Cyclotron II

Description: The white feedthroughs are for connecting the RF high voltage to the D's (not shown). The copper pipe perpendicular to the main pipe serves as the vacuum line. The D's are equipped with screw posts on the side for connecting to the RF power supply leads (curled copper wire). The target is visible in the upper left corner of the image, reflecting light effectively. The target was hard soldered, de-fluxed, and cleaned before each experiment. Copper was selected for the target material due to thermal considerations and its ability to produce short-lived low-energy isotopes compared to longer-lived isotopes from other materials. The heater element at the center of the chamber functions as the ion source for the cyclotron. The D's are positioned correctly. At the bottom of the image, the plate where accelerated ions impact can be seen. The feedthroughs were secured using vacuum wax. The chamber walls are made of stainless steel, while the D's are constructed from brass. The heater uses nichrome wire, with a current of approximately 2.5A passing through it. The project was displayed at a science fair, occupying a space of about 8' by 4' by 3'. The black background with yellow text became a popular design style. On the right side of the image, the cyclotron chamber is shown while the D's are being cleaned for the next experiment. The solvent used for cleaning the brass, xylene and acetone, is visible in the foreground. The cyclotron is depicted during the outgassing phase, necessary to eliminate air molecules trapped on the brass surface that could compromise the vacuum. The blue glow indicates plasma generated by applying 3000V across the D's. The images show the cyclotron in operation; the top image captures a stability check of the oscillation while measuring the output, and the bottom image depicts re-tuning of the tank circuits of the push-pull configuration while adjusting the driving voltage frequency. The high voltage RF power supply built for the D's in the cyclotron chamber is also illustrated. The RCA 811A tubes operate at around 200W each. The white PVC pipe coils function as input and output coupling transformers for the amplifier, featuring multiple taps for various resonant bands. Variable capacitors at the top provide tuning for the amplifier's output and input stages, which must be balanced to prevent the push-pull from collapsing and causing tube implosion. The magnet power supply was designed around a variac. Meters and their shunts are visible at the bottom; the meter on the right employs a short length of 12 Ga copper wire as the current shunt. The large bridge rectifier mounted on a heat sink is located in the upper left, and heavy 10 Ga wire is used in the supply to minimize resistive losses at 22A. A 40A contactor is visible in the bottom left, while the right side features nine 1000uF 250V capacitors and two 2000uF 250V capacitors, providing a total filter capacitance of 13000uF. Although a large filter inductor was initially considered, it was determined that the magnet itself would serve effectively as the inductance for the power supply. Consequently, when the magnet was powered at full capacity (22A), the ripple in the supply voltage remained below 1V (out of 89V). A clearer image of the vacuum system used in the first and second cyclotrons is also available.

The described circuit system is a complex assembly designed for a cyclotron, which is a type of particle accelerator. The integration of various components, such as the RF high voltage feedthroughs, the vacuum line, and the ion source, is essential for the proper functioning of the device. The D's, or dees, are critical components that facilitate the acceleration of charged particles. The choice of copper for the target is based on its thermal conductivity, which is vital for managing heat during experiments involving high-energy isotopes.

The heater element, made from nichrome wire, generates the necessary thermal environment for the ion source, ensuring optimal ion generation. The use of stainless steel for the chamber walls provides structural integrity and resistance to corrosion, while the brass construction of the D's ensures good electrical conductivity. The RF power supply, utilizing RCA 811A tubes, is engineered to deliver consistent high voltage to the D's, with the design incorporating multiple resonant bands to optimize performance across different operating conditions.

The vacuum system is crucial for maintaining an environment free of air molecules, which could interfere with the particle acceleration process. The outgassing phase is a necessary procedure to ensure that the vacuum is not compromised by trapped air. The coupling transformers and variable capacitors are strategically included to fine-tune the amplifier's performance, enabling precise control over the RF power supplied to the D's.

Overall, this circuit design exemplifies the intricate balance of thermal management, electrical engineering, and vacuum technology required to successfully operate a cyclotron, showcasing advanced principles in high-energy physics experimentation.The white feedthroughs are for the attachment of the RF high voltage to the D`s (not shown). The copper pipe normal to the pipe is the vacuum line. The D`s have screw posts on the side for attachment to the RF power supply leads (curled copper wire). You can clearly see the target in the upper left hand corner of the picture. The light is bouncing off of the surface nicely. The target was hard soldered on and de-fluxed and cleaned before each experiment. Copper was chosen for the target metal for thermal reasons, and the possibility of making short-lived low energy isotopes over longer-lived isotopes from different target materials. The heater element in the center of the chamber is the ion source for the cyclotron. The D`s are shown in their proper place. At the bottom of the picture, you can see the plate where the accelerated ions hit. The feedthroughs were attached using vacuum wax. The chamber walls are made of stainless steel. The D`s are made of brass. The heater is nichrome wire, and the current through the heater shown is about 2. 5A. This is what the project looked like when it was setup at the science fair. That is me standing next to it (senior year). The project was somewhat imposing. It exactly filled the space allotted. It was about 8` by 4` by 3`, I seem to remember. The black background with text outlined in yellow became a pretty often mimicked style. I guess I became somewhat of a science fair trendsetter. On the right is the cyclotron chamber while I was cleaning the Ds off for the next experiment. The bottle in the foreground is the solvent I used the clean the brass off (xylene and acetone). This is the cyclotron during the outgassing phase. The chamber needed to be outgassed because the air molecules trapped on the surface of the brass would act as a slow leak, causing the vacuum to be ruined.

The blue glow is the plasma from the 3000V placed across the D`s. These two pics show the cyclotron in operation. On the top, I am checking the stability of the oscillation as I measure the output. On the bottom, I am re-tuning the tank circuits of the push-pull while I change the frequency of the driving voltage. This is the high voltage RF power supply I built to supply the RF power to the Ds in the cyclotron chamber.

The tubes are RCA 811A`s, operating at about 200W per tube. They were hot! The white PVC pipe coils are the input and output coupling transformers for the amplifier. There were multiple Taps on the transformer, allowing me to have several different resonant bands for the amplifier. The varible caps on the top are providing the tuning for the output and input stages of the amp. Each had to be balanced, or the push pull would collapse, and the tubes would implode. The magnet power supply was designed around the variac that I had purchased. On the bottom, you can see the meters and their shunts. The meter on the right uses a short length of 12 Ga copper wire for the current shunt. On the upper left, you can see the large bridge rectifier on a heat sink. Notice the heavy 10ga wire used in the supply to reduce resistive losses at 22A. You can see on the bottom left a 40A contactor. On the right side, you see 9 1000uF 250V capacitors in brown, and on the bottom two 2000uF 250V capacitors.

This gave me a total filter capacitance of 13000uF. I initially thought of adding a large filter inductor to the circuit, but it occurred to me that the magnet itself would be a great inductance for the power supply. So, when I powered the magnet at full blast 22A, I had a ripple in the supply voltage of less than 1V (out of 89V).

Here is a far clearer picture of the essentials of the vacuum system used in the first and second cyclotrons. The Bell ja