A half-year update on the demo fusor and some questions

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Julian Kang
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Joined: Mon Jun 03, 2013 6:41 am
Real name: Julian Kang

A half-year update on the demo fusor and some questions

Post by Julian Kang »

So far, I've managed to buy: a 9kV 30mA neon sign transformer, a vacuum pump with an ultimate pressure of 15 microns and the various wires/attachments needed. The vacuum chamber was generously donated to me by Ross Moffett. It should take about 2 weeks for me to finish, due to the shipping of the radiation detector I plan to buy.

A few questions:

In my search for a radiation detector, I've found two options: 2 CDV-750 (0-200 mR) pens with associated charger, or a CDV-715 Geiger Counter. I've read that the 715 is not a suitable counter for 'normal' uses as it counts in R/Hr (1-5) rather than mR/Hr however I figured that it should be okay since the main purpose of getting the counters is to reassure my parents that no radiation is coming out of the chamber. I wouldn't be running the fusor for long durations anyway, not that it might last more than 30 seconds, so even if mRs of gamma radiation or x-rays left the chamber it would not matter much. Which would be a more suitable option?

The last component I need to build before the demo fusor is functional is a full wave bridge rectifier, made of 4 9kV 30mA diodes (my neon sign transformer is 9kV at 30mA), a smoothing capacitor of 0.03 Farads or 30 milliFarads [1] for a Ripple voltage of 100mV and two bleeder resistors of 32 Ohms (Fast Bleed) [2] and one that has a higher resistance, maybe 500 Ohms for a slow bleed arranged with a ON-OFF-ON switch such that either one is connected in parallel to the capacitor at any given time. I plan to submerge the entire full wave bridge rectifier in vegetable oil placed within a glass/plastic jar before using a vacuum pump to remove the air within it to prevent arcing between the components. I also plan on using fabrics with silica gel to prevent contamination of the vacuum pump, although I'm not even sure if oil in the pump would cause issues.

Just as a final check (this is to reassure my parents that this is safe to do), the demo fusor produces: Alpha, Beta, Gamma and X-Ray radiation. Alpha and Beta radiation are not an issue as Alpha particles can be stopped by a few millimeters of air, and Beta particles by a few millimeters of Aluminium (oh which the plates that comprise my chamber are made of) [3]. Gamma and X-ray radiation are produced by the high voltages used in the demo fusor, but will not leak out as I'm operating under 15kV [4]. However, I'm unable to find calculations as of yet on how much gamma and X-ray radiation is produced by a demo fusor (it would be low at 9kV no doubt, but some math would help when I'm trying to convince people) so a lead/paraffin combo shield is in the works as well as the purchase of either a dosimeter or geiger counter.

Some pictures: http://imgur.com/yvCnkGU,xjZYP6i#0
The latex gloves serve to float the NST away from the floor, which previous experiences have told me that high voltage is able to arc to. A solder-less grid bound with aluminium wires has been made, but has not bee connected to the chamber yet. The hose is a washing machine hose.
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[1] This is based on: (http://www.electronics-tutorials.ws/diode/diode_6.html). I moved the variables around to get: C=(I/V x F)+V with the values 0.03A, 0.1V and 100Hz.

[2] (http://www.learningaboutelectronics.com ... arging.php) with values Vc=50, Vo=9000, t=5, C=0.03

[3] (http://hyperphysics.phy-astr.gsu.edu/hb ... adact.html) Found at the bottom of the page.

[4] I remember reading this somewhere in the FAQs, but am unable to recall where.
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Thanks for reading.
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Richard Hull
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Real name: Richard Hull

Re: A half-year update on the demo fusor and some questions

Post by Richard Hull »

No fusor produces Alpha or Beta radiation or Gamma radiation. Most demo fusors never produce x-rays which are capable of penetrating the chamber. Basically zero radiation of any type in most all demo fusors.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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