Einzel Lens Model

These images are of a 3d model for our einzel lens. The lenses must be custom fitted for copper pipe. Since our copper pipe is held at ground, only the middle cylinder needs to have an electrical connection.

Electrical Feed-throughs

Today we drilled and tapped our 12 electrical feed-throughs. We are using spark plugs because they are heavily insulated and are designed to pass electrical connections into a vacuum.

Vacuum System - Roughing Pump

Today we reached a huge milestone in our project by testing the vacuum system.  We only tested the roughing pump because we didn't have access to liquid nitrogen which we need for the diffusion pump.  The test went wonderfully. In fact, the roughing pump outperformed our expectations by getting the pressure in the vacuum chamber down to about 10^-4 torr.

High Voltage Power Supply & Analog Voltmeter

This video shows both a working analog voltmeter and a working power supply. We acquired this P.S. for 24 dollars off of ebay, so we were unsure whether or not it would be suitable for our purposes. The power supply takes a 24 volt DC input and outputs a high voltage DC, but an external circuit is required to control the output voltage. A potentiometer is used to scale the output voltage with a 1:1000 ratio. When I turn the potentiometer, I change the resistance and thereby change the voltage that enters the power supply's control circuit. When the resistance is high (max 5k ohm) the voltage is 0, and the high voltage output is 0. Inversely, if the resistance is low, the voltage is 15 volts, and the high voltage output is 15kv.

The analog voltmeter runs off of lower voltage than the high voltage output, and therefore, ten 1Mohm and one 10k ohm resistors are strung together in series from the positive side of the high voltage output. The meter reads the voltage across the 10k ohm resistor by powering an electromagnet that moves the needle accordingly.

Eye Protection is Key

Always use eye protection when cutting... Even if the only available eye-wear is a scuba diving mask. This video is of Harry cutting into the SEM's desk mount to create the diffusion pump and baffle feed-through.

High Voltage Power Supply Flame Test

When I plug in the 24 v dc power supply, the voltage is stepped up to as high as 15kv. (adjustable from 0 to 15kv).  The high voltage leads are connected to metal plates and are situated (precariously) parallel to one another. This allows for an electric field to be created between the two plates, thereby stretching the flame which is made up of a mixture of various ions. If you look closely at the flame, whenever I plug in the power source, the flame is stretched apart slightly. This tells us that the power supply is indeed working.

Interestingly enough, when I plugged in the power supply, the high voltage wires moved together because of the voltage difference (opposite charges attract). This shows that these old wires were not insulated with shielding, which consists of a metallic layer of insulation that blocks any potential electric field from exiting the  cable's insulation.

Raster Scan Variable Frequency

This is a video of the same raster scan circuit with a potentiometer integrated in place of a fixed resistor between positive and source of the PNP transistor. Pot. is a 5k ohm logarithmic variable resistor. It will be replaced by a 5k ohm linear pot, and the capacitor will be replaced with a lower rated cap to allow for higher frequencies (more bandwidth).


*Sorry for making you tilt your head*

Cathode filament power supply

This is a video of an isolation transformer, variac and stepdown transformer working in unison to supply a 0-6 vac supply at 60Hz. Next step is to rectify the output to DC so that it can be used to heat up the tungsten filament.


Here are the videos of the rectification process. First, four rectifier diodes are soldered to the AC output to force all of the negative voltage to be positive. Diodes allow current to flow in one direction. By placing multiple diodes in a certain way, it is possible to direct the current in such a way that the voltage between two leads to remains positive throughout the entire wave cycle.

Next, a resistor (10k) is placed between the DC output wires. This is done to remove any and all floating voltage between the two leads. It is, in a sense, a pull down resistor.

Finally, a large capacitor (1000 microfarad) is placed between the dc output leads to smooth the half wave into a linear output. The capacitor is charged continuously to the peak voltage, and since it is a relatively large capacitor, it only discharges once in a while. If we chose a lower capacitor (0.1 microfarads) We would see more ripples in our DC output because the capacitor would discharge more often.

Raster Scan Generator

A raster scan generator uses a 555 timer microchip alongside a transistor, capacitor and resistor circuit in order to produce a linear ramp-up oscillation. This type of oscillation will be used to display the SEM image onto an analog oscilloscope screen.

Breadboard of a 555 timer-based linear ramp circuit. In order to make this variable, a variable resistor will replace one of the fixed resistors.

Diffusion Pump Water Boil Test

Diffusion pumps operate on a principle of inertia that states that objects at rest tend to stay at rest unless acted upon by another force. By heating up oil, a diffusion pump can force the larger oil molecules to change the inertia of air molecules inside of a vacuum chamber. By slamming these high-energy molecules into the air molecules, a diffusion pump is essentially capable of pushing air out of a chamber.

At the bottom of a diffusion pump is a heating element (around which sits the vacuum oil). Above the heating element is an umbrella, which guides the vaporized oil down towards the foreline (exhaust). Once the vaporized oil comes in contact with the edge of the diffusion pump, it condenses and falls back down towards the heating element to start the process over again.

In order to ensure that the diffusion pump remains cool enough to have this condensation occur, external cooling systems must be present. In our system, we use a liquid nitrogen cold trap and water baffle, along with an air-cooling system to preserve the stability of the temperature of our diffusion pump.

CNC Lathe

Anode and wenalt fabrication test

First Day on the Job

Today, we visited Aqua Environment Inc. and met with Phil Slack who gave us a tour of his metal shop. We began work on the electron column, completed fabricating the wenalt cylinder, the anode and began work on the Teflon insulation as well as the aluminum condenser lenses. We also began mapping out potential methods of attaching our baffle to the base plate. Today was a good day.