sew/heat seam new plastic dust cover, evidently the previous dust cover was destroyed. (2013-6-20)
  8. Rubber grommet around edge of CRT potentiometer port needed.
  9. Replace forepump with a (hopefully larger) pump that has a ballast port.
  10. Buy/find some real vacuum valves, turn simple spool pieces to serve as adapters, and electro-pneumatically interlock the valves so that valve sequencing is fool-proof.
  11. Evaluate air-cooled diffusion pump as source of vibration and contamination. Consider Santovac fluid and/or water-cooled pump and/or thermoelectric cold cap.
  12. Consider replacing filament with LaB6 cathode for brighter, sharper images and lower long-term per hour operating costs.

Repair and Enhancement Notes

  • Before repair, disable pumps and high voltage then put it into operation mode by placing a magnet on the operation relay.
  • schematics framed behind SEM are to a similar, potentially slightly more modern model
  • poorly designed wire harness may cause linear op amp and transistor on the J1 board of the power module to fail.
  • camera mounting stage and bellows hood for slow-scan exposure. Proposed (2010-06-15), Completed by Mike, Miloh, and Chris (2010-11-06)
  • CRT V. scan, V bias, H. frequency potentiometers are located on the underside of the CRT module.
  • broken stigmator Y lock tab is in altoids tin in SEM kit box.

How to mitigate vibration:

  1. Measure and pinpoint vibration sources
  2. Dampen vibration from the rough pump-line by one of these methods: routing it through a concrete block and adding a hose extension, sandbag the existing line, or utilize water as a mass.
  3. Hang the column from the ceiling with bungee cord and platform
  4. Potentially relocate the microscope to the server room to diminish dust and increase distance from Mission St.
  5. Create spring clamping specimen slug to keep the specimen from moving.

Specifications

  • Made in Japan
  • Delivered in September, 1975
  • magnifies up to 20,000x
  • outputs to a CRT
  • non-digital, non-NTSC, non-PAL, analog output signal

Documentation

Media: Vacuum_System_Operating_Instructions.pdf - How to start the pump

Media: ISI_Mini-TV_SEM_Manual-Troubleshooting-Reference_Guide.pdf - How to use and fix the SEM

Media: Specimen_Stage_Service_Request.pdf - Why the rotating stage is broken

Media: Cards.pdf - Historic docs

Media: Other_Docs.pdf - Repair notes

Media: Packing_Lists.pdf - Original Packing Lists, the contents of the shipping crate

Schematics

Overall schematics for the TV MINI-SEM (Model: MRS-2-2 WN76-7-01). These schematics are for a model of SEM that is perhaps newer than than the SEM at Noisebridge. It is still an invaluable reference to the technician. Note: This schematic is a mosaic of 9 images stitched together with Hugin 2010.2.0. Some minor alignment issues exist in the content of the schematic. I think alignment can be guessed/interpreted accurately. Available in: LOW RES 1.5MB (4330 x 3109, posterized grayscale, JPEG) and HIGH RES 8MB (8680 x 6217, color, JPEG).

Media: Schematic_of_Photomultiplier.pdf‎

Media: Polaron_Pirani_Schematics-PE_Pir-SW_Issue_4_E5000.pdf - Polaron Pirani sputter coater schematics

Media: Polaron_Pirani_Gauge_Head_for_Sputter_Coater.pdf

Specimen Images

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